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 discrepancies between Tyre & Rim Association and S.M.M.T. tyre loading charts.
| Identifier | ExFiles\Box 170\3\ img174 | |
| Date | 7th December 1938 | |
| Vauxhall Motors Ltd CONTRACTORS TO THE ADMIRALTY, WAR OFFICE & AIR MINISTRY. LUTON. BEDS. TELEPHONE NUMBER 3100 LUTON TELEGRAMS CARVAUX. TELEX. LUTON WHEN REPLYING PLEASE QUOTE OUR REF. 289/MO/RMD. YOUR REF. Handwritten notes: Oy. GRY{Shadwell Grylls} F.{Mr Friese} P. Wagoy We should pass the information about K ply types to Troup & Rims Typed letter: 7th December 1938. Mr. S.W. Grylls. Rolls Royce Ltd., DERBY. Dear Grylls, Yours of December 3rd. I attach Tyre & Rim Association's official loading chart for 16" tyres, and just for comparison the S.M.M.T. corresponding chart which is a commercially inspired affair designed to meet Michelin competition rather than to represent any actual facts. We have thrown the S.M.M.T. chart overboard and have urged various members of the British Tyre Industry to destroy it, since it leads to overloading of rear tyres, bad handling etc. The Tyre & Rim chart states that the load capacity of the average 16" tyre increases about 22 lbs. per lb. of inflation. The S.M.M.T. chart gives an average of over 30 lbs. per lb. of inflation. Obviously they cannot both be right, even allowing for the fact that the S.M.M.T. is based on "full load" (whatever that may be) and the Tyre & Rim chart on 3 passenger load, defined as 150 lbs. on front tyres and 300 lbs. on rear. The Tyre & Rim chart is based on a normal loaded deflection of 13½% of the carcass section, which means the actual transverse measurement of the tyre at the inflation specified. | ||