How did we delude ourselves about 23mm?

[atoz]

The big advantage of 25mm is not so much the ride, it's that you can easily use standard section inner tubes with them- 23's often prefer narrower tubes, which are thinner and easier to puncture.

I remember the Worthy Blue Label 23's that came with my old Claud Butler Brevet many years ago- a rather narrow 22 with skinwalls. They lasted the summer only after unwisely going over the Roman road to Bainbridge with a friend. After that I went for Elans. These days I find Vittoria Rubinos in either 23 or 25mm do the job for me.

[Mick F]

The big advantage of 25mm is not so much the ride, it's that you can easily use standard section inner tubes with them- 23's often prefer narrower tubes, which are thinner and easier to puncture.

Correct me if I'm wrong here.

I use Schwalbe inner tubes.
Mine are 18mm to 28mm tubes for my 23mm tyres.
I think the next size up in width is 28mm to 32mm, therefore if you have 25mm tyres you'd be using 18-28 like I do.

[atoz]

The big advantage of 25mm is not so much the ride, it's that you can easily use standard section inner tubes with them- 23's often prefer narrower tubes, which are thinner and easier to puncture.

Correct me if I'm wrong here.

I use Schwalbe inner tubes.
Mine are 18mm to 28mm tubes for my 23mm tyres.
I think the next size up in width is 28mm to 32mm, therefore if you have 25mm tyres you'd be using 18-28 like I do.

Yes, for Schwalbe. Not for Michelin! Don't know about the others..

[Scunnered]

Statement from DT Swiss website, interesting for their emphasis on comfort:

"The complete bike only makes up for 25% of the overall drag, the wheels even less at 8%, while the rider causes 75% of it. So why is the wheel still important in this calculation? In order to stay aero in the first place, you have to stay comfy no matter the riding situation, because only then will you be able to keep an aero position, which affects those big 75%."

Wider tyres = more comfort -> rider more aero = less drag

[reohn2]

Statement from DT Swiss website, interesting for their emphasis on comfort:

"The complete bike only makes up for 25% of the overall drag, the wheels even less at 8%, while the rider causes 75% of it. So why is the wheel still important in this calculation? In order to stay aero in the first place, you have to stay comfy no matter the riding situation, because only then will you be able to keep an aero position, which affects those big 75%."

Wider tyres = more comfort -> rider more aero = less drag

I'll agree to that,a more comfortable rider rides longer without fatigue,therefore more energy is available for turning the pedals.

[Brucey]

if this were real science we were talking about, Karl Popper would have something to say about it; essentially it would not be difficult to devise a decisive experiment that would attempt to falsify one theory (e.g. 'that 25mm tyres are faster') or another theory (e.g. 'that 35mm tyres are faster'). Maybe Jan Heine has been trying to do that, but it looks more like he is trying to measure variations in something that has a lot of scatter in it instead.

BTW the idea that having fatter tyres is a decisive thing that can make holding an aero position more comfortable and therefore give 'more speed' is somewhat misleading; the thing that makes an aero position effective is good core strength, lots of training in the use of that position, and small refinements in it. The fact that being jiggled up and down is usually not such a big deal is brutally obvious one you examine such bikes; you can invariably easily make changes that would improve comfort (from road vibrations , e.g. more padding on the elbow rests), rather easily.

cheers

[Scunnered]

essentially it would not be difficult to devise a decisive experiment that would attempt to falsify one theory (e.g. 'that 25mm tyres are faster') or another theory (e.g. 'that 35mm tyres are faster'). Maybe Jan Heine has been trying to do that, but it looks more like he is trying to measure variations in something that has a lot of scatter in it instead.

If you want to do it outdoors on a real road then actually it is quite difficult - the coefficient of rolling resistance is tiny compared to other influences and inevitably you do end up with a lot of scatter in the results. I made a determined effort last year to measure Crr and that is what I found.

[Brucey]

I was thinking of something much simpler; rather than an absolute measurement, something more like a back to back (or actually side-by-side) comparison, run multiple times to iron out the scatter, preferably in tailwind conditions. You wouldn't get absolute Crr data that way, but you might stand a good chance of falsification (or not) of various theories which is arguably better, more incisive science. If it works (either way) it is certainly likely to be a better use of one's time and resources.

cheers

[Scunnered]

That's what these guys did to investigate the effect of pressure rather than width:
http://www.velonews.com/2018/06/from-the-mag/optimal-tire-pressure-gravel_468329

But there is one bit I really didn't like, with too much uncontrolled variability: "Both riders started simultaneously on each run, with each taking a single half pedal stroke — the top leg went down to the bottom of the stroke, and then the rider coasted from that point on."

[Brucey]

I've done some ad hoc tests side-by-side and getting the start speed equal is indeed a significant problem. In the experiments I did we rode side by side and only started to coast once we were agreed we were going at exactly the same speed. Ideally the windage and weight of each rider would be the same; the reality is that they will differ and swapping riders (or a control experiment that gives a dead heat on the same tyres) will be required.

cheers

[ratherbeintobago]

So, what’s the recommended 25mm tyre? I have Michelin Pro3s on the bike now which are looking a bit sad and CRC has 25mm Pro4s cheap...