TT clinchers

speedbump
speedbump Posts: 416
edited August 2007 in Workshop
On my TT bike I currently use a 20mm front. This is fine. I need a new rear, so should I replace my current 23 with another 23 or go for a 20 which I presume would create less drag? Which type of tire would roll the fastest for short TTs where puncture resistance is not a great issue?

Thanks

Comments

  • woody-som
    woody-som Posts: 1,001
    I would stick to the 23, but how about a tubular clincher http://www.tufo.com/index.php?lg=en&mn=1&id=38

    I've used the cheaper and heavier version for a while on training rides, handle well, and roll very nicely, also put some sealant in them and punctures are not usually a problem, just keep riding.
  • rjsmith
    rjsmith Posts: 1,924
    Current research seems to suggest that 23mm is the fastest cross section generally. Ok, they are a bit wider but it's something to do with greater energy losses in deformation of a thinner tyre as it grips the road.
  • Johno68
    Johno68 Posts: 110
    I recommend Veloflex Records 700x20c, probably the best clincher for TTs, 140 psi so close to tub pressure.
    John
  • Monty Dog
    Monty Dog Posts: 20,614
    Aha - the old chesnut about narrow tyres being faster...Continental did some research a few years ago that concluded for the same pressure, the contact patch of a narrow tyre is in fact bigger than a wider tyre and that the energy losses from hysteresis i.e. deformation of the tyre carcass were in fact greater than the saving from the reduced frontal area. Narrow tyres also run harsher, don't grip as well and are more likely to puncture so your best option is to run 23mm front and rear. Also, as you're using tri-bars means more weight over the front wheel, which makes front wheel punctures even more likely. Conti Supersonics and apparently pretty quick, but do wear fast and aren't very robust.
    Make mine an Italian, with Campagnolo on the side..
  • Kléber
    Kléber Posts: 6,842
    Narrow tyres are lighter, but this seems to be their sole advantage when you're comparing 20 to 23 tyres. 23s have lower rolling resistance.

    I think it was Zipp who looked into this and designed a 22mm tub as the optimal balance of weight/aerodynamics and rolling resistance. Or it could just be that they used Vittoria to make the pricey Zipp tubs and the Italo-Thai company makes 22mm section tubs already...

    Besides, one manufacturer's 22m is not the same diameter as another's.
  • wildmoustache
    wildmoustache Posts: 4,010
    michelin PR2 light is probably the ultimate lightweight, low rolling resistance tyre for you.
  • jsmithfym
    jsmithfym Posts: 296
    Mitchlin pro2 light very quick tyre or veloflex pave
  • John Stevenson
    John Stevenson Posts: 962
    Wider tyres have less rolling resistance, but skinnier ones have less aerodynamic drag. For time trialling, the latter is probably more important.
    John Stevenson
  • wildmoustache
    wildmoustache Posts: 4,010
    john_stevenson wrote:
    Wider tyres have less rolling resistance, but skinnier ones have less aerodynamic drag. For time trialling, the latter is probably more important.

    depends on the rim width as well though. as i understand it a 19mm tyre on a standard road rim is actually less aerodynamic than a 23mm tyre.
  • NPH
    NPH Posts: 33
    Maxxix Equipe Legere got a 10/10 in Cycling Plus early last year and I've used them ever since. Really light, grippy and positive and no complaints at all. Descended the Alps like I was on rails, and I haven't seen a lighter clincher around.
  • andrewgturnbull
    andrewgturnbull Posts: 3,861
    john_stevenson wrote:
    Wider tyres have less rolling resistance, but skinnier ones have less aerodynamic drag. For time trialling, the latter is probably more important.

    HI there.

    John is correct - aero is more important for a TT. I'd add that you need to match the width of your tyre to the width of your rim. In the past I've always used 19mm tubs for time trialling, but when I bough a Bontrager Aeolus deep section for the front this year I found that the 19s were actually too narrow for the rim and have switched to 20mm tyres.

    Either way I'd guess that 23mm tyres will be too wide if you're using any kind of deep section, tri spoke or disc wheels. And if you're not using aero wheels, then tyres are the least of your worries!

    Cheers, Andy
    http://www.andyturnbull.co.uk
    http://www.stirlingtri.co.uk
  • wildmoustache
    wildmoustache Posts: 4,010
    andrewgturnbull wrote:
    john_stevenson wrote:
    Wider tyres have less rolling resistance, but skinnier ones have less aerodynamic drag. For time trialling, the latter is probably more important.

    HI there.

    John is correct - aero is more important for a TT. I'd add that you need to match the width of your tyre to the width of your rim. In the past I've always used 19mm tubs for time trialling, but when I bough a Bontrager Aeolus deep section for the front this year I found that the 19s were actually too narrow for the rim and have switched to 20mm tyres.

    Either way I'd guess that 23mm tyres will be too wide if you're using any kind of deep section, tri spoke or disc wheels. And if you're not using aero wheels, then tyres are the least of your worries!

    Cheers, Andy

    I totally agree generally with the emphasis on aero, but I wonder on this one. There is some data kicking about that suggests the losses due to low RR are very significant. surely must depend on type of tyre ... i.e. it is possible that a 23mm low RR tyre is faster over a given distance than a 20mm high RR tyre.

    obviously depends on profile and length of course.

    anyway, you're right, make sure the wheels area aero, as well as everything else, and don't worry too much about whether it's a 20 or 23mm tyre.

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