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 the India Tyre & Rubber Company discussing the weight difference between Bentley and Terraplane wheels and tyres.
| Identifier | ExFiles\Box 30\5\ Scan047 | |
| Date | 21th March 1935 | |
| 44462 HEAD OFFICE AND FACTORY: INCHINNAN, RENFREWSHIRE INDIA TYRE & RUBBER COMPANY LTD. MILEAGE DEPARTMENT (AREA "B") 80 CLAPHAM ROAD LONDON, S.W.9 TELEPHONES : RELIANCE 2662/3 OUR REF. R/WBTA YOUR REF. 21st March, 1935. W.A. ROBOTHAM, ESQ., Experimental Department, Messrs. Rolls-Royce Ltd., D E R B Y. Dear Robotham, Mr. Worth has sent me a copy of his letter to you dated 19th March, which I think has given the information which you wanted. I remember your telling me that the difference in weight between five Bentley wheels and tyres and five Terraplane wheels and tyres was ½-cwt. (i.e. 56 lbs.), and in this connection I would like to draw your attention to the fact that Terraplanes are equipped with 6.00-16 4 ply tyres, whereas you will note that Mr. Worth, in his letter, recommends a 6 ply tyre. We manufacture 6.00-16 Aero Cushion and 6.50-16 Aero Cushion in both 4 ply and 6 ply, but we would recommend 6 ply as the most suitable on the Bentley. The difference in weight between the 4 ply and the 6 ply is approximately 2 to 3 lbs. I also think you would find that there is quite a difference in weight between the Bentley hub and the Terraplane hub; also between the Bentley wire wheels and the Terraplane semi-spoked steel wheels, as well as in the Bentley rims, which, I believe, are flanged, while the Terraplane are American unflanged rims. I believe I should be right in saying that the difference in the weight of spokes and rim (excluding the hub) for a 3.25 D wheel (as at present fitted to the Bentley) and a 4.00 D wheel of the same type, which would be suitable for a 6.00-16 Aero Cushion tyre, is about a quarter of a pound. Therefore, I would suggest that the difference in weight you mentioned to me between the five wheels and tyres (Bentley and Terraplane) would be partly accounted for by the fact that the tyres were 4 ply tyres and not 6/ | ||