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).
Pros and cons of different balloon tyre and rim sizes for the 20HP model.
| Identifier | ExFiles\Box 53\3\ Scan108 | |
| Date | 11th July 1928 | |
| [Handwritten top left] V4565 [Handwritten annotation] Actually 6" tyres on 21" rims only raise the car .35" delete gear ratio 2/8% BY.{R.W. Bailey - Chief Engineer}) FROM DA{Bernard Day - Chassis Design}/EV.{Ivan Evernden - coachwork} HS.{Lord Ernest Hives - Chair}) sc.) C. to R.{Sir Henry Royce} BY re. BALLOON TYRES FOR 20HP. It will be recalled that 33 X 6 tyres on 21" rims have been standardised for the 20HP., and that Mr. Royce has asked us to get 6" tyres on as standard as soon as possible. The objection we have to these over the present medium pressure 5¼" tyres on 21" rims is that they are actually 1.200 larger in dia., and raise the car .500". Both of these features are very undesirable. Moreover extensive modifications are required to get the wheel on the rear carrier, and a new axle ratio is called for to maintain our present performance, both of which changes will not be required on India 3. In BY2/G5728., you tell us of a 6" tyre on a 20" rim, overall dia. 32", [text 'which is practically the same as' is struck through] our present 5¼" tyre on 21" rims. We agree that these tyres would admirably fill the gap until India 3., as they can be adopted with the minimum of changes. Would BY.{R.W. Bailey - Chief Engineer} please obtain for us a drawing or a sketch of these rims and tyres, and find out about supplies; and [handwritten 'we' inserted] suggest that HS.{Lord Ernest Hives - Chair} fits a set to an experimental car. We presume there is no serious disadvantage in going to 20" rims for a time, and then on to 19" on India 3. Should R.{Sir Henry Royce} not agree with any of these remarks will he kindly correct them. DA{Bernard Day - Chassis Design}/EV.{Ivan Evernden - coachwork} | ||