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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).
Rear wheel carrier modifications to accommodate different tyre sizes and the impact on coachwork.

Identifier  ExFiles\Box 13\5\  Spare05-page076
Date  12th October 1929
  
X7600

BY.{R.W. Bailey - Chief Engineer} FROM DA{Bernard Day - Chassis Design}/EV.{Ivan Evernden - coachwork}

DA{Bernard Day - Chassis Design}/EV{Ivan Evernden - coachwork}4/M10.12.29.

C. to - SG.{Arthur F. Sidgreaves - MD}
C.
HS.{Lord Ernest Hives - Chair}

P. 2. REAR WHEEL CARRIERS.

X.7830.
X.7600.

While we retain the 21" rims it would appear as though we must raise the rear wheel in order to permit of India, and Goodyear, or Dunlop, tyres of 7" section being fitted to all cars we produce, as soon as possible.

Even should 7" section tyres not be ordered at first they will certainly be fitted subsequently in many cases. In order to cater for this, and for spare wheel covers, we agree to raise the centre from 7.250 to 8.750 above the level top of the frame.

Since this may affect the coachwork of maximum bodies we think that the coachbuilders should give ample notice of the change.

What happens about the increased width of section? Ought we not to move the wheel forward to cater for 7" section, or is there enough room already. From our reading of the drawings it does not appear to be so.

We are testing, and hope to standardise, the Dunlop Reinforced Silent Tread of 7" on a 20" rim, in which case we can cater for the corresponding India and Goodyear covers by dropping the centre of the wheel down to 7.750 above the centre line of the chassis frame. This is shewn on N. scheme 2993. - the experimental Pullman limousine.

We would be glad if Derby would set out the carrier as indicated on this drawing, and also the dual carrier.

DA{Bernard Day - Chassis Design}/EV.{Ivan Evernden - coachwork}
  
  


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