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).
Table comparing tyre specifications for load and pressure for various makes.
| Identifier | ExFiles\Box 39\2\ Scan142 | |
| Date | 1st May 1922 | |
| 1st. May 1922. MAKE OF TYRE SIZE LOAD PER WHEEL IN LBS. PRESSURE [] " IN LBS. MICHELIN Old list dated October 1/21. 120 m/m or 4 1/2" 1,120 60 MICHELIN New list, also dated Oct. 1/21, but revised 20/3/22. 120 m/m or 4 1/2" 1,120 896 50 45 DUNLOP list dated Oct. 1/21. 120 m/m Beaded Edge Cord or 4 1/2" Straight Side Cord 850 1,200 60 70 PALMER CORD 120 m/m 1,120 1,008 896 70 63 56 Note. Palmer 1,120 lbs. load " " 70 lbs. Michelin " " " " 50 lbs. Dunlop " " " " 65 lbs. Dunlop permissible variation is 5 lbs. [] " in pressure for every 75 lbs. variation in load, but minimum pressure permitted irrespective of load is 55 lbs. Michelin minimum pressure is 45 lbs. for wheel load of 896 lbs. Palmer minimum pressure is 42 lbs. for wheel load of 672 lbs. Note. There are two Michelin Lists in existence, both dated October 1st/21, but a revised list was issued at the end of March, which can be distinguished by the figures 20/3/22 appearing in the bottom left-hand corner of the last page. ---------- | ||