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).
The road holding performance of Michelin 'Pilot' tyres and wheels tested near Paris.
| Identifier | ExFiles\Box 146\1\ scan0223 | |
| Date | 30th March 1938 | |
| FJH{Fred J. Hardy - Chief Dev. Engineer} 1245. To Bentley Motors Ltd. Derby...........Rm.{William Robotham - Chief Engineer} Copy to .......... BKY{Millard Buckley - Publicity}- Levallois Sr.I/ET.30.3.38 A set of these are being sent over. Ref. MR. MICHELIN'S "PILOT" TYRES & WHEELS Rm{William Robotham - Chief Engineer} As you know, during a conversation I had with Mr. Marcel Michelin a short time back I was successful in persuading him to get his Experimental Department to build us up a set of 4 wheels upon which it would be possible to fit the best "Pilot" tyres for our purpose that they have so far produced. Obviously, these tyres are not correct in dimensions for a Bentley, neither are the wheels of the type that would ultimately be manufactured for Bentley purposes, but in any case I think we can be grateful to them for their effort as, having tried these tyres, there is no doubt that they constitute a solution to a number of our problems. The first impression one has when driving a car fitted with these tyres is, as one moves off, an impression of comfort and general "silkiness" at low speeds, especially over pavés, which we have so far never attained. This of course is obviously due to low poundages, the maximum poundage for a car such as my demonstrator being I Kgr.650 at the rear and I Kgr.400 in front. Admitting that, owing to the fact that Michelins gave us the best tyres they had for our job, which however were not the right ones, the centre of gravity was automatically lowered by over an inch, so that one naturally has to be careful not to hit things with the undershield. It must also be accepted that, at 4500 r.p.m., the maximum speed of the car seems to be approximately 80 m.p.h. Then, taking these points into consideration, we went out on the most circuitous road near Paris, which is the Vallée de Chevreuse, and here, with three people in the car (WHA., EWP.{Mr Punt} and myself), we put the car through its paces and I can assure you the results are nothing short of amazing. It is useless talking of road holding, as this seems to be 100% and one would like to say more. There is literally no limit to what one can do with the car on the road, in absolute security. On a very cambered road it was possible at maximum revs to take the car well down into the gutter and literally throw it back on to the crown of the road without any attempt at slackening speed or, at any time, getting the car to sway. It just goes where you put it and remains there. All ordinary bends on the French national roads, at the speeds attainable with these small wheels, seemed to be no bends at all; to such an extent that the passenger in the back seat | ||