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 problems with twin wheels on armoured cars and the decision to fit alternative tyres.
| Identifier | Morton\M5\ img004 | |
| Date | 7th October 1920 | |
| To R from DA.{Bernard Day - Chassis Design} Copy to CI. Copy to EM. Copy to HJS. Copy to EFC. Copy to R.R. incorporated U.S.A. X.41098 RECEIVED OCT 7 1920 DA{Bernard Day - Chassis Design}2/CB5-10-20. ---------- X.4195 Re Armoured Cars. ---------------- In reply to your R1/C30-9-20, the tyres fitted to the armoured cars during the war were 880X120 twins on the back wheels, and 895X135 on the front. There were a few cars sent to India which were fitted with N.A.P. Semi-solid tyres. The twin wheels were not a complete success, and as a result of experience of some thousands of cars of all sorts fitted with these wheels, Col. Hutchinson had come to the conclusion that the wheels were not so reliable as single wheels, and they got no better service out of the tyres. The reason for the unreliability of the wheels appeared to be that it was impossible to prevent one of the pair of twin wheels taking all the load, owing to the irregular road surface. The principal reason for the failure of the tyres was that stones got between the twin tyres and ultimately wore their way through the covers. As we have previously explained, it is not intended to go on with the 955X155 Michelin tyres, as they cannot be obtained with sufficient certainty, and it amounts to the Government tying themselves to the Michelin Company, as no one else's tyres will fit these wheels. It is intended to fit 895X150 Palmers. DA.{Bernard Day - Chassis Design} R.{Sir Henry Royce} R.{Sir Henry Royce} 285A (100) (T) (S. G.{Mr Griffiths - Chief Accountant / Mr Gnapp} 648. 19-2-20) G.{Mr Griffiths - Chief Accountant / Mr Gnapp} 2618 | ||