Confused about tyre pressures now.....

Thanks for all your comments. So, if I have previously thought 28psi was comfortable range for outback tracks do I set it as the hot pressure, i.e. starting at 24?

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Originally Posted by Ozzy119

Thanks for all your comments. So, if I have previously thought 28psi was comfortable range for outback tracks do I set it as the hot pressure, i.e. starting at 24?

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In my view and depending on your tyres, no. and once again it all depends on load and speed. Please remember there are several variables involved with this sort of issue but I understand you are looking for a starting point.

Our experience, based on either an LT or AT tyre, no data on HT as never used them in the outback we operate in, and for a heavily loaded 4WD, say around 1800 rear axle weight, would be around 26F and 28R for something like the Oodnadatta track and similar. But speed is no more than 90kph as well. 24psi is too low in what I would call normal situations; heavily loaded and 80-90kph. You would increase temperature and the risk of a tyre failure commensurately. Lower tyre pressures and speed concurrently.

Rob

One rule I picked up in the old days, (pre steel radial tyres) was that if you couldn't hold your hand on the bitumen for ten seconds, you didn't go over 40 mph (70km/h). How things have changed!

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Originally Posted by RobA

24psi is too low in what I would call normal situations; heavily loaded and 80-90kph. You would increase temperature and the risk of a tyre failure commensurately. Lower tyre pressures and speed concurrently.

Rob

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Speaking of temperature, my TPMS also monitors temperature. The default threshold for the over-temperature alarm is 70 degrees C. That seems awfully hot to me, and is probably set for truck tyres.

What are people's view of the temperature threshold allowable on AT tyres before its time to give the tyres a rest ( or pump them up).

70C is actually pretty much average for most tyres normally loaded, I mean AT and LT both of which have higher rolling resistance therefore run warmer. We have seen 90C in rear tyres with an air temperature of 35-40C at highway speeds with a completely stable set of pressures all round. We know a punctured tyre has a temperature of around 98C or more when it fails so we set our temperature alarm at around 85C

Rob

Well written Rob... Whilst I have been guilty of hooking along at times, when travelling (on loose surfaces) 90km/h is about where it's at :)