I am 60 years old and 140lb. I am capable of a long 23 for 10 miles on a fast TT course. I currently ride 23mm clincher tyres and am thinking of changing to 19mm. How much difference in time do you estimate this would make?

Jim Stow, email

Opinions differ about tyre size and pressures in relation to aerodynamics and rolling resistance. A narrower front tyre?s smaller frontal area presented to the wind will be more aerodynamic, and hence it would appear to be of benefit.

You could also assume that a tyre pumped to 160psi would roll faster than one at 100psi. Unfortunately, there are caveats for every perceived benefit, and what may hold true on the smooth boards of a velodrome won?t necessarily offer advantages on the pitted surface of an open road.

One counter argument concerns loss of speed through vibration and deflection of the path of the wheel when using a very high pressure, narrow tyre, sufficient to negate any aerodynamic advantage. Also, the circumference of a wider tyre is usually bigger and likely to contain a larger volume of air, both of which could allow it to travel over uneven surfaces more efficiently.

All things considered, 23c tyres are seen by many to offer the best trade-off for road bikes, but not everyone agrees. The pros use wind tunnel testing and their years of experience to make up their minds, yet there are no conclusive, documented answers.

Why not experiment with different set-ups? As you are only looking for differences in seconds here, focus on the bigger picture. A good preparation, with correct nutrition, fluid intake and a thorough warm-up are likely to affect your results more than your choice of tyre.

Stuart Bowers

Tech writer. Bike-fit expert and Scott UK rider has raced for GB at mountain bike and cyclo-cross