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 of horsepower loss and rolling resistance for different tire sizes and inflation pressures.
| Identifier | ExFiles\Box 160\2\ scan0012 | |
| Date | 28th March 1923 guessed | |
| Oy2-W-32823 -2- 1 - (Continued) Horsepower loss: 10 m.p.h. - 1.52 H.P. 20 " - 3.04 " 40 " - 6.08 " 60 " - 9.12 " 2 - 80 lbs. in front and rear tires Total tire resistance - ~~50.8~~ ~~40.8~~ lbs. Horsepower loss: 10 m.p.h. - ~~1.09~~ H.P. / 1.3~~7~~55 20 " - ~~2.18~~ " 2.7~~1~~ 40 " - ~~4.36~~ " 5.42 60 " - ~~6.54~~ " 8.13 3 - 40 lbs. front and rear (as used in new 32x6 tires) Total tire resistance - 66.8 lbs. Horsepower loss: 10 m.p.h. - 1.78 H.P. 20 " - 3.56 " 40 " - 7.12 " 60 " -10.68 " Increase over 33x5 with standard inflation pressure is 10 m.p.h. - .26 H.P. 20 " - .52 " 40 " - 1.04 " 60 " - 1.56 " These are 32x6 tires of standard wall thickness (4ply cord). With the newer tires which have only 2 plies of cord, which is found to be sufficient to withstand the reduced pressures, the rolling resistances are probably less than the 33x5 at standard pressures. This bears out the statements of the Yellow Cab Company who have standardized the new big tires on the score of fuel economy. Oy. M.{Mr Moon / Mr Moore} Olley | ||