A pioneer of radial-ply tyres, famous for its flexible steel casing “the supple secrets of X”—the Michelin X tyre has been widely copied and remains a very popular cover for those who put road-clinging and longevity high on their list of tyre priorities. The disadvantages of such radial-ply covers has been heavier steering, thump as they ride surface irregularities and, to those who drive very fast, the knowledge that the excellent road-clinging qualities may suddenly change to loss of adhesion at high “g” factors.
It is to supply a tyre as good as their famous “X” with none of these disadvantages that Michelin, so soon after the introduction of their elaborate “XAS” tyres, has brought out the Michelin ZX.
Introduced almost simultaneously in Italy and now the U.K., the “ZX” will gradually supplement the present “X” tyre in the complete car tyre range. As a start, eight sizes, which between them cover all the most popular vehicles on the British market, are being brought out. These are the 145-10, 155-12, 145-13, 155-13, 165-13, 145-14, 155-14. Other sizes will follow later this year. The tyres all carry the marking SR (e.g., 145 SR-10), signifying that they are suitable tor speeds up to 113 m.p.h.
The Michelin ZX has a completely new wider wrap-around tread pattern which offers over 15% more tread contact area than cross-ply tyres and up to 4% more than other standard radials. Its bracing plies are accordingly wider and these are made of a new, more flexible steel cord—”filament fine, supple as silk cords,” say Michelin. The new steel cord is, in fact, processed to an extremely fine tolerance, and Michelin claims that its resilience allied to the round-shoulded tread gives the “ZX” the ability to “ride the punch of uneven surfaces,” taking it smoothly over cats’ eyes, road joints, without transmitting road noise and uncomfortable “thrumps.”
The new, wider tread also has the effect of giving the tyre a more squat cross-section. In other words, it is a low profile radial—another feature adding to its road-holding ability. The tread pattern has been designed to wipe water from the tyre’s path.
Prices of the new “ZX”—which for the British market are all made at Michelin factories at Stoke-on-Trent and Belfast—remain almost the same as the present “X” equivalents.
The new tyre is for all normal cars, whereas the “XAS” is for speeds of up to 130 m.p.h. Michelin does not encourage racing on its tyres, but this is conservative Company policy, and in no way reflects lack of confidence in steel-cord plies. Indeed, we recall instances of cars being raced on Michelin X with very good results—ask George Abecassis, who ran an H.W.M. shod thus, in a Goodwood Nine-Hour Race some years back. At Brands Hatch last month Michelin introduced us to the “ZX” tyre. They had laid on various cars, such as Fords, Triumph 1300, Vauxhall Victor 2000 and Rover 2000TC for demonstration lappery, on standard tyre wear and then on “ZX”s at normal pressures. I drove a few laps in the Rover and found that sliding the corners was very predictable on the “ZX”s, that the noise level, both as squeal and thump, was low and the steering quite light at low speed. “ZX” should soon be as well-known and respected in the tyre world as the World-renowned “X”—W. B.