Interesting debate - fat tyres on road bikes

[Kell]

Was chatting with a guy at work last night who's a keen cyclist, and he was talking about how fatter tyres could make you faster - even though it sounds counter-intuitive.

https://www.youtube.com/watch?v=yrHxQg1OW0A&fe...

[richardxjr]

That was filmed near me He goes off road into one of the Friston forest car parks and climbs up Chapel Hill, Lullington, at the end.

Vid mentions Bicycle Quarterly, penned by Jan Heine who's a guru on such things and takes it to extreme running 47c on 650b rims on his fast randonneur rides. Interesting the Enve appear to be backing these thoughts.

I'm a convert and ride his own 38c Compass tyres which are incredibly comfortable and I'm sure makes me faster (or to be accurate, less slow) on long rides. Even better I run them tubeless on std disk rims, sub 50psi, so they are no heavier than a 25 + tube, I don't get punctures and I don't need carbon frames or finishing kit to take harshness away.

Edited by richardxjr on Friday 14th October 11:31

[Foliage]

Weight is the biggest factor, if they weigh the same they will perform the same ish.

Whats the advantage of fatter tyres?

[TwistingMyMelon]

Just gone from 25c to 32c on my steel commuter road bike

Its like riding through bloody treacle tbh, only done it so they can cope with the gravel muddy tracks through the winter, the tyres are heavy , but I'm definitely not a fan of tyres that size unless I really needed to. I wish I just they went to 28, but these 32cs were £8 each and Ive run them for years with no issues, the bike feels propper dead to ride and about as nimble as a steam engine

Im still a fan of 23c through the summer for light/best bikes , although year on year the roads seem to get worse around me

[anonymous-user]

Foliage said:

Weight is the biggest factor, if they weigh the same they will perform the same ish.

Whats the advantage of fatter tyres?

Smaller contact patch and less rolling resistance, less vibration, better grip in corners.

[ian996]

Foliage said:

Whats the advantage of fatter tyres?

For a given pressure, a fatter tyre will deform less where it contacts the road, so the tyre remains nearer to a perfect circle, which provides less rolling resistance. Sounds sort of intuitive when you think about it, but we never really thought about it back in the dark-ages when I was racing....we just assumed narrower was better.

Downsides are increased rotating weight and poorer aerodynamics.

[richardxjr]

There are fat tyres and there are fat tyres. Check out Compass.

[Gren]

Gone from 25s to 28s on my new bike.

Feels no slower (although the bike is 1.5kg lighter so it bloody well should!) and the comfort is amazing. 20psi makes a difference

[groomi]

ian996 said:

...but we never really thought about it back in the dark-ages when I was racing....we just assumed narrower was better.

Same here. I used to race with 18mm tyres back in the 90's.

[was8v]

Get lightweight, flexible high TPI count tyres like the compass and run them tubeless - which you can do because of the lower pressures required.

Tubeless there is no big weight penalty and means you can rider further in more comfort.

Can't afford compass? My top tip is Vittoria Voyager Hyper at £15 a pop for 32/35/38 form planet x. http://www.planetx.co.uk/i/q/TYVIVOHY/vittoria-voy...

400g 120TPI and I run them ghetto tubeless.

Have a read of this review:

"When we compare the Voyager Hyper to fast road bike tires, rolling resistance is almost just as low. Although rolling resistance is slightly lower than the top performing all-round tires like the Continental GP4000S II (read review) or Vittoria Open Corsa (read review) , it does come very close to tires like the Vittoria Rubino Pro (read review), Michelin Pro 4 Service Course (read review), or Continental Grand Prix (read review) . It's obvious you don't need very thin and light tires to have a low rolling resistance."

"Rolling resistance at an air pressure of 90 psi is comparable to all-round road bike tires pumped up to 120 psi."

http://www.bicyclerollingresistance.com/tour-revie...

Edited by was8v on Friday 14th October 12:40

[was8v]

Narrow tyres just feel "faster" and "connected" as you get more road vibrations at 120PSI.

Most wide tyres feel like riding through treacle because they are heavy and inflexible (commuter puncture strips).

I'd really encourage everyone to fit the widest tyres they can, but choose lightweight ones!

[Foliage]

el stovey said:

Foliage said:

Weight is the biggest factor, if they weigh the same they will perform the same ish.

Whats the advantage of fatter tyres?

Smaller contact patch and less rolling resistance

Surface area isn't a factor in friction, Amonton's second law, friction/resistance is force (mass) x coeffiecient of friction (what the 2 surfaces are made of)

[Foliage]

ian996 said:

Foliage said:

Whats the advantage of fatter tyres?

For a given pressure, a fatter tyre will deform less where it contacts the road, so the tyre remains nearer to a perfect circle, which provides less rolling resistance. Sounds sort of intuitive when you think about it, but we never really thought about it back in the dark-ages when I was racing....we just assumed narrower was better.

Downsides are increased rotating weight and poorer aerodynamics.

Deformation makes sense but why would a larger tyre deform less, that much be in the design and materials used in the tyre. If that's such a big factor when not use solid tyres.

Weight is a massive factor, and adding weight must have a greater negative effect than is gained.

[MC Bodge]

I was pleasantly surprised by the speed and comfort of the (fairly large volume) 28mm Duranos @85psi on my commuter.

[NatAsp]

Foliage said:

Weight is a massive factor

Huh? Surely the effect of weight is minuscule when compared with rolling resistance (when up to speed)?

Unless you are suggesting that weight is a "massive" factor in rolling resistance, but if so Schwalbe seem to disagree https://www.schwalbetires.com/tech_info/rolling_re...

[groomi]

NatAsp said:

Foliage said:

Weight is a massive factor

Huh? Surely the effect of weight is minuscule when compared with rolling resistance (when up to speed)?

Unless you are suggesting that weight is a "massive" factor in rolling resistance, but if so Schwalbe seem to disagree https://www.schwalbetires.com/tech_info/rolling_re...

Rotating mass on a bike in general in a massive factor, as is rolling resistance. I wouldn't want to sacrifice one over the other.

[WestyCarl]

groomi said:

Rotating mass on a bike in general in a massive factor, as is rolling resistance. I wouldn't want to sacrifice one over the other.

Rotating mass is only a factor when accelerating / decelerating, in fact when up to speed it can help slight as the wheels act as a flywheel, hence TT and track riders will have solid discs with better aero and not worry about weight as the speed is relatively stable.

[neenaw]

richardxjr said:

That was filmed near me He goes off road into one of the Friston forest car parks and climbs up Chapel Hill, Lullington, at the end.

Vid mentions Bicycle Quarterly, penned by Jan Heine who's a guru on such things and takes it to extreme running 47c on 650b rims on his fast randonneur rides. Interesting the Enve appear to be backing these thoughts.

I'm a convert and ride his own 38c Compass tyres which are incredibly comfortable and I'm sure makes me faster (or to be accurate, less slow) on long rides. Even better I run them tubeless on std disk rims, sub 50psi, so they are no heavier than a 25 + tube, I don't get punctures and I don't need carbon frames or finishing kit to take harshness away.

Edited by richardxjr on Friday 14th October 11:31

I'm 100% in agreement with this.
I've gone from riding with 25c then 28c tyres and am currently riding some Compass Barlow Pass 38c's and they're no slower than the 25's from what I can tell. Despite this they feel much more comfortable.
I can't imagine that I'll go back to riding skinny tyres any time in the future as there's no benefit to me whatsoever.

I'm off to The Alps next summer for a week and I'm tempted to stick on a set of the Compass 28c's but I might just wait and see and if the current tyres are still working then stick with them.

There's plenty of interesting articles on Jan Heine's blog about tyre sizes and pressures:

https://janheine.wordpress.com/category/components...

[feef]

ian996 said:

Foliage said:

Whats the advantage of fatter tyres?

For a given pressure, a fatter tyre will deform less where it contacts the road, so the tyre remains nearer to a perfect circle, which provides less rolling resistance. Sounds sort of intuitive when you think about it, but we never really thought about it back in the dark-ages when I was racing....we just assumed narrower was better.

Downsides are increased rotating weight and poorer aerodynamics.

Except my skinny road tyres run at 100-110psi, the fat tyres on my MTB are around 35-40psi and simply can't be inflated that high.

theoretically, it's not incorrect, but in practice, I'm not aware of any fat tyres that can be inflated to as high a pressure as skinny road tyres

[groomi]

WestyCarl said:

groomi said:

Rotating mass on a bike in general in a massive factor, as is rolling resistance. I wouldn't want to sacrifice one over the other.

Rotating mass is only a factor when accelerating / decelerating, in fact when up to speed it can help slight as the wheels act as a flywheel, hence TT and track riders will have solid discs with better aero and not worry about weight as the speed is relatively stable.

Indeed, but even most TT courses have hills and corners and a standing start. So as I said, I wouldn't want to sacrifice one over the other.

On track is a totally different matter, but the speeds they're doing it seems aero is everything.