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, comparing woven and cord fabric tyres and recommending pressures based on vehicle weight.
| Identifier | ExFiles\Box 45\1\ Scan213 | |
| Date | 20th June 1921 | |
| contd:- -2- HS{Lord Ernest Hives - Chair}7/LG20.6.21. If it was necessary to run these tyres at 80 lbs. we should say that it was absolutely impossible to use them on Rolls-Royce Cars. We have carried out tests and have proved that with 80 lbs. pressure we get definitely less mileage than we do with 55 lbs. or 60 lbs. pressure. We attribute this to the fact that we have a fairly heavy rear axle on our cars and if we run the car with 80 lbs. pressure the wheels bounce clear of the road and the tread is being scrubbed away when they come in contact again. We found that the tread wore away very rapidly if we ran with high pressures. We suggest that with the cord construction of fabric, it is reasonable to suppose that a lower tyre pressure could be used because the cord fabric should stand more flexing than with the woven fabric without the risk of bursts. As we have mentianed previously, we have not had a single case of a cord fabric tyre bursting. The tyre pressures which we have found most suitable have been on cars up to 45 cwts. 55 lbs. pressure. Cars from 45 cwts. to 55 cwts. 60 lbs. pressure. Cars above 55 cwts. 65 lbs. pressure. We should like to have any recommendations from you on this matter. Yours faithfully, | ||