Tuesday, April 24, 2012

Radials and cross-plies in racing

"The higher mileage and better handling of a radial tyre does not come from a lower running temperature...Tyres are discarded when the treads are worn. If temperature were the culprit they would fail due to reversion of the carcass rubber [reversion is the process by which vulcanized rubber reverts back to its pre-vulcanized state] and/or loss of adhesion between textile [carcass] and rubber due to thermal degradation of the interface polymer. A radial tyre wears better because the tread is braced onto the road and does not squirm or distort as it does in a cross ply, whose tread is deflected by the movement of undertread plies as they move in concert with the total tyre reinforcement. Distortion in a radial tyre is almost wholly accommodated in the side walls. As a consequence of this, the tyre runs cooler.

"The road holding of a radial is superior, but once breakaway point is reached you lose adhesion very rapidly. Where controlled adhesion loss is required, as in a racing car tyre, then a cross ply tyre is used. This problem can be mitigated in a radial by fitting an asymetric tread, with progressive breakaway characteristics." (Nicholas M Doak, Rubber Journal. New Scientist 29 Jun 1972, p772).

Truly, the origins of the modern world can be found in the 1970s. However, Nicholas Doak's letter to New Scientist poses several important questions:

(1) If radial tyres suffer from a sudden loss of adhesion, then does the universal adoption of radial tyres in Formula 1 since 1983 explain why the cars are so rarely held in a controlled slide (Sebastien Vettel, Variante Ascari, Monza 2011 notwithstanding).

(2) How was Gilles Villeneuve able to hold his Michelin-shod Ferrari in so many controlled slides?

(3) Now that Formula 1 has a control tyre formula, why don't we introduce an asymmetric tread, or something similar, to make it easier for the drivers to slide the cars?


BarryDench said...

Would the advance of technology producing modern compounds need to be taken in consideration too? It is mooted that technology in F1 is the basis eventually for our road going vehicles.

I assume the greater adhesion of radials suits most domestic road traffic; not the least because we seldom reach the point where adhesion fails.

I am not sure I would want to drive on our roads with people power sliding all over the place!

Gordon McCabe said...

True Barry, although the Finnish experience suggests that it would generate a nation of excellent rally drivers.