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).
Data sheet and recommendations for 'Speed Special' and 'Super Special' tyres for use in India.
| Identifier | ExFiles\Box 29\4\ Scan256 | |
| Date | 18th December 1934 guessed | |
| 4662 DATA FOR INDIA "SPEED SPECIAL" & "SUPER SPECIAL" TYRES. Size: | Type: | Rim: | Weight in lbs. Cover | Tube. | X Section Inflated. | Eff. Radius. | O.D. Inflated | Rolling Radius --- | --- | --- | --- | --- | --- | --- | --- | --- 5.50-18 | Speed Special | 3.25-18 | 26.5 | 3.09 | 6.09" | 14.12" | 30.28" | 14.4" 6.00-18 | Super Special | 3.25-18 | 29.1 | 4.34 | 6.32" | 14.38" | 30.76" | 14.64" 5.50-19 | " " | 3.25-19 | 27.5 | 4.04 | 6.07" | 14.65" | 31.36" | 14.94" 6.00-19 | " " | 3.62-19 | 30.44 | 4.53 | 6.51" | 14.92" | 32.00" | 15.22" 6.00-20 | " " | 3.62-20 | 31.86 | 4.71 | 6.51" | 15.42" | 33.00" | 15.73" The 6.00-18 "SUPER SPECIAL" was designed to fit the 3.25 rim, which is the same rim as is used for the 5.50-18 "SPEED SPECIAL". If a 6.00-18 tyre were used there would be no need, therefore, to change the rim. In this case, however, the clearance would only be increased .20". We think that probably the most suitable tyre to fit would be the 6.00-19 mounted on the 3.62 rim, which would raise the car .77". If a still greater increase of clearance was required it would be possible to fit 6.00-20, which would increase the clearance 1.27". If a 6.00 section were used, we suggest that the pressures should be 33 lbs. in the front and 28 lbs. in the rear. However, when these tyres are fitted it may be found that slight adjustment in these pressures are required one way or the other. We would not care to recommend pressures much below 28 lbs. as the cars are to be used Overseas, and there is, therefore, a good possibility of abuse due to poor roads and heavy loading with touring equipment. MAXIMUM CARRYING CAPACITY OF 5.50 SECTION ... 11-cwts. PER TYRE " " " " 6.00 " ... 13-cwts. PER TYRE | ||