Outer Limits 4x4 Board

Just put 235 / 75 / 15 on my 1985 1.3lt LWB Sierra.
When I picked her up I was surprised the tyre pressure they put in was 36psi.
I feels way to bumpy.
A sticker inside the driver's door say 20psi ? - which sounds way too low.

What pressure should I be running with these tyres for hwy driving?

Thanks

Dave ><>

Fishin' Dave wrote:Just put 235 / 75 / 15 on my 1985 1.3lt LWB Sierra.
When I picked her up I was surprised the tyre pressure they put in was 36psi.
I feels way to bumpy.
A sticker inside the driver's door say 20psi ? - which sounds way too low.

What pressure should I be running with these tyres for hwy driving?

Thanks

Dave ><>

I had that set up on my LWB for years, Kuhmo mudders. I ran 26 - 30 on road and 10 - 12 off road. I think 36 is only for original tiny tyres, that need more pressure, because they hold less air.. IMO christover

Most tyre outlets put heaps of air in to seat the bead.

I'm running 15PSi on road

Im running bout five I think but its not on the road much. I used to run bout 20 on road and 12 offroad in my 30" mudders but I have lots of dents in my rims.

33mtrs = 25 on road
and 9 offroad

I ran 30psi in my 33s and that wasn't too bad.
When I got the 35s the tyre fitter at work said to run 35psi, but I am running 30 so the centre doesn't wear out too fast.
What it all comes down to is sidewall flex on road.

No Idea wrote:I ran 30psi in my 33s and that wasn't too bad.
When I got the 35s the tyre fitter at work said to run 35psi, but I am running 30 so the centre doesn't wear out too fast.
What it all comes down to is sidewall flex on road.

Is it the lower the tyre pressure the more sidewall flex?

Thanks for everyone's advice.

Dave ><>

yes

i'm running 31 muds, with 20psi on road.. considering letting em down a bit more cos it's pretty firm and there's not much bagging

33 swampers .... 16 - 18 on road !!!
.......................... 5 - 8 off road !!!!!!!

no beadlocs

toobs fitted !!!!

32 Bfg's 8 to 10 off-road depending on conditions 18 to 20 on road

33 swampers 7 to 8 offroad between 3 to 22 onroad (they had HUGE beadleaks )

35 inch Claws 4 or 5 offroad and 12 to 14 onroad no toobes or beadlocks .. suspect I will need one or both of these as I want to run lower pressures after seeing the way droopypete's claws bagged\flexed all over the place

(except one claw that stays at 4psi as it has a stuffed valve that I cant get air into will have to fix that one of these days)

i have a set of 235/75R15`s that i run 25 on the road, 16 offroad and 8 on sand

The Great Gonzo wrote:i have a set of 235/75R15`s that i run 25 on the road, 16 offroad and 8 on sand

Thats about the same for me. If you run the tires to low and you do a lot of onroad driving be prepared to wear out your side blocks quickly.

30/9.5/r15 ran 18 - 20 on road.
8 - 10 off road.

33" claws, about 15 on the road (subject to leaky bead locks).
and 0- 20 off road depending on what I am doing.
Peter.

droopypete wrote:33" claws, about 15 on the road (subject to leaky bead locks).
and 0- 20 off road depending on what I am doing.
Peter.

heheh - i run mine between 0 and 20 psi on road due to leaky beadlocks

greg wrote:

droopypete wrote:33" claws, about 15 on the road (subject to leaky bead locks).
and 0- 20 off road depending on what I am doing.
Peter.

heheh - i run mine between 0 and 20 psi on road due to leaky beadlocks

What are you doing here?
don't you have an alcoholic beverage in a coconut with a straw, 2 little parrasols and a slice of fruit hanging out the top waiting for you?
Get back to rubbing suntan lotion on your good ladys topless body lounging by the pool in the bottom half of a wicked weasel bikini.

Or are you concerned that your post count is taking a hammering and Graham is catching
Peter.

This is my first Suzuki - I also have a Rodeo duel cab 4x4 and a full size Jeep trayback 4x4.
My problem is the Suzi feels "twitchy" - doesn't seem to track straight - It feels like the arse end is unstable.
You know when you have high winds driving a van - you can feel it sort of move around but doesn't change direction.
I've looked at the steering damper - looks OK - shocks and springs are standard and feel ok.
It could just be me not used to it - I'm not sure - I thought it could be sidewall flex - that's why I was asking about tyre pressure.

I've just fitted new rear wheel bearings and have tried a few sets of tyres.

Any ideas?

Dave ><>

Fishin' Dave wrote:This is my first Suzuki - I also have a Rodeo duel cab 4x4 and a full size Jeep trayback 4x4.
My problem is the Suzi feels "twitchy" - doesn't seem to track straight - It feels like the arse end is unstable.
You know when you have high winds driving a van - you can feel it sort of move around but doesn't change direction.
I've looked at the steering damper - looks OK - shocks and springs are standard and feel ok.
It could just be me not used to it - I'm not sure - I thought it could be sidewall flex - that's why I was asking about tyre pressure.

I've just fitted new rear wheel bearings and have tried a few sets of tyres.

Any ideas?

Dave ><>

it comes as a standard feature

check your shocks by removing from the bottom mount and try to compress them - you can take them right out if you want, just more work to do it that way.
Check your spring eye bushes for wear.

The suggested method of determining the best pressure to run tyres on the road is to aim for a difference of 4 psi between cold and hot pressures ie. 24 cold, 28 hot. If the pressure difference is < 4 psi then lower the initial cold pressure (more sidewall flex = more heat = more pressure difference), and visa-versa.

Off road there are more factors that come into play such as the age of the tyre (new = soft and pliable bead - easier to pop off a bead > relatively higher pressure needed than an old, hard bead. Rubber also shrinks slightly as it ages > tighter fit), aspect ratio (higher aspect ratio needs less to keep the bead seated due to more room for sidewall flex), and the type of tyre (radial vs bias ply). Definitly a "suck it and see" exercise.

Checked the shocks, springs etc - to my eye it all appears right.

It occured to me that as I've put bigger wheels on I would need to increase the amount of caster on the front wheels.
Otherwise how could the steering geometry be correct?
Is this a normal practice when you increase the tyre diametre and size?

Dave ><>

ive also had weird things happen to my handling after fittin 235/75's to my sierra. its a swb tho. but it now seems to wander abit on the highway. i went from 225/70's and it also gets the wiggles under hard braking. are these just cause the tyres are bigger and im not used to it. or is it something else. i got 30 psi atm. and stock suspension.

me217

235's are much heavier in construction than the stock tyres. They will have a negative effect on handling, but try lowering tyre pressure to maybe 25 and trying that. 30 is pretty high for a sierra.

Increased rim offset will also add to the wandering effect due to increased leverage. did you change rims at the same time?

nah i'm still runnin stock rims. the rest of the car is stock except for the 1.6 vit engine. my fathers got a landcrusier with 31's on it and it wanders thats y i figured it just could be the bigger tyre. and ill try dropping the pressure. they put 36 in it wen they fitted them but ive already dropped them to 30 cause it wasnt even using an inch on either side of the tyres.

me217

i saw a sierra in the wreckers the other day and the tyre placard said 20 psi front and rear unless loaded up then 20 front 26 rear. it was a late 80's model hard top nt, that seams very low for the manufacture to be sayin,

me217

iv run about 15psi on 31 xterrains the last 6 months both on and off road with no issues, but took the car in for a service and the mechanic decided to put air in, so now they are HARD, i havnt checked the actual psi, but i reckon they are someware around the 35 mark.. scared the bejezus out of me when i picked it up, started rainin, hit a corner and almost 360 down the road! Bloody mechanics!!

me217 wrote:i saw a sierra in the wreckers the other day and the tyre placard said 20 psi front and rear unless loaded up then 20 front 26 rear. it was a late 80's model hard top nt, that seams very low for the manufacture to be sayin,

me217

Your car weighs about a tonne less than most cars, it requires lower than normal pressures.

My LWB 93 Vit on 225/75R15's = 30 on road, 15 off road, 8 for emergencies

10- 12 lbs on road
6-8 offroad
rides smoooth