Hi,
My car (SAAB Aero 9-5) uses 235x45x17 tyres and they are meant to be inflated to 35 PSI for for normal speeds and 3 passengers etc.
I have now got fitted XL (Michelins). What should the correct pressure be?
Many thanks, Charles
PS. I am coming to a figure of 41 PSI but it is a bit calculated and a bit picked from thin air.
My Allroad uses XL tyres, 32psi front and rear, unless fully loaded.
The tyre will have a maximum load and a maximum pressure on the sidewall.
It you know the axle loads you'll actually be putting through the tyre, a good starting point is a simple pro-rata pressure.
So if the tyre can take 800Kg at 40 psi, but your front axle load is 1400Kg (700 Kg per tyre), you can start with 35 psi.
This is how caravan tyre pressures are often worked out.
Tyres vary in the correct pressures.
When I was doing heaps of miles tyre changes were frequent. The best way was to read the actual tyre if the centre was worn inflation too high, worn edges too low. This was all within 4 psi. They should be flat across the tyre.
Yes ... only by the time you can figure that out it is too late to save the tyre.
For anyone who may look in the future, michelin told me that for a SAAB
9-5 2008 model, 260 BHP, tyres 235x45x17, for Pilot Sport 3 XL tyres the figures are:_Standard_ Front: 35psi Rear: 33psi
_Laden_ Front: 44psi Rear: 42psi.
I will go with that and see ...
Cheers Charles
The point was to say each tyre has its own optimum pressure. You can tell i n the first couple of thousand if anyone cared to look.
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