Outer Limits 4x4 Board

Can you run different tyre pressures from front to back.Im running 35 inch maxxis mudzillas and if i air down the front the car is all over the place.So i was wondering if i run 25 in the front and 15 in the back will this change my front to back ratios....? Or does this work

you talking about on road? off road?

and 15psi, you have the chance of rolling a bead off the rim if you're not careful

15 psi on a Mudzilla will be fine.
I run less psi with 35inch MTR's on a 10 inch rim.

As for different front to back................it could cause wind up in the driveline but i think it would be fine.

This is my uneducated guess though.

Are you running more pressure in the front cause its too hard to steer??

If your going all over the place your probably driving too fast for the pressure your running so the rear pressure your running would be too low at speed.

If you air down to around 15psi... you shouldn't really be going that fast to be all over the place

Just air down to maximise the amount of grip you require, and drive accordingly

Im in coffs harbour and we have some steep tracks so you have to air down.problem is driving between tracks i was just trying to find a happy medium.I use to drive all day with 18psi in my BF Goodriches but low pressure in the maxxis tyres being a rag tyre if you get up to 20 ks The car wanders uncontrolably where as the B FS it made no difference

Could also have an alignment problem. Hitting a rut or hole at anything other than crawling speed can put your front end out, knock off wheel weights etc.

Different pressures will be ok. There are also different weights on each end of the 4WD. I wouldn't worry too much about wind up until you want to pull it out of 4WD again, the driveline will be strong enough to handle it.

I recall reading somewhere a different method of finding pressures - this one was designed for use in sand IIRC, but no doubt it could be used anywhere. Basically, you choose the contact patch length that you want, and then measure the contact patch length using a piece of board at the front and rear of the tyre. Eg drop the fronts to 15 psi, slide the board in under the front and back of the front tyre and then measure the gap between the boards. Then do the rear so that the pressure used in the tyre produces an equivilent gap between the boards. As you load the 4WD differently or use different tyres with different carcasses, the pressures can be adjusted to suit.

I've not tried it, but it sounded like a good idea. Better than guessing at least.

This is how I came up with my base pressures when I changed over to Bias tyres.
http://www.slunnie.com/coppermine/thumb ... p?album=35

Well i gave it a go ,ive been out the last two days on some extreme tracks with 30 psi in the front and 20psi in the back and i had good traction and light direct steering with no bind up at all in the transmittion {stiil shifted in and out of 4wd the same as usual}

chops wrote:and 15psi, you have the chance of rolling a bead off the rim if you're not careful

I have been running 35's on 8" rims for the last 5yrs at 10psi front & 8psi rear & never run a tyre off the bead. (have cut & flipped rims though) I think if you were to run at say...front 30psi & rear below 10 it would make a difference as it would be like running 35's up front & 33's/34's rear

Yep i recon your right,you would have to keep them within 10 psi of each other.I didnt have much time to fiddle around with it this weekend because i was showing another club around the area but next time out i will drop the steer tyres as low as is comfortable and then put the back tyres 10psi lower>That way in comps you could get more speed and steer still with good grab.

10psi is cool to do high speeds on too

Yeah different pressures front & rear are fine, wouldn't think that 25psi would cause you to have steering issues, try 10psi

I used to run about 3psi in my zook, and I dont think there is any air in my buggy tyres

Beadlocks are the answer, go as low as you can without screwing up the rim, and the pressures could be different front to rear, eg. if you got a big diesel your gunna need more air in the front.

If you aint got beadlocks, you will need more air, and if you got to drive at speed you will need more.


Mock

isn't the circumfrance of the tread the same no matter the pressure...

bad_religion_au wrote:isn't the circumfrance of the tread the same no matter the pressure...

That sounds like a dam fair call to me.

I dont know thats why i asked ...is it ?????

scotyz wrote:I dont know thats why i asked ...is it ?????

well think about it, if you cut your tire and laid it out flat on the ground, that's how much distance you travel every rotation.

if you lower your pressures, it doesn't remove any tread, so the distance travelled will be the same

35’s – SWB MQ… I ran as low as 8psi in the rears and 12-15psi in the fronts and never beaded a tyre. I wanted some steering from the front, where as the rear is trailing and it only has to form to rocks.

I run 8 - 10psi in 31's on my zook and it goes ok. Yesterday my ARB compressor gave up, 10psi and brakes full of mud from LCMP to Kilcoy, mmmm good fun.

This whole thread is irelivant without knowing the vehicle these 35" mudzilla's are on (if I have missed this detail I am sorry)

15 PSI in a zook is fine (that is is my normal on road pressure, except for long trips)
15 PSI in a Hummer is a bit low

And as far as the 15/25 PSI question, look at it this way, if you had a hilux with a Chev, winch bar and winch over the front axle and an empty aluminium tray in the rear, you would be expected to run differing pressures front to back.

We need the type of vehicle for this discution to advance.
Peter.

Its a 60 series landcruiser running a 1hz diesel with aftermarket turbo.50mm body lift 50mm spring lift .ironman springs,drop shackles,15x10 us racer rims with 3 inch negative offset.Maxxis mudzillas 35x13.5x15 . front and back arb air lockers.Monza seats.Custom made winch bar with a warn high mount winch.Rancho rs9000 shocks with in cab adjuster.Long range tank.full size spare wheel in the back.cargo barrier.duel batteries with Parana system.

I run 10psi same tyre but on an 88 4runner
When I got the tyre started on 20 then 15 now on 10 and willing to try 8 on 10 they started to form over rocks on all the higher pressures they did'nt seem to.
You have to ask your self whats more important driving over shit at 5kph or driving on tar at 100kph.
I know what my choice is