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).
Analysis of tyre wear on E.R. Hall's 4½ Litre Bentley during the Ulster T.T. Race.
| Identifier | ExFiles\Box 90a\6\ Scan111 | |
| Date | 21th September 1936 | |
| x26 21st September, 1936. FILE ULSTER T.T. RACE SEPT. 5th, 1936. TYRE WEAR ON E.R.HALL'S 4½ LITRE BENTLEY. The tyres used in the first practice were 6.00/19 front and 7.00/19 rear. It was found impossible to get the necessary engine speed with the 7.00 tyres. It is interesting to note, however, that the wear on these tyres after five laps on wet roads was 0.0107" per lap equivalent to 42 laps on the nonskid pattern. The speed was approximately 77 m.p.h. The rear tyres were changed to 6.50/19 and all remaining practice and also the race, was run on this size of tyre. Front tyres were run at a pressure of 31 lbs, and at the end of 17 practice laps the nearside tyre showed a loss of 0.0057" per lap equivalent to 75 laps. The offside tyre showing a loss of 0.0082" per lap equivalent to 53 laps. Eight laps were run on slightly wet roads, and nine laps on dry roads. The tyre pressure at the end of practice on each day was 34-lbs. The rear tyres were started at a pressure of 31-lbs, and afterwards changed to 28-lbs. At the end of twelve laps the wear on the nearside was .0135" per lap, and on the offside 0.0138" per lap. Three laps were done on slightly wet roads, and with only 5 galls. of petrol in the tank. Five laps on the practice car were done with insufficient shock absorbers, the result being very bad heel and toe or wavy wear. This made the tyres very difficult to measure accurately. In 1935 during practice the wear on the front tyres, (5.50/19) was .012" per lap and on the rear tyres (6.50/19) it was 0.015" per lap. On the morning of the race the rain was very heavy, this condition lasted for the first 15 laps. After that the roads dried up very quickly, so that the tyres ran half the race very wet, and the other half dry. No stop was made during the race, and the average speed was 80.81 m.p.h. The fastest lap was 83.77 m.p.h. The offside tyres, both front and rear, wore down much faster than the nearside tyres, which is contrary to the wear in 1935. The figures are as follows:- Front. Rear: Wear per Laps till Wear per Laps till lap smooth. lap. smooth. Nearside. .00233" 183 .00486" 90 Offside. .00426" 100 .0067" 66 | ||