For Thruxton only the hard compound – developed specifically with the track’s demands in mind – is used.
Adding a further challenge is the BTCC grid’s mix of front-wheel-drive and rear-wheel-drive cars, as well as different car setups favoured by teams, which don’t get many chances to test at Thruxton and have to aggressively chase the optimum set-up in practice.
The unenviable task of trying to juggle the demands of all of the teams in the pitlane falls to Dunlop Motorsport UK Events Manager Michael Butler.
“Thruxton is the most abrasive, high-load circuit on the calendar,” he says. “Around here a BTCC car is on full throttle for 75% of the lap and never really in a straight line; it is always turning. Less than 5% of the circuit is straight. The kerbs through the complex, Church and the chicane are very aggressive – if you hit one of those you’re a passenger in the car.”
It’s not just the wear rate that is a factor – indeed, Butler is confident the compound is well suited to the track – but Thruxton punishes the actual construction of the tyre.
Butler and his band of tyre engineers issue the race teams with operating guidelines aimed at maximising tyre life and preventing punctures. Teams aren’t obliged to heed the advice and occasionally one or two will take a risk on a setup that strays outside of recommended parameters.
In addition to advised cold and hot tyre pressures and suggested settings for camber and caster, the tips include a suggestion to avoid hitting kerbs in the first five laps of a practice session or race.
“The tyre pressures are still building up in the first five laps and tyres have not reached their optimum operating temperature,” says Butler. “The tyre sidewalls will over-deflect upon impact with the kerb, and this runs a risk of a failure.”
On front-wheel-drive cars the left-front takes the most punishment around Thruxton, and on rear-drive cars such as the BMW 125i M Sport and Subaru Levorg, it is the rear-left that soaks up the most abuse.
“The track surface is very coarse and you have to remember that the track doesn’t really get used very much for racing during the season so there isn’t a lot of rubber laid down," explains Butler. "It is very green when we get here for practice. It is all about tyre management. Being quick for two or three laps doesn’t mean anything around here. You need to be consistent over each of the 16 laps.