Tyres 23 v 25mm Pros & Cons

ai_1

bernithebiker wrote:

For your test to have any real meaning, you would need to average out the mean wind speed for each tyre.

For example; 23's, 10 rides, wind speed 12mph, from 240'.

Then 25's, 10 rides, wind speed 14mph from 190'.

See what I mean? Unless you have that info (which I doubt), and unless the 2 mean windspeeds are very similar, you can't really draw conclusions about the 1 or 2 watts that might come from the tyres. Aero factors have vastly more impact on your speed.

And lets not even get into fitness levels, fatigue, rain on road, etc. etc.

I think you're missing the point about mitigating influence of weather, form etc by using many tests over an extended period randomly switching between tyres. With large numbers of tests the average impact of wind, fitness and other effects WILL converge so that the average speed result should be pretty well normalised. Ideally you might also remove any obvious outliers from the data but even without doing so, a large sample largely negate any distortion they might introduce.

meanredspider

If you do the same ride over and over and over again (I think I did the commute for 4 years) with a Garmin you become acutely aware of those things that influence it. For instance, I tried Bontrager Hardcase tyres for a couple of weeks and concluded that I was nearly 1mph slower as a result (to validate this opinion, a colleague tried them for a month a year later and concluded exactly the same thing). One of the good and bad things about Inverness is that the weather is remarkably constant. It never gets very warm (20C counts as hot) and the wind is remarkably consistent too (both, I assume, are the result of being close to an awful lot of sea).

@BtB - I'm not sure what you want to conclude. That 25c aren't better? That they're the same? That they're worse? IIRC you ride 23c - why do you choose those and how did you reach that conclusion? How do YOU know that the difference between the tyres on real roads is only a few Watts?

Again, I'm not concluding that my test was definitive and that anybody that rides 23c is an idiot. But I have at least tried to compare them in a pragmatic way and concluded that I lose nothing from riding 25c so that's what I do. Usual disclaimer YMMV

markhewitt1978

That's the point isn't it, that we know that 25mm are more comfortable to ride, and we also know that they are, at worst, no slower than 23mm, therefore there's no downsides?

bernithebiker

Ai_1 wrote:

bernithebiker wrote:

For your test to have any real meaning, you would need to average out the mean wind speed for each tyre.

For example; 23's, 10 rides, wind speed 12mph, from 240'.

Then 25's, 10 rides, wind speed 14mph from 190'.

See what I mean? Unless you have that info (which I doubt), and unless the 2 mean windspeeds are very similar, you can't really draw conclusions about the 1 or 2 watts that might come from the tyres. Aero factors have vastly more impact on your speed.

And lets not even get into fitness levels, fatigue, rain on road, etc. etc.

I think you're missing the point about mitigating influence of weather, form etc by using many tests over an extended period randomly switching between tyres. With large numbers of tests the average impact of wind, fitness and other effects WILL converge so that the average speed result should be pretty well normalised. Ideally you might also remove any obvious outliers from the data but even without doing so, a large sample largely negate any distortion they might introduce.

To some extent, yes, and it depends on the number of rides you're doing - obviously the more the better.

But experience has shown that testing for gains on major items like wheels and body position is quite difficult for a normal rider in the open air. That's why most tests are done either in wind tunnels or inside, in a velodrome. There you can remove many of the problematic variables.

But trying to discern something as minute as 1 or 2W is, IMO, impossible for an amateur rider on the open road.

I would say that even if your 23 tests were at an average wind speed of 12mph from 240', and your 25 tests at 14mph from 210, your results are out already. And that assumes that traffic conditions, temperature, fatigue, tyre pressure, body position, etc. etc. are all precisely the same.

ai_1

bernithebiker wrote:

Ai_1 wrote:

bernithebiker wrote:

For your test to have any real meaning, you would need to average out the mean wind speed for each tyre.

For example; 23's, 10 rides, wind speed 12mph, from 240'.

Then 25's, 10 rides, wind speed 14mph from 190'.

See what I mean? Unless you have that info (which I doubt), and unless the 2 mean windspeeds are very similar, you can't really draw conclusions about the 1 or 2 watts that might come from the tyres. Aero factors have vastly more impact on your speed.

And lets not even get into fitness levels, fatigue, rain on road, etc. etc.

I think you're missing the point about mitigating influence of weather, form etc by using many tests over an extended period randomly switching between tyres. With large numbers of tests the average impact of wind, fitness and other effects WILL converge so that the average speed result should be pretty well normalised. Ideally you might also remove any obvious outliers from the data but even without doing so, a large sample largely negate any distortion they might introduce.

To some extent, yes, and it depends on the number of rides you're doing - obviously the more the better.

But experience has shown that testing for gains on major items like wheels and body position is quite difficult for a normal rider in the open air. That's why most tests are done either in wind tunnels or inside, in a velodrome. There you can remove many of the problematic variables.

But trying to discern something as minute as 1 or 2W is, IMO, impossible for an amateur rider on the open road.

I would say that even if your 23 tests were at an average wind speed of 12mph from 240', and your 25 tests at 14mph from 210, your results are out already. And that assumes that traffic conditions, temperature, fatigue, tyre pressure, body position, etc. etc. are all precisely the same.

I don't think he's trying to discern a 1 or 2W difference. He's simply looking to see if there's an average speed difference. If a significant difference is apparent that would suggest the possibility of a significant difference between the tyres. That's about it. Regarding traffic conditions, fatigue, tyre pressure, body position etc etc all being assumed precisely the same.... No - they do not have to be the same on each ride, they are assumed to vary similarly regardless of the tyres and therefore should converge over a large sample size or in the case of tyre pressure to be linked to the tyre being tested and therefore part of the tested element.

All experimental testing makes assumptions and has to cater for errors. Statistical error analysis is a major part of analysing any test results whether they come from a relatively unconstrained test protocol like this or a very tightly controlled one with a wind tunnel and rolling road. Wind tunnels aren't error free either you know!

bernithebiker

Trying to discern a small increase in average speed correlates to trying to discern a small saving in Watts consumed / wasted by the bicycle, it's the same thing.

meanredspider

bernithebiker wrote:

Trying to discern a small increase in average speed correlates to trying to discern a small saving in Watts consumed / wasted by the bicycle, it's the same thing.

It's not the same thing. To illustrate the point - ride on ice on slick tyres and studded winter tyres on a twisty road - I can tell you which will consume more watts but I can also tell you which will be fastest. It's an extreme example solely to illustrate that watts on a steel roller only tells you a small part of the picture. Why do the pros use different tyres for Paris-Roubaix - so they can be slower? Again, extreme, but illustrates the point.

Furthermore (repeating the question I made earlier) how do YOU know it's only a small saving in Watts? It seems to me that you're making an assumption based upon some unrepresentative testing yourself. How has that been validated?

sloppyschleckonds

markhewitt1978 wrote:

and we also know that they are, at worst, no slower than 23mm, therefore there's no downsides?

Can you link anything that substantiates this?

markhewitt1978

SloppySchleckonds wrote:

markhewitt1978 wrote:

and we also know that they are, at worst, no slower than 23mm, therefore there's no downsides?

Can you link anything that substantiates this?

From the discussions we've had in this thread.

meanredspider

Or the experts

http://pelotonmagazine.com/chatter/wolf-vorm-walde/

Or here

http://www.cyclingweekly.co.uk/news/lat ... ter-160403

In fact, unless you're riding incredibly fast on a perfect surface (ie velodrome) it seems hard to find anybody who doesn't think 25c is the better option.

I'm bored of this now. Feel free to criticise my approach or the other data available and do as you please. Whilst there's plenty of criticism of both of these, there's deafening silence when it comes to someone having done a better test or having convincing data to support the 23c case.

northpole

An upside for using 23mm tyres - less work at the side of the road if you are visited by the p*ncture fairies - lots more air needed to inflate a 25mm tyre!

Peter

(Stuck with 23mm on the front due to lack of clearance)

markhewitt1978

northpole wrote:

An upside for using 23mm tyres - less work at the side of the road if you are visited by the p*ncture fairies - lots more air needed to inflate a 25mm tyre!

Peter

(Stuck with 23mm on the front due to lack of clearance)

But even then, it's less about how much air that has to go in but more about the effort needed to get it up to a usable pressure. The usable pressure being less for 25mm.

ai_1

markhewitt1978 wrote:

northpole wrote:

An upside for using 23mm tyres - less work at the side of the road if you are visited by the p*ncture fairies - lots more air needed to inflate a 25mm tyre!

Peter

(Stuck with 23mm on the front due to lack of clearance)

But even then, it's less about how much air that has to go in but more about the effort needed to get it up to a usable pressure. The usable pressure being less for 25mm.

Ditto. I'd much rather be using my mini-pump to get a 25mm tyre to 85psi than to get a 23mm tyre to 100psi.

ai_1

bernithebiker wrote:

Trying to discern a small increase in average speed correlates to trying to discern a small saving in Watts consumed / wasted by the bicycle, it's the same thing.

More power = more speed with all else being equal.
I don't disagree.
However, what you said was he can't draw conclusions about the 1 or 2W savings that might come from tyres. As I understand it he did not claim to be trying to demonstrate a difference of 1 or 2W he was simply comparing data from a large sample of equivalent rides with the two tyres to see if there was a significant difference. Had his intention been to demonstrate a 1 or 2W difference then his test would have been ill-conceived because you are correct, this is very minor and would not have represented a statistically relevant difference in his data sets. However the result he has come out with suggests the difference may be much more than this. Or there is an issue with the data. As has already been accepted, it was not a rigorous test, but that does not necessarily make it pointless or silly as you seem to be suggesting.

bernithebiker

Ai_1 wrote:

bernithebiker wrote:

Trying to discern a small increase in average speed correlates to trying to discern a small saving in Watts consumed / wasted by the bicycle, it's the same thing.

More power = more speed with all else being equal.
I don't disagree.
However, what you said was he can't draw conclusions about the 1 or 2W savings that might come from tyres. As I understand it he did not claim to be trying to demonstrate a difference of 1 or 2W he was simply comparing data from a large sample of equivalent rides with the two tyres to see if there was a significant difference. Had his intention been to demonstrate a 1 or 2W difference then his test would have been ill-conceived because you are correct, this is very minor and would not have represented a statistically relevant difference in his data sets. However the result he has come out with suggests the difference may be much more than this. Or there is an issue with the data. As has already been accepted, it was not a rigorous test, but that does not necessarily make it pointless or silly as you seem to be suggesting.

What he said was that he was 0.5mph (almost 1km/h) faster on 25mm's.

Hard to say how many watts saved in rolling resistance this would equate to (we would need to know what the actual speed was - 30km/h?) - probably more than 2W, at a guess at least 10.

Which brings us to more problems (in my mind). Notably, that savings of 10W and above simply by going from 23's to 25's is highly unrealistic.

My opinion is that tyre changes, be it (from a high quality low rolling resistance 23, or a 'normal 'magic' 25), are likely to be in the order of less than 5W, which makes such a change extremely hard to identify out on the open road.

(By the way, the reason pros use 25's on Paris-Roubaix is for the better impact absorption from the paves, resulting in better control and less fatigue. Correct me if I'm wrong, but as far as I'm aware, the peloton has not made a wholesale move over to 25's for normal racing).

IShaggy

Here's some back of the fag packet calculations -

80kg riding on the tops on flat tarmac with 23mm tyres at 20mph = 220w (approximately)
15% of the effort is spent overcoming rolling resistence, 3% drivechain loss, and 82% air resistance.
So rolling resistence is 33w.
If you change to 25mm tyres and find that you are 0.5mph faster, then you must have reduced rolling resistance by approximately 10-15w. So that's a reduction rolling resistance of 30-45%.
I've assumed that there are no aerodynamic differences between the 23 and 25mm tyres. With narrow - 19mm rims - aerodynamics may in practice be adversely affected. But this may be the other way round for wider rims.

A 30-45% reduction in rolling resistance would be a wonderful thing. And I would sell my granny for it. But it just does not ring true, and nor does it come close to what other studies have shown.

Having said that, the next set of wheel I buy will have wide rims and I will pair 25mm tyres with them. I expect to get a very slight improvement in ride comfort and a very slight improvement in aerodynamics and rolling resistance. I don't expect to see any significant difference in overall speed.

stevie63

bernithebiker wrote:

(By the way, the reason pros use 25's on Paris-Roubaix is for the better impact absorption from the paves, resulting in better control and less fatigue. Correct me if I'm wrong, but as far as I'm aware, the peloton has not made a wholesale move over to 25's for normal racing).

The following was taken from an RCUK article on wider tyres:

We also got in touch with Lars Teutenberg who acts as technical consultant to Orica-GreenEDGE and IAM Cycling on behalf of Scott Racing, who supply both WorldTour teams with bikes. We wanted to start by confirming that pro teams were willingly using 25mm tyres, just like the rest of us, to further their riding comfort and handling.

This was clearly the case in direct rider feedback from both the Orica-GreenEDGE and IAM teams, with Teutenberg at pains to emphasise that 25mm is now the width of choice on both squads’ Shimano Dura-Ace C50 wheelsets.

However it would seem that the reason is still for comfort and handling not for extra free speed.

bernithebiker

IShaggy wrote:

Here's some back of the fag packet calculations -

80kg riding on the tops on flat tarmac with 23mm tyres at 20mph = 220w (approximately)
15% of the effort is spent overcoming rolling resistence, 3% drivechain loss, and 82% air resistance.
So rolling resistence is 33w.
If you change to 25mm tyres and find that you are 0.5mph faster, then you must have reduced rolling resistance by approximately 10-15w. So that's a reduction rolling resistance of 30-45%.
I've assumed that there are no aerodynamic differences between the 23 and 25mm tyres. With narrow - 19mm rims - aerodynamics may in practice be adversely affected. But this may be the other way round for wider rims.

A 30-45% reduction in rolling resistance would be a wonderful thing. And I would sell my granny for it. But it just does not ring true, and nor does it come close to what other studies have shown.

Having said that, the next set of wheel I buy will have wide rims and I will pair 25mm tyres with them. I expect to get a very slight improvement in ride comfort and a very slight improvement in aerodynamics and rolling resistance. I don't expect to see any significant difference in overall speed.

Good post which all makes sense.

As for any aero gains, we all know that increasing the surface area that you present to the wind, increases drag.

Simple maths suggests that 25mm tyres have about 8% more frontal area than a 23.

Then, the Cd gets involved, which, if claims are to be believed, is lower for a 25 on a wide rim.

So a 25 well paired with a matching rim, could have a lower Cd than a 23. But you wanna make sure of that, cause it needs to be at least 8% lower just to offset the higher surface area.

meanredspider

IShaggy wrote:

If you change to 25mm tyres and find that you are 0.5mph faster.

I've said in this thread not to get hung up on the 0.5mph difference. I've clearly stated that it's a rough test and that the conclusion I've drawn is that 25c are at least no slower than 23c for me (with the other benefits thrown in). The 0.5mph was just the difference in the average measurements I made. That might be 0.5mph +/- 0.5mph.

As seems to be the conclusion of this thread (from how I'm reading it) - 25c are no slower than 23c but confer other benefits which are of use to riders like better comfort and handling. These benefits, who knows, might actually make you quicker. Or not. Given free choice, there seems to be little harm in using 25c

IShaggy

Here's some advice from Zipp -

http://www.zipp.com/support/faq/faq.php

Firecrest wheels with wider tire beds
The best aero and lowest rolling resistance is obtained with front 23mm and rear 25mm width tires running at the recommended tire pressures.

Older narrow rims - pre-Firecrest
Tire choice depends highly on user preference and conditions. To summarize, a 21mm has superior aerodynamics with our rims; a 23mm is larger and subsequently has better ride quality and rim protection, but at a slight aero penalty. Here are some questions you can ask that will help guide your decision:

Triathlon/Time trial? In general – 21mm.
Road racing? In general – 23mm.
Training and/or daily riding? 23mm+
Dry? 21mm at normal recommended pressure.
Wet? 23mm at a slightly lower pressure.
Smooth roads? 21mm at normal recommended pressure.
Rough roads? 23mm at a slightly lower pressure.
User prefers slight aero benefit of 21's at the expense of a little ride comfort, rim protection, and rolling resistance? Use 21mm.
User prefers slightly better ride comfort, rim protection, and rolling resistance of 23's at the expense of a little aero? Use 23mm.
Rider weighs less? 21mm.
Rider weighs more? 23mm.

meanredspider

bernithebiker wrote:

Good post which all makes sense.

As for any aero gains, we all know that increasing the surface area that you present to the wind, increases drag.

Simple maths suggests that 25mm tyres have about 8% more frontal area than a 23.

Then, the Cd gets involved, which, if claims are to be believed, is lower for a 25 on a wide rim.

So a 25 well paired with a matching rim, could have a lower Cd than a 23. But you wanna make sure of that, cause it needs to be at least 8% lower just to offset the higher surface area.

Except you're missing the fact that your tyres are attached to a bike. Most down tubes are far wider than 25mm. The only frontal area that is affected by the tyre width is below the BB (about 40%) which has dropped the difference to around 3.5% (of just the wheel - ignoring the bike, rider, helmet etc). The Cd of the tyre combination though might well impact the entire wheel (and could improve flow over the whole frame if done right). Testing tyres on the road isn't the only complex part of this story.

thegreatdivide

Please make it stop. Please.

markhewitt1978

thegreatdivide wrote:

Please make it stop. Please.

Depends if you're going to use rim brakes or disc brakes? 25mm should also stop faster due to increased contact patch.

andi1363

25 surely expose more sidewall to flints etc and suffer more sidewall failures. Anecdotal evidence from my training buddies suggest this may be true.

mfin

Jesus christ you lot, you can ride bikes for decades, going through stacks of different gear and anyone who has done so will tell you there's no significant speed to be had from going from 23 to 25. Handling difference? I'd like to bet most people on here can't even push a tyre anywhere near it's limits because they have a mixture of a lack of technique and no guts, but they will still mention handling, that's a laugh.

If you want to ride 25s go ride them, who knows, if you're fat then yes they might bring some more comfort for you. As for all this psuedo science, why not just leave it to scientists rather than thinking that your pissing about with a cycle computer and some c grade gcse maths is the same.

meanredspider

mfin wrote:

As for all this psuedo science, why not just leave it to scientists

I'm a Fellow of the Institution of Mechanical Engineers and manage a team of 90 scientists and engineers - does that count?

As for handling, you don't need to take a tyre to its limits to appreciate the handling characteristics of a tyre, however manly and butch you think you are.

robbo2011

It's really simple. If you ride on 25 mm tyres, then you are a pussy and need to MTFU.

23mm tyres are for real men. I ride 21mm tyres.

bernithebiker

robbo2011 wrote:

It's really simple. If you ride on 25 mm tyres, then you are a pussy and need to MTFU.

23mm tyres are for real men. I ride 21mm tyres.

I once rode some 19mm's. Medal?!

I know I predicted 6 pages, but maybe we can keep it to 5?

Over 80kg and find 23mm's a bit uncomfy? Go with 25's.

Under 80kg and have no issues with 23 comfort or handling? Stick with them.

(Do yourself a favour and ride a Veloflex Carbon 23mm tub, then decide.......)

ai_1

mfin wrote:

Jesus christ you lot, you can ride bikes for decades, going through stacks of different gear and anyone who has done so will tell you there's no significant speed to be had from going from 23 to 25...

And yet for some reason things change and somehow the new ways turn out to be better than the old. If only there were an explanation!

mfin wrote:

...Handling difference? I'd like to bet most people on here can't even push a tyre anywhere near it's limits because they have a mixture of a lack of technique and no guts...

Correct, I rarely push a tyre to it's limits. But then I've never mentioned handling so I'm not going to bother telling you where to go.

mfin wrote:

...If you want to ride 25s go ride them, who knows, if you're fat then yes they might bring some more comfort for you...

Who knows? I do and I can explain why too - although i don't see much point. Now stop being ignorant and insulting and make an actual point instead.

mfin wrote:

...As for all this psuedo science, why not just leave it to scientists rather than thinking that your pissing about with a cycle computer and some c grade gcse maths is the same.

Yep, there's lots of pseudo science. I daresay you've perpetrated some yourself?
But again, no need for the insults. There's no call for it plus you're way off the mark in some cases. I'm an engineer with a MSc in aerodynamics. There's no reason you need to know that, but why do you assume we're at the level of "c grade gcse maths"?

I know your post is intended as a commentary on the participants in a conversation you're mocking but the only person it really reflects on is you, and very poorly.

bernithebiker

Er, should I mention I have a degree in mechanical engineering too?!

But only a 2:2 and I never actually used it for anything (apart from cycling forums....!)