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).
Coefficient of friction for different tyre types and resistance to skidding on various wet road surfaces.
| Identifier | ExFiles\Box 158\1\ scan0084 | |
| Date | 29th October 1935 guessed | |
| -2- (5) An increase of about 15% in coefficient was observed for low pressure balloon tyres compared with standard balloon tyres with contact areas only 60% as large. This increase substantiates the theory that the total frictional resistance of tyres on roads is the sum of the true frictional resistance and the mechanical resistance, the latter increasing with contact area. (6) A fairly definite increase in coefficient of friction was observed with decrease in temperature. (7) The relative resistance to skidding for wet surfaces, beginning with the highest, was as follows:- High type asphaltic pavements, tar macadams, asphalt retread and oiled gravel, untreated gravel, Portland cement concrete, mineral-surfaced asphalt plank, brick, asphalt penetration macadam with soft seal coat, fine aggregate type asphalt plank, steel traffic plates, hard wood plank, mud on concrete or other hard surfaces, and snow, sleet, and ice covered surfaces. C.G.W. | ||