"Paul Jones" <"katpaul"@dodo.com.au(nospam)> wrote in message
news:[email protected]...
> The conti's have a higher pressure rating in the 20mm size.
>
> Would this make up for that deformation?
>
I can't quantify these effects (it is very difficult). But we can learn something from simple
physics and materials science.
The tension force in the tyre wall is proportional to the tyre width and to the pressure.
Continental's literature states that the carcase construction for the 20, 23 and the 25 mm models is
the same (for the GP3000), so the wall stress (i.e. resistance to bursting) is also proportional to
the width and the pressure. So we can put 23/20 times the pressure into the 20 mm tyre as the 23 mm
tyre and have the same wall stress. Does this result in less rolling resistance? I doubt it. I
understand that the narrower tyre working at the higher pressure is slowed more by road roughness.
Remember, too, that we are dealing with small changes in very small forces here. My son and I
estimated the rolling resistance of a bicycle with high pressure tyres on a smooth floor to be about
2 newtons.
What is your application for these tyres? Unless you are racing successfully at the very highest
level there are many more fruitful things to be concerned about than the fine detail of tyres -
working on the engine for example. My advice is to forget about 20 mm tyres, buy 23 or 25 mm ones
and don't pump them up so hard that your teeth rattle. Tyres provide practically all the
"suspension" of a road bicycle.
John Retchford
