The Case for Lower Tyre Pressures

[Arthur Heaton]

How accurate can we drop from 120-110 psi to 80 - 90.How reliable are the gauges on track pumps ?How much air is leaked out removing the pump ??

[Martin Hayman]

Modern track pumps are pretty good. I would expect to get within ±5 psi of the stated pressure. Leakage from the tyre on removal is negligible.

[Bill Inabinet]

The US RoadBikeRider has just reported on a surprising new tyre test in the Seattle 'Bicycle Quarterly'. The protocols and results have been reviewed and confirmed by industry experts and are summarized in the latest RBR edition (Issue No. 269 - 11/09/06 ie 9 November 06). Significantly, they confirm the information outlined by Uncle Al above regarding tyre width and inflation pressure. To quote RBR 'Some test conclusions will be particularly enlightening if you're riding on narrow, high-pressure clinchers seeking more speed via lower rolling resistance. Your skinny tires may not be as fast as you think'.While some very interesting findings were found (eg tyres with cotton casings were faster than nylon casings, butyl tubes were faster than latex tubes, tubular tyres performed worse at very high pressure), the most relevant finding to this forum was summarised as follows:- 'Tire pressure has only a small effect on the rolling resistance of most tires. Narrow 23-mm tires seem to roll fastest at pressures of 105 psi (7.2 bar) or more. However, running these tires at 85 psi (5.8 bar) for improved comfort increased the test times only 2%. Wider 28-mm tires are as fast at 85 psi as they are at higher pressures'.Importantly, the tests confirmed that a lower tyre pressure does not significantly affect rolling resistance. When associated with the greater comfort, better handling and better puncture resistance perhaps it's time for those running high pressures to reconsider or at least give the 85-95 psi recommendations a go.The full eight-page report on tyre performance can be found in the Vol. 5 No. 1 issue of the Seattle 'Bicycle Quarterly' and can be ordered from http://www.bicyclequarterly.com.

[Martin Hayman]

This sounds like pretty sound science to me and confirms what we feel in our posteriors when we go out on the bike.