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).
Letter detailing the results of tire trials, focusing on tread widths and their effect on steering performance.
| Identifier | ExFiles\Box 42\5\ Scan045 | |
| Date | 25th May 1927 | |
| X3895 Oy1-E-52527 RECEIVED JUN 11 1927 May 25th, 1927. Mr. R.{Sir Henry Royce} W. H.{Arthur M. Hanbury - Head Complaints} Bailey, Rolls-Royce, Ltd., Derby, England. (Copy for attention Mr. Hives " " Mr. Haldenby) Dear Mr. Bailey: Re Tires We have recently called for a width of tread on the ribbed front tires (U.S., Fisk and American Dunlop - on trials car) of 4-1/2" maximum. Actually the treads vary between 4-3/8" and 4-1/2". This was a result of conferences with tire makers and actual test of ribbed tires with treads of this width. It is approximately the tread width of the 5" U.S. ribbed tires formerly used. The original 5-3/4" U.S. ribbed tires have a tread width of 5-1/2". These have given excellent results on three or four hundred Silver Ghost cars with the "two start" steering, but necessitated hardening all worms to prevent squeaks and sticking due to the greater effort required to steer the cars at low speed. The 5-1/2" tread tires did not prove satisfactory however with the 1.8" pitch dia. Phantom steering gear, and we find the 4-1/2" tread is superior both as regards ease of parking and freedom from "joggles" on the road. This agrees with Mr. Hives' findings I believe. The new ribbed tires for the front wheels have therefore 4-3/8" to 4-1/2" tread-width with four or five ribs, according to the maker. The maximum mileage to date has been 16,000 miles on the front wheels of the local demonstration car, on a set of Fisk 33x6-3/4" tires with 4-1/2" tread. Yours very truly, Maurice Olley | ||