Myth that 650B is slower than 700c? - Jan Heine

[RobJ]

Just as I was debating this myself for my current project....

https://www.renehersecycles.com/myth-19-700c-wheels-are-faster/

[doomridesout]

Hard to follow his premise because he doesn’t stick with one use case, but at least one assertion is certainly wrong: low CRR 700x28 is faster than the equivalent outer diameter 650b fat slicks.

I’m a Jan fan and it doesn’t mean he’s wrong about everything in there, but if you’re just going to speak in absolutes, the fastest 700c tires are faster than the fastest 650b tires.

I also wonder about the lack of definition between “smaller bumps” and “bigger bumps” w/r/t gravel and angle of attack. What’s the break point? Is the thick gravel common in the Midwest full of big or small bumps?

[shoota]

Is the thick gravel common in the Midwest full of big or small bumps?

Yes.

[Mark McM]

I'm guessing that Jan Heine didn't see any distinct difference in rolling resistance for several reasons: The difference between 650b and 700c isn't very much (particularly since 650b tires are typically wider, so as he points out the outer circumferences are just about the same); and because he used a relatively small sample size with a large number of uncontrolled variables.

Here is another study (https://hadland.wordpress.com/2013/01/15/rolling-resistance-theory-and-practice/), that used a much larger sample size and much larger variation in wheel diameters. In this study, there are often very large variations in rolling resistance between tires of the same wheel size, but taken as a whole, a trend can be seen for an inverse relationship between wheel size and rolling resistance:

https://hadland.files.wordpress.com/2013/01/lafford-chart.jpg?w=739

Even still, Jan Heine's assertion is essentially true: The difference in rolling resistance purely due to 650b vs. 700c is quite small, perhaps lost in the noise of all the other variables that affect rolling resistance. In the trend line on the graph above, the difference in average rolling resistance between 650b and 700c is maybe between 1% and 2%. That's likely less than the difference in production batches of the same make, model and size of tire.

[jtbadge]

Pseudoscience sells.

[Clean39T]

He's not talking aero either, iirc.

Sent from my Pixel 2 XL using Tapatalk

[unterhausen]

I dont think angle of attack is all that important. I ride 700cx32 and I ride with someone who uses 650bx42. We are roughly the same speed except he always rides away from me on rough chip seal.

[Tall]

Here is another study (https://hadland.wordpress.com/2013/01/15/rolling-resistance-theory-and-practice/), that used a much larger sample size and much larger variation in wheel diameters. In this study, there are often very large variations in rolling resistance between tires of the same wheel size, but taken as a whole, a trend can be seen for an inverse relationship between wheel size and rolling resistance:

Okay, but this other study is no good in answering the question whether a larger tire is faster than a smaller one, holding all other variables constant. BQ tested the same tire in different sizes; the dataset for the other study combines all kinds of tire sizes and models. There's also no statistical analysis of the data; just an Excel trend line. From merely looking at the plot, it's pretty obvious that this isn't a linear relationship, and therefore using a trend line is not appropriate.

[m_sasso]

Appears as there was little or no consideration of weight variables, did Jan try pedalling up hill?

[Jaybee]

Okay, but this other study is no good in answering the question whether a larger tire is faster than a smaller one, holding all other variables constant. BQ tested the same tire in different sizes; the dataset for the other study combines all kinds of tire sizes and models. There's also no statistical analysis of the data; just an Excel trend line. From merely looking at the plot, it's pretty obvious that this isn't a linear relationship, and therefore using a trend line is not appropriate.

Agree with this. The r-squared value on that regression must be near “random”.

[Mark McM]

Okay, but this other study is no good in answering the question whether a larger tire is faster than a smaller one, holding all other variables constant. BQ tested the same tire in different sizes; the dataset for the other study combines all kinds of tire sizes and models. There's also no statistical analysis of the data; just an Excel trend line. From merely looking at the plot, it's pretty obvious that this isn't a linear relationship, and therefore using a trend line is not appropriate.

No study can gather and analyze all the data required to answer every question. And it can be risky to try to extrapolate beyond what data measured. But this study does a good job at illustrating both it's and Jan Heine's assertion: That variations in rolling resistance between different tires (and other variables) is much larger than variations due to wheel size alone, and the difference due only to the changing between 650b and 700c are essentially insignificant compared to other variables.

Given this data, and other data comparing the rolling resistance of the same model of tire from different production batches, it is not unlikely that you could find two examples of the same model of 650b tire from different production batches where one tire was faster than a particular 700c tire, and one tire was slower than that same 700c tire.

In other words, choosing 700c over 650b just because of the idea that 700c wheels are faster is missing the forest for the trees.

[Hawker]

I really don't belong in this discussion but this is a serious question.

If there is a general consensus that a 650b tire isn't necessarily slower than a 700x25 tire...how far does that extend? What about a 600b tire or a 500b tire? Will a smaller wheel/tire combo be slower at some point just by virtue of it's reduced size?

[Mark McM]

I really don't belong in this discussion but this is a serious question.

If there is a general consensus that a 650b tire isn't necessarily slower than a 700x25 tire...how far does that extend? What about a 600b tire or a 500b tire? Will a smaller wheel/tire combo be slower at some point just by virtue of it's reduced size?

Let me first point out that Jan Heine doesn't claim, nor does his data show, that rolling resistance doesn't vary inversely with wheel size. His point is that the difference in rolling resistance between 650b and 700c (even if all else is equal) is small enough to be considered insignificant.

There have been lots of tests and data showing that yes, smaller diameter wheels have more rolling resistance (all else being equal). I don't think anyone is questioning that. But there are lots of variables in rolling resistance, and wheel diameter is far from being the most important. If you look at the data in the graph shown earlier, rolling resistance of a variety wheels and tires from 305mm diameter to 622mm (700c) are shown. The data shows that there is a very large spread in rolling resistance even for the same wheel size. The data shows a general trend for the larger wheels having lower rolling resistance than smaller wheels, but as can be seen in the spread of the data, the correlation between wheel diameter and rolling resistance is quite loose, over the range of tires available.

[82Picchio]

Myth: 650B is faster than 700c.

See what I did there.................

[FlashUNC]

I tend to think if this were the case and bike manufacturers had sorted this data out, there'd be some Tour teams riding All Road bikes. And yet they're all still on 700c bikes.

[Mark McM]

I tend to think if this were the case and bike manufacturers had sorted this data out, there'd be some Tour teams riding All Road bikes. And yet they're all still on 700c bikes.

In the 1990s, some teams tried using 650c wheels (smaller than 650b) during mountain stages, under the theory that they were lighter so they'd climb faster. They gave up on them after they found that any small advantage they had was far outweighed by the disadvantages of a lack of wheel interchangeability (particularly on narrow mountain roads were only the neutral support motorcycles could reach riders quickly, and which were unlikely to be carrying spare 650c wheels).

Rapid interchangeability of wheels is a big concern in racing, so wheel size standardization is important. Rapid interchangeability has been the main reason for the slow adoption of disc brakes in pro road racing. Having to deal with different wheel sizes is even worse.

[R3awak3n]

I tend to think if this were the case and bike manufacturers had sorted this data out, there'd be some Tour teams riding All Road bikes. And yet they're all still on 700c bikes.

sure but just a few years ago people were on 23c tires and now some are on 26c. Pressures were also a lot higher. I am sure they had done tests before as well. Tire size will keep going up I am sure and we will see maybe one day you will see different tire size, maybe not.

[Spdntrxi]

in my experience 650b is slower then 700c but it's never been apples to apples comparison. In the end I don't mind.

[FlashUNC]

In the 1990s, some teams tried using 650c wheels (smaller than 650b) during mountain stages, under the theory that they were lighter so they'd climb faster. They gave up on them after they found that any small advantage they had was far outweighed by the disadvantages of a lack of wheel interchangeability (particularly on narrow mountain roads were only the neutral support motorcycles could reach riders quickly, and which were unlikely to be carrying spare 650c wheels).

Rapid interchangeability of wheels is a big concern in racing, so wheel size standardization is important. Rapid interchangeability has been the main reason for the slow adoption of disc brakes in pro road racing. Having to deal with different wheel sizes is even worse.

Discs are ascendant in the pro peloton now. And given that teams are doing more just wholesale bike changes in TTs and for some road stages rather than futz with wheels, the interchangeability seems a bit of a nonstarter.

If Special Ed thought they'd sell more bikes with 650b winning Roubaix, I tend you think you'd see it out there. They run that stupid Headshok out there after all.

[marciero]

The blog cited by MarkMcM (not really a "study", they just plotted some data, though there is a regression under the hood) states that the trendline in the graph shows

the general truth of the theory that rolling resistance decreases with tyre diameter


But you have to be careful with claims like this. In fact, even with less variation-or no variation about the trendline (R^2 =1) you cant conclude this is generally true.

For one thing, after a quick look at the data I would bet anything that slow, touring-type treads are disproportionately represented among the wider tires/ smaller BSD. Just a guess, but all the skinnys are like Pistas and Supersonics. In other words, the difference in RR may be related to tread, not wheel size. Of course, we know this is true.
It would be easy to code the tires as "supple" "not supple", or even score them on some scale, and include that as a variable in a multiple regression fit. That would be an improvement. Or simply exclude the clunky tires. Or do other types of pre-processing. Still, with the wide variety of brands, treads (they even include "ground off" treads), etc, it appears that this data is ill-suited to reveal any relationship between wheel size and rolling resistance, and probably ill-suited even to meaningfully describe variation in RR among tires of similar size.

[Jan Heine]

I enjoyed this discussion. I think it's important to distinguish two questions here:

1. Is an average 650B gravel tire slower than an average 700C racing tire. The answer is yes.

That leads to the second question:

2. Is the speed difference due to the wheel size? Or due to other factors? To answer that question, we kept all other variables (tire construction, tire width, tire pressure, bike, rider, surface, etc.) the same, and just changed the wheel size.

The answer to this question is 'No.' Wheel size doesn't have a meaningful impact on a tire's speed. Of course, in theory it does, but the effect is so small (for the three common wheel sizes) that it's not significant. It's like turning all your spoke nipples so the flats are parallel to the airflow might change your aerodynamics in theory, but in practice...

In theory, 650B wheels climb faster than 700C: smaller rims, shorter spokes and smaller-diameter tires save a little weight. However, the effect once again is too small to matter: Wtness pro racers riding wheels that are 10 cm larger than the required UCI minimum.

However, most riders who use 650B wheels do so because this allows running a wider tire in the same bike. This leads to the third question:

3. The real comparison for most is 700C x 38 vs. 650B x 48 (and not tires of the same width in different wheel sizes). Which is faster on smooth roads? And how about gravel? That one is the topic of a future post. Stay tuned!

Commercial interests
Rene Herse tires are available in 700C, 650B and 26" in widths from 26 mm to 55 mm. We cover the entire spectrum, so our research on wheel size and tire width isn't influenced by commercial interests. And if our testing found that 23 mm tires were faster, we could make those, too. Or 60 mm tires, for that matter.:)

Jan Heine
Rene Herse Cycles
Reborn in the Cascade Mountains
www.renehersecycles.com (https://www.renehersecycles.com)

[marciero]

...
The data shows a general trend for the larger wheels having lower rolling resistance than smaller wheels, but as can be seen in the spread of the data, the correlation between wheel diameter and rolling resistance is quite loose, over the range of tires available.

Even with good data and a proper analysis that controls for the various variables, you cant make this claim with any level of certainty without some measure of fit (like a p-value, confidence interval), which would tell you if the result is likely to have occurred by chance. In other words, a different sample may give entirely different results. The relationship is weak and the variation is large, again, only for this data set. With good data that includes lots of tires with similar casings among all the wheel sizes, and proper analysis, you can bet that you would get much less variation. In that case claims about general trends may or may not be valid, even if the correlation is weak.

[Davist]

I have been somewhat surprised at how well my 650s roll. they're 2.1 vs 32 on my 700 wheels. Yes they take a bit more effort but not too bad. Conversely, didn't the XC mtb community go back to 700c (29er) en masse? They rolled better over big bumps which Jan calls out I guess as another "myth" as the sizes he test are close in outside diameter.

I'm a skeptic of most of his stuff for a while, ("planing" etc) moreso ever since he blamed a price increase on a weak dollar which couldn't be further from the truth, don't get me wrong, I'm glad to pay for my hobby's esoterica and understand you may need a price increase to keep the lights on.

[Hellgate]

If the wider, smaller diameter tire is at the same pressure as the narrower, larger diameter tire it is effectively at a higher pressure and will roll faster as the relative pressure is higher. Oh, and it's the outside circumference of the TIRE that matters, not the wheel circumference.

Kind of a silly article.

[GOTHBROOKS]

ive had ppl on dahons and bikefridays built up with drops and da7800 tell me they climb faster than 700c road bikes because they are using the same gear ratios to move a smaller wheel.
i can sort of see that maybe being true for climbing, but i cant say i feel the same for the flats.

[Heisenberg]

no one on this board is fast enough for the minute differences to matter, or to even notice them, tbh.

[merckx]

no one on this board is fast enough for the minute differences to matter, or to even notice them, tbh.

This.

[prototoast]

If there were such a big difference between a 650B and 700C wheel, all else equal, why stop there?

[Gummee]

I've got 2 identical bikes that should fit 700x38 and 650b x ?? to make a comparison at some point in the near future.

I even have a 650b wheelset I can temporarily rob from my Ritchey.

Should be interesting

M

[m_sasso]

Commercial interests
Rene Herse tires are available in 700C, 650B and 26" in widths from 26 mm to 55 mm. We cover the entire spectrum, so our research on wheel size and tire width isn't influenced by commercial interests. And if our testing found that 23 mm tires were faster, we could make those, too. Or 60 mm tires, for that matter.:)

Jan Heine
Rene Herse Cycles
Reborn in the Cascade Mountains
www.renehersecycles.com (https://www.renehersecycles.com)

Thats odd, didn't know you made tires? I always was under the assumption they were made for you by Panaracer Corporation and you had your name put on them, is this myth/claim true or false?

You know Jan they say "Any publicity, be it good or bad is money making publicity". Controversy and contention promotes discussion and publicity. I don't reject you making a buck, just don't insult us by stating you have no skin in the game.

Thanks,

[fiamme red]

Thats odd, didn't know you made tires? I always was under the assumption they were made for you by Panaracer Corporation and you had your name put on them, is this myth/claim true or false?

Thanks,
MarcI'm sure that Jan wrote "we could make those" as shorthand for "we could have those made." Of course they are made by Panaracer.

https://www.renehersecycles.com/panaracer-hand-made-tires/

[Heisenberg]

Thats odd, didn't know you made tires? I always was under the assumption they were made for you by Panaracer Corporation and you had your name put on them, is this myth/claim true or false?

You know Jan they say "Any publicity, be it good or bad is money making publicity". Controversy and contention promotes discussion and publicity. I don't reject you making a buck, just don't insult us by stating you have no skin in the game.

Thanks,

ah, you're "THAT GUY".

thanks,

[mhespenheide]

If only some plucky underdog start-up bike racing team would capitalize on the marginal gains of switching to 650b!

[mhespenheide]

Joking aside, I'm looking at switching to 650b myself. I'm surely not fast enough to care about the gains/losses of a couple percent. 700c x 30-32mm is my current sweet spot, but I could easily see that changing. I do think the classic rolling resistance lab measurements are not the whole story and that the suspension effect of larger tires can give an improvement in the real world.


I'm just skeptical of any performance gains. Surely INEOS/Mercedes and Bahrain/McLaren have at least looked into it.

[simonov]

Thats odd, didn't know you made tires? I always was under the assumption they were made for you by Panaracer Corporation and you had your name put on them, is this myth/claim true or false?

You know Jan they say "Any publicity, be it good or bad is money making publicity". Controversy and contention promotes discussion and publicity. I don't reject you making a buck, just don't insult us by stating you have no skin in the game.

Thanks,

Dude, his point is that whether he said one or the other is faster it wouldn't matter commercially because he sells both.

[simonov]

Joking aside, I'm looking at switching to 650b myself. I'm surely not fast enough to care about the gains/losses of a couple percent. 700c x 30-32mm is my current sweet spot, but I could easily see that changing. I do think the classic rolling resistance lab measurements are not the whole story and that the suspension effect of larger tires can give an improvement in the real world.


I'm just skeptical of any performance gains. Surely INEOS/Mercedes and Bahrain/McLaren have at least looked into it.

His blog post didn't really talk about performance gains in the world that those teams live in, it talked about how 650B isn't really slower by the simple fact the rim is a smaller diameter. Especially over rough roads when you account for the fact that tire circumference has more to do with the supposed "roll over" benefits than the rim circumference. When you look at the whole package a 25mm race tire on a Bora WTO on an aero race bike is always going to be faster than a fatty gravel/all road/general use tire. But that doesn't seem to be what Jan is getting at.

But in the world where Jan plays, my experience backs up what he's saying. I've got a set of 650x42 Babyshoe Passes on one bike and 700x32 Stampede Passes on another and out on the road in the real world, the 650B is better. The smaller outer diameter makes it feel like a road bike when accelerating as opposed to having to get that big diameter 32 rolling. And the extra volume makes it incredibly comfortable on pavement and incredibly capable on gravel. I've yet to find a drawback.

[oldpotatoe]

Jan is a big proponent of 650b..didn't he say that someday, all bikes would be 650b? Doubt that but of course he's going to say, "rolling resistance between 700c tires and 650b tires are 'essentially' the same"(paraphrased)..even if it IS a false equivalency(tire width, weight, etc)...so..."they are just as good, change to 650b people!!".....:)

[gone]

I’ve said this before in similar threads (this topic comes up a lot here).

I’ve got a ride that I do when there’s a strong (30 MPH plus) south wind. It goes north into the wind for the first 17 miles which are also the hilliest part of the ride and a section goes through town (stop signs). I hit mile 17 usually with a moving average of 11 MPH or so and then try to get my overall moving average above 18 MPH in the remainder of the ride where I’ve got the tail wind. Miles 17-52 are rolling terrain with one section at about mile 30 which has a couple of longer climbs.

I’ve done this ride a bunch of times on either my 700C equipped Hampsten or my 650b equipped Calfee Adventure. The two bikes weigh within ounces of each other, their geos are similar, I’ve set up the contact points as close to identical as an obsessive person can get them. For completeness, the Calfee has Compass 42mm 650b’s, the Hampsten has Vittoria Paves (since changed to Corsa Controls but I haven’t done this ride with them yet).

The Adventure has never been faster than the Hampsten. Not once. Ever. OK, there are a ton of variables (exact strength of the wind, level of effort, ...) but the sample size is pretty large so I’d think at least once the Calfee would equal or exceed the Hampsten. This has not happened, even once.

So in calibrated idiot testing (where I supplied the idiot) the “650b is faster” theory doesn’t hold up. Oh, and this is in central Texas (chip seal roads) so in theory the 650b “advantage” or being faster over rougher roads due to the larger tire being able to more effectively roll over irregularities doesn’t hold up.

FWIW, YMMV and all that.

I will say the 650b is a hell of a lot more comfy though.

[weiwentg]

Jan is a big proponent of 650b..didn't he say that someday, all bikes would be 650b? Doubt that but of course he's going to say, "rolling resistance between 700c tires and 650b tires are 'essentially' the same"(paraphrased)..even if it IS a false equivalency(tire width, weight, etc)...so..."they are just as good, change to 650b people!!".....:)

He has said (https://www.renehersecycles.com/predictions-for-the-2020s/) that he thinks that all-road bikes will eventually all be 650B. Relevant quote is:

All-Road Bikes will move to 650B wheels

The massive stability of huge 700C wheels may make sense on 29er mountain bikes, but it’s not ideal for all-road bikes. Smaller wheels are the answer – the reduced weight and diameter of rims and tires restores the nimble handling riders love on their road bikes.

There’ll be continued resistance to 650B from some bike makers – I’m looking toward Wisconsin here – but the difficulty of fitting a wide 700C tire on a performance bike, especially on smaller frames, will win them over, too.

When he says “all-road”, I think he means all road-oriented gravel bikes, as opposed to the more MTB-like gravel bikes which he calls adventure bikes. That’s the paragraph above the quote I pasted.

[RobJ]

So in calibrated idiot testing (where I supplied the idiot) the “650b is faster” theory doesn’t hold up. Oh, and this is in central Texas (chip seal roads) so in theory the 650b “advantage” or being faster over rougher roads due to the larger tire being able to more effectively roll over irregularities doesn’t hold up.


I don't suspect anyone would think that a 650x42 would be faster than a 700x28 on standard or rough chip seal. And the article wasn't making that comparison nor concerned with that environment. Running over gravel, chunky terrain, B-roads is where the difference is less negligible and the basis of the article.

Whether Jan's test was carried out correctly etc. I will let the others argue those merits.

[FlashUNC]

If they're better over bad roads, then why no 650b at Strade Bianche, Flanders, or Roubaix?

Again, Specialized I'm sure would love to sell the first 650b winning Roubaix bike. And yet the pros and manufacturers for pro teams are steering clear and sticking with 700c.

[colker]

If 650b is better than 700c why was 26in so maligned to the point of extinction?
If smaller and fatter is better than why bike thinkerers had to kill 26in?
I don´t care if it´s marketing. Tell me i need to change bike color just because. I like fashion. What i can´t stand is not making any sense and pretending to.

[joosttx]

If 650b is better than 700c why was 26in so maligned to the point of extinction?
If smaller and fatter is better than why bike thinkerers had to kill 26in?
I don´t care if it´s marketing. Tell me i need to change bike color just because. I like fashion. What i can´t stand is not making any sense and pretending to.

sigmoidal curves??

[R3awak3n]

If they're better over bad roads, then why no 650b at Strade Bianche, Flanders, or Roubaix?

Again, Specialized I'm sure would love to sell the first 650b winning Roubaix bike. And yet the pros and manufacturers for pro teams are steering clear and sticking with 700c.

Aren't the "bad roads" limited in those races? I bet if the whole race was cobbles, tires would get bigger. I always wonder why not run a bigger tire even at those races, like a 35mm but then get reminded that only a small portion is on a road that would benefit it.

[Jan Heine]

There are two ways to work with suppliers. One is to go to the big Taipei Bike Show and see what's on offer, then put your name on it. That is how many small companies work – you see the same products with different brand names in Europe, the U.S., Japan, etc.

Another is to develop your own products and find the best supplier for them. That is how we work. We're too small to forge parts, make tires, etc. – all of which requires huge facilities that must run almost around the clock to stay in business.

For example, our cranks are made in a factory that also makes the top-end models for one of the big component makers. (The production numbers are too small to make them in their own factories.) Nobody says that those cranks aren't made by the big makers, or that they are the same as our Rene Herse cranks.

Similarly, our tires are made by one of the best makers of tires in Japan, but to our specs, with our tooling, and with the materials we've designed together with the experts from that factory. It's been a close collaboration, which has benefitted their tires as much as ours. We've been pretty open about who our suppliers are, because we wanted to show that we work with the best suppliers and aren't cutting corners. However, that has sometimes created the myth that we are just rebranding other companies' stuff. Anything that carries the Rene Herse name is our own product. We also sell things made by others (SON hubs, Berthoud saddle, etc.), but under those names, because we don't feel that simply adding a brand name adds anything to the products.

To your second point, Rene Herse Cycles doesn't care whether you run our 700C or 650B tires, so there is no need to skew the evidence one way or the other. Of course, any time a maker talks about a product they make, it's both information, and, by the simple fact that they are showing their name, advertising. That is inevitable, and the alternative is not hearing from those who know the most about the products cyclists use and care about.

Jan Heine
Rene Herse Cycles
Reborn in the Cascade Mountains
https://www.renehersecycles.com (www.renehersecycles.com)



Thats odd, didn't know you made tires? I always was under the assumption they were made for you by Panaracer Corporation and you had your name put on them, is this myth/claim true or false?

You know Jan they say "Any publicity, be it good or bad is money making publicity". Controversy and contention promotes discussion and publicity. I don't reject you making a buck, just don't insult us by stating you have no skin in the game.

Thanks,

[FlashUNC]

Aren't the "bad roads" limited in those races? I bet if the whole race was cobbles, tires would get bigger. I always wonder why not run a bigger tire even at those races, like a 35mm but then get reminded that only a small portion is on a road that would benefit it.

It's not the whole course, but races are won or lost on the bad stuff, not the good stuff. If 650b really is that superior on the bad stuff and a wash on the good stuff you'd think pro teams would be flocking to it and manufacturers would be marketing the hell out of it.

And yet...crickets.

[rain dogs]

If "wider tires are faster", "lower pressure is faster" and "the difference between 650b and 700c is too small to be meaningful"

Then I'ma waiting for the 700x25c at 95ish psi vs the 650bx50c at 20ish psi 40km road TT showdown!

DO THIS TEST NOW! :banana: Would it be a close one? Does 700c even stand a chance?

[fiamme red]

If they're better over bad roads, then why no 650b at Strade Bianche, Flanders, or Roubaix?

Again, Specialized I'm sure would love to sell the first 650b winning Roubaix bike. And yet the pros and manufacturers for pro teams are steering clear and sticking with 700c.In Paris-Roubaix, in order to win, first you have to get to the cobbles at the front of the bunch. 650b tires would slow riders down significantly on the pavement that precedes the cobbles, compared with skinny 700c tires.

[FlashUNC]

In Paris-Roubaix, in order to win, first you have to get to the cobbles at the front of the bunch. 650b tires would slow riders down significantly on the pavement that precedes the cobbles, compared with skinny 700c tires.

That's not what the blog in the OP to this thread states. It states the differences are negligible on smooth pavement.

So if 650b is the equal of 700c on the smooth stuff, and better on the bumpy stuff, then why are pros and the big manufacturers ignoring it? And you're not exactly taking "skinny" 700c tires for the course anyways.

Either they've got different data or there's some other reason.

[Jan Heine]

This is a fascinating topics that we've often discussed this on our long rides. We once photographed Guiseppe Saronni's bike (https://www.renehersecycles.com/charity-drive-and-saronnis-colnago/) from the year he won the worlds. It was a beautiful Colnago with 650C wheels. When I looked at the photos from the worlds, I was surprised that he raced (and won) on 700C wheels. So he clearly tried 650C, even had a custom bike made, but then he raced 700C. Why?

It's a fascinating piece of game theory. Let's assume you are one of the three absolute favorites, and your chance of winning is 30% if all goes well. (There's a 10% chance an outsider will win.) Your chance of flatting the race is 5%. The exact numbers don't matter –*I picked some that are favorable to the smaller wheels.

In that scenario, I can think of four possibilities:

1. If you're significantly stronger that all the others, you'll win on identical equipment. Running smaller wheels provides no advantage – you're winning anyhow! – but you risk losing if you flat. Run 700C wheels!

2. If you gain enough from the smaller wheel that you'll win the race for sure (100%) as long as you don't flat (5%), you should absolutely run the smaller wheels. You'll have a 95% of winning on 650C vs. a 30% on 700C. To hell with wheel interchangeability – run 650C wheels!

3. If the advantage from the smaller wheel is so small that it increases your chance of winning by 1% – but a flat (5%) means you'll probably lose, then run 700C wheels!

4. You can't be sure whether the theoretical advantage of 650C wheels on the climbs and in the sprint isn't outweighed by some – overlooked – disadvantage. This could be that the bike doesn't handle as well during the descent, or even something as far-fetched as the bearing resistance being greater because the wheels spin faster. The best insurance is to be on the same equipment as the racer next to you, because then you'll have even chances - and a 30% chance of winning is better than a unknown chance of winning because of an unknown, not quantifiable issue.

No. 4 is a very conservative approach, but it's one that I've found with every racer I've worked with in the past. It makes sense, because it means that they don't have to think about their equipment and can focus on the race. And 100% focus is required to win. Which brings us to:

5. You have a small gain from the smaller wheels, let's say 2%, but you worry the entire race whether you've made the right choice. Your chance of making the right move is decreased by 5%. You should run 700C and focus on the race and not your bike!

So you have five scenarios, and only one suggests that you should run 650C wheels –*even though in all scenarios, 650C wheels are faster!

Jan Heine
Rene Herse Cycles
Reborn in the Cascade Mountains
www.renehersecycles.com (https://www.renehersecycles.com)

In the 1990s, some teams tried using 650c wheels (smaller than 650b) during mountain stages, under the theory that they were lighter so they'd climb faster. They gave up on them after they found that any small advantage they had was far outweighed by the disadvantages of a lack of wheel interchangeability (particularly on narrow mountain roads were only the neutral support motorcycles could reach riders quickly, and which were unlikely to be carrying spare 650c wheels).

[mhespenheide]

I'm just going to say thank you to Jan for sticking around and continuing the discussion, and also for bringing game theory into the mix. Applied math makes me happy.

[merckx]

Oh, boy.

[Coalfield]

The point not made often enough is : There is NO IDEAL TIRE in the world of adult cycling. It's Horses for Courses. And sometimes those courses have widely varying terrain and surfaces. The ideal tire depends upon many things; like total weight on rig, speed ridden, rider skill at handling off-road, etc.

Being a 700c guy, I asked a 650b guy who was touring about his wheel/tire choice of a 48mm tire. The tour was 5 days (hotel stops, so moderate loads) almost all pavement or very hard packed, but the route had a day of mostly gravel with a mountain pass on the way. He chose the tire so he could cruise on that downhill section of Forest Service gravel road. The rest of the trip he gave up some rolling resistance, but he felt better prepared. Me - I would have taken that downhill more slowly and run 700X35 (the biggest that fits my bike) at a much higher pressure than he for the overwhelming # of pavement miles.

I'm not too adventurous on non-suspension road/gravel bikes and confess that front suspension and mtb tires give me more confidence when the off-roads get sketchy. Disc brakes are also desirable for long descents on gravel or where the pitch goes steep. And my roadies don't have discs yet, nor 650b.

It muchly depends on 'how you roll'.

[Heisenberg]

it’d be fun if Jan and Josh Poertner did a podcast together.

[Jan Heine]

Oh, boy.

Question in 1988: If aerobars are faster, why didn't Francesco Moser – who had a whole team of scientists backing him up – use them?

Moser's record attempts were fascinating examples of looking for marginal gains inside the box, and ignoring the potential for huge gains outside the box. Triathletes already were using aerobars, and Greg LeMond's 8-second Tour win was just a year away!

Jan Heine
Rene Herse Cycles
Reborn in the Cascade Mountains
www.renehersecycles.com

[marciero]

For kicks I went and downloaded the data from the blog post (https://hadland.wordpress.com/2013/01/15/rolling-resistance-theory-and-practice/) cited earlier and did some analysis.

First, the graph in the blog is misleading. Note there are actually only 12 different wheel sizes, with several different samples-brands and models- for each. The ordering of those on the y-axis within each wheel size appears to be alphabetical; that is, completely arbitrary from a numerical perspective. It’s inappropriate and misleading to order non-numerical data this way. It looks as if you have a lot more y-data than you do.

Below is what the scatterplot should actually look like, along with a regression line. “ISO” is the wheel size. You can see the variability within wheel sizes. I’ve also swapped x and y axes, as it is conventional to plot the “response” on vertical.
The second plot has brands color coded. I’ve labelled some as “tour”. Many I didn’t. The dots are perturbed slightly horizontally to make more readable. I was trying to see if klunky tires are more concentrated in smaller sizes and fast ones in 700c, but it’s confusing with so many colors.

Caveats for what follows: Bad data, no pre-processing, checking of assumptions on data, etc. Purely for illustration and entertainment!

The negative slope is reflected in the correlation of -0.27. Values for correlations are between -1 and 1, with -1 and 1 being a perfect correlation, negative and positive, resp. So this correlation is weak. But the statistical analysis shows that ISO is in fact a statistically significant predictor of RR, with the probability our results occurred by chance essentially zero. I would have guessed this not to be the case. But there may be something else going on here that artificially deflates that probability. And even if we are certain that there is a weak correlation, it could be due to tread, casing, and other factors.

The repeated measurements of RR for the same size tire probably requires more careful analysis. If you do the regression using the means for each wheel size, for example, the correlation is actually stronger, at -0.70, which is quite strong. But the statistical significance has decreases. But again, caveats…
Lastly, it would have been easy to do the above with wattage loss (which is how they determined RR, based on the perfect correlation between the two) instead of rolling resistance, as they have that data.

[Edit: I am dubious of the statistical significance obtained. Will have to re-check my work when I get a chance.]
[Update: nope, they check out.]

[marciero]

Here it is with means (aka "averages") for each wheel size

[muz]

Here it is with means (aka "averages") for each wheel size

I think mean is not a good statistical measure in this case, because some of the tires could be optimized for other criteria than rolling resistance. Perhaps it makes more sense to use only the best rolling tire for a given size.

[marciero]

I think mean is not a good statistical measure in this case, because some of the tires could be optimized for other criteria than rolling resistance. Perhaps it makes more sense to use only the best rolling tire for a given size.

Maybe not. Hence my caveats. That's probably the main issue with the data set. The treads range from touring to cross to "ground-off treads", and are not coded for that. There are also new and used tires. Also the distribution of these types of tread may vary among the different sizes. Still, under some assumptions, using the mean might at least make some sense.

[merckx]

Question in 1988: If aerobars are faster, why didn't Francesco Moser – who had a whole team of scientists backing him up – use them?

Moser's record attempts were fascinating examples of looking for marginal gains inside the box, and ignoring the potential for huge gains outside the box. Triathletes already were using aerobars, and Greg LeMond's 8-second Tour win was just a year away!

Jan Heine
Rene Herse Cycles
Reborn in the Cascade Mountains
www.renehersecycles.com

Of course I was being flippant when I posted the pic of Moser rolling on a monster wheel. It was an attempt to illustrate the complexity of defining ideal wheel size when discussing bicycle and athlete efficiency.

Regarding Moser's equipment choices, I would only be speculating if I offered my insight. He had/was already pushing the UCI equipment compliance protocol when he rolled out his disc-wheeled machine in '84. And I recall that it was a poke in the eye for some former record holders. Perhaps his hour record team didn't believe it was necessary to achieve their objectives with an aero bar bolted to his cow horns. Their choice to use an over-sized wheel was perhaps already pushing the UCI to the edge. Were bolt-on bars approved in '88? Now I've done it; speculated.

[Clean39T]

It's not the whole course, but races are won or lost on the bad stuff, not the good stuff. If 650b really is that superior on the bad stuff and a wash on the good stuff you'd think pro teams would be flocking to it and manufacturers would be marketing the hell out of it.

And yet...crickets.

Well, you still have to stay away on the roads and contest a sprint (real or for-the-fans) in the velodrome. And that means making compromises - unless you can self-destruct your bike and take one from neutral service while in the final break....

[Clean39T]

i'm just going to say thank you to jan for sticking around and continuing the discussion, and also for bringing game theory into the mix. Applied math makes me happy.

+1

[Mark McM]

For kicks I went and downloaded the data from the blog post (https://hadland.wordpress.com/2013/01/15/rolling-resistance-theory-and-practice/) cited earlier and did some analysis.

...



Hey, nice work! I originally posted that article because it was the first one the popped up in a quick google search that had a simple chart that could be posted. There's been plenty of other studies and experiments on this done by researchers in much more commercially significant wheeled vehicle industries (railroads, automobiles, trucks, agricultural equipment, etc.) which have pretty much established that larger wheels tend roll better (all else being equal), so it shouldn't be surprising to find that larger bicycle wheels tend to roll better.

In the interest of more data, here's an interesting study that tried to determine if MTB wheel diameter has an affect on rolling resistance (https://pdfs.semanticscholar.org/29c9/2056990cbafd7692b1089d5a9b85da58b5db.pdf) (i.e. 26" vs. 29"). There's lots of data here to chew on as well.

[spoonrobot]

Riding 650bx42 compared to 700cx25 is good for at least an additional hour on a 200k, two hours on a 300k and honestly I hated riding the wider tire so much for long distance paved rides I couldn't find the motivation to try it on a 400 or 600.

God help you if there's any wind because then you're really going to slow down with wide tires.

There's a reason basically nobody who cares about speed, on pavement, has moved to demi-balloon size tires, in 700c, 650b or 26". They're just too slow compared to a ~1" wide racing tire.

[Ruimteaapje]

Jalabert experimented with 650c wheels in a couple of mountain stages in his Team Giant time as did Tony Rominger with team Mapei-Clas a few years earlier. And offcourse there was a lot of experimenting with 26", 24" and even smaller wheels in triathlon in the late 80's and early 90's

https://photos.smugmug.com/Print-Gallery/Laurent-Jalabert/i-h355VGk/2/133f6a46/XL/WATSON_JALABERT_00001362-669-XL.jpg
https://pbs.twimg.com/media/B-DxAjaCUAEG6kR.jpg

[marciero]

Hey, nice work! I originally posted that article because it was the first one the popped up in a quick google search that had a simple chart that could be posted. There's been plenty of other studies and experiments on this done by researchers in much more commercially significant wheeled vehicle industries (railroads, automobiles, trucks, agricultural equipment, etc.) which have pretty much established that larger wheels tend roll better (all else being equal), so it shouldn't be surprising to find that larger bicycle wheels tend to roll better.

In the interest of more data, here's an interesting study that tried to determine if MTB wheel diameter has an affect on rolling resistance (https://pdfs.semanticscholar.org/29c9/2056990cbafd7692b1089d5a9b85da58b5db.pdf) (i.e. 26" vs. 29"). There's lots of data here to chew on as well.

Thanks. Was an interesting exercise, though I dont think we can draw conclusions from this little bit of analysis, given the issues with the data. There is also the issue of practical significance vs statistical significance. With large sample you can often get stat significance for negligible amounts of improvement. If I did the above with the wattage instead of RR that might have been clearer since easier to interpret. I checked their watts vs RR and they are in perfect correlation- they must have used a formula to compute the RR- so the analysis would be equivalent-same stat significance, etc. On the other hand, the marginal improvements may be swamped by variation within tire sizes. You touched on that theme in an earlier post.

The BQ test did use wattage, and showed no stat significant difference. Even with small sample sizes I put much more stock in that analysis because the test and data collection was actually designed for the purpose. The test used the same tire, width, and pressure, but varied only the wheel size so as to isolate that variable. I'd be interested in a test with the same casing and tread, but with width and pressure optimized for the size-perhaps arbitrarily, but we have an idea of pressures that work well. So at that point you have effective wheel size-outer diameter-almost the same for 700 vs 650b. At the end of the day we only care about speed/watt differences. Other tests could seek to attribute differences to width, pressure, aerodynamic. Jan/BQ has done a lot of that already. I think they've done a lot of legitimate, albeit low-cost, testing that, taken collectively, comprise a pretty strong body of evidence. Most of the tests seem to try to isolate one variable. But even if each of those show no statistical (or practical) significance you could still get a significant difference varying all of them.

[oldpotatoe]

That's not what the blog in the OP to this thread states. It states the differences are negligible on smooth pavement.

So if 650b is the equal of 700c on the smooth stuff, and better on the bumpy stuff, then why are pros and the big manufacturers ignoring it? And you're not exactly taking "skinny" 700c tires for the course anyways.

Either they've got different data or there's some other reason.

It isn't...because the tire widths and weight of the two tires are NOT the same.
Riding 650bx42 compared to 700cx25 is good for at least an additional hour on a 200k, two hours on a 300k and honestly I hated riding the wider tire so much for long distance paved rides I couldn't find the motivation to try it on a 400 or 600.
God help you if there's any wind because then you're really going to slow down with wide tires.
There's a reason basically nobody who cares about speed, on pavement, has moved to demi-balloon size tires, in 700c, 650b or 26". They're just too slow compared to a ~1" wide racing tire.

[unterhausen]

ive had ppl on dahons and bikefridays built up with drops and da7800 tell me they climb faster than 700c road bikes because they are using the same gear ratios to move a smaller wheel.
My only small wheel bike experience is a couple of rides on Moultons. They feel faster. I think that's because there is a feeling of speed from the road vibration, which is an observation that Jan has made. And certainly, a high-end small wheel spins up quicker than the equivalent bigger wheel. That's pretty meaningless to overall speed, but I'm pretty sure you can feel it.

[oldpotatoe]

a high-end small wheel spins up quicker than the equivalent bigger wheel

The mass to accelerate a bicycle is the mass of the bike and rider..wheel 'flywheel' effect is lost in the noise. I wish I could find the test...in the 90s..measured energy to spin a wheel to a certain speed..a 300g rim and a 600g rim..difference was something like .1 of 1% difference..

Tri-people 'thought' 650c wheels were faster. More aero, lighter but higher rolling resistance because they were spinning faster..

I actually got yelled at by Dan Empfield(original owner of Quintana-Roo) when I said the above..he wanted me fired(we were a QR dealer-ProPeloton).

[NHAero]

I imagine that in the real world the speed the cyclist is moving at figures into this calculation, because wind resistance watts increase exponentially and wider tires have larger cross section.
I don't have a 650b bike. I have ridden the Anderson with 700x28 and 700x37 tires and don't perceive a difference in speed over my regular routes with the larger tire at lower psi. I also have the drop bar 26er Litespeed running 26x2.2 Conti Speed Kings, and I'm slower on that bike. Maybe 1 mph. But I ride solo with average speeds of 14-15.5 mph. I can imagine the difference being larger for a 25 mph ride average.
I also don't know what other factors come into play between the two bikes, but I imagine the MTB is less aero than the road bike, beyond considerations of the tires. Weight isn't much different. I think I'm a bit more upright on the Litespeed and that may be the largest factor.

[unterhausen]

I said it didn't make you faster, which was the mistake you made. Physics says that torque = moment of inertia times rotational acceleration. I am pretty sure you can feel a significant change in moment of inertia. Same for being able to feel a significant difference in weight. "Spin up faster" was a misleading way of saying this.

[FlashUNC]

It isn't...because the tire widths and weight of the two tires are NOT the same.

Well the blog that started this thread says otherwise.

This is stated with the same certitude as the old “narrow tires are faster” – and it’s just as wrong. Simply put, there is no evidence that 700C wheels roll faster than 650B (or 26″), and much data to show that they all roll at essentially the same speed.

A 700C x 28 wheel has the same diameter as a 650B x 48 mm, so the angle of attack will be the same for both. This shows the absurdity of the argument. Of course, wheel makers want to tell you that you need two wheelsets, and tire makers would rather add a ‘fast-rolling 700C version’ to their lineup than develop a truly fast gravel tire.

So my point is either the pro teams have a different set of data that says otherwise -- I'm sure the major manufacturers have tested this -- or there's some other reason why the pros aren't on 650b for the rough stuff.

[Black Dog]

The mass to accelerate a bicycle is the mass of the bike and rider..wheel 'flywheel' effect is lost in the noise. I wish I could find the test...in the 90s..measured energy to spin a wheel to a certain speed..a 300g rim and a 600g rim..difference was something like .1 of 1% difference..

Tri-people 'thought' 650c wheels were faster. More aero, lighter but higher rolling resistance because they were spinning faster..

I actually got yelled at by Dan Empfield(original owner of Quintana-Roo) when I said the above..he wanted me fired(we were a QR dealer-ProPeloton).

Thanks for calling out the spins up faster myth for what it is. Yes lighter wheels with less mass away from the hubs do have less rotational inertia to overcome but exactly like you said the effect of the bike + rider combination is so small to not be noticeable and only "slows" you down during accelerations and the energy is always returned as soon as you freewheel. I know someone is going to say that the 200 grams they saved on a light set of wheels is very noticeable and they have set PRs on climbs etc but the physics is so insignificant when compared to the placebo. And yes, a 4000 gram set of wheels will actually feel a bit slower slower than a 1300 gram set of wheels. But these are not the differences that we actually deal with. Marketing never does pay much attention to reality.

[oldpotatoe]

I said it didn't make you faster, which was the mistake you made. Physics says that torque = moment of inertia times rotational acceleration. I am pretty sure you can feel a significant change in moment of inertia. Same for being able to feel a significant difference in weight. "Spin up faster" was a misleading way of saying this.

Not a mistake I made since I said the differences are lost in the 'noise'. Yes, there is a difference but 'significant' one you can 'feel'?..doubt it, IMHO. I think the 'feel' some 'feel' is more due to wheel stiffness than 'flywheel' effect.

'Feel', 'significant'? Subjective.....

[oldpotatoe]

So my point is either the pro teams have a different set of data that says otherwise -- I'm sure the major manufacturers have tested this -- or there's some other reason why the pros aren't on 650b for the rough stuff.

Probably, because the races where there is definite 'rough stuff', where a 650b 'may' be an advantage, are very few(110 or so days of racing per year...how many rough stuff days? Guessing less than 5) and the frame makers frames can't easily accommodate 650b wheels..particularly when you see how many pro teams are 'all disc, all the time'....So...watching the 'market'(bike race sponsorship is still all about maketing and advertising) and demand for 650b bikes(low), the relative number of high end 650b tires vs 700c tires and yes, tubular versions of both tires and rims...Not surprised the frame, tire, rim, wheel makers are not spending the $ on 650b 'stuff'...

[colker]

My only small wheel bike experience is a couple of rides on Moultons. They feel faster. I think that's because there is a feeling of speed from the road vibration, which is an observation that Jan has made. And certainly, a high-end small wheel spins up quicker than the equivalent bigger wheel. That's pretty meaningless to overall speed, but I'm pretty sure you can feel it.

Add the shorter wheelbase to the mix.

[joshatsilca]

Well the blog that started this thread says otherwise.

So my point is either the pro teams have a different set of data that says otherwise -- I'm sure the major manufacturers have tested this -- or there's some other reason why the pros aren't on 650b for the rough stuff.

I can tell you 100% that nobody at the ProTour level is thinking about wheel diameter.. only a few of the teams are even looking at tire width/rolling resistance and pressure with any seriousness at this point!! In general, outside of the top couple of teams and athletes, pro racing is much more about logistics than anything else.

My overall view on all of this is that the starting point for any of it should be tire width and frame size/rider size and then drive into wheel diameter from there. We get so hung up on 'this is better' or 'this is faster' and all of the gyrations to try and 'prove it' that we forget that pretty much all of this stuff likely has some optimal use case.. I agree with Jan, if you're going some moderate speed on some poor surfaces, a 650bx42 or 47 or 50 is going to be no slower than a 700x28 but will be way more comfortable.. and if the surface gets really rough, or soft, it may be faster.

Now for a pro at 26-30mph, different story as the energy equation is so much more aero heavy at those speeds.

[steamer]

Add the shorter wheelbase to the mix.

My Moulton TSR had a 42.5" wheelbase.