Shore rating depends on the carpet you are racing on, our carpet is relatively low grip and 30-32 shore are popular, although there are others happily running on 35 and 37 shore tyres depending on car setup.
35 shore is a good starting point with tons of life from them, if you need more grip go softer and don't be afraid to mix and match tyres, I think I'm in the minority of using the same shore all round as most of my club members tend to use one grade harder on the front (e.g. front 32sh, rear 30sh or front 37sh, rear 35sh) to make the car more stable.
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