low presures on the highway dddanger dddanger 
their is a rule of thumb ive heard around the traps many times under 30 psi and under 80kph
you can also use the 4psi rule also;
Drive for about 1 hour – 30 mins minimum, but try not to go too much over 1 hour. Check the tyre pressures, if they have gone up by LESS than 4psi, your starting pressure was TOO HIGH, drop 2 psi now, and remember to use a 2psi lower start pressure tomorrow. If the tyre pressures are still not going up by 4psi after the next hour of driving, you still shouldn’t drop any more unless you change road surfaces etc, otherwise you could end up damaging tyres. If they still don’t go up, you need to start about 4psi lower tomorrow, and then see what happens.If your tyre pressures go up by MORE THAN 4psi, your starting pressure was TOO LOW! Add more air NOW. To work out how much to add, subtract the pressure they should have ended up at from the end pressure you’ve just measured. Ie, they started at 20 psi & so should end up at 24 psi if all is correct, but they are now 29psi, therefore 29 minus 24 leaves 5. So add at least ½ of that 5 psi now; and use original start pressure plus your final add amount as tomorrows start point, ie. original start = 20 psi plus the 2.5 psi added today, start tomorrow on 22.5 psi.
You need to do that for every type of driving and road surface you drive on. It will take some time, but the end result is that you will learn very quickly to work out what pressure you should be running now, and what you should drop it to when you change road surface/driving needs, ie. 4wd rock crawling versus 4wd high speed good condition dirt with odd sandy patches!
. These muddies I rate highly in all road conditions and will purchase set number 2 soon 
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