[Deego]

I just fitted a set of 30s on my sierra what tyre pressure should I be running on road and whats a good pressure when offroading on sand and rock.

[mrw82]

Google 4psi rule.

[atari4x4]

http://lmgtfy.com/?q=4psi+rule

i'd start off with whats recommended on the tyre placard for road going pressures, in sand you could start at 15psi & go as low as 10psi, similar sort of tyre pressures for rocks & off road etc.

just keep in mind that the reduced pressures means that you can roll a tyre off the bead easily, eg be aware of your steering input.

[Deego]

Ok thanks mate

[Reubs]

Sierra on 30"s - IMO no higher than 18PSI EVER!

8-10PSI off-road should be OK.

[Rossco]

I got a tyre repaired at a tyre shop and they filled my 30s to 45 PSI. First I drove I the hospital to have my spine realigned and two new kidneys and then I let them all down to 20 for on road use.

[Daves4wd]

I ran 20 psi in mine on road and 10 psi off road and it was fine

[masterA]

22-25 on road and 8-10 off road for 15x7 - 31" Simutomo
22 on road and 9-10 off road for 15x7 - 30" Maxis Bighorns

Sierra is a very light car and high pressures mean a very bumpy ride and your back/neck is going to hate you for it

[ChrisRinai]

really that low for road use??? hmmmm......... i will have to drop mine right down then and see how it drives, currently on 34psi ( 31 x 10.5 x 15 Copper STT's ).

i did notice that for beach/dune driving in Lancelin ( first time 4wd'ing ) i had to keep dropping the psi to get the car to roll well enough on the sand, i think we ended up down to 8psi to get the tyres baggin'!!

[Tyron]

I use 10psi offroad with 31"s i'll probly go down to 7-8 with the 33"s
it's also about your driving style aswell. If you drive like an idiot. you'll always cause damage if you deflate your tyres a significant amount
I wouldnt like to go down to below 25 on road. mainly due to steering performance, tyre wear and fuel consumption.
But that's just me

[ChrisRinai]

Tyron wrote:

I use 10psi offroad with 31"s i'll probly go down to 7-8 with the 33"s
it's also about your driving style aswell. If you drive like an idiot. you'll always cause damage if you deflate your tyres a significant amount
I wouldnt like to go down to below 25 on road. mainly due to steering performance, tyre wear and fuel consumption.
But that's just me

yeah we started at 15psi but the car kept bogging down into the sand and didn't roll nicely/gently when coming to a stop ( was pretty soft ) so we reduced them some more, may have been 10psi but pretty sure when ended up at 8.

for the road, might drop my tyres down some more to 30 and see how she drives, lately i've been dropping them down a couple of psi trying to get a bit of a softer ride, she was a pretty hard ride with the near on 40psi Coopers & leaf springs!!!!

[Reubs]

ChrisRinai wrote:

really that low for road use??? hmmmm......... i will have to drop mine right down then and see how it drives, currently on 34psi ( 31 x 10.5 x 15 Copper STT's ).

i did notice that for beach/dune driving in Lancelin ( first time 4wd'ing ) i had to keep dropping the psi to get the car to roll well enough on the sand, i think we ended up down to 8psi to get the tyres baggin'!!

Yep, do a search for 'tyre pressure' and read through the 1000 or so other threads on this topic.

FYI the standard Sierra placard calls for 20PSI on a 205/70R15. A Commodore has about the same size tyre but weighs nearly twice as much as the Sierra so it needs 34PSI.

Larger tyres need less pressure to support the same weight. If you properly measure the contact patch under a 31" tyre on a sierra at 20PSI you will be amazed at how little tyre actually contacts the ground.

I drive every day on 215s at 22PSI on a Sierra. The same size on my Vit have about 24PSI due to the Vit being heavier. These pressures are higher than recommended as I do a lot of highway driving.

My Sierra with 31s has only ever had 15-20PSI on the highway. 20PSI is too high. 18PSI is a comfortable medium but 15PSI feels okay as well.

[Blkfxx]

I run ~18 psi on road, 30" maxxis buckshots on 6in wheels.

[Gwagensteve]

18-20 on road, as has been said.

Off road, the lower you go the better the tyres will work until you run out of diff clearance or the tyres fall off the rims.

I'd avoid going under 8 PSI without beadlocks, but I wouldn't run over about 12 off road.

Your tyres will probably work their best at around 5psi on rock and sand. If they don't stay on the rims at that pressure, that's a different problem. It is possible to run 5PSI without beadlocks though.

I know guys who don't run more than 10 PSI on road (with 33" bias ply tyres)

Steve.

[Matthew]

Gwagensteve wrote:

It is possible to run 5PSI without beadlocks though.

Yep, when I had fresh 29s and 15x7" rims 5psi was the go, after a few months though they would burp air under 8psi.

[norcorider]

I run 22onroad, 12 on sand and 7-9 on mud/rock 15x8 rim

[KEENSY85]

ChrisRinai wrote:

really that low for road use??? hmmmm......... i will have to drop mine right down then and see how it drives, currently on 34psi ( 31 x 10.5 x 15 Copper STT's ).

i did notice that for beach/dune driving in Lancelin ( first time 4wd'ing ) i had to keep dropping the psi to get the car to roll well enough on the sand, i think we ended up down to 8psi to get the tyres baggin'!!

I always around town with 28 and that was pretty good any lower and the Tyre felt to heavy,that was with 30" Yokohama muddys

[Bruce]

KEENSY85 wrote:

ChrisRinai wrote:

really that low for road use??? hmmmm......... i will have to drop mine right down then and see how it drives, currently on 34psi ( 31 x 10.5 x 15 Copper STT's ).

i did notice that for beach/dune driving in Lancelin ( first time 4wd'ing ) i had to keep dropping the psi to get the car to roll well enough on the sand, i think we ended up down to 8psi to get the tyres baggin'!!

I always around town with 28 and that was pretty good any lower and the Tyre felt to heavy,that was with 30" Yokohama muddys

Each to their own I guess. 28PSI
WAY too high for a zook on road JMO but as I said, each to their own.

[atari4x4]

Bruce wrote:

KEENSY85 wrote:

ChrisRinai wrote:

really that low for road use??? hmmmm......... i will have to drop mine right down then and see how it drives, currently on 34psi ( 31 x 10.5 x 15 Copper STT's ).

i did notice that for beach/dune driving in Lancelin ( first time 4wd'ing ) i had to keep dropping the psi to get the car to roll well enough on the sand, i think we ended up down to 8psi to get the tyres baggin'!!

I always around town with 28 and that was pretty good any lower and the Tyre felt to heavy,that was with 30" Yokohama muddys

Each to their own I guess. 28PSI
WAY too high for a zook on road JMO but as I said, each to their own.

^^^ he must have small girly arms

[Benny90]

wow no wonder mine is so damn stiff and bouncy!!! running my 30" muddies at 30PSI and about 16 off road..
will be dropping mine down to about 24ish on road then.. any lower and i think steering will feel crap?

[Tyron]

do a comparison. leave them at 40 for a tank. see how many kms you get.
drop them down to 20 and see how much more fuel you're using.

[Gwagensteve]

You can't seriously be advocating 40psi on road for a Sierra? That's just dangerous.

Steve.

[Tyron]

I'm not advocating it at all. nor am I saying 20 is a bad idea.
It should be a consideration of a few things
Such as Tyre wear, comfort, fuel consumption & braking
There are more factors than just "comfort" when considering tyre pressure.

[SierraDan]

Tyron wrote:

I'm not advocating it at all. nor am I saying 20 is a bad idea.
It should be a consideration of a few things
Such as Tyre wear, comfort, fuel consumption & braking
There are more factors than just "comfort" when considering tyre pressure.

Suzuki's tyre placard says 20(ish?) for a reason. Because it is the best pressure for, tyre wear, comfort, fuel, braking and handling.

[Tyron]

SierraDan wrote:

Tyron wrote:

I'm not advocating it at all. nor am I saying 20 is a bad idea.
It should be a consideration of a few things
Such as Tyre wear, comfort, fuel consumption & braking
There are more factors than just "comfort" when considering tyre pressure.

Suzuki's tyre placard says 20(ish?) for a reason. Because it is the best pressure for, tyre wear, comfort, fuel, braking and handling.

We're going to go off the tyre placard for running 30 inch tyres?
If we're going to be sticking to rules and regs let's not use the 30 inch tyres.
I tried my 31's at 20 psi and hated it sluggish and turning was a bitch in a car without p/s, wouldn't run them below 30. My personal preference.
Btw alot more fuel economic.
Try what you like and the decide

[christover1]

I found 25 is a happy medium for my Vitara on 31's.
I tried 29 in the Vit and 22 on the trtailer, for the long highway run to Beachport.
I was amazed at the increase in fuel economy.
Ride was harsher, though.

Off road I use 15 for easy and 10 for medium, and 8-9 for real difficult tracks.

[Tyron]

christover1 wrote:

I found 25 is a happy medium for my Vitara on 31's.
I tried 29 in the Vit and 22 on the trtailer, for the long highway run to Beachport.
I was amazed at the increase in fuel economy.Ride was harsher, though.

Off road I use 15 for easy and 10 for medium, and 8-9 for real difficult tracks.

My point exactly. Thanks Christover

[zukmeista]

Tyron wrote:

christover1 wrote:

I found 25 is a happy medium for my Vitara on 31's.
I tried 29 in the Vit and 22 on the trtailer, for the long highway run to Beachport.
I was amazed at the increase in fuel economy.Ride was harsher, though.

Off road I use 15 for easy and 10 for medium, and 8-9 for real difficult tracks.

My point exactly. Thanks Christover

And of course a LWB Vitara weighs exactly the same as a sierra

[Tyron]

zukmeista wrote:

Tyron wrote:

christover1 wrote:

I found 25 is a happy medium for my Vitara on 31's.
I tried 29 in the Vit and 22 on the trtailer, for the long highway run to Beachport.
I was amazed at the increase in fuel economy.Ride was harsher, though.

Off road I use 15 for easy and 10 for medium, and 8-9 for real difficult tracks.

My point exactly. Thanks Christover

And of course a LWB Vitara weighs exactly the same as a sierra

I was amazed at the increase in fuel economy.
Was the point.....

[shep]

Hard top Sierra with g16a and 30x9.5 mtr wranglers I ran 14 psi on road and 7 psi off. Never had a issue and it drove nicely.