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).
Letter from Vauxhall Motors discussing tyre pressure limits and typical tyre sizes for American passenger cars.
| Identifier | ExFiles\Box 170\3\ img183 | |
| Date | 3rd January 1939 | |
| oy. Vauxhall Motors Ltd CONTRACTORS TO THE ADMIRALTY, WAR OFFICE & AIR MINISTRY. TELEPHONE NUMBER 2600 LUTON LUTON. BEDS. TELEGRAMS CARVAUX, TELEX, LUTON WHEN REPLYING PLEASE QUOTE → OUR REF 289/MO/HMD. YOUR REF Rm{William Robotham - Chief Engineer}/Gry.{Shadwell Grylls}10/MH.{M. Huckerby} 3rd January 1939. Mr. S.W.Grylls. Rolls Royce Ltd., DERBY. Dear Grylls, Yours of December 22nd. Limit pressure on 4 ply tyres is based on the chances of blow out on long runs in hot weather. Actually the 28 lb. inflation limit on 4 ply tyres is not strictly adhered to and 4 ply rear tyres are frequently inflated to 30 and 32 lbs. cold. For an axle load of 1150 lbs. at the rear with three passengers, I should use a 6½" - 16" four ply tyre at 32 lb, allowing slight overload, if I wanted to save weight or money, or a 7" - 16" four ply tyre at 27 lbs for maximum comfort. In actual practice American passenger car tyres are :- 5½ - 16 4 ply for smallest cars. 6 - 16 " for Chev.Master, Ford, small Pontiac, etc., 6½ - 16 " for the smaller eights and larger sixes. 7 - 15 or 7 - 16 " for the "upper medium" cars and some "lower medium" 7½ - 16 6 ply for the "mammoths" 8¼ - 16 " for super-mammoths like Packard 12. These tyres are available all over the world, which is a strong argument for using them. | ||