Thread: How does this sound for tyre pressure

You're over complicating it.

This is a very good guide for typical Australian high speed dirt road travel:

http://www.l8ter.com/wp-content/uplo...essure-pdf.jpg

Those tyres you have are very tough and can cope with lower pressures. As stated in the lower Rh corner of the guide you can adjust pressures by eye to equalise the contact path length.

Nope. I wouldn't do it..

Having said that - I wouldn't run a P38 at 28/38 either.

How does it feel!

With a FFR 109 years ago after shifting weight forward (toolbox on top of the winch etc) finished up with 15psi front and 60 psi rear

Are talking for bitumen or dirt roads?

When i had that size tyres (maxxis bighorns) on a disco 1 i ran 40psi front and 36-45 rear depending on loads (i generally left ot at 38 unless it was a long, laden trip).

With any tyre i pump them to a pressure that looks good to the eye and then monitor them for wear and adjust accordingly. I have always ended up between 36-45 for a 4wd.

Cant help for dirt roads as i dont do much of that.

Cheers

Dan

Thanks for the drawing For now I was talking bitumen though just to get started.

In the mean time I found another formula that simplified reads

front axle weight / ( 2x max load tyre) x max pressure and if I take my numbers once again I end up with:

front: 1260 / (2 x 1380) x 5.5 = 1.9 or 28psi again
rear: 1260 / (2 x 1380) x 5.5 = 2.6 or 38psi again

Funny enough, back to what land rover suggested. I am confused

I'll air them up whatever "looks and feels" right for me for now but I am curious the the science behind all this.

@tombie, why would you not air a p38 up to those pressures and what WOULD you do?

Thanks!

-P

Originally Posted by jcamp

How does it feel!

With a FFR 109 years ago after shifting weight forward (toolbox on top of the winch etc) finished up with 15psi front and 60 psi rear

reading that makes me cringe.

I'm glad you are driving it.

It must understeer like a pig in ****......

I set things up with a little less maths.

For asphalt I air up until the side wall stops standing up and add 5-10 psi.
After 1 hour stop and fairly quickly check pressures.
From the first reading with a cold tyre I look for a 4psi rise( some stiffer LT tyres look for 6psi maximum).

On high speed dirt deflate till you see the side wall "bag out"/softening, drop a further 5 psi.
As above it should be checked but it's fairly hard to actually do this.

For rock crawling harder tracks drop another 5psi and this is my start point in sand also.

For the record I run BFG KM2 mud tyres. LT 235/85R16's.
The Defender and van sit with @50kg to spare on each axle, close to 4ton GCVW.
Front and van 44-46psi.
Rear 60-64psi, 52psi with no trailer.
Any less and I see scrub marks on the side walls and it feels "loose" to drive.
I also cheat and use a tyre moniture rather than stop after the 1 hour mark.