What pros/cons with using 25mm instead of 23mm tyres?

Jungli
Jungli Posts: 201
edited December 2008 in Workshop
Hi all

I have been given a pair of Ultremo R tyres in 25mm size. I usually use 23mm tyres and ride mainly UK sportives at the moment...

As above, what are pros and cons?

Ta

J

(They are actually still very light at only 200g for each tyre)

Comments

  • softlad
    softlad Posts: 3,513
    if you notice any difference at all, it will probably be a slightly smoother ride - given the 'huge' increase in width that 2mm gives.. ;)
  • whyamihere
    whyamihere Posts: 7,708
    Pro - Slightly smoother.
    Con - Slightly slower.

    You probably won't notice though.
  • redddraggon
    redddraggon Posts: 10,862
    They can be run at a lower lower pressure, more contact with tarmac and so improves the grip.
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  • thexvw
    thexvw Posts: 135
    More comfort, maybe less speed, but unless your racing....
  • Hi there.

    The slower/faster question is not clear cut... Wider tyres of identical construction inflated to the same pressure have been shown to have _less_ rolling resistance than the equivalent narrow tyre.

    The wider tyre will be marginally less aerodynamic though - and will weigh slightly more.

    You can reduce the pressure to increase the contact patch and hence the grip - but this will be a trade off against increased rolling resistance. The difference between 23 and 23mm tyres isn't enough for this to be significant in a road tyre. i.e I might reduce the pressure down to 90-95psi in wet conditions to improve grip, but this would work just as well on a 23 as on a 25psi - neither would be particularly susceptible to snakebites in this range.

    Contact area is a function of pressure, not width. The only difference is that the contact patch on a narrow tyre will be longer and narrower hence more of the sidewall will flex as the tyre rolls, hence increased rolling resistance.

    But the differences are very small between 23 and 25mm.

    Cheers, Andy
  • Monty Dog
    Monty Dog Posts: 20,614
    Although only 2mm more in diameter it's nearly 20% increase in tyre volume which makes a significant difference. Research also demonstrates that for the same given pressure, a fatter tyre loses less energy and provides more grip than a skinnier one.
    Make mine an Italian, with Campagnolo on the side..
  • Monty Dog wrote:
    Although only 2mm more in diameter it's nearly 20% increase in tyre volume which makes a significant difference. Research also demonstrates that for the same given pressure, a fatter tyre loses less energy and provides more grip than a skinnier one.

    Hi there.

    You're right!

    20% sounded a lot, but I am quite sad... so I checked the numbers... Assuming that the inner tube is toroidal and mounted on a 622mm rim, the difference comes out as a 18.3% increase.

    Probably more relevant is the 8.9% increase in surface area, which should translate to 8.9% more rubber on the road at a given pressure - which does help handling.

    Takes longer to pump up though!

    FWIW 23mm is pretty much the standard for road racing, unless there are cobbles involved.

    Cheers, Andy
  • Tranced
    Tranced Posts: 165
    nearly 20% increase in tyre volume which makes a significant difference.
    as in good or bad difference.
    Your next comment indicates fatter is better.... correct?
    Embrace cynicism…. see the bigger picture!!!!
  • softlad
    softlad Posts: 3,513
    FWIW 23mm is pretty much the standard for road racing, unless there are cobbles involved.

    but the OP rides sportives, where a 25mm tyre would probably see a few benefits...
  • softlad wrote:
    FWIW 23mm is pretty much the standard for road racing, unless there are cobbles involved.

    but the OP rides sportives, where a 25mm tyre would probably see a few benefits...

    Original post? [scratches head and scrolls up] Ok - never read that...

    Yeah 25mm will be fine.

    Cheers, Andy
  • markos1963
    markos1963 Posts: 3,724
    My head hurts :cry: If fatter tyres are supposed to be faster/better why don't racers use big balloon tyres?
  • redddraggon
    redddraggon Posts: 10,862
    markos1963 wrote:
    My head hurts :cry: If fatter tyres are supposed to be faster/better why don't racers use big balloon tyres?

    Because they use tubs rather than clinchers.
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  • softlad
    softlad Posts: 3,513
    markos1963 wrote:
    My head hurts :cry: If fatter tyres are supposed to be faster/better why don't racers use big balloon tyres?

    Because they use tubs rather than clinchers.

    something tells me that is not completely accurate - if only for the simple fact that as many race teams use clinchers these days...

    The trade off is rolling resistance v comfort - there is only a relatively small cross over where the efficiency of both is optimised, and that tends to be in the 23 - 25mm range...
  • redddraggon
    redddraggon Posts: 10,862
    softlad wrote:
    something tells me that is not completely accurate - if only for the simple fact that as many race teams use clinchers these days...

    That's definitely not accurate, you watch any pro race, and they'll be riding Boras/Zipps/CCUs/Hyperons/Lightweights/DA tubs/etc. You might see them riding Fulcrum Zeros or Campag Shamals sometimes, but I bet they'll be the tub version.

    Tubs are a definitely a huge majority in the pro peleton, with the likes of FdJ "playing" with tubeless systems.
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  • markos1963 wrote:
    My head hurts :cry: If fatter tyres are supposed to be faster/better why don't racers use big balloon tyres?

    Because they use tubs rather than clinchers.

    Red, red, red...

    The same width/rolling resistance arguments surely apply equally to tubs and clinchers?

    The reason they don't ride balloon tyres is that once you get above a certain point, the increased weight and aerodynamic penalties start to outweigh the rolling resistance gains.

    To get the best out of an deep section aero rim you want to have a tyre of approximately the same width.

    Cheers, Andy
  • liversedge
    liversedge Posts: 1,003
    I couldn't fit 25mm armadillos on my bike, they rubbed on the top of the fork and the top of the seat stays. I had to deflate them to get them past the brake blocks too - and that was with them opened up nice and wide!
    --
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  • redddraggon
    redddraggon Posts: 10,862
    The same width/rolling resistance arguments surely apply equally to tubs and clinchers?

    Yes, but with tubs, they are "rounder", and can be run at lower pressures with a lower risk of snakebites, so basically you can "sort of" make a 23mm tub behave like a 23mm clincher or 25mm depending on the pressure you pump it too....
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  • markos1963
    markos1963 Posts: 3,724
    markos1963 wrote:
    My head hurts :cry: If fatter tyres are supposed to be faster/better why don't racers use big balloon tyres?

    Because they use tubs rather than clinchers.


    THATS IT! my heads exploded. Why did you have to throw that one in?
  • softlad
    softlad Posts: 3,513
    softlad wrote:
    something tells me that is not completely accurate - if only for the simple fact that as many race teams use clinchers these days...

    That's definitely not accurate, you watch any pro race, and they'll be riding Boras/Zipps/CCUs/Hyperons/Lightweights/DA tubs/etc.

    I'm not just talking about pro teams - I should have been clearer - I meant 'racers' in general, which the OP originally referred to. That means anyone from club racers up to the pro peloton..

    Incidentally, tubulars are just as susceptible to pinch flats as clinchers...
  • softlad
    softlad Posts: 3,513
    so basically you can "sort of" make a 23mm tub behave like a 23mm clincher or 25mm depending on the pressure you pump it too....

    No. The tyre's carcass does not expand beyond its notional '23mm' width (I use 23mm as an example). All that expands is the tube contained within it - and therefore the pressure that the tyre runs at...
  • redddraggon
    redddraggon Posts: 10,862
    softlad wrote:
    so basically you can "sort of" make a 23mm tub behave like a 23mm clincher or 25mm depending on the pressure you pump it too....

    No. The tyre's carcass does not expand beyond its notional '23mm' width (I use 23mm as an example). All that expands is the tube contained within it - and therefore the pressure that the tyre runs at...

    I never said it did......I used the word "behave", - my dog could behave like a cat, but he's still be a dog.
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  • redddraggon
    redddraggon Posts: 10,862
    softlad wrote:
    Incidentally, tubulars are just as susceptible to pinch flats as clinchers...

    And that statement is just rubbish......
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  • redddraggon
    redddraggon Posts: 10,862
    Tubulars are less prone to pinch flats than clinchers, since the rims don't present the sharp edges of the clincher flanges.
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  • softlad
    softlad Posts: 3,513
    edited December 2008
    softlad wrote:
    Incidentally, tubulars are just as susceptible to pinch flats as clinchers...

    And that statement is just rubbish......

    Seriously - I really don't give a stuff what Sheldon Brown (RIP) says. Real life personal experience tells me otherwise. Come back when you've raced for several seasons on both and then say it ain't true...
  • Monty Dog
    Monty Dog Posts: 20,614
    Well, I've been racing on tubs for countless year - a few more than several - and never suffered from a pinch flat and since I've been generally riding fatter section tyres for the last few seasons, never suffered them with clinchers either. If someone want to know the science, it's on the Continental tyres site and is to do with energy losses due to hysteresis. There were countless debates on this a few years ago & I can't be bothered searching for it. Typically, the naysayers have never tried it, so aren't exactly capable of making a reasoned argument. Finally, if 25mm racing tyres were such a bad idea, then why in the last few years have the likes of Vittoria, Schwalbe and Continental introduced them?
    Make mine an Italian, with Campagnolo on the side..
  • softlad
    softlad Posts: 3,513
    The point I am trying to make is that if you hit an obstacle on the road - like a pot hole, small rock, piece of wood, etc - then provided you hit it hard enough you are just as likely to pinch flat on tubs are you are on HPs. A bloke in front of me in the bunch once flatted both his tubs after hitting a pot hole - Ironically, several other riders on HPs rode over it without issue.

    Tubular rims still have edges - granted the profiles are slightly smoother than clincher rims, but they are still there nonetheless...

    Incidentally - how do you know that 'countless' is more than 'several'..? ;)