Bakedbean100:
I dont know, i dont have any spares but i don't really want to wreck my current tyres.
At Barkston you do a lap and then have to queue up to do another one. If you give it five minutes to let the tyres cool (or spend a couple of minutes driving slowly through a puddle) the tyres last a lot longer. I know Javelin do rental MX5s so it might be worth asking if they could rent you some wheels and tyres.
Other handy hints:
More pressure in the rear tyres makes them break away at lower speed (I've used anything up to 60psi on tracks depending on track layout and power).
When you do your sighting laps make a note of how much steering lock you are using for each corner. When doing your fast laps if you find you're using more steering lock then you are in to the start of understeer, and if the rears let go at this stage it'll be a handful to catch. Avoid understeer.
Don't forget to check the wear of your front tyres too - just because the back is sliding doesn't mean that the front tyres aren't doing a lot of work.
Get a passenger ride with someone who can transition (change the direction of the slide from right to left) consistently and watch how they are steering. It's one of those things that takes ages to work out for yourself, but is easy once you know how to time a throttle lift with the steering technique.
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