Thread: tyre pressure

Lots of variables. Even the same tyre on different width rims will be a little different.

Temperature rise is a good indication of suitable pressure on road. The tread and sidewall flex, when under-inflated generates heat. Over temp at highway speeds leads to tyre failure.

I had 33 x 10.5 x 15 bfg muddies (load rating 'C') on my rangie for years and still have them. I normally ran them at approx 40psi on the highway, but one weekend trip to the Cells, I drove to Wauchope in a hurry and never realised till later that I only had 18psi in the tyres (had not aired up from previous off road trip).

Not having noticed anything untoward on that occasion, I studied tyre temps running similar low pressures in those particular tyres on highway trips. Over a number of occasions I found the temp rise ok and believe that no damage had occurred. I have since done many long trips on those tyres and they are still ok.

I have a set of 325/85 R16 Michelin XML on my rangie at the moment. They are branded for 2300kg and don't flex much with only 10psi in them.

I don't recommend what I did, except for short runs when you have evidence that the temp rise is small and the vehicle handles well.

I do like to run about 40 psi on highway to reduce rolling resistance.

I totally agree with what others have said about inflating high enough to not cause greater wear in the middle of the tread. I don't see a need for 48psi in muddies on a disco.

But I don't agree with high pressure on rocky roads after the damage I experienced running 40psi on the Plenty Highway (I kept telling myself to let them down, decided to wait until the next stop, but forgot each time). The tyres I had then, suffered a lot (hundreds) of cracking between the tread blocks.

So many variables, particularly tyre volume and construction, then surface to be driven on, etc.

On my old BFG MT's in 255/85 on the 130 (mostly tares around 26-2700kg) I never went above 36psi on the highway all round, often used to run down around 33psi, and 26psi on gravel, although I'd often leave them at the highway pressures as I could be on either surface on any given day, depending on work.

On the Maxxis 762's in the same stated size (and they are slightly bigger in measured section and tread width) I've been running 40psi all round so far as they are more supple in the case than the BFG's, and I may even sneak them up from there yet.

More tyres blow-out from under pressure than too much.The idea that low pressure causes the tyre to bend around rocks etc is a load of crap.I meet people all the time that complain about wrecked tyres,I never run below 36psi except in the desert (25psi) and I have travelled alround this country,including tassie and have never ever ruined a single tyre.For normal driving I put 40 in the front and 36 in the back. Pat

I think he's running a fender.

Who did you get the michies off, and what pattern are they?
I know the WA guys who do the canter conversions import the xzl's in the 9.00 inch 16's and some other sizes, but I am unfamiliar with that type. there are 2 pattern for the xzl's, the bigger ones go a bit more A/t than lugs

tell me more, with pics please
Sorry for the hijack

As to the rim changes, yes. On the pepperpots, 6.5" rims with a tube, 35 was perfect, but on 7 inch rims with no tubes I had to up the pressure. 20psi is my default off road pressure, though loaded I leave the rears at 25. that was for both Moreton sand and Sundown rocks. On the Cape trip, with a full load i expect to run 60psi in the front and the max 75psi in the rear. Around 30-35 when the black top stops. You just keep fiddling. 40 psi all round on most of the larger tyres is a good starting point.

CC

yes tyre temps are a simple indicator of how hard they,re working. But at the other end you shouldn,t pump up 265/75s 2 say what others can with 33s.
Regards Max P

I run 37 in the front, 39 in the rear in my day to day travels. If I run what LR told me its like using solid steel wheels. I may get more km/tank and longer tyre life but frankly, I dont give a flying.....

I have never understood why people run more pressure in the back than front for day to day driving.All the weight is in the front so that is were the higher pressure should be.My defender is sloppy in the front and hard and skittish in the back set up that way,it also steers alot nicer with more in the front. Pat

Originally Posted by PAT303

I have never understood why people run more pressure in the back than front for day to day driving.All the weight is in the front so that is were the higher pressure should be.My defender is sloppy in the front and hard and skittish in the back set up that way,it also steers alot nicer with more in the front. Pat

I agree Pat, but most are going off the book or tyre placard.
In mine it says;
110's 28psi/48psi front/rear (7.50/16's)
130's 40/75psi front/rear for all load conditions !

Imagine running 75psi with nothing in the back on the original XZL's ? No thanks.