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).
Consensus of experience from large tire companies on the performance of passenger car tires on wide base rims.
| Identifier | ExFiles\Box 156\3\ scan0246 | |
| Date | 25th October 1940 guessed | |
| CONSENSUS OF EXPERIENCE OF LARGE TIRE COMPANIES WITH PASSENGER CAR TIRES ON WIDE BASE RIMS. 1. TREADWEAR. An average of all treadwear tests by all companies shows an improvement in the rate of treadwear of from 20 to 22 percent for tires on the widest combinations as compared with those on the present recommended (narrowest) rim combinations. The treadwear improvement for the intermediate tire and rim combinations is less than that quoted for the widest combinations, but no definite figures are available. All treadwear results are based on 2 lbs. lower inflation on tires mounted on wide base rims. The average figures quoted are taken from the results of a large number of tests covering both front and rear tires and several sizes. Hence this is a very general statement and is not maintained as a specific prediction. 11. WIPING & UNEVEN WEAR. The make of car used, and the route driven seriously affect front wheel wear and any discussion of this subject should be undertaken with this in mind. Three of the rubber companies report that there is no difference in the tendency toward uneven wear on wide rims as compared with the conventional rims. One Company however, has had some tests in which the tires on wide rims showed somewhat more tendency toward uneven wear. All front wheel tests were run with 2 lbs. lower air pressure in tires mounted on wide rims. 111. CURB BLISTERS AND RIM DAMAGE. One company has had considerably more experience on this subject than the others. They have found that while wide rims will scrape curbs that after a few experiences, the driver apparently will learn to adapt his driving habits in a manner similar to that which occurs with white side wall tires. On one large taxicab fleet, where a tire has been used on a rim with an overhang similar to that of the widest rim set-up for several years, no complaints of rim or tire damage have been reported, even though some rims have reached 200,000 miles. 1V. STABILITY OR CORNERING POWER. In evaluating stability, the car used and the method used have a tremendous effect. However, the tire companies agree that stability is better with a wider rim and apparently the increase in the stability factor is approximately proportional to the increase in rim width. There is no standard method for the evaluation of stability factor, and all results vary with the car used. We feel that this is a matter for each car manufacturer to work out for his individual car and in his own way. All the work that has been done on stability has used the same 2 lbs. pressure differential noted above. | ||