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).
The requirements for fitting interchangeable tyres to a 20 HP chassis.
Identifier | ExFiles\Box 53\3\ Scan042 | |
Date | 25th March 1927 | |
W/S. (c): c. to Hs.{Lord Ernest Hives - Chair} X4565 BY6/G.25.3.27. [STAMP: RECEIVED MAY 26 1927] re FITTING INTERCHANGEABLE TYRES ON EXISTING STRAIGHT SIDED WIRE WHEELS - 20 HP. CHASSIS. ------------------------------------------ In regard to the proposal to allow customers to fit 33 x 5.77 Dunlop Interchangeable Balloon tyres on existing wire wheels with straight sided rims, in addition to the question of fitting R.R. shock dampers to the front axle, the following points will require attention :- 1/- Chassis up to 30 in Series F should have the left hand lock reduced from 41° to 35° to provide clearance between the larger tyre and the shock damper cylinder, also the right hand lock should be reduced from 36° to 32° to provide clearance between the larger tyre and the side steering tube. [Handwritten: O.K.] 2/- Chassis from 31 in F.{Mr Friese} series to 43 in J.{Mr Johnson W.M.} series should have the left hand lock reduced from 41° to 39° and the right hand lock reduced from 40° to 36°. 3/- The side spare wheel carriers will require altering to suit the larger diameter tyre. [Handwritten: O.K.] 4/- The coachwork clearance for the rear wheels should be increased, and the rear wings will require modifying, also the same will apply to the front wings. In addition to this, we believe that according to information received on several occasions from the Coachbuilding Dept. at London the existing size of tyres foul the front portion of the front mud wings when on maximum lock, therefore this foul will be considerably greater with the larger tyres now proposed. [Handwritten: O.K.] 5/- The existing rear spare wheel carriers will not be suitable for wheels with the larger tyres, as the whole of the wheel will require lifting which means that we shall have to make new rear carriers. Certain difficulties will arise if the wheel is carried in a higher position viz. the tyre will foul the hood when folded back, the tube of the carrier will possibly foul the coachwork, and the tyre will be practically touching the petrol tank and the rear cross member. [Handwritten: O.K.] | ||