Tyre width

[quixoticgeek]

One of the big things for the pro's has been a move to wider tyres, moving from 21/23 to 25 or in some cases 28, as science has shown them to be faster due to lower rolling resistance, enough to offset the extra drag of a wider tyre.

What I don't get tho is there must be a point where the extra width doesn't improve the contact patch, and the aero drag starts to counter act any savings in rolling resistance. The question then is: where is the sweet spot? How much slower is a 37mm tyre than a 35 or 32?

I know I'm over thinking this, but I'm stuck unable to ride for a couple of days and my brain is going weird places.

J

[LittleWheelsandBig]

The break point is related to wind speed and weight (affects rolling resistance) and tyre construction.

[Brucey]

it is fair to say that a heavier rider (plus bike plus load)  will see more rolling resistance so may benefit relatively more if the Crr is reduced.

It is also the case that if the rider/bike is not very aerodynamic, the additional aero drag of wide tyres is liable to be a smaller fraction of the whole.

Thus for two separate reasons a touring/commuting rider is likely to find his optimum at a different place to someone riding a road-racing bike.

cheers

[fuaran]

Depends on how smooth the road is.

[mrcharly-YHT]

You have to get very fat before losing the benefits.

Our faithful testing site has found that a 2.35" tyre made by Schwalbe has possible the lowest rolling resistance available:
https://www.bicyclerollingresistance.com/mtb-reviews/schwalbe-big-one-2016

I think that there is another problem though; grip.

These low rolling resistance tyres are all slicks. I like the comfort and low rolling resistance of my 35mm voyager hypers, but they have a big, slick contact patch, and if I ride up something slimy, they slip.

If I were riding on 25mm tyres, the higher pressure per unit area would get more grip in those conditions.

[Samuel D]

As some have already said, the width that consumes least power depends on many factors including:

IDEAL TYRE IS NARROWER <> WIDER
light rider <> heavy rider
strong rider <> weak rider
high speed <> low speed
front wheel <> rear wheel
low-hysteresis tyre <> high-hysteresis tyre (e.g. with high puncture resistance)
smooth road <> rough road
flexible fork <> stiff fork (e.g. disc brakes)
low-hysteresis rider <> high-hysteresis rider*
dense atmosphere <> thin atmosphere (e.g. hot day in the mountains in the eye of a hurricane)
headwind <> tailwind
box-section rim <> rim with aerodynamic features.

I think it’s fair to say that most people would be better off with wider tyres and lower pressures than they run. Contrariwise, a light rider with box-section rims and low-hysteresis tyres in a fast group on good roads might do best with a 23 mm tyre or even narrower. There should be a greater spread of common tyre widths than is currently the case (though matters have obviously improved tremendously in the last few years).



* It would be useful to have some rules of thumb for vibration tolerance. Do fatter riders lose more or less power from vibration? (Presumably more.) Tall versus short? Women versus men? Fast versus slow? Tight grip or loose grip on the handlebar? Etc. We know next to nothing about suspension losses except they can be enormous.

[dim]

I've learned different:

if you are looking for speed, you need to match the tyre width with the rim width. I had HED Belgium Plus wheels built (wider rim), and 25mm tyres match the rim width (i.e. the tyre width = 25mm, some tyres such as Conti GP 4000 SII measure a lot wider than what is advertised) .... My current tyres are IRC Formula Pro RBCC tubeless and the 25mm tyres measure 25mm on my rims

If you want comfort, then a wider tyre is better, but you will be slower

[mrcharly-YHT]

Contrariwise, a light rider with box-section rims and low-hysteresis tyres in a fast group on good roads might do best with a 23 mm tyre or even narrower. There should be a greater spread of common tyre widths than is currently the case (though matters have obviously improved tremendously in the last few years).

It seems that racing teams and technical analysis disagree with you.

Most racers are light (compared to general population) and are using 25mm or wider.

[LittleWheelsandBig]

Are any top-level professional teams using tyres wider than 25mm, other than at Paris-Roubaix?

[dim]

https://www.youtube.com/watch?v=Py9Loc8xjoo

[Samuel D]

It seems that racing teams and technical analysis disagree with you.

Not sure that’s so. Racers don’t use box-section rims these days. The aero penalty for a wider tyre is smaller with a deep-section carbon rim optimised for the tyre width, so the ideal tyre skews wider and the penalty of a too-wide tyre is diminished.

Remember too that pro racers use what their sponsors provide and the surrounding culture believes to be fast. They are not immune to the vagaries of fashion or marketing hype – if anything, they are particularly susceptible to it.

All the same, I think they currently ride about the fastest width available in many cases, perhaps erring slightly toward the side of comfort since the speed penalty is so small.

Tom Anhalt has done some good work trying to get to the bottom of this question, for example here.

Note that his chart at the bottom is for 35 km/h and a load of 38 kg. My front tyre has less load than that and I most care about speed when battling through open air at speeds above 35 km/h, so my ideal tyre (front, at least) might be narrower than his chart suggests.

Since aero drag increases with the square of speed but rolling resistance stays about the same at any speed, drag rapidly increases in importance at speeds above Anhalt’s; by the same token, at speeds below 35 km/h, rolling resistance quickly gains importance.

For these reasons, you wouldn’t catch me doing a long audax on 23 mm tyres by choice, although I know many heavier cyclists than I do so, even when using tyres with a steep rolling-resistance penalty in narrow sizes (i.e. puncture-resistant tyres).

[sojournermike]

It seems that racing teams and technical analysis disagree with you.

Not sure that’s so. Racers don’t use box-section rims these days. The aero penalty for a wider tyre is smaller with a deep-section carbon rim optimised for the tyre width, so the ideal tyre skews wider and the penalty of a too-wide tyre is diminished.

Remember too that pro racers use what their sponsors provide and the surrounding culture believes to be fast. They are not immune to the vagaries of fashion or marketing hype – if anything, they are particularly susceptible to it.

All the same, I think they currently ride about the fastest width available in many cases, perhaps erring slightly toward the side of comfort since the speed penalty is so small.

Tom Anhalt has done some good work trying to get to the bottom of this question, for example here.

Note that his chart at the bottom is for 35 km/h and a load of 38 kg. My front tyre has less load than that and I most care about speed when battling through open air at speeds above 35 km/h, so my ideal tyre (front, at least) might be narrower than his chart suggests.

Since aero drag increases with the square of speed but rolling resistance stays about the same at any speed, drag rapidly increases in importance at speeds above Anhalt’s; by the same token, at speeds below 35 km/h, rolling resistance quickly gains importance.

For these reasons, you wouldn’t catch me doing a long audax on 23 mm tyres by choice, although I know many heavier cyclists than I do so, even when using tyres with a steep rolling-resistance penalty in narrow sizes (i.e. puncture-resistant tyres).

Excellent link, but ignores 'suspension' or 'hysteretic' losses in the rider. In practice a more comfortable ride can save far more power than the loss moving from up in tyre size. Also, it assumes the same pressure is appropriate for each tyre size, when in practice I run bigger tyres at lower pressures than smaller tyres. Not saying your conclusions are incorrect, but there is quite a lot more going on that isn't wrapped into the test (and I can appreciate why - this already a very detailed and extensive set of testing and analysis). Jan Heine commented somewhere that he thinks that 32s are perfect for 700C.

Mike

[Samuel D]

Excellent link, but ignores 'suspension' or 'hysteretic' losses in the rider.

Anhalt didn’t ignore suspension losses but accounted for them by applying his usual 1.5× factor to the rolling-resistance values he measured on his drum. I think Damon Rinard came up with that scaling factor, but Anhalt says it tests out on the road. Andy Coggan thinks it should be 1.4×. Obviously it depends on the road and (to an unknown extent) the rider.

You might still argue that applying the same scaling factor to all tyres doesn’t tell the whole story. Frankly frankie’s signature applies here!

Jan Heine commented somewhere that he thinks that 32s are perfect for 700C.

Depends on all the variables discussed above…

[sojournermike]

Excellent link, but ignores 'suspension' or 'hysteretic' losses in the rider.

Anhalt didn’t ignore suspension losses but accounted for them by applying his usual 1.5× factor to the rolling-resistance values he measured on his drum. I think Damon Rinard came up with that scaling factor, but Anhalt says it tests out on the road. Andy Coggan thinks it should be 1.4×. Obviously it depends on the road and (to an unknown extent) the rider.

You might still argue that applying the same scaling factor to all tyres doesn’t tell the whole story. Frankly frankie’s signature applies here!

Jan Heine commented somewhere that he thinks that 32s are perfect for 700C.

Depends on all the variables discussed above…

Agree - I was expounding Frankly's views at more length.

Also agree on variables and dependence - not sure a single scaling factor works really, but it's just not simple. Plus fashion is a real driver for both wide and narrow tyres. In a different field, one of the key advantages that Carl Lewis had was that he understood that he didn't need to be fastest over 60m to win over 100m and he was able to hold/carry his speed for longer than most around him.

[zigzag]

attributes of a fast wheel: light supple tyres not wider than a rim, tubeless/latex tubes/tubular, smooth tyre-rim interface, oval(ish) shape of rim+tyre cross section, light rims, low number of aero spokes. optimal tyre width depends a lot on the road surface and speed - i can not imagine a combination of wide rim and tyre that would be faster than the usual 23-25mm on tarmac surfaced roads (perhaps 28mm for chip seal surfaces).

[rogerzilla]

I used to like Conti GP in 18mm!  Personally I'm happy with 23mm tyres but I don't race.  The 23mm will almost always be lighter, and the tyre construction can make a lot more difference than 2mm in width.  I've ridden on very stiff, slow Specialized 25mm tyres and very supple, fast 23mm Vredestein tyres.

[Bolt]

I think that there is another problem though; grip.

These low rolling resistance tyres are all slicks. I like the comfort and low rolling resistance of my 35mm voyager hypers, but they have a big, slick contact patch, and if I ride up something slimy, they slip.

If I were riding on 25mm tyres, the higher pressure per unit area would get more grip in those conditions.

So true and thanks for pointing this out.  I have to admit that until your post I hadn't made the connection between wide slick tyres and lack of grip.  I rode LEL this year on 42mm slicks and was truly scared at the lack of grip in the wet.  However they were really fast and comfy on dry roads where my sphincter wasn't going "sixpence... half a crown"

[dim]

I think that there is another problem though; grip.

These low rolling resistance tyres are all slicks. I like the comfort and low rolling resistance of my 35mm voyager hypers, but they have a big, slick contact patch, and if I ride up something slimy, they slip.

If I were riding on 25mm tyres, the higher pressure per unit area would get more grip in those conditions.

So true and thanks for pointing this out.  I have to admit that until your post I hadn't made the connection between wide slick tyres and lack of grip.  I rode LEL this year on 42mm slicks and was truly scared at the lack of grip in the wet.  However they were really fast and comfy on dry roads where my sphincter wasn't going "sixpence... half a crown"

thats where tubeless comes into play ....

I'm currently using the 2017 IRC Formula Pro RBCC tubeless on my Hed Belgium Plus rims .... amazing grip, roll fast, grip like superglue and have good puncture resistance .... they also last long .... I opted for the 25mm which measure 25mm on my rims and I use 70 psi for the front and 75 psi for the rear (some people use less pressure, but this is what works best for me .... i.e speed and comfy ride)... no worries about pinch flats, and punctures self seal with the Orange sealant

The 2017 IRC Formula Pro RBCC tubeless  are not the fastest rolling of the IRC, and I'm using these for my winter riding (I would use these on long rides such as LEL and PBP and other long rides)

However, in Spring, I will switch to the IRC Roadlite Tubeless, which are much lighter and roll faster. I have however read, that they are a bit wider than what is advertised, so I will get the 23's and they should measure 25mm which will be perfect for my rims

There's a few more tubeless tyres that I want to try, such as the Hutchinson Fusion 5 Galactik and a few others

so .... IMHO, tubeless tyres are the way forward. I'm seriously considering buying a used Scott Addict 10 that I will use for some audax rides aswell as commuting, and the first thing that I will do is have some dent light wheels built, with a Dynamo hub, but the rims will be tubeless ready

Tubulars will be phased out very soon (nothing new being developed/offered for a long while now).

[Brucey]

Tubulars will be phased out very soon (nothing new being developed/offered for a long while now).

I don't think the pros will change from tubs any time soon. 

cheers

[dim]

Tubulars will be phased out very soon (nothing new being developed/offered for a long while now).

I don't think the pros will change from tubs any time soon. 

cheers

mark my words ...,. tubs are like Betamax .... even when you shop for rims so as to build wheels, nothing newfor tubs  is offered 

tubs are history .... tubeless is the way forward .... Even Schwalbe has said so ... on tubeless ready rims, you can use tubeless or clinchers

[Brucey]

.... even when you shop for rims so as to build wheels, nothing newfor tubs  is offered  ....

you've drunk too much kool-aid, maybe...?   There is a lot of noise about tubeless for the road but basically it is still half-baked, at best. 

A half decent tub on a sprint rim is still a lighter, stronger, stiffer wheel with a faster tyre on it.

Crucially you won't break your neck immediately when a tub is flat and you can ride a few miles like that.

There are a few instances where even pros might (and I emphasise might) be better off on something with sealant inside it but that still isn't a tubeless tyre. 

Tubeless tyres are for amateurs who ride at the weekend and who are convinced that they must have the latest thing. They are easier to live with in that use than tubs. Whether they are 'worth it' vs tubed tyres is up for debate; as you well know they still get slashed wide open by pieces of glass, so it does not mean that you can safely ride on flimsy tyres all year round, or that you won't have to fix any punctures by the side of the road.

 They are 'the future' for tyre manufacturers because they stand to make a lot of money out of them. They are hardly likely to develop the product ready for sale and say 'there are not the future', are they.... ....

 This does not automatically make them suitable for pro-level racing, though...

cheers

[dim]

.... even when you shop for rims so as to build wheels, nothing newfor tubs  is offered  ....

you've drunk too much kool-aid, maybe...?   There is a lot of noise about tubeless for the road but basically it is still half-baked, at best. 

A half decent tub on a sprint rim is still a lighter, stronger, stiffer wheel with a faster tyre on it.

Crucially you won't break your neck immediately when a tub is flat and you can ride a few miles like that.

There are a few instances where even pros might (and I emphasise might) be better off on something with sealant inside it but that still isn't a tubeless tyre. 

Tubeless tyres are for amateurs who ride at the weekend and who are convinced that they must have the latest thing. They are easier to live with in that use than tubs. Whether they are 'worth it' vs tubed tyres is up for debate; as you well know they still get slashed wide open by pieces of glass, so it does not mean that you can safely ride on flimsy tyres all year round, or that you won't have to fix any punctures by the side of the road.

 They are 'the future' for tyre manufacturers because they stand to make a lot of money out of them. They are hardly likely to develop the product ready for sale and say 'there are not the future', are they.... ....

 This does not automatically make them suitable for pro-level racing, though...

cheers

so ... which new tubs have been offered on the market in the past 12 months? .... name them

only reason that pro's still use tubs is because they are sponsored and if they have a puncture, they can still ride a few km before the van reaches them ....

with tubeless, they can ride till the end

same as disk brakes .... was froned upon, but next yeqar, they will be the 'in thing'

[LittleWheelsandBig]

Tubular rims are a lot better than tubeless, inherently so.

[Bolt]

For tubeless to become a truly viable option for road bikes it will need the industry to come up with a universal standard for rims and tyres rather than the half arsed "tubeless ready"... "or not" option that is currently being pitched at the amateur market.

[dim]

Tubular rims are a lot better than tubeless, inherently so.

yea .... but the tyres are not