Monday, May 22, 2006 at 11:15
Geez Willem, sorry about that, remind me to buy you a warming ale if we ever catch up lol.
The load rating @ maximum pressure is the key to every tyre. I'm no mathematician, but by my figures (assumed only), your tyres would be running a tad soft. This is how I work tyre pressures out, using your figures.
Tyre maximum load rating 1550kg, divided by 80psi = 19.375 kilo per psi.
19.375 kilo per psi X 35psi = 678.125 kilo's per tyre
678.125 kilo's per tyre X 2 = 1,356.25 per axle x 2 axles = 2,712.5 kilo's total vehicle load.
This presumes you have a perfect 50/50 load distribution between the front and back axles, which you won't have. A weighbridge when loaded will give you the right figures.
I always add 6psi to the load figure I get for highway running, and generally this will always give you about a 4psi heat build up after an hours running.
On dirt road, I just drop this 6psi and go back to my original figures. Mud, sand and rough surfaces are a different ball game, but the formula above will give you the best traction, mileage and fuel economy out of the tyres, the way the tyre designers intended.
I think this is where a lot of people get confused. The original Bridgestones on my GU III had the maximum load/ pressure @ only 36psi, not 80psi like the Coopers, but the formula works equally as
well on Bridgestone and any other make of tyre.
Sorry about being long winded, I'll make up for it over that ale ;-)
Cheers,
Peter
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