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).
Decisions on wheel size, rim type, and tire section, with comparative data.
| Identifier | ExFiles\Box 19\3\ Scan412 | |
| Date | 28th May 1930 | |
| Oyl/DM.{D. Munro}28.5.30 -2- We have to decide:- (1) Wheel size:- My impression at leaving was that we had to find ways of using the 19". What does Cadillac 16 use? (2) Rim type:- English Dunlop and proposed American standards on the well-base rim are being brought in line. Collyer has all this at his finger tips. (3) Tire section:- Mr. Collyer can show you sections of the various tires including, probably, the latest Fort Dunlop and may be able to recommend suitable types of casing to overcome the troubles of joggle and heavy steering. This does not necessarily mean tying ourselves up to American Dunlop tires, but I think we should try them with other types. Comparative sizes are as follows, from measurements here :- 19 x 7 U.S. Royal Cord. 20 x 7 Fort Dunlop. Well-base. Max. width tire section - S.S. 6.9 6.93 Lemon says - 6.98 Tread width - 4.6 Unloaded circumference at 35 lbs. 104.625 107.5 Corresponding dia. (Lemon 33.3) 33.4 34.2 Effective running circumference at 35 lbs (approx. 1500 lbs load) 98.125 102.5 Corresponding dia. 31.3 32.7 Wheel revs/ mile. 646 618 Weight of Dunlop wire wheel. 39.125 # 37 # " " cover. (Lemon 34.67) 33.681 41 " " tube. (Lemon 5.12) 3.5 4.875 " " band. (Lemon .89) 1.0 Total wheel and tire at 35 lbs. 78.75 83 oy. Maurice Olley | ||