13-1-71 13-1-71 14-1-71 -iN OXTON COMPLETE WITH "SPACE-MAN" HELMET, DAVID OXTON SHOWS WHAT A TIGHT FIT DRIVERS ARE IN TODAY'S CARS. THE AUSTRALIAN FRANK MATICH, SEEN HERE ON HIS WAY TO A SECOND PLACE AT PUKEKOHE LAST WEEK, WILL BE A STRONG CONTENDER FOR VICTORY AT WIGRAM ON SATURDAY. THE AMERICAN FORMULA A CHAMPION JOHN CANNON, ABOVE, IS NOW MEMBER OF THE STP TEAM, AND HE IS LIKELY TO BF. WELL UP AVONG THE LEADERS AT WIGRAM ON SATURDAY. 42 POL THE SALOONS ALWAYS PROVIDE EXCITEMENT AT WIGRAM, AND ON SATURDAY THERE WILL BE A BIG PROGRAMME OF SALOON RACES. HERE CHRISTCHURCH DRIVER CLYDE COLLINS THRILLS PUKEKOHE SPECTATORS WITH SOME SPIRITED TAIL-OUT CORNERING. Tyre In world motor-racing today, competition between tyre manufacturers is so close that fortunes can easily change several times in a season. • A company obviously "on top" and providing the most suitable tyres at one race, may well find itself left behind by its rivals at the next meeting. The development of racing tyres is a continuous process. Efforts are chiefly concentrated on two aspects of development-design and compounding. The first step in the design of a racing tyre is to establish diameter and tread width, then the profile. Be fore a tyre goes into production it is studied throughout the speed range to determine its exact profile at maximum speed. The shape of a tyre may change considerably as the speed at which it is turning increases from rest to 200 m.p.h. Another important consideration is the aspect ratio of the tyre-the height • of the casing, from its bead to Develop its shoulder, in relation to! the tread width. Many racing tyres now have an aspect ratio as low as 33 per cent; this compares with a ratio of between 70 and 80 per cent on most radial passenger car tyres. The casing material used for racing purposes is very similar to that used for highperformance road tyres, except that the cord angles are extremely low to enhance stability at high speed. Higher angles are used-on road tyres to improve both ride and resistance to puncturing. The casing is also thinner than on road tyres to minimise heat build-up. The main considerations which affect the choice of the compound are heat resistance, traction, teat resistance and wear. Tyre compounds contain about 15 ingredients and the choice of tread rubber can make a difference of as much. as five seconds a lap од 2 circuit with a lap time of, about 1.5 minutes. ment Lady Wigram likely to be vital in series By PETER GREENSLADE The Lady Wigram Trophy race on Saturday already shows every sign of being the vital one in this year's seven-race Australia- New Zealand Tasman championship. The reason is that Australian are definitely Tasman title Neil Alien and Wellington's contenders, expatriate Austra- Graham McRae, with 15 and lian Frank Gardner and the 13 points respectively, have former Australian champion ¡already pulled out useful leads Kevin Bartlett. over the other major conten- Neither has scored a point ders for the Tasman title. so far. Frank Matich, last year's To get into contention they Australian Grand Prix winner, must be among the front and winner of the 1970 New runners on Saturday. Zealand Grand Prix and Lady Bartlett's Mildren Chevro- Wigram • race, is now lying ¡let has been plagued by minor third with 6 points. , who New Zealand's international troubles, and Gardner, pion, and the American Form- series, crashed his new Lola T192 • when lying fourth after ula B champion, Mike Eyerly, about twelve laps at Puke- have only 4 points each. kohe. CONTENDERS Although the McLaren M10Bs of Allen, McRae and These four drivers must try Matich have been running to make every post a winning well so far, Cannon has not post at Wigram or their been so lucky with his. chances will fade away, with only one New Zealand race to MISHANDLE come at Invercargill, before Allen heads home to three A slowly deflating tyre race circuts with which he is dropped him back to fifth at very familiar. Levin and he occupied But Wigram is even more same place at Pukekohe last important for two drivers who week when his car started to mishandle. Afterwards it was found that a rear shock absorber had broken. Cannon could prove to be the dark horse in the Wigram field, • although one cannot dismiss the chances of Amon who, after his first race in a Formula 5000 car last Saturday, should be better equipped to get the most out of the STP Lotus 70 Boss Ford. Qualifying trials for grid positions for the rolling start will be held tomorrow and VIcRae's 103.76 miles an hour lap record, set in the pre liminary event last year, will : certainly freiris, although it will remain the official figure until it is! beaten on race day.