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Old 01-07-2013, 02:54 AM   #11
jadatis
 
Drives: no camaro
Join Date: Oct 2011
Location: Holland
Posts: 7
For determinating tire-pressure-advice, the tire-and car-makers use a formula that I got hold of once and went running with.
For normal cars the European formula , wich is also used in America for normal ( P-tires) and XL( reinforced,extraload) since 2005, is proven save .
But before 2005 in America a formula was used that came to lower pressures and so more deflection of the tire then it can savely stand.
So you see that there is more to tell about tire-pressure.

But now the formula. In this formula the actual load on the tire is used, also with the maximum load and maxloadpressure ( wich is not the maximum pressure) of the tire. This maxloadpressure is called the reference-pressure in the formula( further Pr).
Pr has to be highenend up for higher speed then mostly the reference-speed of 160km/99m/h. Seldomly used is the camber angle( alighnment tires like this on the axle/-\ instead of |-|) wich also highenes up the Pr but only above 2degr .

So If you can give me the GAWR's ( gross axle weight ratings) and type of tire for the Pr, I can calculate a save lowest to use pressure for fully loaded.
Also maximum speed of the car ( or fastest you ever ride) is usefull.
And if you have low aspect ratio tires ( =AR the 40 in fi 235/40 ZR 18 92 W) the Pr has to be highened up to , or the maximum load of the tire has to be lowered.
This is a thing I lately discovered, so also give the exact sises like written above with the Loadindex ( 92) and speedcode letter ( W). Ten I can judge the correction for low AR.

If you can give the empty weight and weight devision front/back , and the way you normaly load the car, I can calculate a normal-use advice.
Mind then that the actuall weights are easyly misyudged, weighing would be the most shure.

Last edited by jadatis; 01-07-2013 at 02:55 AM. Reason: subscribing forgotten
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