ECONOMICAL SPEED.
[To the Editor of the SPECTATOR.]
SIR,—Referring to the letter and your footnote on the above subject in your current issue, I made a number of experiments some years ago which clearly established the fact that the higher the gear and the lower the speed the less the consump- tion of petrol for a given distance.
The following table gives a set of typical tests with a 15.9 h.p. car :— 12 15 20 25 — — — — is
- 27 _ _1111-P•g• 39 37 33.5 31
Each result is the mean of runs in opposite directions.
Whilst the air resistance is, no doubt, an important factor, I think that tyre friction is a still greater one, as the higher the speed the less will the power spent in compressing the tyre at the front side be compensated by the recovery of the tyre at the rear side. Experimental data are much needed as to both tyre road resistance and tyre adhesion.—I am, Sir, 1st gear (bottom) 2nd „ 3rd „
4th „ (top)
m.p.h. 5 11.25 • • • • • •
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