Tyre pressure??!?

**Young Angus** · 5th March 2012, 06:30 AM

I haven't searched but this is a simple question.

I have 245 Cooper R16s on my Disco, great tyres (cheers Frank!) and I went to do a routine check of the pressure yesterday and opened the manual just to check what it says they should be at and the thing said that for a normal load the front should be at 24psi (or 26 I can't remember now) and 34 or 36 on the rear (also can't remember exactly)...but mine are all sitting on 38psi which was obviously done on purpose by the previous owner and Ritters where I last got it serviced so I'm sure this isn't just a random number picked out of a hat.

Are any of these values better to run than the others or should I be looking at a tyre manufacturers website? I'm not doing any off road driving right now so just want good road tyre pressure and obviously want to get the best life out of them I can.

Any advice would be greatly appreciated on this seemingly simple matter

**PhilipA** · 5th March 2012, 08:24 AM

Ritters where I last got it serviced so I'm sure this isn't just a random number picked out of a hat.

Ha HA Ha!!!
It is a random number picked by a teenage apprentice.

The factory manual cold pressures are 28 front and AFAIR 38 rear for all loads.
This is for a 205X16 and theoretically this could be lowerd for a 245 as it has greater volume.
I run a couple of pounds higher at 30and 40 on my RRC with 245 70x16 Bridgestones , but 28 gives the best ride handling. It reduces the impact on the front components and you will notice the better ride. It also reduces steering rattle on bumps.
I have no shoulder wear etc and the tyres are wearing well.

You may get better wear with really high pressures but in your case if you carry a big load then the rears are probably a bit underinflated. Also if you have a big bullbar and winch you should run slightly higher but 38 is being a masochist.
Regards Philip A
Regards Philip A

**Young Angus** · 5th March 2012, 02:00 PM

Hahaha damn well I may re-evaluate then. So 38 seems good for the rear and I do have a pretty big TJM bullbar/winchbar on the front but no winch...maybe 32 - 34 or not even that high for the front? I don't mind a slightly bumpy ride but I want the tyres to wear well without hurting too many front components unnecessarily...or is that just the trade off?

**PhilipA** · 5th March 2012, 03:24 PM

Just try out a few variations from 30PSI up, and see what suits you.

If you are happy with 38 then do it but remember the tyres are a part of the suspension and the compliance is what gives a good ride and a longer footprint helps with directional stability and resisiting shimmy.

I am not a fanatic with tyre mileage but I seem to get good service and (touch wood) I have never had a tyre deflate off road since 1977. I change them at about 4MM anyway as they are useless off road below that.
Regards Philip A

**68wicksy** · 5th March 2012, 07:39 PM

I went throught this about a year ago when I fitted 245/75/16's. The idiot at the tyre shop put 38psi all round, and the handling was pretty bad. Oversteered quite badly.
After much experimenting I settled on 2psi above factory for 235/70/16's. Handles much better, and the tyres are wearing really well. Hope this helps. I also have a heavy steel winch bar, and it handles the weight just fine.

**Young Angus** · 6th March 2012, 01:33 PM

Cheers I think I'll give that a try

**loanrangie** · 6th March 2012, 01:43 PM

I have been slowly upping my tire pressures over the last few years, started at 32 but now run my 245/70/16 BFG AT's at 40psi since i drive mine daily at highway speeds. This gives less rolling resistance and firms the suspension up nicely for the highway - lower will give less response not more.

**Ollie** · 6th March 2012, 09:14 PM

I am sure I read this on this forum.
Choose a pressure check all tyres at cold go for a reasonable drive and check the tyre pressures when warm, the difference should be 4 psi high than cold. Adjust and test again until the 4 psi differential is reached. Work ok on our Disco2 Cooper ATRs.
Regards Ollie

**OffTrack** · 6th March 2012, 09:36 PM

...

**PhilipA** · 7th March 2012, 09:17 AM

Choose a pressure check all tyres at cold go for a reasonable drive and check the tyre pressures when warm, the difference should be 4 psi high than cold. Adjust and test again until the 4 psi differential is reached. Work ok on our Disco2 Cooper ATRs.

I often wonder about this one. How do you tell when just having two tyres in the sun in the morning and two in shade gives a difference of 2PSI.

With regard to those who put very high pressures in, have a look at the other thread which refers to the graph of rolling resistance vs pressure, stating that it is not linear and you have to have at least 10% over inflation to gain 1% less rolling resistance.
Why do we continually second guess what the manufacturer says, who does research and considers such things as load on axles etc?

Regard s Philip A

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