Quote:
Originally Posted by stonenewt
What was said is they realise that there are so many unknowns that they can't actually answer the question accurately! Instead they gave a huge amount of advice and procedures on dialling in finding correct pressure.
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They were lying to you then. Michelin can recommend the correct tire pressure for any tire they make and any vehicle that tire will fit.
Bear in mind you have to ask them the right question which is what is their recommended tire pressure for the BRZ fitted with the Michelin Pilot SuperSports in 225/45x17 size for the street. After they tell you that isn't the stock size they will be able to advise you what the recommended pressure is...for street applications.
There is no correct tire pressure for competition applications for the simple reason that you're not trying to drive on the street.
The initial post asks what can be done to improve handling on the street with the tires chosen. Frankly, 35 psi should present no problems whatsoever even if the ideal static cold pressure should be 34 psi for the slightly larger size.
For the curious, it seems obvious that the car is supported by distorting the tire carcass by a set amount proportional to the vehicle weight, the object being to maintain the contact patch in the correct shape intended by the tire manufacturer. Tire pressure for any particular tire is selected by vehicle weight.
Period.
If the internal volume of the 215 tire is x litres and the internal volume of the 225 tire is, let us estimate, x plus 5% of x, then obviously the required pressure to ensure the tire is distorted by the correct amount should be about 5% lower.
Now if you actually look at tire grip plotted against load and tire pressure you can see that raising tire pressures above those recommended for street use will generally increase overall grip for any normal street driving. This is a diminishing returns process and usually adding 2 psi above recommended will produce the best result.
Suggesting that overheating the tires by driving on the street will mean the tire pressure will go above optimum is stating the obvious and to no useful purpose.