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).
Performance report on 'Rapson' tyres fitted to vehicle 98 NK, detailing noise, riding qualities, and pressure loss.
| Identifier | ExFiles\Box 39\1\ Scan108 | |
| Date | 13th June 1924 | |
| X1238 Chateauroux, Indre. France. June 13th, 1924. "HS{Lord Ernest Hives - Chair}". DERBY. "Rapson" tyres fitted on 98 NK. NOISE. Tyres make very little noise. They are considerably quieter than "Dunlops", especially on pavé. RIDING QUALITIES. These tyres seem to ride considerably harder than "Dunlops", although the same tyre pressure is used, viz. 40 lbs. front and 45 lbs. rear. The rubber used for the covers appears to be very hard. This combined with an inadequate tread produces very poor road gripping qualities. On a wet macadam road, it is almost impossible to drive the car at a speed over 45 m.p.h., owing to rear wheel skids and side slip, even when not braking. When the first tread is almost worn away, the rubber that fills up the annular grooves in the second tread comes loose, and in rotating with the wheel comes in contact with the mud wings, and makes a terrible noise. We have stopped the car and detached pieces of rubber as much as 4 feet long from the tyre. LOSS OF PRESSURE. Loss of pressure in these tyres is almost negligeable. N°7 (O.S.R.) lost 5 lbs/sq. in. after 2310 miles. N°2 (O.S.F.) lost 3 lbs/sq. in. after 1596 miles. N°5 (N.S.R.) lost 2 lbs/sq. in. after 1631 miles. N°1 (N.S.F.) has lost none up to 2476 miles. Average speed during tests approx. 36 m.p.h. A.J.LIDSEY. | ||