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).
Comparison table of different front road spring types and their test specifications.
| Identifier | ExFiles\Box 43\2\ Scan244 | |
| Date | 29th March 1928 guessed | |
| FRONT ROAD SPRINGS. TYPE. | Loaded lbs. | Loaded camber. | Initial camber after test. | Centres. | No.of leaves. | Type of clips. | lbs. Bulk weight ---|---|---|---|---|---|---|--- Actual American 1100 lbs.(A8546) | 1,170 | .500 neg. | 3 21/32" | 43 1/2" | 14 | American 'D' | 41 1/4 Made to instructions on American sheets. 1100 lbs(Silico Manganese.) | 1351 | .500 " | 4 3/32" | 43 1/2" | 14 | " | 42 1/4 Made to T.F.& S design. 1100 lbs. Silico Manganese. | 1100 | .500 " | 3 5/16" | 43 1/2" | [text crossed out] 14 | N.sch. 2406 | 40 3/4 A.{Mr Adams} 8546. Chinese pattern. | 1155 | .500 " | 3 5/8" | 43 1/2 | | | Note : All springs have been polished. | ||