Quote:
Originally Posted by ShinyMew
The tyre placard on the driver's side door jamb for my Isuzu Trooper suggests a maximum 210 kPa (30 psi) for the front wheels and 230 kPa (33 psi) for the rear wheels.
To adjust the pressures I use an automatic tyre pump at a service station roughly 15 minutes down the road. It lets me set the desired pressure and inflates the tyre to that.
Based on Metro's MPG chart, it would seem to me that 40 psi is best (anymore is only go to net very marginal MPG gains at the increased risk of uneven tyre wear, blowouts and ride quality).
However, because the placard recommends different pressures for the front and rear of the car, will adjusting the tyres for equal pressure all around be imprudent? Also, as the tyres will have been moving for at least 15 minutes by the time I get to filling them, should I be aiming to fill them to slightly less than 40 psi? Is it better to fill them up when the outside temperature is cold or hot? I live in Victoria, Australia, where the mean minimum temperature for 2014 in my area was 10.4c and the mean maximum 19.9c (though our summers are known to have several days of 30-45c heat).
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First, may I suggest that you postpone inflating your tires until the last thing before you return home. Inflate them to 5 psi above where you want them to be cold, carefully return home, then adjust the pressures in the morning when they are cold.
It doesn't matter if the outside temperature is hot or cold. What is important is the starting pressure when the tires have not been operated for a while - that is what we refer to when we talk about *cold* tires. You'll want to adjust the *cold* pressure as the ambient temperature goes up and down - about 1 psi for every 10°F (Let's see what this is in metric values: 0.12 bar for every 10°C)
And, it would be a good idea to maintain the pressure split front to rear to maintain the handling split front to rear.