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).
Impact of gear ratios and tyre sizes on car performance.
| Identifier | ExFiles\Box 77\3\ scan0193 | |
| Date | 10th September 1920 | |
| R.R. 225A (100 T) (S.H 159, 11-8-20) G.{Mr Griffiths - Chief Accountant / Mr Gnapp} 2800 Contd. -3- EP{G. Eric Platford - Chief Quality Engineer}2/F10.9.20. 4. Our tests show the gear ratio to be a very important item in this respect. In our comparative tests of a pre-war and post-war car which give the same performances under the same conditions, there was a marked difference if one has 135 mm standard tyres and the other oversize tyres on rear wheels, either car showing an advantage in hill climbing and acceleration at slow engine speeds if fitted with the smaller tyres. The advantage of a car fitted with a low geared axle was the more marked. 5. It is surprising to note with excellent low speed torque on our early model pre-war engines, i.e. those fitted with smaller carburetters and induction pipes. To accomodate such customers as explained above, we may have to fix our latest extra ring pistons and 15 tooth axle, but the low geared axles arenot yet in production. In the case of Mr. Hanbury's car, I do not think this is a question of ordinary tuning up, as I know that Mr. Hanbury is sufficiently in touch with us to make the best of such information. (He also has a good mechanic in Henning). I feel that this would be a very good car to deal with as above suggested, and we have for some time been anxiously expecting it at the works to give some attention in this respect, as we understand from Sales Dept. that the car was not very satisfactory as regards power, although records of this on the dynamometer were fairly favourably comparatively. MADE IN ROLLS-ROYCE EP.{G. Eric Platford - Chief Quality Engineer} | ||