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 performance comparing different brands, pressures, and wear conditions.
| Identifier | ExFiles\Box 158\2\ scan0017 | |
| Date | 17th May 1939 | |
| -3- (2) Effect of variation in tyre pressure (see curve sheets 1,4, & 7). Increasing the tyres pressure by 10 lb.in.sq. has the effect of reducing the power loss with India and Dunlops new and worn by about 3% at 95 m.p.h. and 25% at 90 m.p.h. Avons show an improvement of nearer 20% at 95 m.p.h. and 15% at 90 m.p.h. All tyres show an improvement of about 15% at 80 m.p.h. Reducing the pressure by 12 lb/in.sq. results in increasing the loss with Dunlops New and Worn, and Avon by some 30% at 75 m.p.h. and 17% at 60 m.p.h. Under these circumstances India losses are quite excessive, being in the region of 60% higher at 60 m.p.h. (3) Comparison of new tyres with partly worn tyres. (See curve sheet 3). This is purely a comparison between new Dunlop tyres and tyres having 1/3 their tread remaining. The losses appear to be the same up to 70 m.p.h. but from 80 to 100 m.p.h. the worn tyres give 8 to 10% less loss. (4) Comparison between the loss obtained on the initial run with a new tyre with that obtained with new tyres on subsequent runs. (see curve sheet 3, 5.) Since one of the Avon tyres threw its tread on its first run, only Dunlop and India tyre figures are to hand and these give differing answers. A brand new Dunlop is 12% worse at 100 m.p.h. 6% " " 95 m.p.h. 5% " " 90 m.p.h. The India on its first run was 31% worse at 95 m.p.h. 26% " " 90 m.p.h. 24% " " 80 m.p.h. The tyre noise from the Indias on their initial run was far greater than on any subsequent run and tremendous in comparison with that from any other tyre tested. | ||