OK, I am now about to display my ignorance, but I guess that is how you learn.
In my handbook, various tyre pressures and sizes are quoted, for four makes of tyre (all for 18" diameter rims - 8.5" front, 10.5" rear).
The rears are all the same size (295/35), but different pressures are quoted for different tyres: 32 psi for Bridgestone Expedia S02 and Pirelli P Zero; 29 psi for Michelin MXX3 SX Pilot and Goodyear GS Fiorano F1.
At the front, there appears to be a choice of size: 235/45 for Michelin and 255/40 for Bridgestone, Pirelli and Goodyear. Pressures, however, are 32 for Bridgestone and Pirelli; 29 for Michelin and Goodyear, i.e. the same as for the rears.
Can anyone tell me why the size for the Michelin option on the front is different from that for the other three?
And why are the pressures different for the different makes, despite that the sizes are the same (except in the case of the Michelin option on the front)? It would not have surprised me to find that the pressures varied for different sizes (e.g. at the front), but I do not understand why they should be different for different makes of the same size. Is it something to do with sidewall construction, perhaps?
Finally, my car is running Michelin Pilot Sport in 255/40 on the front and Bridgestone Potenza RE050A in 295/35 on the rear (yes, I know I should have the same make at both ends, but I never drive my car anywhere hear its limits, so I am inclined to leave them be until one end wears out). I am using 32 psi all round - is this a sensible setting? Should I, for example, be using 29 psi in the Michelins?
As usual, any thoughts would be very welcome.
yes on the 550 owner's manual are indicated four tyre brands, and Michelin was the unique that proposed for the F550 a little section in respect to the other brands, for his tecnical reasons.
During those years Michelin usually differentiate from the other brands with little tyres section, their battle horse was the MXX3, not available from lots years ....replaced first by Pilot Sport and after by PS2 and now from PSS.
This tyre is available on the Michelin Classic tyres line in this sections (205/55 16 & 245/45 16).
In every case it was an experiment for me, because with the 575 (same tyres of 550) also michelin proposed the 255/40 for the front as per attached owner's manual page.
However I never seen one 550 with the 235/45 .... !
In really, about the four tyres indicated on the 550 owner's manual, today nothing are more available .... Unfortunately also the Great S02 are not available...
The different pressures (cold pressure) of the different tyres kinds are due to both different side wall construction and different capacity to dissipate heat.
However to know if you use a correct pressure for the tyres the indicator is the wear of the three areas of the tyre: external, central and interior, controindication of this system is the more km to do for have a return check.
Personally i think your pressures are correct, in theory on the front michelin you need to used the 29 psi but also 32 is not so bad, the car have a heavier front and the difference between 32 and 29 is less.
If you drove in those condition for more km, you can check the wear lik the attached pictures.