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 life and performance on various car models, referencing specific mileage figures and Dunlop load capacity tables.
| Identifier | ExFiles\Box 109\5\ scan0073 | |
| Date | 5th August 1938 | |
| 664 also 1332 To Hs.{Lord Ernest Hives - Chair} from Rm.{William Robotham - Chief Engineer} Rm.{William Robotham - Chief Engineer}15/MH.{M. Huckerby}5.8.38. TYRES. With reference to Sg.{Arthur F. Sidgreaves - MD}6/D.28.7.38. Whenever we bring out a new car we seem to get complaints of insufficient tyre life. As an example, we attach Sg.{Arthur F. Sidgreaves - MD}6/E.24.7.35, and our reply Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}7/MJ.29.7.35. 300cc EX. Today Sg.{Arthur F. Sidgreaves - MD} comments on the fact that the P.III tyres give a very satisfactory life. Our records in France show that the Wraith tyre life is well up to that which we obtained on the P.III. As an example, in the very hot weather we had last year two 6.50 x 17 rear tyres did 5,643 miles at Chateauroux. This year, the 6.50 x 17 tyres were removed from the rear at 5,274 to fit the larger wheels but they were not worn out. At the same time two front tyres did 8,005 and 9,354 respectively. It is difficult to believe that fundamentally a small change in tread pattern, such as introducing the 2,000 tooth alteration, would have been brought in had it appreciably affected the wearing qualities of the tyre. If we refer to the Dunlop table of the load carrying capacity of the tyres we have recently used on the 25/30 and the Wraith we find CHASSIS. TYRE SIXE. MAX. AXLE LOAD. 25/30 6 x 19 26 cwt. Wraith 6.50 x 17 30 cwt. that is, according to Dunlop figures, we have not over-loaded the Wraith type any more than we did the 25/30. Referring to the mileage on your own car, you did 3,893 on the rear and 5,245 on the front. The front track was, of course, out of adjustment. The tyres were not completely worn out but had lost their non skid pattern. | ||