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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).
Various tyre types and their dimensions for the 20 HP chassis.

Identifier  ExFiles\Box 106\4\  scan0099
Date  31th August 1928
  
X5810

Hs{Lord Ernest Hives - Chair}/AJL. 31.8.28.

20 HP. WHEELS AND TYRES. X5820

The appended table gives the more important dimensions of tyre types which have been used or are being used on the 20 HP. chassis.

The first on the list is the tyre and wheeel very recently standardised, the second is a stronger and reinforced edition of the first; in strengthening up this tyre a very considerable change in dimensions and weight has been made, viz: it is much larger in diameter, wider in section and heavier.

If these tyres are permitted to be used, all of the [strikethrough]advantages[/strikethrough] to be gained by standardising the 32 x 6" tyre, with the exception of increased riding comfort, will be lost - viz: instead of lowering the chassis .100" it will be raised .275", top gear ratio will be higher, a total increase in weight of 30 lbs. per chassis and very extensive alterations to spare wheel carrier, luggage grid and incidentally to the petrol tank will be necessary.

The third tyre on the list is the std. 5¼" tyre on 21" rims, the fourth is a reinforced edition of the above.

The 32 x 6" tyre on 21" rim has been run experimentally but not standardised.

hs{Lord Ernest Hives - Chair}/A.J.Lidsey.
  
  


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