Race Circuit Surfacing
The January issue of The Queen’s Highway, official journal of the Asphalte Roads Association, contained an article by Ian Dussek, who raced an H.R.G., on the surfacing of modern race circuits. Rigid construction, as at Brooklands, Avus and Montlhéry, says the author, has given way to circuits such as Goodwood, Silverstone and Zandvoort that are asphalt surfaced. Monza banked circuit is an exception and has been boycotted by drivers, and Avus is not in favour, although more asphalting is scheduled there this year.
Goodwood is claimed to have probably the finest surface in Europe, but at the Nürburgring there have been complaints of glare aggravated from coming off glare-free asphalt onto concrete.
In 1961 Dunlop carried out tests before Goodwood was resurfaced, repeating them on the new surface the following year. They found that an F1 Cooper, lapping at approx. 103 m.p.h. in the dry, 90 m.p.h. in the wet, wore Dunlop D9s at the rate of 53 miles per mm. in practice and at 45-50 miles per mm. under racing conditions. The repeat test was done on Dunlop D12 tyres, which gave 50 miles per mm. and 80 miles per mm., respectively and as this tyre wears inure rapidly than the D9, the latter, on the new surface, should give a 100% improvement in respect of tread wear. The case of Moss in a sports Ferrari is quoted, tread wear being 13 racing miles per mm. at Easter 1962, compared to 11 in August 1961. It has been found by Road Research Laboratory methods that, at Goodwood, skid resistance figures of 0.69 to 0.78 (average 0.74) have been obtained at Madgwick Corner where there is slight rubber deposit from the cars, and, at Fordwater, 0:82 to 0.89 (average 0.85) where cars are not depositing rubber. At Silverstone, Woodcote Corner shows 0.66 to 0.73 where there are heavy deposits of rubber and 0.77 on less affected parts of the course. A figure of 0.60 is considered suitable for motorways.
Surface temperatures may rise into three figures, assisted by the black top dressing, so that a surface of maximum inherent stability is essential. Lake asphalt mixtures act as good binders; the use of high hysteresis tyres accentuates the desirability of obviating high road surface temperatures, whether caused by atmospherics or the action of tyres on the road surface. The varying specifications of Gussasphalt with which Avus was resurfaced in the summer of 1955 and that used at Goodwood in 1961 are given in the article. I would add that in 1937 the Brooklands Campbell road circuit was laid of concrete paving, reinforced with RR 6-inch Expamet expanded steel.
There is also an article on the earliest steam rollers and their uses in this issue of The Queen’s Highway.– W. B.