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 Rapson Tyre & Jack Coy. Ltd. regarding steering-wobble issues due to tyre pressure differences.
| Identifier | ExFiles\Box 28\4\ Scan224 | |
| Date | 27th December 1924 | |
| Telephone - MALDEN 190,191 & 192. Telegrams - RAPSONIO, NEW MALDEN,SURREY. COPY. RAPSON TYRE & JACK COY. LTD. NEW MALDEN, SURREY. Your Ref: BJ6/H231224 Our Ref: FLR/DLM. 27th. December, 1924. Messrs. Rolls-Royce, Limited, DERBY. Dear Sir, For attention of Basil Johnson, Esq., General Manager. With reference to your letter of the 23rd. instant, for which I beg to thank you, you evidently wrote this before receiving my second letter in which I informed you that the steering-wobble troubles caused by Rapson tyres to H.R.H. The Prince of Wales' new Rolls-Royce car had been satisfactorily solved. I agree with all you say as to the different effect produced on different cars by different makes of tyres. With the Prince's car I traced the trouble as being chiefly due to the difference in pressures between the Rapson Oversize tyre and the Dunlop standard size tyre. As you are probably aware, we recommend lower pressures for our Oversize tyres than other manufacturers do for their standard size tyres and the difference between the Rapson and the Dunlop tyres tested on the Prince's car in the first instance was 12 lbs., the Dunlop's being inflated to 52 lbs per square inch and the Rapson's to 40 lbs. per square inch. You will appreciate that a tyre depends a great deal on air pressure for its stability and the harder it is pumped, the less chance there is of it rolling from the beads. The 33 x 5 straight side tyre which you standardise on your 40-50 H.P. model fits the 32 x 4½ rim and is therefore, oversize. We have two sizes of Oversize tyres to fit this same rim, the actual measurements of these being 35½ x 6 and 34 x 5½. On discovering that the steering-wobble on the Prince's car was being caused due to the considerable difference in the inflation pressures between the Rapson and the Dunlop, I decided to fit the smaller size tyre of the two we manufacture and inflated this to 50 lbs per square inch. These tyres were tested at maximum speeds on the road and track, the results in both instances being perfect, | ||