Isuzu D-Max Rodeo Denver (2003 - ) - 08 3.0 Tyre pressures - rear seems high

Honest John Back Room » Technical matters
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Sat 13 Dec 2008 16:44
08 3.0 Tyre pressures - rear seems high - Dave N
The tyre pressures for this (245/75-16) should be 31(F) and 41(R), for both loaded and unloaded. Assuming the weight distribution unladen is about 50/50, that means the rears are carrying 1 ton unladen, and 2 tons laden.

41psi seems a bit high considering when unladen they are only carrying the same weight as the fronts - possibly less. The reason I ask, is that even with studded tyres, there isn't much rear grip and I'm considering reducing the rears to the same as the front. Will I have a problem with this, do you think?
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Sat 13 Dec 2008 17:00
08 3.0 Tyre pressures - rear seems high - Number_Cruncher
Reducing rear tyre pressures is always something to be very careful of. The reason is, that making the rear tyres less stiff moves the overall handling balance of the car towards oversteer.

As per usual, I'm not talking about the Top Gear type of provoked gross oversteer, but about the more fundamental response of the car, which you want to be understeering as a baseline, under all conditions.

However, it sounds like the vehicle manufacturer has taken the view that most people don't re-adjust tyre pressures every time they load the vehicle, and that specifying a laden pressure all the time errs on the side of safety.

If you do chose to reduce the pressures, do so gradually, at about 2psi a time, making sure that the vehicle remains safe, and take out the minimum.

I would imagine that the rear tyres should remain at a slightly higher pressure than the fronts to maintain a fundamental understeer characteristic.

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Sat 13 Dec 2008 23:13
08 3.0 Tyre pressures - rear seems high - gordonbennet
Have a very good read of your manual, as we very seldom load the hilux fully we run at the lowest normal setting 30psi, which seeing as how similar the 2 vehicles are i would have thought about the same for you.
edit...thats 30psi all round.
And the vehicle handles remarkably well for such a lump, much nicer in the cold for having winter tyres on though.

The ride must be hell at that pressure.

Edited by gordonbennet on 13/12/2008 at 23:14

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Sat 13 Dec 2008 23:38
08 3.0 Tyre pressures - rear seems high - Hamsafar
Maybe it was to improve the mpg and / or help to move to a lower CO2 band?
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