More on the benefits of wider rubber and lower psi

[thwart]

From Jan Heine's blog: https://janheine.wordpress.com/2016/06/14/suspension-losses-confirmed/

[stephenmarklay]

From Jan Heine's blog: https://janheine.wordpress.com/2016/06/14/suspension-losses-confirmed/

So when will we see 32’s in the grand tours?

[R3awak3n]

probably soon. regardless of if this is actually true or not, if they can now sell 32mm tires to a wide range of people that currently have 25mm or 28mm, they will get right on it.

I like wide tires, my next road bike will definitely have clearance for 32mm tires

[weisan]

don't forget one other element mentioned in there...suppleness.

[stephenmarklay]

I can’t fit a big tire in my CSI but running veloflex masters in 25 at 80-85 is damn smooth.

[JAGI410]

Great, now I'm even more anxious for my Compass 700x38s to arrive.

[Sierra]

Interesting article.

How do the wider tires (avec lower pressure) perform on long climbs, generally; steep climbs when you're off the saddle?

[El Chaba]

In my own admittedly unscientific observations, I feel as though a slightly narrower tubular absorbs road shock as well as a wider clincher...by about 2-3 mm...That is a 22mm tubular absorbs road vibrations like a 25 mm clincher....Also, it will take a lot of convincing to sway me that a 30 mm clincher is faster on asphalt than a 22-23 mm tubular....and by a lot of convincing I mean that there is no way....

[spoonrobot]

How do the wider tires (avec lower pressure) perform on long climbs, generally; steep climbs when you're off the saddle?

IME, about the same as narrower tires. I've found the wide/low tires are generally slower while pedaling on smooth flat roads.

This is interesting reading:

https://en.wikipedia.org/wiki/Rolling_resistance#Primary_cause

[dan682]

I'm curious about where rider weight falls into the equation? I'm relatively light at 145lbs and can get away with running 23s at 80f/90r psi without pinch flatting. If I switched to say 28s, I could run them as low as around 60psi which would be great for a long ride, but would feel mushy cornering or sprinting in a race. What about a 100lb racer for an extreme example, would a 25 or 28 be faster than a low pressure 23?

[benb]

Mushy cornering on 28s at your weight would probably just mean you were on the wrong rim.

If you put the 28 on a wider rim and run it at 60psi it won't feel mushy.

I'm about 170, I run 55psi in the front tire and 80psi in the back with 28s. I don't have wide rims and maybe occasionally I can feel a little mushiness but not really. No pinch flats and the handling is great.

I am trying to decide what to put on my Space Horse.. it has 38s on it right now that are wearing out. I anticipate taking it on both our week vacations this summer as it's the only bike I can pull our Burley trailer with. I have a set of 28s that I took off my Domane to put faster 26s on, but I am also debating buying something like the 30/32/35 compass tires with minimal tread. All of those negate a lot of my ability to go offroad but there won't be a lot of that on these vacations. Both vacations I'd rather take my Domane but the trailer thing kind of makes that hard.

[bobswire]

Pretty soon we'll all be riding fat bikes.

http://i63.tinypic.com/2vxhfug.jpg

[LegendRider]

Has anyone tried the pressures recommended in the chart here?

https://janheine.wordpress.com/2010/10/18/science-and-bicycles-1-tires-and-pressure/

The front tire pressure recommendations are awfully low.

[ColonelJLloyd]

Has anyone tried the pressures recommended in the chart here?

https://janheine.wordpress.com/2010/10/18/science-and-bicycles-1-tires-and-pressure/

The front tire pressure recommendations are awfully low.

It all has to do with your personal fit and weight distribution. You can use a bathroom scale and a wall or spotter to figure out your own.

The more upright your position the more weight distributed to the rear tire.

[Tickdoc]

I'm just now getting use to 25s. Anything bigger makes me feel like I'm on the lake tubing.

[donevwil]

Has anyone tried the pressures recommended in the chart here?

https://janheine.wordpress.com/2010/10/18/science-and-bicycles-1-tires-and-pressure/

The front tire pressure recommendations are awfully low.

Hmm, never seen this chart before. Guesstimating my weight distribution, the pressure I've dialed in on both 32 Grand Bois Cypres (~7000 mi) and 38 Compass Barlows (~1000 mi) are only 2-3 psi away from what the chart reads. I appear to be a little low in the rear and a little high in front. Pretty darn close, though.

[drewellison]

Hmm, never seen this chart before. Guesstimating my weight distribution, the pressure I've dialed in on both 32 Grand Bois Cypres (~7000 mi) and 38 Compass Barlows (~1000 mi) are only 2-3 psi away from what the chart reads. I appear to be a little low in the rear and a little high in front. Pretty darn close, though.

I went through the excercise of actually running my weight distribution on both wheels. We might assume we're 45/55 or 40/60, but I was actually something like 35/65. So that means my rear tire is supposed to be about twice the pressure or my front tire. Okay ...

Also, who says 15% drop is optimal? Maybe it's 20%. Maybe it's 12%. Maybe different tires have different optimal drops.

I would assert that this is just a general guide from which to start looking at tire pressure. It's not a rule.

Assuming that tire drop should be the same front and rear (should it be?), a good way to determine is to look at the wet strip on your front and rear tires as you ride slightly damp roads. The width of the wet strip indicates how much drop you've got going, assuming both tires are the same.

There are lots of assumptions in this chart, and I'm not sure that there's much proven basis for those assumptions.

[ColonelJLloyd]

Pretty sure that's exactly what the author has said.

I would assert that this is just a general guide from which to start looking at tire pressure. It's not a rule.

[Johnny P]

I have been riding 28s this season at 60 psi and really like how it feels. Very comfortable.

[donevwil]

I went through the excercise of actually running my weight distribution on both wheels. We might assume we're 45/55 or 40/60, but I was actually something like 35/65. So that means my rear tire is supposed to be about twice the pressure or my front tire. Okay ...

Also, who says 15% drop is optimal? Maybe it's 20%. Maybe it's 12%. Maybe different tires have different optimal drops.

I would assert that this is just a general guide from which to start looking at tire pressure. It's not a rule.

Assuming that tire drop should be the same front and rear (should it be?), a good way to determine is to look at the wet strip on your front and rear tires as you ride slightly damp roads. The width of the wet strip indicates how much drop you've got going, assuming both tires are the same.

There are lots of assumptions in this chart, and I'm not sure that there's much proven basis for those assumptions.

My tire pressures are always based on ride and feel so I don't care where my "drop" falls or what it means for that matter. My point is that my preferred pressures happen to be very close to those in the chart.

One data point, sure, but it's my data point.

[benb]

I set up my pressures from that chart... it works great for me with a little bit of wiggle on tire drop and weight distribution.

I run on the assumption of 66% of my weight on the back tire and 34% on the front tire. So I have a pretty big difference in pressure front to back.

If you read into the literature on weight distribution it is not at all apparent that running more handlebar drop actually means you have more weight on the front tire and need more pressure in the front tire. That is mostly forum pseudoscience.

Guys who run more drop and reach also tend to run more setback which pushes their weight back.. if you look at the articles on this the randonneur bike setups are the only ones that really have more weight on the front tire.

[teleguy57]

In my own admittedly unscientific observations, I feel as though a slightly narrower tubular absorbs road shock as well as a wider clincher...by about 2-3 mm...That is a 22mm tubular absorbs road vibrations like a 25 mm clincher....Also, it will take a lot of convincing to sway me that a 30 mm clincher is faster on asphalt than a 22-23 mm tubular....and by a lot of convincing I mean that there is no way....

My also unscientific POV is to agree with you; I feel that a clincher (on a wider rim) needs to be 2-3mm wider than a tubular to give similar ride quality to the tubular. And I still like the way the tubs accelerate and corner more than the clincher.

[Ciavete]

Watching Le Tour. Analyst Paul Sherwen says riders are using @ 120 psi.

Leaves me wondering if higher is faster, if more punishing.

I'm enjoying 85 on HED Belgiums, though felt a little mushy at moments during a steep climb yesterday.

[spoonrobot]

Latest from Silca is that it depends on the road surface.

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

[johnniecakes]

I'm just now getting use to 25s. Anything bigger makes me feel like I'm on the lake tubing.

This, 25's look so fat

[palincss]

Your eye gets used to things. I recall from 1991 until 2002 I had a Titanium road bike and commuters that were either fat-tube aluminum or oversize steel. Then in 2002 I got another standard diameter steel tube frame and it was startling, even shocking how tiny the frame tube diameter seemed.

Similarly if you spend a lot of time riding 32 - 42mm tires, when you look at 23 or 25mm tires they seem ridiculously narrow.

[Mark McM]

Your eye gets used to things. I recall from 1991 until 2002 I had a Titanium road bike and commuters that were either fat-tube aluminum or oversize steel. Then in 2002 I got another standard diameter steel tube frame and it was startling, even shocking how tiny the frame tube diameter seemed.

Similarly if you spend a lot of time riding 32 - 42mm tires, when you look at 23 or 25mm tires they seem ridiculously narrow.

This makes me wonder - are round tube steel frames faster than round tube carbon fiber frames?

As we know, aerodynamics is the largest part of drag, and for the most part, aerodynamic drag is more significant than weight except on the steepest of hills. While fat tubed carbon fiber frames may be both lighter and stiffer than traditional diameter steel tube frames, the fat tube carbon frame should have more aero drag than the skinny tube steel frame. I wonder how steep the hill has to be for the lighter carbon frame to make up for the heavier steel frame.

[sandyrs]

Watching Le Tour. Analyst Paul Sherwen says riders are using @ 120 psi.

Leaves me wondering if higher is faster, if more punishing.

I'm enjoying 85 on HED Belgiums, though felt a little mushy at moments during a steep climb yesterday.

Pro teams are notoriously protective of their tire pressure information during the Classics and it wouldn't surprise me if they carried that through to the Grand Tours, instructing their mechanics to flat-out lie when asked about riders' pressures.

[guido]

I have been running Barlow Pass 38s at 4500 RSIU* for sometime and I have never been faster.









* ReallySmallInflationUnits 1 psi = 1000 RSIU

[sandyrs]

I have been running Barlow Pass 38s at 4500 RSIU* for sometime and I have never been faster.









* ReallySmallInfaltionUnits 1 psi = 1000 RSIU

Similarly, on my CX bike with Bon Jon Pass (35mm) tires at 50/55 psi, I have not gotten any slower. I still would not reach for them for a road race (they feel kinda weird when sprinting) but the vast majority of my miles currently happen on these tires.

[rwsaunders]

Has anyone tried the pressures recommended in the chart here?

https://janheine.wordpress.com/2010/10/18/science-and-bicycles-1-tires-and-pressure/

The front tire pressure recommendations are awfully low.

Mark...once I went over 155#, I found the chart to be useless...:cool:

[Kirk007]

I'm doing my own unofficial test this summer and so far, for paved surfaces, I'm not sensing any advantages to Compass 32s over 28s (Vittoria Corsa graphene). And Veloflex arenbergs are better than both on decent pavement and not far behind on broken pavement when paired with a low profile rim like nemesis or campy neutrons.