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 Dunlop providing tyre rolling radii data for various sizes.
| Identifier | ExFiles\Box 157\3\ scan0121 | |
| Date | 16th January 1940 | |
| 1332 DUNLOP RUBBER CO.,LTD. TELEGRAPHIC ADDRESS: "DUNLOPS, PHONE, BIRMINGHAM" TELEPHONE: ERDINGTON 2121 (P.B.X) EXTENSION No. 394. YOUR REF: Rm{William Robotham - Chief Engineer}/FJH.{Fred J. Hardy - Chief Dev. Engineer}2/EA. OUR REF: JAD/HM.{Capt. W. Hallam - Head Repairs} Car Manufacturers' Divn. FORT DUNLOP ERDINGTON BIRMINGHAM 24 Messrs. Rolls-Royce, Ltd., DERBY. 16th January, 1940. Dear Sirs, With further reference to your letter of the 9th January, we give below figures representing the rolling radii of the various tyres enumerated and would confirm that in each case these apply to the Fort construction. It should be explained that the figures quoted obtain when the tyre is inflated cold to the correct pressure for the imposed load and when it has reached its normal running temperature. Provided these two conditions are operative, figures may be regarded as accurate to plus or minus 1% at 30 m.p.h. For higher speeds the rolling radius will increase slightly, and if closer accuracy is required for speedometer calibration, you may wish to consider taking actual measurements under running conditions. Size. Rolling Radius. 6.00-16 on 4.00 rim 13.55" 6.00-16 on 4.50 rim 13.55" 6.50-16 on 4.50 rim 13.90" 6.50-16 on 5.00 rim 13.90" 7.00-16 on 5.00 rim 14.35" 7.50-16 on 5.00 rim 14.75" As requested, a copy of our Tyre Data Card, reference SC3/5S, is enclosed. Yours faithfully, For DUNLOP RUBBER COMPANY, LTD. Encl: | ||