Has anyone experimented with them. The door car on my JCW states 44 psi front 35 rear. when inflated to this the car drive awful. When I collected the car I saw they were on 32 psi all round and the car drove much better. i just thought the dealer had inflated them incorrectly.
If you look at the Mini tyre plates, the pressure tends to increase as the profile decreases but what also needs to be taken into account is the speed rating of the tyre for the car. I think you would find the pressure is correct for the speed rating of the tyre with the JCW allegedly being the high speed model. This would allow the tyre to hit an obstruction at high speed without compressing the tyre to the rim compared to a 65 profile tyre. Now consider that aside from legal speed limits, most race tracks have a good road surface with minimal disruption compared to a normal road (less potholes etc). Should you be driving at a high speed (over the legal limit) and strike a pothole and your tyre pressure is under the recommended pressure, you may compress the tyre enough to not only damage the tyre wall but also buckle the rim on a 40 profile tyre. Also consider, your most likely running on a sports tuned suspension which will give a harsher and harder ride quality again. My R53 Gen 1 has a tyre pressure for a 205/40/18 84 W rated tyre as 2.5 bar for 2 pers and 2.8 bar for 4 pers and luggage. One of the key considerations is the 84 (load index) and W (speed rating).
Gen1 Facelift R53 with SS+ running 205/45/17s. Door pillar says 2.3bar all round.
Took off the run-flats and put on standards last week. Magical ride improvement. Had them put at 33psi all round. Felt it had lost some instancy and turn-in. So this evening went to 36psi front, rears still 33psi. Need to see what change/difference that makes to feel and ride.
Very surprised such a small change in psi can make such a noticeable difference. Feel and turn-in back to similar to the run-flats. Ride appreciably 'harsher'........but nothing like the run-flats. Bit more crashy on the big ones and small ones more noticeable.
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