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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).
Tyre pressure tests and an explanation of steering wobble issues on Chassis 9 G.III.

Identifier  ExFiles\Box 4\9\  09-page092
Date  24th August 1925
  
X5840

Hotel de France,
Chateauroux,
Indre. France.

To: "HS{Lord Ernest Hives - Chair}"
From: G.W.Hancock.

--------------------------

Chassis 9 G.III.

We have received your letter of the 22nd inst., and have noted the comments therein.

All our tests were carried out with standard "Dunlop" tyres. The pressures were - front 40 lbs. per square inch, rear 45 lbs. per square inch. We had them, for one week only, 45 lbs. front and 55 lbs. per sq. inch rear, but we dropped them again because of the hot weather. Actually, these pressures, after the car has run a few miles, would be 45 lbs. front, and 50 lbs. per sq. inch rear. We have always checked our tyre pressures carefully, and we do not run tyres after shewing the canvas. This is for safety. We have not, at any time, run with high pressure tyres for any time, only in our experimental tests, which were given together with the reports. We have full records of all tyres used during the test of 93 HK{Col. T. Harker - Sales} over here. These, if you wish them, can be despatched immediately.

Our explanation of the steering wobbles developing up on 93 HK{Col. T. Harker - Sales} was that we received tyres and tubes which were afterwards found to be very much out of balance - tubes long valve type, and our variation of results of tests was due to the quick wear of front tyres, which meant the continual changing of same, which before it was noticed we had one day tyres practically balanced, and another day they would be very much out of balance. We got to the bottom of this trouble, and drilled our wheels so that we could balance all tyres up, after which the wobbles were almost extinct - as our reports shew towards the end of the test. Our experimental tests prove to us that with higher tyre pressures the wobbles were almost negligible, but what we did complain of with higher pressures was that it made the steering more unstable, i.e. a pot-hole would cause the car to dive very easily across the road, the steering feeling very light.

We are at present running the Goshawk car with the tyre pressures - 40 lbs. front, and 45 lbs. rear. Will you please let us know whether you require these altered.

G.W.Hancock,
  
  


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