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 Avon India Rubber Co. Ltd. discussing tyre tread pattern modifications, mould production, and testing.
| Identifier | ExFiles\Box 156\3\ scan0137 | |
| Date | 12th May 1939 | |
| 1331 ESTABLISHED 1885 [AVON Logo] SYMBOLS OF ENDURANCE CHAIRMAN MAJOR R.F. FULLER, J.P. DEPUTY CHAIRMAN SIR HERBERT E.{Mr Elliott - Chief Engineer} BLAIN, C.B.E., M.INST.T. JOINT GENERAL MANAGERS R.H. COMLEY. O.F. SWANBOROUGH. SECRETARY & ACCOUNTANT E.H. LOVELL, A.C.I.S. The AVON INDIA RUBBER CO. Ltd. SERVICE DEPOTS, LONDON-BIRMINGHAM BRISTOL-MANCHESTER NEWCASTLE-GLASGOW BELFAST. Telegrams RUBBER, MELKSHAM. Telephone MELKSHAM 120 (6 Lines). Codes A.B.C. 5TH EDN, WESTERN UNION, BENTLEY'S & M's PRIVATE CODE. LONDON OFFICE, MABLEDON PLACE, ST.{Capt. P. R. Strong} PANCRAS, LONDON, W.C.1. HEAD OFFICE & WORKS, MELKSHAM, WILTS. JGM/NAW. 12th May, 1939. Rolls Royce Ltd., DERBY. For the attention of:- Mr. S.H. Grylls. [Handwritten initials 'A.H.' are written across the line above] Dear Sirs, We thank you for your letter of 9th May. We regret that owing to the absence of the undersigned this has not been answered sooner. When we widened the grooves in our new pattern, a number of other changes had to be made at the same time. If we had only increased groove widths the studs in the centre portion of the tread would have become too flimsy and rapid tread wear might have followed. Moreover, the increased distance between studs removed a certain amount of mutual support. We had therefore simultaneously with widening grooves to widen each stud in the centre portion; then in order to maintain pitch length which we felt was of some importance in relation to noise we had to reduce the number of studs in each group from five to four. At the same time we did fear that the new pattern might despite our precautions be rather more liable to wear of the type you have described. We have ordered one extra 6.50/16 mould to take care of your requirements. The mould maker has not yet received his castings so that if it is considered advisable to revert to the original five-stud narrow groove design, or to adopt some compromise between the two for your cars only, we still have time. Before giving a conclusive opinion on this point, however, we would like you to send us two tyres, one representative of the type of wear given by the newest mould and the other representative of the original five-stud design. Unless the difference between those two tyres is very marked we would be inclined to stay with the present pattern because the tendency to pick up stones which was demonstrated by the original five-stud narrow groove design during the severe weather last Christmas was very marked. When, however, we have examined the tyres you will send us we will be able to give a more definite statement on this point. | ||