Bring on the fat(ter) tyres

[misterhorsey]

http://cyclingtips.com/2016/08/cyclingt ... pressures/

And the lower pressure.

Not sure if this has been posted before. Long podcast. Worth a listen.

I've let a lot of air out. Plush ride. Seemingly no loss in speeds.

[silentC]

Have been riding with a guy who is running 40mm tyres on his road bike. He put them on because he wants to do a bit of gravel grinding but I tell you what, he doesn't have a great deal of trouble keeping up with the rest of us on 23s and 25s. Says he notices it a bit on the hills, but he says the weight difference between these and the 25s he was running before is about 300 grams. Seems like a lot to me, but that's what he said. They are tubeless. Maybe he put too much latex goop in them.

[g-boaf]

I've got two near identical bikes, one with 23mm tyres running 110psi, and one with 25mm running 100-110psi (occasionally less if I don't check them). The one with the 25mm tyres is 6.6kg because of the wheels it has, but I don't notice much difference between them on hills. They are both quick. But the one on 23mm tyres with alloy wheels is very, very harsh over bumps.

[Thoglette]

Not sure if this has been posted before. Long podcast. Worth a listen.

Thought I had. (Oh yes, over here) But worth it's own thread. Not surprisingly Zipp and Compass actually make wide, supple tyres in 700C. Almost as expensive as wide, handmade tubulars too

Unfortunately for me, I moved from 622 to 630 a decade ago when that was the only way to get a 32mm wide tyre (bar 26"). Next time I wear the brake tracks out.....

[cyclotaur]

The biggest diff I find in ride quality is down to tyre pressure... plus choice of knicks !!

[bobbythebrit]

I've got two near identical bikes, one with 23mm tyres running 110psi, and one with 25mm running 100-110psi (occasionally less if I don't check them). The one with the 25mm tyres is 6.6kg because of the wheels it has, but I don't notice much difference between them on hills. They are both quick. But the one on 23mm tyres with alloy wheels is very, very harsh over bumps.

I thought the idea of installing wider tyres was so that you could dramatically drop the pressure needed (to around 80 or so). Am I wrong on this subject or is there more to it than just that?

I'm considering putting some 25mm tyres on when I next need some.

[silentC]

I run my 25s at 90 in the back and 80 in the front.

Yesterday I got a pinch flat and my crappy little pump couldn't get more than about 60psi into the back wheel, so I rode home on that. It felt a bit spongy on the climbs but otherwise not really that noticeable. I suppose I'd be much more a candidate for pinch flats running very low pressure like that.

[misterhorsey]

I used to run 23s at about 100psi. I've dropped them down to 80psi. I'm around 63-65kg.

The ride is plush. And although I'm a bit out of shape, on certain segments of the Yarra Boulevard Strava is telling me I'm nearing times I used to achieve when I was much fitter.

The podcast gets into the nitty gritty. But a higher psi = a stiffer ride (which may feel more rigid and faster) basically means more energy is transferred into your body, and thus your body has to counteract those forces. Having a lower psi allows the tyre to deform and absorb more of that energy for a net savings of energy you put to achieve an equal speed. Or something like that.

A lower psi does feel more comfortable, and also actually feels slower . But the data suggests that the feel is misleading.

Anyway, it's worth experimenting. It's also cheaper than upgrading your frame for a significantly more comfortable ride.

[Thoglette]

I thought the idea of installing wider tyres was so that you could dramatically drop the pressure needed (to around 80 or so). Am I wrong on this subject or is there more to it than just that?

I'm considering putting some 25mm tyres on when I next need some.

There is more to it than just that. Tyre carcass construction counts. A non-vulcanised tyre with high thread count will be more supple than a vulcanised and/or armoured tyre of the same size. So a 23mm tyre can be faster than a 32mm tyre.

And traditionally that was the case, with wide tyres tending to "touring" or "puncture proof" construction and "open tubular" construction only available in narrow tyres (or actual tubulars). Cheap tyres tended to be universally stiff.

But, IMHO, it is size that dominates. The change from 19mm to 23mm (yes, I used to ride 19mm tyres) or 23mm to 28mm is a 50% increase in volume. Going 23mm to 32mm is doubling the volume and drops the pressure for my rear wheel from 100psi to 60psi.

I'm now firmly in the school of "the fattest tyres you can fit" as purchasing additional suppleness is always more expensive than just going wider.

Frank Berto's chart (from Jan Heine's article on pressure) is included below

[bobbythebrit]

I thought the idea of installing wider tyres was so that you could dramatically drop the pressure needed (to around 80 or so). Am I wrong on this subject or is there more to it than just that?

I'm considering putting some 25mm tyres on when I next need some.

There is more to it than just that. Tyre carcass construction counts. A non-vulcanised tyre with high thread count will be more supple than a vulcanised and/or armoured tyre of the same size. So a 23mm tyre can be faster than a 32mm tyre.

And traditionally that was the case, with wide tyres tending to "touring" or "puncture proof" construction and "open tubular" construction only available in narrow tyres (or actual tubulars). Cheap tyres tended to be universally stiff.

But, IMHO, it is size that dominates. The change from 19mm to 23mm (yes, I used to ride 19mm tyres) or 23mm to 28mm is a 50% increase in volume. Going 23mm to 32mm is doubling the volume and drops the pressure for my rear wheel from 100psi to 60psi.

I'm now firmly in the school of "the fattest tyres you can fit" as purchasing additional suppleness is always more expensive than just going wider.

Frank Berto's chart (from Jan Heine's article on pressure) is included below

Interesting, thanks for the info!

[richard.allan]

I first saw that chart a few years ago when I was riding an Apollo hybrid bike that came with 40mm treaded tyres. I had fitted some good 35mm Michelin tyres which I was inflating to 90 psi (about the max pressure). I was doing some searching on bike fit when I came across the chart so I thought I would give it ago. When I was setting up the bike fit (with some help) I weighed myself on the bike, front and rear. I can't remember the exact weights, I have them written down somewhere, but I ended up reducing the front tyre pressure to 50 psi and the rear to 60. I remember the first ride after that was much more comfortable and also faster than I had done it before.

I bought a Giant Defy Advanced 2 about 18 months ago. The rear tyre didn't last long because of a sidewall split and I replaced it with a 28mm Continental GP 4000S II. I don't know if it's a bit odd to run a different size tyre front and rear but it suits me. The original tyres are 25mm. I did the whole weighing thing again (there are also apps to do this) and I'm now running 75 psi in the front and 100 psi in the rear and I'm pretty happy with that.

[hamishm]

The rear tyre didn't last long because of a sidewall split and I replaced it with a 28mm Continental GP 4000S II. I don't know if it's a bit odd to run a different size tyre front and rear but it suits me. The original tyres are 25mm. I did the whole weighing thing again (there are also apps to do this) and I'm now running 75 psi in the front and 100 psi in the rear and I'm pretty happy with that.

Why so much in the rear? I am putting 70-80 psi in my 28mm 4000s II. It's comfortable, reliable and I'm just as fast (or faster) than I was on 25mm until recently.

[richard.allan]

Well, that's the pressure suggested in the chart (and also the app I have) for my riding weight. But, having listened to the podcast linked above this morning I am going to experiment with decreasing the pressure maybe 5 psi at a time. I'm also going to replace my front tyre with a 28mm when needed rather than sticking to 25mm.

My partner now rides the hybrid I mentioned in my previous post & I'm also going to decrease the pressure for her & even soften the front forks a bit.

[vosadrian]

The podcast gets into the nitty gritty. But a higher psi = a stiffer ride (which may feel more rigid and faster) basically means more energy is transferred into your body, and thus your body has to counteract those forces. Having a lower psi allows the tyre to deform and absorb more of that energy for a net savings of energy you put to achieve an equal speed. Or something like that.

Going by that rationale, surely thinner tyres/ more pressure is faster on smooth surfaces, as less "energy" goes to body as there is less energy for the tyre to transmit. On a perfectly smooth road there would be zero energy the body has to counteract. This being the case, would not thin tyres and high pressure be fastest on smooth roads, and fat tyres with less pressure on bumpy roads (chip gravel/dead road), and there would be some crossover in the middle.

Personally I am 70kg and run about 110psi in 23s. Suppleness does not really bother me too much, but a squirmy tyre does. There is no indication my setup is slow.

[RonK]

The podcast gets into the nitty gritty. But a higher psi = a stiffer ride (which may feel more rigid and faster) basically means more energy is transferred into your body, and thus your body has to counteract those forces. Having a lower psi allows the tyre to deform and absorb more of that energy for a net savings of energy you put to achieve an equal speed. Or something like that.

Going by that rationale, surely thinner tyres/ more pressure is faster on smooth surfaces, as less "energy" goes to body as there is less energy for the tyre to transmit. On a perfectly smooth road there would be zero energy the body has to counteract. This being the case, would not thin tyres and high pressure be fastest on smooth roads, and fat tyres with less pressure on bumpy roads (chip gravel/dead road), and there would be some crossover in the middle.

Personally I am 70kg and run about 110psi in 23s. Suppleness does not really bother me too much, but a squirmy tyre does. There is no indication my setup is slow.

Heretic!

You would dare to question the opinion of the infallible Jan Heine?

You should be burned at the stake.

[Thoglette]

This being the case, would not thin tyres and high pressure be fastest on smooth roads, and fat tyres with less pressure on bumpy roads (chip gravel/dead road), and there would be some crossover in the middle.

We get close to smooth roads at an indoor velodrome. White lines on fresh hot mix come close, too.

You would dare to question the opiniin of the infallible Jan Heine?You should be burned at the stake.

Actually, if you read/listen to what Jann says, you'll find he agrees with vosadrian. He has provided a fair bit of data about the where and when of the cross over points too.

It's when people (like me ) turn it into a dogma ("the fattest tyre that will fit") that the nuances get lost.

[vosadrian]

This being the case, would not thin tyres and high pressure be fastest on smooth roads, and fat tyres with less pressure on bumpy roads (chip gravel/dead road), and there would be some crossover in the middle.

We get close to smooth roads at an indoor velodrome. White lines on fresh hot mix come close, too.

You would dare to question the opiniin of the infallible Jan Heine?You should be burned at the stake.

Actually, if you read/listen to what Jann says, you'll find he agrees with vosadrian. He has provided a fair bit of data about the where and when of the cross over points too.

It's when people (like me ) turn it into a dogma ("the fattest tyre that will fit") that the nuances get lost.

I didn't read the source, but it makes sense to me. About half my riding is on pretty smooth roads and the other on pretty ordinary road including some pretty dead chip gravel roads. Most of the bad roads are in bunch rides, so not too fussed to lose a few Watts on a non-ideal surface when I have no problem staying with the bunch anyway.

I have never actually tried wider tyres. I have had people tell me how good they are, but I never noticed them suddenly get faster or slower. They tell me how much smoother it is, but I have no issue with how smooth my setup is so no need to try. Most of my wheels seem to be designed for 23s so I use 23s. I am sure there are some aero considerations using wider tyres on aero wheels that are not specifically designed for wider tyres. Swissside do a lot of aero testing of wheels and they seem to recommend Conti GP4k 23s as the ideal tyre for their wheels.

[koshari]

personally i cannot pick the difference with regard to drag between 23 and 25mm but i definately had a lot more pinch flats on 23s.

[silentC]

I would have thought aero benefits would be as marginal as the rolling gains being reported with wider tyres, they probably cancel each other out, unless you are on a velodrome track.

I run 25s because that's what my new bike came with and I didn't see any reason to change. I'm happy with them and I see a lot of the other guys are changing to 25s too.

[Thoglette]

I do suggest that some of the speculators go and read/listen to the original materials referenced above. There's been more than a decade of experimentation and measurement by Zipp and Heine.

[richard.allan]

Yeah, I agree. Listen to the podcast & then comment. You guys sound like the pros they talk about in the podcast.

A lot of people are adverse to change. Personally, I like to give new ideas a go & then make up my own mind. Otherwise we'd all just be stuck in the past...

[singlespeedscott]

The gist of the pod cast is that a supple, fatter tyre is no slower that a supple narrow tyre. It's just that the wider tyre will provide you with more comfort and grip on rough/wet roads.

[richard.allan]

Well that's a tad simplistic.

[Thoglette]

Well that's a tad simplistic.

Yes, but some people are "too time poor" to actually access and comprehend the articles.

[richard.allan]

They couldn't listen to it on a ride?