Wide tyres - I just don't get it

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warrior4life
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Re: Wide tyres - I just don't get it

Postby warrior4life » Thu Nov 15, 2018 12:56 pm

First Aspect wrote:
zefs wrote:About comfort, I tested today between my bikes back to back.

Bike 1: Race geometry - 17c internal with 25mm tires (26mm actual) -> Hutchinson Performance Tubeless
Bike 2: Endurance geometry - 19c internal with 25mm tires (28mm actual) -> GP4000sii with butyl tubes

Bike 1 was more comfortable at same psi (80 - 90) despite Bike 2 being an endurance Giant Defy which is supposed to be more forgiving. I think tire casing plays a big role, GP4000sii is known as a more stiff/harsh tire.

That said for simple tarmac I think 25mm tires are still optimal.
So you changed 4 variable there. Tyre brand, bike, inner tube, internal width. #gcndoesscience


On a similar note

Ihad two pairs or Cero AR30 wheels, one with 25mm tyres and one with 23mm. Ar30's at the time were 19mm wide.
I went out on the 23mm tyres, got two miles out and got a flat.
I walked back and switched to the 25's.
This was in 2012. pre wide tyres really.
I remember at the thinking 25mm are so much comfier and roll better, its just a shame they're slower.
Knowing what I know now I'd say on anything but a perfect surface 25's feel better. Super smooth 23's roack hard.
Aero wise its barely noticable.

Currently I'm riding 28's, once I got my head around the lower PSi they feel great also.

zefs
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Re: Wide tyres - I just don't get it

Postby zefs » Thu Nov 15, 2018 14:15 pm

There is a sweet spot depending on surface, bad roads with bumps vs smoother tarmac.
Thing is some people also confuse the "optimized for 28c tires" of wheel manufacturers and put a 28mm tire on such rim, which then measures 30-31mm which isn't optimal for their setup. Add that you need to use less air pressure for wider tires the difference is noticeable on speed (it's slower) but the comfort/handling improves which is great if that's what you are after.

Wider tires don't give better puncture protection though and depending on how low you go with air pressure, the opposite is true since the contact patch increases.

trek_dan
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Re: Wide tyres - I just don't get it

Postby trek_dan » Thu Nov 15, 2018 16:10 pm

The width of tub rims don't make any difference to the tyre, unlike clinchers or tubeless. 23c will have less contract patch.

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First Aspect
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Re: Wide tyres - I just don't get it

Postby First Aspect » Thu Nov 15, 2018 18:51 pm

trek_dan wrote:The width of tub rims don't make any difference to the tyre, unlike clinchers or tubeless. 23c will have less contract patch.

Contact patch depends on the pressure in the tyre and on the bike. My understanding would be that if the pressure in two tyres of differing widths is the same the size of the contact patch is the same, albeit of different shape. Hence all the stuff you hear about rolling resistance. Which is not something that article considered anyway.

zefs
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Re: Wide tyres - I just don't get it

Postby zefs » Thu Nov 15, 2018 19:28 pm

Not the air pressure, but air volume must be the same and also the carcass material would make a difference in contact patch.

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First Aspect
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Re: Wide tyres - I just don't get it

Postby First Aspect » Thu Nov 15, 2018 20:40 pm

zefs wrote:Not the air pressure, but air volume must be the same and also the carcass material would make a difference in contact patch.
Yes I'm sure tyre construction is a factor, but if you inflate a 25c gp4000 to 60 psi, and inflate a conti gp4000 space hopper to 60psi and put the same load on each, the contact patch will be the same size. The clue is in the "i".

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sungod
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Re: Wide tyres - I just don't get it

Postby sungod » Thu Nov 15, 2018 21:40 pm

thegreatdivide wrote:
sungod wrote:
thegreatdivide wrote:To be fair, a Lightweight Obermayer is a wheel with ancient aerodynamic qualities. It's an overpriced, side wind catching vanity purchase that'll send you into ditch every time a bus overtakes.

if you'd ridden them for years you'd know that with the correct width tyres they don't catch the sidewind any more than other wheels, less in fact than much shallower rims such ambrosio nemesis (though the higher spoke count on those may be a factor there)

in spite of being overtaken by many buses and other large vehicles they show no propensity to send me into ditches, nor off mountain roads, so you are provably wrong there too

obermayers also have great lateral stiffness, astonishing strength, and are light, so very light, no other wheel comes close

but as you are clearly speaking from ignorance, you wouldn't know any of that

sounds more like you are just bitter that you can't afford them


EDIT - I actually couldn't give a flying f*ck.

i was spot on then
my bike - faster than god's and twice as shiny

neeb
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Re: Wide tyres - I just don't get it

Postby neeb » Thu Nov 15, 2018 22:04 pm

First Aspect wrote:And Neeb, as someone who claims to work in biology (which is an ology after all) you have actually managed to take 2W at the outside (less than or equal to 1% in power, lets say, with error bounds considerably more and which is extremely generous as it is), but quoted data at more like 5%,which is exactly the same value in willymetres.

FA, if you look back at what I actually posted you will see that the only "data" I "quoted" was an entirely hypothetical example designed to illustrate how one might notice a consistent trend in the relationship between power and speed over multiple rides on the same route. At no point did I say that 23mm vs. 25mm tyres caused me to ride 0.5mph faster (I assume you were referring to the 19.7-20.7mph vs. 19.2-20.2mph example and are equating a +/- 2.5% average speed difference with a +/- 5% power difference at around 20mph, who knows.. I'll give you the benefit of assuming that you didn't think my example equated to a 5% speed difference!).

I've no idea what the exact aerodynamic advantage of 23mm vs. 25mm tyres is (on optimal rims or otherwise), I never claimed to. So I didn't "take" 2W from anywhere. I was describing my observations and explicitly stated from the outset that they would not be statistically signifcant:

"Yes - I have multiple average speeds and average power figures for a couple of 30-40 mile routes - not controlled conditions obviously and doubtless not enough repetitions to be statistically robust given the other significant variables (basically wind and 2 or 3 traffic lights), but strongly indicative."

To which you replied:

strongly indicative eh? On a good day in the summer I'm about 5 to 7% faster on the same bike over the same route than on a bad day. How much faster are you on 23c tyres than 25's exactly, because I'm sure as hell buying a set of your 23c tyres if you can really tell the difference over that much scatter in your data

In the process not only being unnecessarily confrontational but completely inappropriately equating the variation in your own absolute speeds with what I was talking about, which was variation in the relationship between power and speed.

Obviously the extent to which such variation due to a single cause would be statistically significant would depend on its magnitude, the sample size and variation due to other factors. But even if 23mm tyres only equated to a 2W difference, if this was completely consistent it would be detectable given a large enough sample size, even if other factors caused speed from one ride to the next to vary by considerably more than a figure equating to 2W power.

But this isn't the point of course - I wasn't claiming to be demonstrating anything, I was stating what my impressions were, which I am quite entitled to do at less than 95% confidence intervals, thank-you-very-much!!

First Aspect wrote:Woodster - we know that GCN does science is fun. It is like a busman's holiday for me. What suprises ME about this forum is how intractable people are and how little traction reasoned argument makes. Perhaps that's why I descend into poking people with a stick so quickly. This too is more fun than repeatedly banging my head on the keyboard.

And why do you think reasoned argument makes so little traction on forums? Has it occured to you that it's because there is always someone like you around who is determined to polarise the debate by being confrontational, thus forcing people into defensive positions that they can't easily back down from - quite often positions that they didn't even advocate in the first place?

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First Aspect
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Re: Wide tyres - I just don't get it

Postby First Aspect » Thu Nov 15, 2018 22:50 pm

So the data you quoted in response to me asking for some has now been downgraded to hypothetical. Okay. I think where we are as a consequence is that you think 23c tyres "feel" faster, yes? Jolly good.

It wasn't *my* rational argument I was referring to by the way. I just went straight in at ascerbic this time because someone else's rational arguments were already being scoffed at.

I'm interested to know why you think you know more about science than I do. Don't you need a set of rexel coloured pencils to study biology?

neeb
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Re: Wide tyres - I just don't get it

Postby neeb » Thu Nov 15, 2018 23:25 pm

First Aspect wrote:So the data you quoted in response to me asking for some has now been downgraded to hypothetical. Okay. I think where we are as a consequence is that you think 23c tyres "feel" faster, yes? Jolly good.

It wasn't *my* rational argument I was referring to by the way. I just went straight in at ascerbic this time because someone else's rational arguments were already being scoffed at.

I'm interested to know why you think you know more about science than I do. Don't you need a set of rexel coloured pencils to study biology?

No - you didn't ask me for data, you asked me if I had measured speed. I said that I had. Later on I provided a hypothetical example of how a small but consistent variation in the power / speed relationship might be detected over multiple rides, using hyothetical data. This was not actual data provided in response to your imaginary request for it.

As I said in response to cycleclinic's post above I think 23mm tyres both feel faster and are faster. I do not have statistically robust evidence for the latter however, nor am I intending to submit a paper to Nature on it.

I suspect that I know more about (at least many aspects of) science than you because your attitude as dispalyed here is more like that of an embittered technician than a scientist. If you are actually a phycisist or an engineer and this is your idea of public outreach there are probably courses you could go on.. I would never dream about being that arrogant and insulting to laypeople on a public forum devoted to my own subject area.

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First Aspect
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Re: Wide tyres - I just don't get it

Postby First Aspect » Fri Nov 16, 2018 04:28 am

I'm sorry for polarizing the debate and forcing you into an entrenched position you are finding it hard to back down from.

You got it in one. My job is cleaning test tubes that scientists do stuff with.

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meanredspider
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Re: Wide tyres - I just don't get it

Postby meanredspider » Fri Nov 16, 2018 04:31 am

Svetty wrote:
thecycleclinic wrote:mean spirit rider


Brilliant! :D :D


It’s very old zzzzzz It’s just that Malcolm likes to play the man rather than the ball. It’s why I don’t bother coming on here other than to remind myself why I don’t and see the same old tripe re-cycled.
ROAD < Scott Foil HMX Di2, Volagi Liscio Di2, Jamis Renegade Elite Di2, Cube Reaction Race > ROUGH

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meanredspider
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Re: Wide tyres - I just don't get it

Postby meanredspider » Fri Nov 16, 2018 04:35 am

Svetty wrote:
meanredspider wrote:
thecycleclinic wrote:The difference in drag by using a narrow tyre is quite measureable. Here is just one set of data from hambini's blog.
What it clearly show is the difference in drag between a narrow and wide tyre is not just down to the width of the tyre but also the width difference between the tyre and rim. the difference may not be huge but if your buying aero wheels it is shame to squander half the gain by fitting a wide tyre.

Image


Gotta love a bit of pseudoscience

The entire Enve data set is something like 183W +/- 1W

He’s used a charting technique that hides how small the difference is. I’d like to see that data with the confidence intervals plotted too. The accuracy of the PM must account for more than the difference let alone the other MSA influences.

I haven’t read the blog (I’m on a phone in Shanghai right now) so I can’t comment on the Shimano data set differences.


The graph is at a relatively modest 19mph and whilst the difference is small it is consistent. At higher speeds it will be more significant and for a serious tester will be worth exploiting as it's 'free speed' albeit small.


How do you KNOW that at higher speeds it will be more significant? It simply isn’t that simple, I’m afraid. These days I manage about 350 engineers testing our products and a good proportion of that is air flow. With insight like yours, I can make all of those guys redundant.... :roll:
ROAD < Scott Foil HMX Di2, Volagi Liscio Di2, Jamis Renegade Elite Di2, Cube Reaction Race > ROUGH

Svetty
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Re: Wide tyres - I just don't get it

Postby Svetty » Fri Nov 16, 2018 09:08 am

Speaking pedantically you are right - I don't KNOW for sure 100%. But I wouldn't mind betting that a tyre:rim interface/combo that is draggy at 30kph IS going to be more draggy at 50. I've not seen much data on aero wheels that shows that the faster you go the less drag they produce but if you have it I'm sure the industry would be pleased to have the opportunity to expand the existing knowledge base.
FFS! Harden up and grow a pair :D

rossa867
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Re: Wide tyres - I just don't get it

Postby rossa867 » Sat Nov 24, 2018 12:38 pm

Hey, im a final year student looking to improving comfort between a bicycle and its user. I would greatly appreciate the time taken to fill in my survey, many thanks. https://www.surveymonkey.co.uk/r/FH2W2BR

neeb
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Re: Wide tyres - I just don't get it

Postby neeb » Sat Nov 24, 2018 13:12 pm

rossa867 wrote:Hey, im a final year student looking to improving comfort between a bicycle and its user. I would greatly appreciate the time taken to fill in my survey, many thanks. https://www.surveymonkey.co.uk/r/FH2W2BR

Survey completed, but I had some issues with it:

- For Q3 only one choice is possible for "cause of discomfort" experienced on a bicycle. I answered "fatigue", which I imagine everyone has experienced at one time or another. Some people will also have experienced multiple other causes of discomfort. This question should clearly allow multiple answers.

- On answering this question I was presented with "If you're answer above does not relate to component set-up or selection please skip to the final question". Firstly it would be advisable to correct the grammar here ("you're"). Secondly, as above, this is going to exclude eveyone from the core part of the survey whose single answer to Q3 didn't relate to component / set-up selection, even if they do regularly experience discomfort associated with such things.

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First Aspect
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Re: Wide tyres - I just don't get it

Postby First Aspect » Sat Nov 24, 2018 17:05 pm

neeb wrote:Firstly it would be advisable to correct the grammar here ("you're").

Jees, and this from a guy who did a degree requiring use of a crayon set, including several shades of green. Give the guy a break, he is just trying to get a degree.

It is irrational I know, but I've taken a dislike to you since you pulled the "I know more about science than you do" card to support a silly argument.

You probably don't, by the way.

neeb
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Re: Wide tyres - I just don't get it

Postby neeb » Sat Nov 24, 2018 18:00 pm

First Aspect wrote:
neeb wrote:Firstly it would be advisable to correct the grammar here ("you're").

Jees, and this from a guy who did a degree requiring use of a crayon set, including several shades of green. Give the guy a break, he is just trying to get a degree.

It is irrational I know, but I've taken a dislike to you since you pulled the "I know more about science than you do" card to support a silly argument.

You probably don't, by the way.

Yup, he's trying to get a degree in product design / market research so presentation is important. Do you think it would be better if he didn't change it and no-one told him about it, FFS?

The difference between you and me is that my dislike of you is entirely rational, as anyone can see from the thread above. I didn't "pull" anything, you started out by implying that I didn't know anything about science and I informed you otherwise. And I didn't say what you've mistakenly quoted. Probably I know a lot more about some areas than you do and visa versa.

You are basically just a deeply unpleasant person who can't deal with the fact that your cynical, arrogant and divisive attitudes towards other people don't always have the effects you intend.

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First Aspect
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Re: Wide tyres - I just don't get it

Postby First Aspect » Sat Nov 24, 2018 18:11 pm

In just said "for example, speed" and then you just went rouge. I have said absolutely nothing about my own background or qualifications, because honestly it is irrelevant. Only you did that and only you suggested that I'm a lowly embittered lab tech.

Design is nothing to do with grammar.

It wasn't that bad a questionairre. I tried to be helpful to him.

neeb
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Re: Wide tyres - I just don't get it

Postby neeb » Sat Nov 24, 2018 18:45 pm

First Aspect wrote:In just said "for example, speed" and then you just went rouge. I have said absolutely nothing about my own background or qualifications, because honestly it is irrelevant. Only you did that and only you suggested that I'm a lowly embittered lab tech.

Design is nothing to do with grammar.

It wasn't that bad a questionairre. I tried to be helpful to him.

Like most truly unpleasant people you use sarcasm and passive-agressive tactics to make your points and then use that indirectness as a basis for denial and distortion later on.

Your "for example, speed" comment was obviously highly sarcastic.

Your "What do I know about Science and Engineering" comment was clearly communicating "I know far more about Science and Engineering than you do".

Show me where you were trying to be helpful to rossa867. I was offering constructive criticism.


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