Tyre Inflation Pressures

[kevinluigi23]

I'm no expert on cars but the recommended tyre pressures on the inside of the door frame have somewhat baffled me. They recommend anywhere between 200 and 300 kilopascals depending on what you are carrying/towing. 200 equates to 29psi. I thought that sedans usually have their tyres inflated to 32psi and that 4wd would have a higher pressure. I was always told to pump up my old NE Pajero to 40psi for road driving and less for offroad action. I am assuming that these tyres are different spec to the old Pajero's tyres.

For road driving, what should I be pumping my stock standard NS Pajero tyres to? Also should the pressure be the same for all 4 tyres or different for front/rear?

[mrbitchi]

Every tyre is different. The tyre placard only relates to the standard OEM tyres supplieid by MM.

I run my LT Coopers at 36psi normally. Seems to give good wear for me.

If you're uncertain what to run, try the 4psi test.
Start out with your tyres at a given cold pressure, say 34psi.
Go for a good drive, say 50K or so then measure your pressures.
If the increase in pressure (due to tyre temperature increase) is 4psi then you have the correct starting pressure. If the increase is greater than 4psi your starting pressure was too low causing too much tyre flex, hence too much heat. Try again starting from a higher pressure. If the increase is less then 4psi then the starting pressure is probably too high. You can run tyres at a higher pressure, some do to get better fuel economy, but you will have a harsher ride and risk wearing out the centre of your tyres prematurely.

Hope this helps....

[matthewfnorbert]

all tyre places i have been recommend min 40psi, i have run 42psi in last two trucks and tyre life has been excellent.. too low (as per placard) and you will wear them out quickly.

[mrbitchi]

As I said every tyre is different. No way I want my tyres that hard though ;-(

If the pressures are too low you'll start to see excessive wear on the edges. Adjust to suit.

[Wal]

all tyre places i have been recommend min 40psi, i have run 42psi in last two trucks and tyre life has been excellent.. too low (as per placard) and you will wear them out quickly.

Now is that 40psi cold or warmed up?

[matthewfnorbert]

Now is that 40psi cold or warmed up?

hot, for my coopers atr's they said 42-44 hot!!

[Yellowfin]

I also run my GY SA's in 18" at 36 for onroad which is 80% of time and up or down offroad depending on load and terrain.

[mrbitchi]

You should never set tyre pressures when hot. Manufacturers inflation pressures are stated as COLD pressure.

Having said that, if you start at 36psi cold and them check pressures when hot they should read about 40psi, assuming that 36psi is the correct starting point for your car/tyre/driving/ambient temperature conditions. (see 4psi test above)

[kevinluigi23]

Thanks. I'll give the 4psi test a go tonight and see how it goes. What about having the same tyre pressure across all 4 tyres? Should the front and back tyres be of the same pressure?

[mrbitchi]

Depends on the weight of your vehicle. If you normally run empty in the back then a couple of ponds less is the go. I have a drawer system and a bit of gear in mine at all times so I run the same all round.