[matt91112011]

Hi guys,

Put some 31x10.5r15 simex centipedes on my vit about two weeks ago. Ran them at 15psi both times.

Drove mainly mud last week. And they performed great. Couldn't climb a steep rutted tree root rocky part on one track so installed a rear locker before I went out this weekend, went up that track same part no worries this week, thanks to the rear locker and it being a bit dryer this weekend.

Tyres were at 15psi again drove mainly rocky tracks this weekend and down hill mainly and I found the rear end always trying to slide past the front. Is this a locker issue or a tyre pressure issue?

What pressure do you guys run in mud and on rocks? The place I go has alot of each so I need a pressure that works for both.

What's the lowest pressure you can run without breaking beads?

Thanks

Matty

[fire60]

I have the same tyres on my 92 swb I run 10 PSI in mud with no bead locks and not had an problem. I have gone down to 8PSI but with some really hard driving in deep mud, I have de beaded twice at this pressure.

[BlueSuzy]

I used to run 10-12 anywhere to be safe.

Alot of guys run alot lower on here.

I once went out with a guy who had 0 in his sierra/simex's as they have a uber stiff sidewall, never popped off..

What locker have you got?

Rear overtaking the front seems to be the locker , you drive to suit though. Any steep smooth slippery side slopes, the locker will slide out, if open, it wouldnt happen as much.

[monley]

I run my tyres at 7-8psi for all the wheeling i do! I have only ever broken one bead and that was because it was literary ripped of the bead and i had to get snatched out at 90degeers to where i was stuck.

[alien]

matt91112011 wrote:

simex centipedes

rear end always trying to slide past the front.

thats half the answer there... the tread pattern on the pedes isnt so good on cross slopes, infact its pretty woeful IMO.

when i had mine i found they didnt truly bag out till around 2psi (tested in the driveway) - but i never went lower than 7 offroad and just took it easy going around any corners doing higher speed stuff.

They are very stiff in the sidewall. I know some USA folks go for a run on the street with theirs at low pressure to "soften" the sidewall but i doubt thats even effective.

I did have to run tubes in my simex though as the bead always got mud in it causing slow leaks.

[zooky08]

lowest i ran was 6psi with my swampers before i ripped the bead

[Brett]

Comes down to what size rim your running.

[alien]

i'll clarify - i ran 15x7 -15 rims.

[matt91112011]

Sweet thanks guys, Ill start with 10psi and go down from there.

Rim size is 15x7 offset -13

I don't think I have tubes in my tyres. So what happens if I break a bead? How do I pump it up again?

What do you guys run on the road? I'm running 30psi does that sound about right?

Cheers

[alien]

i ran my simex at 22psi front and 18psi rear on the road for an even contact patch - even then it still wore the center fast.

they wont last long on the road - mine went down to 50% tread being driven about 300km a week within about 9 months. lol

as for fixing a busted bead - do a youtube search =) carby cleaner and a lighter works a treat, but cover your eyebrows! haha

[bakerboy]

or onboard air my BFG AT's are forever getting crap in the bead, i swap the flat tyre with my spare, place the busted tyre under my rear bumper and get the jack out. this will seperate the tyre and rim and i use my onboard air to clean the bead, then use it pump it up because it is high volumeflow it will reset it

[MacDaddy]

matt91112011 wrote:

I don't think I have tubes in my tyres. So what happens if I break a bead? How do I pump it up again?

What do you guys run on the road? I'm running 30psi does that sound about right?

Cheers

There is a couple of ways to reseat the bead, you can put a ratchet strap in the middle of the tyre tread, and tighten it up, to bow the tread, and bend the sidewalls out, while pumping it up, a high capacity air compressor is a must....

Or an easier way, is to put a squirt of propane, or even some " Start Ya Bastard ", inside the tyre, as long as its flammable, and ignite it, it will go BANG, but your bead will be reseated, then just pump it up...

30psi is too much for a Vit, must be a hard ride, the tyre placard says 24psi, from memory, for a Vit, so try that, and enjoy a softer ride...

[Damo]

Last time I was out I ran 6 psi with no probs.235/85r16 on 16x7s

[stockman]

I run 10psi on and off road with 31's.

[atari4x4]

stockman wrote:

I run 10psi on and off road with 31's.

10psi on road, you must get wicked fuel economy & tyre life.

[stockman]

atari4x4 wrote:

stockman wrote:

I run 10psi on and off road with 31's.

10psi on road, you must get wicked fuel economy & tyre life.

I don't drive it much. Just to and from the tracks and to work once every blue moon. Fuel economy has dropped to 300 per tank, but that's still alot more then other Sierra's get on stock tyres.

[Gwagensteve]

matt91112011 wrote:

Sweet thanks guys, Ill start with 10psi and go down from there.

Rim size is 15x7 offset -13

I don't think I have tubes in my tyres. So what happens if I break a bead? How do I pump it up again?

What do you guys run on the road? I'm running 30psi does that sound about right?

Cheers

Don't go too much under 10. Simex's fall off beads if you look at them funny because they are stiff in the sidewall. It's not important what size - they all do it. They will probably start to work properly a 5-6 psi, you'll have to stay a long way above that or get some beadlocks.

Some tyres (with tubes) will stay on the bead at 5-6 psi and not fall off, but not Simexes.

If you are experimenting with low tyre pressures, it's critical you have a reliable compressor (preferably with an air tank) and some basic knowledge about how to reseat a bead. Tubes are helpful to avoid loosing a bead, but it is still possible to pinch a bead or rip the valve stem off if the tyre slips on the wheel.

I don't think I'd run over 24psi on road, maybe 20. A simex is much stiffer than a stock tyre so won't need as much air.

Steve.

[stockman]

Gwagensteve wrote:

matt91112011 wrote:

Sweet thanks guys, Ill start with 10psi and go down from there.

Rim size is 15x7 offset -13

I don't think I have tubes in my tyres. So what happens if I break a bead? How do I pump it up again?

What do you guys run on the road? I'm running 30psi does that sound about right?

Cheers

Don't go too much under 10. Simex's fall off beads if you look at them funny because they are stiff in the sidewall. It's not important what size - they all do it. They will probably start to work properly a 5-6 psi, you'll have to stay a long way above that or get some beadlocks.

Some tyres (with tubes) will stay on the bead at 5-6 psi and not fall off, but not Simexes.

If you are experimenting with low tyre pressures, it's critical you have a reliable compressor (preferably with an air tank) and some basic knowledge about how to reseat a bead. Tubes are helpful to avoid loosing a bead, but it is still possible to pinch a bead or rip the valve stem off if the tyre slips on the wheel.

I don't think I'd run over 24psi on road, maybe 20. A simex is much stiffer than a stock tyre so won't need as much air.

Steve.

If you run a tube would it be worth having two valves? One for the tube and one for tubeless. That way if you pinch the tube you could rely on tubeless to get home.

[alien]

wont work cos the tube hole would still be open =)

if you're going to drill a 2nd hole in ur rim (illegal) might as well put internal beadlocks in the rim.

[stockman]

alien wrote:

wont work cos the tube hole would still be open =)

if you're going to drill a 2nd hole in ur rim (illegal) might as well put internal beadlocks in the rim.

Sorry. I was thinking if it was a pinch flat.

[alien]

same thing still.. a tube's valve just pokes through the valve hole, its not sealed against the rim. so if the tube goes flat the valve stem falls into the rim and leaves the valve hole open.

[SierraDan]

I usually run 8psi anywhere offroad.

Had them at 2psi on the weekend just to see. Went great!

[stockman]

blonde moment

[matt91112011]

Thanks for all the replies guys, I'll try 24psi on road and 10 off.

I don't have a high volume compressor. Are the ARB ones high volume?

Cheers

[Gwagensteve]

There's a very small arb compressor which is sold for lockers only.

There is a single motor compressor, which is adequate - better than most electric compresspors, or the new twin motor compressor which looks to be awesome.

For bead reseating you really need a tank though.

Steve.

PS you are sort of on the money stockman - ideally you'd carry a spare tube, tube repair kit, some tyre levers, and if all that fails, you'd carry a couple of tubeless valve stems so you could ditch the tube altogether and run tubeless if you really wrecked everything tube-wise.

[TryHard]

i have herd the new ARB Compressors are able to run air tools not sure if this is true but would be a Awesome thing to be able to do run locks /air tools /pump tyres faster we may hate arb some times but they do seem to have some good products
http://www.arb.com.au/media/press/July2 ... essors.pdf

[Ella]

ive had issues with tearing out valves running low pressure with tubes, the wheel turns and the tire doesnt when you get a big gob of grip kind of the same sort of condition where youd normally de-bead the tire.

[Gwagensteve]

TryHard wrote:

i have herd the new ARB Compressors are able to run air tools not sure if this is true but would be a Awesome thing to be able to do run locks /air tools /pump tyres faster we may hate arb some times but they do seem to have some good products
http://www.arb.com.au/media/press/July2 ... essors.pdf

6CFM will run an efficient air tool, very comfortably with a tank.

A guy in the Vic club is running a 6CFM endless air system and wants to run a new ARB compressor in parallel= 12cfm

He's running 35 13.5 Krawlers @ 5spi offroad - they take a while to air up, even at 6 cfm

I think the new ARB compressor offers the best bang for the buck available. Engine compressors are cheap but do need lots of time and effort to set up.

Steve.

[Junior_91]

I run 4psi with my swampers and they haven't come off unless i have ripped a valve out.

[Gwagensteve]

I'm sure you do - but swampers aren't 'pedes.
I've seen 36" pedes come off rims at 16 psi - I'll grant you that was on a LWB patrol, but still.....

Steve.