Tyre widths & bike choice confusion

[400bhp]

There's a world of difference between a well built & badly built wheel. Even using the same components!

Interestingly this season the pros teams are riding more & more on 25-28mm tyres with the likes of ZIPP & HEAD designing rims to accommodate these wider tyres properly. You'd also be astonished at some of the pressures being put in the tyres, they're much lower than one expects.

Yes I would be - care to elaborate and do you know any of the reasons given?

 

[GrasB]

Yes I would be - care to elaborate and do you know any of the reasons given?

Well, with the latest wide rims being aerodynamic with wider tyre there are sub-0.5w differences in aero drag between a 19mm & 28mm wheels at 60km/h.

Firstly the pro-peleton mostly rides on tubulars not clinchers, which makes a difference to how wider tyres react to surfaces. That said wider tyres roll faster over less than perfect surfaces, even at 5-10psi lower tyre pressure. This means that there is less vibration induced fatigue which over a hard 5 hour stage/rage outweighs the minor aero deficit.

Why low tyre pressures? For a given surface texture go too high & your coefficient of rolling resistance increases. On truy 'flat' surfaces like in a velodrome this pressure is so high it's a non-issue, on roads it can be as low as 70psi for a 23mm tyre! The Crr profile looks like a lopsided V with the over-pressure being much steeper than under-pressure. For this reason it's better to run the tyres at lower pressures. I've seen pressures down at 80psi for lighter riders on 23mm tyres.

 

[fossala]

If the roads aren't to good round where you live, have you tried looking into a steel bike like the equilibrium? I have got one and it is so much more gentle than my alu. Weighs about slightly less as well!

 

[defy-one]

The roads aren't too bad, but some use that horrible aggregate , as it's cheap and longer lasting. I'll go for a bike that can take 25 or even 28mm tyres. That way a tyre change will help, should the need arise.

 

[RhythMick]

25 & 35 on the same bike ???
good point about fitting and setting up. i have a Stows in Slough and Dedworth, and an Evans in Greenford ... and everyone in Central London :-)

Haha no. I use 25mm when I'm purely riding on roads for long distances. I change to 35mm between Sportives, so I can ride on trails with the kids without worry. Also it means I train on harder load and then it's a bit easier on the Sportives.


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[RhythMick]

If the roads aren't to good round where you live, have you tried looking into a steel bike like the equilibrium? I have got one and it is so much more gentle than my alu. Weighs about slightly less as well!

Agreed, that's what swayed me to the Kaffenback instead of the Uncle John.


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[Andrew_P]

Well, with the latest wide rims being aerodynamic with wider tyre there are sub-0.5w differences in aero drag between a 19mm & 28mm wheels at 60km/h.

Firstly the pro-peleton mostly rides on tubulars not clinchers, which makes a difference to how wider tyres react to surfaces. That said wider tyres roll faster over less than perfect surfaces, even at 5-10psi lower tyre pressure. This means that there is less vibration induced fatigue which over a hard 5 hour stage/rage outweighs the minor aero deficit.

Why low tyre pressures? For a given surface texture go too high & your coefficient of rolling resistance increases. On truy 'flat' surfaces like in a velodrome this pressure is so high it's a non-issue, on roads it can be as low as 70psi for a 23mm tyre! The Crr profile looks like a lopsided V with the over-pressure being much steeper than under-pressure. For this reason it's better to run the tyres at lower pressures. I've seen pressures down at 80psi for lighter riders on 23mm tyres.

I wanted to go for the Zipp 101 clinchers due to the wider rim, but @ £900 couldn't justify it. I think it will dribble down to the mid range wheels fairly soon

 

[Sittingduck]

I think you'll be fine on 23 or 25mm tyres. The difference between which is (IMHO), negligible if not non-existant.

 

[400bhp]

Well...................technical babble........

 

[Part time cyclist]

I ride a specialized Sirrus on conti gator skin 28's I still have the original Alex a14 rims but they have been rebuilt 4 times 3 times by the original supplying bike shop under warranty and the last time by my local little bike shop run by an oldish fellow who spent a great time telling me how he builds wheels since then I have ridden in excess of 2500 miles without any problems ( touch wood)

 

[NeoCaesar]

I was getting punctures at a rate of one a week riding the crappish 23mm Bontragers that came with my bike but I was riding that round the city like a lunatic (Aberdeen traffic is interesting) and riding on less than suitable cyclepaths. Put 28mm Continental Puncture resistant tyres ( I forget which ones). Commute is noticably more comfortable on rough roads (gone from 120psi to 100) and the bike still has the sleek look. I definitely recommend a wider tyre for commuting and I guess it's a trade off for how wide you go -sacrifice speed and looks for comfort and tread.

 

[GrasB]

Yes I would be - care to elaborate and do you know any of the reasons given?

...

You asked me to elaborate & you got elaboration... what's the problem!?

 

[400bhp]

...

You asked me to elaborate & you got elaboration... what's the problem!?

I was half joking, however what does:

there are sub-0.5w differences in aero drag between a 19mm & 28mm wheels at 60km/h.

mean in the real world?

Firstly the pro-peleton mostly rides on tubulars not clinchers, which makes a difference to how wider tyres react to surfaces. That said wider tyres roll faster over less than perfect surfaces, even at 5-10psi lower tyre pressure. This means that there is less vibration induced fatigue which over a hard 5 hour stage/rage outweighs the minor aero deficit.

That's a qualitative statement. Have the teams done any proper research into this?

The Crr profile looks like a lopsided V with the over-pressure being much steeper than under-pressure. For this reason it's better to run the tyres at lower pressures. I've seen pressures down at 80psi for lighter riders on 23mm tyres.

No idea what you are talking about.

Do you know what proportion of pro teams use wider tyres?

Seems like self fulfilling bollox to me.

 

[Andrew_P]

Seems like self fulfilling bollox to me.

The only thing I picked up on when looking at wheelsets is the vast majority of normal road bike users run 23-25mm tyres and the rims on most Alu road wheels are truly designed for 19mm tyres. To stop the tyre moving under load you inflate to 110-120psi which makes it more lumpy on the road. With a wider rim you can run 23mm tyres at lower pressures without effecting the rolling resistence, so you win with comfort without penalising rolling..

As you say though could be a load of bollards but it has a kind of logic to it.

 

[BSRU]

I guess it's a trade off for how wide you go -sacrifice speed and looks for comfort and tread.

Wider tyres do not mean slower tyres, I used to commute on 35mm Vittoria Randonneur Hyper Folding City Tyres and when I changed to 28mm GP4 Seasons there was no difference in my average speed.