From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Tyre pressures, balancing comfort, wear, and a comparison with a Marmon car.
| Identifier | ExFiles\Box 39\2\ Scan092 | |
| Date | 13th October 1921 | |
| contd:- -2- that is that we are quite prepared to sacrifice that amount of efficiency for the extra comfort. If we disregard re-treading tyres which we believe is not recommended by the leading tyre manufacturers then we maintain it is no use tyre manufacturers expounding the wonderful advantages of the cord fabric if the rubber tread wears away a long time before the cord casing deteriorates. One should have a tyre in which the wear of the tread and the deterioration of the casing is balanced. We also maintain that different makes of cars with different types of springs, axle weight, and axle control, may require different tyre pressures, for instance, we have a Marmon Car of which the weight and horse power are practically the same as our 40/50 H.P. The mileage for the tyres on there is 8000 to 9000 on the rear. The difference in the comfort with the high and low pressures on that car is not nearly as marked as on our own car. We believe on the Marmon car you would get definitely less mileage if you ran with very low pressures. For our own chassis, if we take 5000 miles to be the average life of a rear tyre, then we feel sure that there is no risk of the casing bursting with low tyre pressures. We suggest that if you took a car and pumped the tyres up to 65 lbs. and took some of the Michelin Officials for a short ride on a bumpy road, and then let the tyres down to 50 lbs., I think you would convince them that it was unreasonable for them to expect us to recommend to our customers tyres which the makers demanded should be pumped to very high pressures. Hs.{Lord Ernest Hives - Chair} | ||