New tire rolling resistance test - 23mm, 25mm, 28mm & 32mm GP5000 tires

[Mark McM]

Just posted to the BicycleRollingResistance.com web site is a new special test on various sizes of the Continental GP5000 tire. Like many tests, the first part of these tests measures rolling resistance at several fixed pressures. But the 2nd part of the test is the more interesting, where the rolling resistance is measured with pressures selected to achieve a specific tire deflection/stiffness (i.e., a specific shock absorption/comfort). This 2nd part shows that in real world usage (real world pressures), there is not a big difference in tire rolling resistance between even the widest and narrowest version of the GP5000.

Here's the test (https://www.bicyclerollingresistance.com/specials/grand-prix-5000-comparison).

[m_sasso]

Now they need to combine wind resistance in these tests to get a partial picture of real world performance!

[pjbaz]

Hmmmm, maybe I will try the 25c size ... I did buy a pair last year, just never used them lol. #23formeusually

[weisan]

http://alicehui.com/bike/gifs/ezgif-2-d1a949a2cabd.gif.

[Mark McM]

Now they need to combine wind resistance in these tests to get a partial picture of real world performance!

There can often be more variables in aerodynamic testing than rolling resistance testing, so when throw tires into the equation it becomes even more complicated. But that hasn't stopped some groups from trying.

For example, Flo Cycling, a maker of aero wheels, ran some tests on a variety of different tires to find the best tire for a combination of aerodynamics and tire rolling resistance. However, they only used one model of their wheels, and the results of their test may not be applicable to other wheels. Still, their test and results are interesting (the test and results can be found here (http://flocycling.blogspot.com/2016/06/flo-cycling-a2-wind-tunnel-tire-study.html)).

One interesting thing from this test is that the highest aerodynamic drag power with any of the tires tested was only about half the lowest rolling resistance drag power of any of the tires tested - i.e., rolling resistance is a much bigger factor in wheel performance than aero drag. When Flo combined aero + rolling drag, the best combination was not the one with the lowest air resistance, it was the one with the lowest rolling resistance tire (in fact, that combination actually had the 11th best aero drag out of 20).

Also of note is that Flo used a speed of 21.75 mph for the test. While many companies report wind tunnel results at much higher speeds (30 mph is a typical speed), and therefore exaggerate aero benefits, the Flo results are reported for a speed that probably more closely matches most people's actual speeds. In at least one regard, Flo's results confirm my own personal experiences - I can barely detect speed differences between aero and non-aero wheels, but I can easily detect speed differences between high and low rolling resistance tires.

[cmg]

From the video,
Test conditions

•Speed of 29 km/h / 18 mph
•Total wheel load of 42.5 kg / 94 lbs
•700 x 17C wheel
•Temperature between 21.5-22.5 °C / 71-72 °F
•Diamond plate drum surface
•77 cm drum diameter
•Tires are run in for 30 minutes at 60 psi / 4.1 bar

If you're new to our site, below is a YouTube video that gives you an idea about our set up. This video shows the spin-up of a Continental Grand Prix 5000 25-622. When measuring rolling resistance, the tire is run at a constant speed.

Then how do they measure? Is the torque provided by the spinning drum the same for the different weights of the tires in order to get the wheel up to a constant speed? Do they cut the power to rolling device, measure the force the tire exerts on the spinning drum to it keep spinning? Measure the rotational force of the spinning wheel and compare to the force exerted by the spinning drum? What parts the moving bits are they measuring? just isolating the rolling resistance does tell all that is needed to spin a wheel.

[Mark McM]

Here's part of the web page where they describe the test (https://www.bicyclerollingresistance.com/the-test):

Measurements are taken with an Arduino microcontroller equipped with custom software and hardware. Our setup calculates the average power required to keep the drum at a set speed for a period of 30 seconds. Using our custom setup to measure input power results in a very accurate measurement.

After a warm-up period of 30 minutes, three measurements are taken. We then calculate the average of these three runs. After a correction for the electric motor efficiency and subtraction of the power required to spin the drum and wheel to the set speed, the result is the rolling resistance of the tire.

The page also includes a listing that appears to be a read out of motor speed, voltage, and current.

From this, I surmise that they are measuring the (electrical) power going into the motor to maintain a constant drum speed. That should be sufficient, as long as they have calibrated the motor efficiency, and the zero load power.

[saab2000]

It’s interesting that the resistance increases as pressure decreases. This is contrary to what we’re always told, making me thing their testing drum should be updated to more realistically simulate real conditions. Or else we’re not always being told the truth... :rolleyes:

[kppolich]

Decreased pressure to me means that more of the tire would be in contact with the ground at any given time, increasing resistance. Width and pressure are interesting.

Road surface is the kicker

[Mark McM]

It’s interesting that the resistance increases as pressure decreases. This is contrary to what we’re always told, making me thing their testing drum should be updated to more realistically simulate real conditions. Or else we’re not always being told the truth... :rolleyes:

It's been known for a long time that the rolling losses internal to the tire itself increases with decreasing pressure. What has come into better appreciation in recent years is that vibrational losses external to the tire (some times called 'suspension losses' or 'impedance losses') decrease with decreasing pressure. Josh Poertner at Silca wrote up a series of blog posts about this:

https://silca.cc/blogs/journal/part-4a-rolling-resistance-the-history-and-previous-works

The BicycleRollngResistance.com tests measure the internal tire losses (Poertner refers to this as the 'casing losses'), so their data will show a decrease in resistance with increasing pressure. Other testing has shown that tires with lower casing losses also have lower suspension losses, so the BicycleRollingResistance should still be reliable for indicating the relative differences in total rolling resistance between tires, even for real world conditions.

[tylercheung]

What about grip and handling - does anyone test the G-force required to induce skid?

[ultraman6970]

Somebody told you the opposite?? interesting :) Remember a guy in university, he was not able to comprehend how is that the less the volume you have more pressure.

My main thing with all these tests is that some are way too biased, some guy put a new tire in the market and they made up stuff in the lab so the new tire is super fast compared with other ones eventhought defeat the logic of how physics works.



It’s interesting that the resistance increases as pressure decreases. This is contrary to what we’re always told, making me thing their testing drum should be updated to more realistically simulate real conditions. Or else we’re not always being told the truth... :rolleyes:

[old_fat_and_slow]

Yea, skinny tires inflated to umpteen psi still rule !!!

[Hellgate]

It’s interesting that the resistance increases as pressure decreases. This is contrary to what we’re always told, making me thing their testing drum should be updated to more realistically simulate real conditions. Or else we’re not always being told the truth... :rolleyes:That data has been on the site for a while. People have become obsessed with lower pressure and LARGER tire for comfort. Mainly due to the gravel uprising... In other words, if you're not on terrible roads, use a higher pressure.

I still run 95 psi on 25mm and people think I'm nuts, but the roads I ride are relatively smooth as crank it up!

[bikinchris]

It’s interesting that the resistance increases as pressure decreases. This is contrary to what we’re always told, making me thing their testing drum should be updated to more realistically simulate real conditions. Or else we’re not always being told the truth... :rolleyes:

I don't know who said that. I always understood that too much pressure and too little pressure were both going to increase rolling resistance.

[robertbb]

I recently switched from 23mm GP4000S2's to 25mm GP4000S2's.

I use 17c (internal) wheels exclusively (Zonda, Shamal and Bora) and tubes are always Michelin A1 Aircomp butyl.

I always ran 85PSI on the 23mm tyres, and interestingly, after multiple rides on the 25mm trying both lower and higher pressures I ended up settling on the exact same pressure for the 25mm tyres. I felt this gave me the best combination of grip, speed and comfort.

The marketing told me I should be able to drop pressure by 10PSI or more, but notably the tyre felt unstable and slow right up to that 85PSI mark.

[pasadena]

Zipp still recommends 23's as the fastest tire size, on the front wheel at least.
It's the combination of aero and rr.

Anecodally, the fastest clinchers I've ridden are Sworks 24's.
Waiting to try GP4000IIs (late to the party) when my Schwalbe 1's wear out.

[joshatsilca]

I recently switched from 23mm GP4000S2's to 25mm GP4000S2's.

I use 17c (internal) wheels exclusively (Zonda, Shamal and Bora) and tubes are always Michelin A1 Aircomp butyl.

I always ran 85PSI on the 23mm tyres, and interestingly, after multiple rides on the 25mm trying both lower and higher pressures I ended up settling on the exact same pressure for the 25mm tyres. I felt this gave me the best combination of grip, speed and comfort.

The marketing told me I should be able to drop pressure by 10PSI or more, but notably the tyre felt unstable and slow right up to that 85PSI mark.

From 23 to 25mm on a 17c rim your equivalent tire spring rate psi will go from 85 to 82psi, not sure who is saying 10psi, but that is way off.
Josh

[robertbb]

From 23 to 25mm on a 17c rim your equivalent tire spring rate psi will go from 85 to 82psi, not sure who is saying 10psi, but that is way off.
Josh

Surely a measly 3 psi differential is within a margin of error?

Either way, look at Schwalbe's recommended pressure differences from 23mm to 25mm - it's 13 to 15psi reduction:

https://www.cyclingweekly.com/news/product-news/whats-the-correct-road-bike-tyre-pressure-270668

I'd read similar elsewhere and seen the same thing repeated on YouTube videos from GCN and others...

So of course having always run my 23's at 85psi, I pump up my 25's to 60psi and out I go for a test ride and think... holy sh*t this is cr*p!

And it contines to be crap until I arrive at 85psi...

[drewskey]

Hey Weisan - added some commentary.

https://media.giphy.com/media/1k3RuPSxbjVbJfg6W9/giphy.gif

[weisan]

Hey Weisan - added some commentary.

https://media.giphy.com/media/1k3RuPSxbjVbJfg6W9/giphy.gif

I like it!

[oldpotatoe]

This 2nd part shows that in real world usage (real world pressures), there is not a big difference in tire rolling resistance between even the widest and narrowest version of the GP5000.

OMG!! Not A Big DIFFERENCE??? The interweb may explode...:)

[saab2000]

Take my above comments with a grain of salt.

I've loved my 23mm tires on wide (20mm interior width) rims for several years and may start going to 25mm due to my seemingly ever expanding waistline and the fact that the roads are crappy where I live.

I do run lower pressure and have found it to be nice, with no apparent loss of speed. Just increased comfort.

The reason I mention the lower pressure and people saying it decreases rolling resistance is that supposedly a rock hard tire will deform less over the texture of the road surface. Lower pressure will allow the tire to deform more and actually provide lower rolling resistance overall. I don't know the science.

But I run my 23s at about 80 PSI and 25s a bit lower and they ride very nicely. In fact, I've found a cotton clincher on wide rims like I use now to be close enough to the ride of a quality tubular that my tubular usage has gone down dramatically in the past few years.

I'm speaking here only about paved roads and road tires. Tires and pressures for unpaved roads are a whole 'nuther ball of wax.

[soulspinner]

Run latex for the biggest difference, regardless of width.

[MoparPorsche]

Run latex for the biggest difference, regardless of width.

Latex over tubeless?

[johnniecakes]

Way too much thought for this guy. I have always run 23's inflated to the proper sidewall squeeze pressure and off I go! Never owned a pressure gauge for bikes. Now the cars are another matter, they get the pressure onthe door jam twice a year.

[soulspinner]

Latex over tubeless?

Full disclosure haven't run tubeless.

[slambers3]

Anyone here with hands-on experience on GP5000?

[oldpotatoe]

Anyone here with hands-on experience on GP5000?

https://forums.thepaceline.net/showthread.php?t=232545&highlight=GP5000

[joshatsilca]

Surely a measly 3 psi differential is within a margin of error?

Either way, look at Schwalbe's recommended pressure differences from 23mm to 25mm - it's 13 to 15psi reduction:

https://www.cyclingweekly.com/news/product-news/whats-the-correct-road-bike-tyre-pressure-270668

I'd read similar elsewhere and seen the same thing repeated on YouTube videos from GCN and others...

So of course having always run my 23's at 85psi, I pump up my 25's to 60psi and out I go for a test ride and think... holy sh*t this is cr*p!

And it contines to be crap until I arrive at 85psi...

OK, so just looked at the Schwalbe chart and can tell you that chart is what happens when marketing guys make charts... I love how each optimal pressure is exactly a round number in bar!! Amazing!

As the guy who develops and has developed tire pressure strategies for 10+ years for guys like Cancellara, Wiggins, Sagan, and so many others, I can tell you that this chart is straight up wrong from a performance point of view. Now for most people, doing most things, it's probably fine, but if you are after optimizing for performance this isn't it.

Optimal pressure will be different for different surfaces, but if you have a number a safe rule of thumb is that equivalent small bump stiffness of the tire can be achieved at ~2% per millimeter of width change.. so every mm larger in measured casing size you need 2% lower pressure, but again, for the same surface.. as surfaces increase or decrease in roughness, your baseline pressure changes

Part 1 of our episode on Asymmetry starts to get into this topic and brings some context from racing: https://marginalgainspodcast.cc/asymmetry-part-1/

[El Chaba]

I concluded some time ago that the move to wider tires for the road was largely driven by the search for something...anything...that could mitigate some for the extra stiffness that was characteristic of the uber-oversize tubed frames that have come into fashion. It was convenient that a larger tire could be run at a slightly lower pressure for some comfort gains without a big hit in increased rolling resistance.

[merckx]

I concluded some time ago that the move to wider tires for the road was largely driven by the search for something...anything...that could mitigate some for the extra stiffness that was characteristic of the uber-oversize tubed frames that have come into fashion. It was convenient that a larger tire could be run at a slightly lower pressure for some comfort gains without a big hit in increased rolling resistance.

I believe this to be dead-on.

[colker]

I concluded some time ago that the move to wider tires for the road was largely driven by the search for something...anything...that could mitigate some for the extra stiffness that was characteristic of the uber-oversize tubed frames that have come into fashion. It was convenient that a larger tire could be run at a slightly lower pressure for some comfort gains without a big hit in increased rolling resistance.

... but is it faster now?

[Mark McM]

What about grip and handling - does anyone test the G-force required to induce skid?

Tire traction can be more difficult to test under controlled conditions than many other tire properties (including rolling resistance), which is unfortunate, since traction is probably the most important property of a tire (if the tire doesn't have traction, then you may not get far enough down the road for other things like rolling resistance and puncture resistance to matter).

The only organization I know of that has published the results of bicycle tire traction tests is Tour Magazine, which periodically does wet weather tire traction tests. These tests consist of rolling down a hill and then riding around a corner on pavement that is constantly being wetted with a water sprinkler. The tester rides through the corner at increasing speeds until the tires slip out (and the rider falls). The test rider wears padded clothing, and rides a special bike that allows them easily jump off if the tires slip, but it should be obvious why this kind of testing isn't done very often.

[Mark McM]

Zipp still recommends 23's as the fastest tire size, on the front wheel at least.
It's the combination of aero and rr.

I'd take that recommendation with a grain of salt, particularly if they don't mentions specific tires, based on the work that Flo cycling did on combined tire/aero testing.

When Flo set about designing their carbon clincher rims, they needed to model the shape of both the tire and wheel together. Based on their previous testing, and the tests published by others, they discovered that the Continental 23mm GP4000 tended to test well aerodynamically, so they based their aerodynamic model around that tire.

After Flo produced their new wheel, they tested it in a wind tunnel with a variety of tires, and not surprisingly, it had nearly its best performance with the 23mm GP4000 (that's what they designed it for, after all). But when they combined aero drag with rolling resistance, they found that the wider 25mm GP4000 had a lower total drag - the lower rolling resistance of the wider tire more than made up for the extra aero drag.

I have no reason to doubt Zipp's claim that 23mm tire has the lowest drag on their wheels, if only aero drag is considered. But when you add in rolling resistance, I wouldn't be surprised if an excellent rolling, but slightly wider, tire ended up being better. Particularly if compared to a poorly rolling 23mm tire.

It used to be that riders selected tires based on which gave the best aero performance with their wheels. But in the future, I suspect that it will be the other way around - riders will select wheels, based on which gives the best aero performance with their tires. And we'll see aero wheels getting wider, to better match wider tires (this is already happening).

[Mark McM]

Take my above comments with a grain of salt.

I've loved my 23mm tires on wide (20mm interior width) rims for several years and may start going to 25mm due to my seemingly ever expanding waistline and the fact that the roads are crappy where I live.

I do run lower pressure and have found it to be nice, with no apparent loss of speed. Just increased comfort.

The reason I mention the lower pressure and people saying it decreases rolling resistance is that supposedly a rock hard tire will deform less over the texture of the road surface. Lower pressure will allow the tire to deform more and actually provide lower rolling resistance overall. I don't know the science.

But I run my 23s at about 80 PSI and 25s a bit lower and they ride very nicely. In fact, I've found a cotton clincher on wide rims like I use now to be close enough to the ride of a quality tubular that my tubular usage has gone down dramatically in the past few years.

I'm speaking here only about paved roads and road tires. Tires and pressures for unpaved roads are a whole 'nuther ball of wax.

If you look at the Josh Poertner blog article referenced earlier, you'll see that there is a inflation pressure "sweet spot" to minimize rolling resistance. Decreasing the pressure further will increase rolling resistance due to casing losses, and increasing pressure will increase rolling resistance due to suspension losses. This sweet spot will vary with tire width, surface roughness, rider size, and other factors.

Since you're an aviator, maybe you'll appreciate the analogy between the pressure sweet spot, and the speed/power curve for air drag:


Tire Air Pressure vs. Rolling Resistance:

https://cdn.shopify.com/s/files/1/0309/9521/files/Screen_Shot_2016-07-05_at_11.30.31_AM_grande.png?13001567160131315240



Aircraft Speed vs. Power
http://www.aviation-history.com/theory/lift_files/fig11.jpg

[Mark McM]

I concluded some time ago that the move to wider tires for the road was largely driven by the search for something...anything...that could mitigate some for the extra stiffness that was characteristic of the uber-oversize tubed frames that have come into fashion. It was convenient that a larger tire could be run at a slightly lower pressure for some comfort gains without a big hit in increased rolling resistance.

My observations have led to a different conclusion. Decades ago, most people rode wider tires than often seen today - 1" (25mm) tires were uncommonly narrow, and most people rode tires between 1 1/8" (28mm) and 1 3/8" (35mm) wide (these were the days before Kevlar bead tires and hooked rims). Pressures were typically in the 70 - 90 psi range.

Then, starting in the early '80s, people started believing that narrow, high pressure tires must be faster, and tires and rims capable of handling high pressures started being made. During the time that frame tubes started growing in size/diameter, typical tire widths started shrinking and tire pressures increasing - 23mm tires became common, and many were even riding 20mm tires, at pressures up to 120 psi or more.

The move toward wider tires today isn't to mitigate the extra stiffness of modern frames (even the old frames from yesteryear had too much vertical stiffness to provide much shock absorption) - its to mitigate the ridiculously high pressures that people been using during the last few decades.

[saab2000]

If you look at the Josh Poertner blog article referenced earlier, you'll see that there is a inflation pressure "sweet spot" to minimize rolling resistance. Decreasing the pressure further will increase rolling resistance due to casing losses, and increasing pressure will increase rolling resistance due to suspension losses. This sweet spot will vary with tire width, surface roughness, rider size, and other factors.

Since you're an aviator, maybe you'll appreciate the analogy between the pressure sweet spot, and the speed/power curve for air drag:


Tire Air Pressure vs. Rolling Resistance:

https://cdn.shopify.com/s/files/1/0309/9521/files/Screen_Shot_2016-07-05_at_11.30.31_AM_grande.png?13001567160131315240



Aircraft Speed vs. Power
http://www.aviation-history.com/theory/lift_files/fig11.jpg

It is an interesting graph, to be sure. Mostly it's one for the student pilots who learn about this stuff but in what I do today it's a bit of a different game. Of course, the same principles apply. Our speed and altitude selection is based on a lot of factors and this graph isn't something we would consider but it is, of course, an accurate depiction.

As to rolling resistance, you are correct that there are many different variables.

I've got a bike incoming that is designed as an "All Road" road bike and I'm wondering where I'll end up with the tires. I'm thinking probably 35mm. They'll still probably be ridable on the roads but not too narrow for my liking on unpaved roads. The 38s I'm running now are almost a tad too big for me and sometimes feel a bit sluggish.

I'm not yet ready for the 650x50s that some folks enjoy!

[robertbb]

OK, so just looked at the Schwalbe chart and can tell you that chart is what happens when marketing guys make charts... I love how each optimal pressure is exactly a round number in bar!! Amazing!

As the guy who develops and has developed tire pressure strategies for 10+ years for guys like Cancellara, Wiggins, Sagan, and so many others, I can tell you that this chart is straight up wrong from a performance point of view. Now for most people, doing most things, it's probably fine, but if you are after optimizing for performance this isn't it.

Optimal pressure will be different for different surfaces, but if you have a number a safe rule of thumb is that equivalent small bump stiffness of the tire can be achieved at ~2% per millimeter of width change.. so every mm larger in measured casing size you need 2% lower pressure, but again, for the same surface.. as surfaces increase or decrease in roughness, your baseline pressure changes

Part 1 of our episode on Asymmetry starts to get into this topic and brings some context from racing: https://marginalgainspodcast.cc/asymmetry-part-1/

I really appreciate this response Josh! :beer:

It's great to get insight from someone who legitimately knows what they are talking about and is willing to take the time to help the average punter who most certainly is not Cancellara, Wiggins or Sagan ;)

Curious as to your thoughts on that margin of error though. With such small changes to pressure required in moving from 23-25 or even 25-28, one wonders if the average floor pump/pressure gauge is up to the task!

I choose butyl tubes simply because the pressure I start a ride with is likely to be the pressure I finish it with. While I enjoyed running latex tubes for a while, if I went out on a century and had a stop for lunch/coffee, I'd find my pressure had dropped so much that any RR gains of the latex tube were probably negated and even inversed towards the end...

[pasadena]

ZIPP:
The aero improvement of the 23mm tire over a 25mm+ tire outweigh any relative losses in rolling resistance.

When Si on GCN did a KOM hillclimb challenge video, Zipp also recommended 23's as the fastest tire width.



I have no reason to doubt Zipp's claim that 23mm tire has the lowest drag on their wheels, if only aero drag is considered. But when you add in rolling resistance, I wouldn't be surprised if an excellent rolling, but slightly wider, tire ended up being better.

Pretty good article from Slow Twitch:

The new standard / minimum tire size is 25-26mm. The old standard of 23mm is dead. NOTE: When I say 25mm, I mean the INFLATED size on a modern clincher rim (so the tire label probably says 23mm). Anything under a measured 23mm, on a modern wide rim is DEFINITELY dead, short of some rare special cases.

The ‘What Should I Use’ Cheat Sheet

-If you’re a pro, aspiring pro, or just super-duper fast, use a tire that’s labeled 23mm (inflating to 25-26mm).

-If you’re an average, middle-of-the-pack person, trying to be competitive and have fun, use a tire that’s labeled 25mm (inflating to 28-29mm).

-If you’re a fat-tire-lover like me, and want to feel like you’re riding a magic carpet, use a tire that’s labeled 28mm (inflating to 31-32mm). With any luck, more new wheels will emerge, making this a legitimate aerodynamic choice.

https://www.slowtwitch.com/Tech/What_s_the_Best_Tire_Size_for_Me_in_2018__6822.htm l

[joshatsilca]

I really appreciate this response Josh! :beer:

It's great to get insight from someone who legitimately knows what they are talking about and is willing to take the time to help the average punter who most certainly is not Cancellara, Wiggins or Sagan ;)

Curious as to your thoughts on that margin of error though. With such small changes to pressure required in moving from 23-25 or even 25-28, one wonders if the average floor pump/pressure gauge is up to the task!

I choose butyl tubes simply because the pressure I start a ride with is likely to be the pressure I finish it with. While I enjoyed running latex tubes for a while, if I went out on a century and had a stop for lunch/coffee, I'd find my pressure had dropped so much that any RR gains of the latex tube were probably negated and even inversed towards the end...

robertbb, thanks for the comment and thanks for giving me a great opportunity to plug some SILCA pumps with super accurate gauges!! In all seriousness though it was the last 10+ years of doing this that inspired us to make super accurate gauge pumps, and if you read our Road to Roubaix Blog (https://blog.silca.cc/road-to-roubaix-the-complete-story-1) story you'll see that we considered this secret so secret that I travelled around Europe with a $1000 gauge for a few years in a pelican handgun case and we only used it out of site of other teams and the media.. Now we make a handful of pumps with specially tuned digital sensors to achieve 0.5psi accuracy at these types of pressures which are used by more teams than those we 'officially' work with.

As for latex, look at the modern latex, we sell tubes made by Vittoria which have a new formula with graphene in them and leak so much slower than the old ones. When we plotted Cancellara's roubaix run in 2010, we measured his tires to have nearly 1psi per hour loss.. so we tuned pressures so they would be perfect a few hours into the race when he was on the worst cobbles.. The new generation of latex tubes might lose 4-5psi per 24 hours, and will save you 2-5 watts per tire which is a bigger savings than a full ceramic bearing upgrade for about 1/50th the price!!

[sfo1]

Seems that tire size needs (or should be paired with) rim inner - outter measurements?

A GP 4000 25mm on a rim that is 17 id - 25 od vs same tire on a rim that is 20 id - 28 od will perform very different, no?

Maybe we all drink the cool aid and spend more $ to gain one watt?



ZIPP:
The aero improvement of the 23mm tire over a 25mm+ tire outweigh any relative losses in rolling resistance.

When Si on GCN did a KOM hillclimb challenge video, Zipp also recommended 23's as the fastest tire width.



Pretty good article from Slow Twitch:

The new standard / minimum tire size is 25-26mm. The old standard of 23mm is dead. NOTE: When I say 25mm, I mean the INFLATED size on a modern clincher rim (so the tire label probably says 23mm). Anything under a measured 23mm, on a modern wide rim is DEFINITELY dead, short of some rare special cases.

The ‘What Should I Use’ Cheat Sheet

-If you’re a pro, aspiring pro, or just super-duper fast, use a tire that’s labeled 23mm (inflating to 25-26mm).

-If you’re an average, middle-of-the-pack person, trying to be competitive and have fun, use a tire that’s labeled 25mm (inflating to 28-29mm).

-If you’re a fat-tire-lover like me, and want to feel like you’re riding a magic carpet, use a tire that’s labeled 28mm (inflating to 31-32mm). With any luck, more new wheels will emerge, making this a legitimate aerodynamic choice.

https://www.slowtwitch.com/Tech/What_s_the_Best_Tire_Size_for_Me_in_2018__6822.htm l

[pasadena]

Seems that tire size needs (or should be paired with) rim inner - outter measurements?

A GP 4000 25mm on a rim that is 17 id - 25 od vs same tire on a rim that is 20 id - 28 od will perform very different, no?

Maybe we all drink the cool aid and spend more $ to gain one watt?

Yes, you're right about that line of thinking.
My general understanding is, in cross-section, a U shaped tire is more aero than a O shaped tire.

Personally, I just don't sweat it. I like geeking out and webwheeling about it but in reality...

In a race, I just care about conserving energy. Light, aero wheels w/ tires I trust.
Someone said, generally all XXmm depth wheels are about the same aero savings.
So yeah, there are just so many other factors in a race, to me, it just doesn't matter.

For PR's, 'baseline' matters more. I want to keep my equipment consistent.
I note, if I try for a PR, did I use my carbon wheels or alloys. That way, I can just focus on my physical gains.

So, in that regard, it doesn't matter what you own.

In all honesty, the biggest gains I feel are when the tires are new.
New Rubino Pros feel great! :) New Sworks tires feel awesome!
When they start flat-topping? I'm sure you loose more watts there than anything else.

[joshatsilca]

Yes, you're right about that line of thinking.

In all honesty, the biggest gains I feel are when the tires are new.
New Rubino Pros feel great! :) New Sworks tires feel awesome!
When they start flat-topping? I'm sure you loose more watts there than anything else.

We have data on this in our Tires and Aero Blog post: https://blog.silca.cc/part-5-tire-pressure-and-aerodynamics

You are correct, that next to having the proper size tire for your rims, replacing them as soon as they begin to show wear makes a very big difference!!

[Mark McM]

ZIPP:
The aero improvement of the 23mm tire over a 25mm+ tire outweigh any relative losses in rolling resistance.

When Si on GCN did a KOM hillclimb challenge video, Zipp also recommended 23's as the fastest tire width.



Pretty good article from Slow Twitch:

The new standard / minimum tire size is 25-26mm. The old standard of 23mm is dead. NOTE: When I say 25mm, I mean the INFLATED size on a modern clincher rim (so the tire label probably says 23mm). Anything under a measured 23mm, on a modern wide rim is DEFINITELY dead, short of some rare special cases.

The ‘What Should I Use’ Cheat Sheet

-If you’re a pro, aspiring pro, or just super-duper fast, use a tire that’s labeled 23mm (inflating to 25-26mm).

-If you’re an average, middle-of-the-pack person, trying to be competitive and have fun, use a tire that’s labeled 25mm (inflating to 28-29mm).

-If you’re a fat-tire-lover like me, and want to feel like you’re riding a magic carpet, use a tire that’s labeled 28mm (inflating to 31-32mm). With any luck, more new wheels will emerge, making this a legitimate aerodynamic choice.

https://www.slowtwitch.com/Tech/What_s_the_Best_Tire_Size_for_Me_in_2018__6822.htm l

As discussed in the SlowTwitch article, there is no single tire width that will always be best. Different riding conditions may favor different widths. As mentioned, here's a few factors that may influence the optimal tire widths:

Surface roughness - rough surfaces increase suspension losses, which can be mitigated with wider tires

Speed - rolling resistance is a larger percent of drag at lower speed, so decreases in rolling resistance with wider tires may outweigh losses due to aerodynamics; conversely, aero drag increases with the square of speed, so narrower tires may be best at the highest speeds.

Rider weight - rolling resistance is proportional to rider weight, whereas weight doesn't affect aero losses, so the wider tires may be better for heavy riders, and narrower tires may be better for lighter riders

Crosswinds - wind drag in cross winds is increased when the tire width is greater than rim width, so narrow tires may be best in strong cross winds.


For 135 lb. Caleb Ewan doing a 45 mph final sprint with a crosswind, Zipp's recommendation for a 23mm tire is certainly correct. But for a 210 lb. rider doing a Grand Fondo at 18 mph, a 25mm or 28mm tire is probably more optimum, even on the same wheels.

[sfo1]

so how does one calculate their optimal tire size for their rim ID/OD?

Suppose you use a 25mm GP5000 tubeless with a rim that has 19mm ID and a 28.4mm OD? Would that create a 'u shape' or an 'o shape?'

Would a rim with 17id - 25od be better since its narrower and the od is 25mm?

I guess the q becomes for a 25mm GP5000 tubeless, what is the optimal rim ID/OD for fast & versatile?



We have data on this in our Tires and Aero Blog post: https://blog.silca.cc/part-5-tire-pressure-and-aerodynamics

You are correct, that next to having the proper size tire for your rims, replacing them as soon as they begin to show wear makes a very big difference!!

[joshatsilca]

so how does one calculate their optimal tire size for their rim ID/OD?

Suppose you use a 25mm GP5000 tubeless with a rim that has 19mm ID and a 28.4mm OD? Would that create a 'u shape' or an 'o shape?'

Would a rim with 17id - 25od be better since its narrower and the od is 25mm?

I guess the q becomes for a 25mm GP5000 tubeless, what is the optimal rim ID/OD for fast & versatile?

Excellent question!! There is a core problem in the industry now that there aren't really standards for those sidewall sizes of tires... so traditionally the size was outer casing width when installed on a 13 or 15c rim.. there was even a movement a while back to use a special tool and naming system to fix this and sadly it died out! Leaving us with different manufacturers doing all sorts of different things.

We have a graph of measured sizes on our site so you can see an example of the trends, but with each new tire size and each new rim inner width it just gets worse. Technically, there is a thing called the ETRTO which is now part of ISO that controls this but it was safety based and people have completely abandoned it.. by ETRTO, the widest rim you could use for 23mm tires is 17c and things like that.

Here is our data set with various size GP4000 on various rim sizes:
https://blog.silca.cc/tire-size-pressure-aero-comfort-rolling-resistance-and-more.-part-1-how-we-got-to-now

For aerodynamics the key is for the rim to be at least 105% the measured tire with.. this rule is pretty old, I coined it in 2000 when rim shapes were much simpler, but still holds true in nearly every example I can think of..

As for U vs O shaped tires, the wider the bead seat the more U shaped the tire can be, however, the greater the risk of tire blowoff as the bead width grows, so ETRTO says that anything wider than 17C is a risk, some manufacturers say 19.5mm is the limit and others don't say anything, but I've personally seen 23mm tires come off of 21mm bead width rims on more than 1 occasion so it's helpful to understand the risks and limits.

[sfo1]

So (for aero) on a 25mm tire the wheel OD should be at least 26.25?

On the ID (again assuming 25mm), a 19mm should be a max “safe” width?

Not a lawyer nor looking for any certainty (but I did just finish a fine Manhattan), but I am in the middle of a build and have not finalized wheels. I ride 25mm GP5000 tubeless and was narrowing my search.

Any swag at min/max ID/OD for these tires on a disc road machine?

[El Chaba]

My observations have led to a different conclusion. Decades ago, most people rode wider tires than often seen today - 1" (25mm) tires were uncommonly narrow, and most people rode tires between 1 1/8" (28mm) and 1 3/8" (35mm) wide (these were the days before Kevlar bead tires and hooked rims). Pressures were typically in the 70 - 90 psi range.

Then, starting in the early '80s, people started believing that narrow, high pressure tires must be faster, and tires and rims capable of handling high pressures started being made. During the time that frame tubes started growing in size/diameter, typical tire widths started shrinking and tire pressures increasing - 23mm tires became common, and many were even riding 20mm tires, at pressures up to 120 psi or more.

The move toward wider tires today isn't to mitigate the extra stiffness of modern frames (even the old frames from yesteryear had too much vertical stiffness to provide much shock absorption) - its to mitigate the ridiculously high pressures that people been using during the last few decades.

This was the trend. Tubulars can't be removed from the equation, though. until the late 70's there was no performance tire alternative to tubulars. At that time, racing tires had narrowed slightly, but the top racing tires from Wolber, Clement, d'Allesandro, etc. were in the 23-25 mm range. There was a desire to make the clinchers *look* like the tubulars and to approach their performance as much as possible. A big problem was getting the tire to stay on the rim at the pressures that would be required for a narrow tire. Michelin was the major player and worked (primarily) with rim makers Mavic, Super Champion, Rigida, etc to develop hook beaded rims. Michelin heavily marketed their "Elan" model which looked incredibly narrow at the time. When the "aero" craze hit in the early 80's it was game over for wider tires.

[dddd]

It seems to me that the narrow tires and rims of the 70's and 80's made more sense in the context of that era's aluminum rim technology, when having a wider rim and/or tire came with a pronounced weight and/or aero penalty.

When the Open Pro rim finally arrived in the 90's, with it's wider 15mm inside width, an equillibrium of tire and rim sizes seemed to sensibly land at 23mm tire size on these wider (yet still lightweight and strong) rims.

For riders whose speed averages below the CAT1 level, 25mm tires on the i15mm rims was and is still a great setup and fits nearly all frames ever made.
The 25mm tire size allows some manipulation of tire pressure without undue risk of pinch-flatting in most cases.

It is only with the latest rim technologies (both metal and composite) that wider tires make sense in the realm of racing performance on paved roads, with budget concerns limiting choices in a lot of cases. So it's become a very complex combination of needs evaluation combined with smart shopping and keeping abreast of the various performance parameters of what is on the market (all at any point in time).

[hobbanero]

Josh's posts on suspension losses are really interesting, and point towards a lower pressure for overall speed. This test uses a diamond plate roller, rather than a smooth one, to try and capture some of the suspension benefit.

[HTupolev]

It seems to me that the narrow tires and rims of the 70's and 80's made more sense in the context of that era's aluminum rim technology, when having a wider rim and/or tire came with a pronounced weight and/or aero penalty.

When the Open Pro rim finally arrived in the 90's, with it's wider 15mm inside width, an equillibrium of tire and rim sizes seemed to sensibly land at 23mm tire size on these wider (yet still lightweight and strong) rims.
The 70s weren't an era of super-narrow rims and tires. Most high-performance road bikes came stock with tubulars in the ~25mm range, while the more entry-level clincher-equipped bikes tended to have 28s or 32s. Hooked-bead 700c and 27" clincher road rims from the late 70s and early 80s usually had inner widths in the ballpark of 17mm.
This didn't carry a serious weight penalty, as quality single-walls rims could actually be reasonably light; the original 17mm-internal rims on my 70s touring bike are only a few tens of grams heavier than an Open Pro, and they're hardly a weight-weenie part.
And while aerodynamic drag will tend to be higher for a wider tire, that's not necessarily true of wider rims. It's often quite the opposite, which is why modern aero rims are often as wide or wider than their intended tires. Also, rim aero wasn't something that anyone was paying attention to in the 1970s.

Tire widths took a very sharp nosedive in the mid-to-late 1980s.

[dddd]

The 70s weren't an era of super-narrow rims and tires. Most high-performance road bikes came stock with tubulars in the ~25mm range, while the more entry-level clincher-equipped bikes tended to have 28s or 32s. Hooked-bead 700c and 27" clincher road rims from the late 70s and early 80s usually had inner widths in the ballpark of 17mm.
This didn't carry a serious weight penalty, as quality single-walls rims could actually be reasonably light; the original 17mm-internal rims on my 70s touring bike are only a few tens of grams heavier than an Open Pro, and they're hardly a weight-weenie part.
And while aerodynamic drag will tend to be higher for a wider tire, that's not necessarily true of wider rims. It's often quite the opposite, which is why modern aero rims are often as wide or wider than their intended tires. Also, rim aero wasn't something that anyone was paying attention to in the 1970s.

Tire widths took a very sharp nosedive in the mid-to-late 1980s.


Peugeot and some others were fitting 20mm 700c clinchers to bikes in the late 1970's, though racers still mostly used tubulars for all but perhaps training miles.

I didn't really notice when clinchers started to be used for racing (I was into motorcycle racing then mountain bikes during those years), but as the narrow clincher tires got better and rims like the O4CD became available, they became more viable for a lot of sporting use if not high-level racing.
Using a pair of Mod58 Singlewall clincher rims as opposed to the typically i13mm narrow clincher rims had enough of a weight penalty to be noticed, and the aerodynamics would have suffered as well. By the mid-80's those rims had a minimum of 36 spokes in nearly all cases (versus 32h for the narrow double-walled rims). I actually used Mod58 touring rims for training rides with a variety of tires from 20mm to 25mm (printed size on those was 25 or 28mm respectively).
I was light enough not to notice any flex with the Mod58's, but the wheels felt quite heavy versus any O4CD wheelset.

Prior to the Open Pro rim with it's 15mm inside width, the 13mm inside width was a wide as anyone seemingly knew how to make for sporting use at modest weight and with good durability! So these i13mm rims made perfect sense for the 23mm tires that were becoming the standard heading into the 90's (riders finally having decided that 23mm tires were better overall than 20mm tires).
It did seem to be the case in the early 90's that a slightly wider pair of tires added far less weight than a slightly wider pair of rims, that is until the wider Open Pro rim appeared (replacing the i13mm Reflex rim).

So to me, it all made sense in evolutionary terms, other than perhaps the ten years it seemed to take for riders to start using 25mm tires on those ubiquitous Open Pro rims! But as for the 20mm tires, their only net virtue was that they kinda looked like tubular racing tires and so had marketing value.

Editing here to note that tires labeled as 25mm or 28mm in the late 1970's and into the eighties were actually several millimeters narrower than that.
In that era of seemingly weird sizing "standards", tires labeled as 700x25c often also carried embossed lettering showing "20-622".
Similarly, even in the early 90's, a tire labeled as 700x32 might have embossed lettering showing 26-622, and which measured about 26mm wide on an i15mm rim.
So the later "20mm" tires were sized the same as many earlier "25mm" tires, and which I find typically measure about 21mm on period narrow rims.
And those older "28mm" tires typically measured barely 24mm on narrow rims. A lot of Specialized tires come to mind from that era, because they were so popular, but others followed suit. It wasn't until the 23mm size arrived that printed tire width was, suddenly, in the ballpark.

[froze]

Now they need to combine wind resistance in these tests to get a partial picture of real world performance!

EXACTLY!!! some years ago I saw a wind tunnel test done, I think it was the reason Conti came out with the Attack line of tires, where a 23mm tire was used on the front and a 25 on the rear, and the test discovered that the combination was a tiny bit faster...HOWEVER, that stupid test didn't take load conditions into consideration. Seems like everyone wants to test for one or the other but not both at the same time! I still use a 23mm tire on the front and a 25 on the rear because of that test I read, I just don't use Conti tires, also not saying I'm right, I do it because both tires wear out at about the same time and I don't have to bother with rotating my tires! But I think if they're going to do tests like this they need to add on the effects of wind.

[dddd]

EXACTLY!!! some years ago I saw a wind tunnel test done, I think it was the reason Conti came out with the Attack line of tires, where a 23mm tire was used on the front and a 25 on the rear, and the test discovered that the combination was a tiny bit faster...HOWEVER, that stupid test didn't take load conditions into consideration. Seems like everyone wants to test for one or the other but not both at the same time! I still use a 23mm tire on the front and a 25 on the rear because of that test I read, I just don't use Conti tires, also not saying I'm right, I do it because both tires wear out at about the same time and I don't have to bother with rotating my tires! But I think if they're going to do tests like this they need to add on the effects of wind.


Good points, I remember those mis-matched Conti's being 22mm and 24mm front and rear.

But it is incredibly difficult to accumulate "combined effects" data over the varying conditions of roads and wind conditions.
Different riders have different drafting habits, and regional riding conditions are hugely variable in terms of pavement conditions, speed variations and wind conditions, not to mention that, for testing, a single rim and tire have to be chosen for each test!
If we were to be very sophisticated about all this, then likely the results would point to completely different front and rear rims and tires being used on the same bike at the same time, just to be optimized for some specific set of riding conditions and for a specific rider.

I can imagine a future bike computer or app that evaluates the rider's riding conditions over time (including speed, grade, wind vectors and vibrations), accumulates the data, then refers to a database of tire and wheel parameters to suggest an optimal pairing of wheels, tires and pressures.
And while we're at it, the same computer might be logging data on all of the rider's blood chemistry and vital signs parameters over the course of the ride, to be evaluated by yet another computer algorithm which makes suggestions in real time.

[19wisconsin64]

These tires were supposed to be my secret speed weapon this season, but thanks to the original poster I'll just have to train harder like everyone else. No really..... I was really counting on those watts.

Fixed gear, 25 mm, tubeless GP 5000 installed on wider clincher carbon aero rims. It will be interesting to see how these will compare to my old and fast carbon fiber tubular Easton TKO wheelset at the track that ran with 25 mm Continental Competition tires.

The new rims i purchased have an inner width of approx. 20-21 mm. The velodrome the wheels will mostly be ridden on is located in Queens, New York City - the much loved but much in need of re-surfacing Kissena Velodrome. The track is so bumpy that at high speeds regular high pressure tires bounce and skittle along the track in some places. Hopefully this new setup will be easier to push along at higher speeds. My road bikes now have wider rims, the HED Belgium plus, and with a 25-28 mm tire boy do these wider tires make a difference in speed!

[sfo1]

Seems wide road now starts at ~20mm inner.



Fixed gear, 25 mm, tubeless GP 5000 installed on wider clincher carbon aero rims.

[robertbb]

robertbb, thanks for the comment and thanks for giving me a great opportunity to plug some SILCA pumps with super accurate gauges!! In all seriousness though it was the last 10+ years of doing this that inspired us to make super accurate gauge pumps, and if you read our Road to Roubaix Blog (https://blog.silca.cc/road-to-roubaix-the-complete-story-1) story you'll see that we considered this secret so secret that I travelled around Europe with a $1000 gauge for a few years in a pelican handgun case and we only used it out of site of other teams and the media.. Now we make a handful of pumps with specially tuned digital sensors to achieve 0.5psi accuracy at these types of pressures which are used by more teams than those we 'officially' work with.

As for latex, look at the modern latex, we sell tubes made by Vittoria which have a new formula with graphene in them and leak so much slower than the old ones. When we plotted Cancellara's roubaix run in 2010, we measured his tires to have nearly 1psi per hour loss.. so we tuned pressures so they would be perfect a few hours into the race when he was on the worst cobbles.. The new generation of latex tubes might lose 4-5psi per 24 hours, and will save you 2-5 watts per tire which is a bigger savings than a full ceramic bearing upgrade for about 1/50th the price!!

The very first floor pump I ever bought when I first started cycling about 15 years ago is a Silca Pista floor pump from a shop that was closing down here in Melbourne. Paid AU$90... I still use it today... quality stuff! Not sure I can justify a new pump.

But I am curious to give those latex tubes a go. Which ones are they exactly? And how do they go with carbon rims... (Campagnolo Bora)?

[jpritchet74]

But I am curious to give those latex tubes a go. Which ones are they exactly? And how do they go with carbon rims... (Campagnolo Bora)?

If you do long twisty descents that require heavy braking then don't do it. The rims can heat up and cause the tubes to POP. Otherwise do it. I use latex with my carbon clinchers and don't worry about it at all because I never ride where I would have a long twisty descent that would require heavy braking, so my rims don't get hot.

[froze]

The very first floor pump I ever bought when I first started cycling about 15 years ago is a Silca Pista floor pump from a shop that was closing down here in Melbourne. Paid AU$90... I still use it today... quality stuff! Not sure I can justify a new pump.

But I am curious to give those latex tubes a go. Which ones are they exactly? And how do they go with carbon rims... (Campagnolo Bora)?

I have a 40 some odd year old Silca that needs to be rebuilt completely but the cost to rebuild (kit was $68 if I remember correctly) it exceeded just buying another pump, so i opted to get a Birzman Maha Apogee IV floor pump instead that I got on sale for $30.

I can't find those new Vittoria latex tubes, all the ones I see for sale in the US appear to be the old latex tubes that will leak air out fast, no mention of a new formula to prevent that anywhere on the boxes or description, so not sure if the new latex tubes Vittoria simply didn't mention the fact on the boxes or if the new ones just haven't made it to market yet.

[froze]

If you do long twisty descents that require heavy braking then don't do it. The rims can heat up and cause the tubes to POP. Otherwise do it. I use latex with my carbon clinchers and don't worry about it at all because I never ride where I would have a long twisty descent that would require heavy braking, so my rims don't get hot.

But if you're riding on aluminum rims descending long twisty mountain roads you have no worry about latex popping, I did that for years in hot S California mountains and never blew a latex tube...but that was using AL rims which dissipate heat far better than CF rims. But that does make me wonder about something, if the pros are using CF rims and latex tubes racing in mountains why aren't they worried about the tubes popping?

[vincenz]

I concluded some time ago that the move to wider tires for the road was largely driven by the search for something...anything...that could mitigate some for the extra stiffness that was characteristic of the uber-oversize tubed frames that have come into fashion. It was convenient that a larger tire could be run at a slightly lower pressure for some comfort gains without a big hit in increased rolling resistance.



I agree, and also the larger tube shapes are more aero, which leads to the same shape developed for wheels, which tires could then match, and all made possible by better rubber technology.

What I would love to see is a plastic bike developed to have the SAME comfort of ti or steel, but with the aero properties and lighter weight.

[ColnagoC59]

i've thought about this.

Ride what feels good and makes you happy. For 99% of us none of this matters.

[Mark McM]

But if you're riding on aluminum rims descending long twisty mountain roads you have no worry about latex popping, I did that for years in hot S California mountains and never blew a latex tube...but that was using AL rims which dissipate heat far better than CF rims. But that does make me wonder about something, if the pros are using CF rims and latex tubes racing in mountains why aren't they worried about the tubes popping?

The pros are by and large still using tubulars. Their tubulars have latex tubes, but the tubes are insulated from the rim through several layers (glue, base tape, tire casing), as compared to a clincher, where a portion of the tube may be pressed against the rim sidewall. If the pros need to worry about anything regarding brake heat, its melting their tubular glue. (Rolled tires due to melted glue is a rarity with well glued tubulars, but it can still happen.)

[vincenz]

I believe tubulars are used by pros also because they are safer during a flat vs clinchers.

[saab2000]

I believe tubulars are used by pros also because they are safer during a flat vs clinchers.

They're also lighter and not insignificantly if that matters to anyone. But yes, deflated safety is not to a disregarded.

[sfo1]

If pro's had to change their own flats, tubs would have been abandoned decades ago....

[Mark McM]

I believe tubulars are used by pros also because they are safer during a flat vs clinchers.

And more specifically, they are safer to ride during a flat vs clinchers. Most cyclists have no reason to ride a flat tire, so being able to ride on a flat makes little difference.

[Mark McM]

They're also lighter and not insignificantly if that matters to anyone. But yes, deflated safety is not to a disregarded.

The small difference in wheel weight is insignificant, and besides, the lower rolling resistance of clinchers more than makes up for the weight difference (even when climbing and sprinting).

[froze]

The pros are by and large still using tubulars. Their tubulars have latex tubes, but the tubes are insulated from the rim through several layers (glue, base tape, tire casing), as compared to a clincher, where a portion of the tube may be pressed against the rim sidewall. If the pros need to worry about anything regarding brake heat, its melting their tubular glue. (Rolled tires due to melted glue is a rarity with well glued tubulars, but it can still happen.)

Silly me I should have remembered that about tubs insulating the heat, thanks for the reminder.

I did hear of people who melted their glue, but mostly this occurred with tandem riders who were running tubs back in the day descending mountains, but some of those guys didn't know how to brake to try to prevent that by alternating brakes and stab braking; and some got the idea of using a rear hub drum brake in addition to rear calipers, the hub drum brake wasn't designed to stop the bike, it was more like a drag brake to slow down the bike a bit on long descents so to take some of the heat off the rim, but I don't recall too many using that drum brake I guess because of the added weight.

I looked up the cost of those Conti 5000's...ok then, I won't be spending about $150 for a pair of tires that's for sure, my god man a pair of those tires cost more then one tire for my pickup truck! And the tires on a vehicle are far more technologically advanced with far more material to make it then a bicycle tire.

I

[zap]

And more specifically, they are safer to ride during a flat vs clinchers. Most cyclists have no reason to ride a flat tire, so being able to ride on a flat makes little difference.

We had a front tire blow out (@ 35mph) on our tandem as we were on a slight descent.........one of several thoughts during the event was.........wish we had tubulars. Aluminum rim (tire just got shredded) on pavement is pretty damn slippery........especially when you need to turn in order to avoid that guardrail.

[Expedited]

Check out the tubeless rolling resistance results, spectacular stuff. If it's just as puncture resistant as the previous model then the new TL tires are a huge win.

[El Chaba]

Any rolling resistance test that doesn't conclude that the Veloflex Criterium tubular is the world's fastest bicycle tire is a flawed test.....:banana: