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-   -   How to determine what tire pressure (http://www.jeepforum.com/forum/f15/how-determine-what-tire-pressure-1813978/)

4x4Jeep 11-21-2013 12:46 PM

How to determine what tire pressure
 
i have 245/75/16 MTR's (old style), i've been running them at 32 psi for as long as i can remember. 32 psi is what the stock tire says it should be for my jeep.

recently i've been trying to figure out how to get rid of this wobble (NOT DW) i have at 50+ mph and someone sent this article to me (click off-roading FAQ>Death Wobble) http://www.rmsoffroad.com/cool-stuff

so it basically says to fill your tires up to the max tire pressure....? this doesn't sound right. my max is 80 psi, yet i've been running about 32 (on-road). so today i tried filling up to 50 psi instead just see if it made a difference. i haven't driven it above 40 mph since i filled them up more, but it rode a lot rougher just at 50 psi.

by the way i'm just wanting to know for daily driving use, not off-road.

4x4Jeep 11-22-2013 09:46 AM

yea, so not only does it ride rougher now, but also did not correct my problem at 50+

DiscountTire 11-22-2013 05:30 PM

What exactly are you feeling at 50mph? If it feels like a vibration that cause could be a number of things but I would recommend having your tires checked for balance. If they are out of balance the pressure shouldn't make a difference.

As for the correct pressure... You should set your current tires to a pressure that will carry the same load as your factory tires at the recommended factory pressure. (We can help with this.) My system recommends 40psi for a 245/75R16 Goodyear MTR with Kevlar on a 2001 Jeep Grand Cherokee

geroux 11-23-2013 12:03 AM

If you're running the factory tire size, run the recommended pressure.
If not, it looks like Discount offered a recommendation.

There is also the chalk test. Air up, draw a chalk line across your tread and drive about 200'. Observe if the chalk has been removed uniformly. If you are aired up, at first it'll probably wear in the middle first. Keep airing down a little at a time and repeat until the chalk line is removed uniformly.

wilson1010 11-23-2013 01:40 AM

Tire pressure will have nothing to do with the problem you described. Go back to 32 psi. You were fine there.

If you feel the wobble (not DW) in your hands its the front end, if you feel it in your seat its the rear. Start with balancing one or both ends, report from there.

4x4Jeep 11-23-2013 09:45 AM

Quote:

Originally Posted by DiscountTire (Post 17932762)
What exactly are you feeling at 50mph? If it feels like a vibration that cause could be a number of things but I would recommend having your tires checked for balance. If they are out of balance the pressure shouldn't make a difference.

As for the correct pressure... You should set your current tires to a pressure that will carry the same load as your factory tires at the recommended factory pressure. (We can help with this.) My system recommends 40psi for a 245/75R16 Goodyear MTR with Kevlar on a 2001 Jeep Grand Cherokee

thanks. it's defiantly a wobble, much milder version of DW. i've been through everything checked and replaced things that it could be and i also had an alignment and balanced my wheels.


Quote:

Originally Posted by wilson1010 (Post 17942402)
Tire pressure will have nothing to do with the problem you described. Go back to 32 psi. You were fine there.

If you feel the wobble (not DW) in your hands its the front end, if you feel it in your seat its the rear. Start with balancing one or both ends, report from there.

if it has nothing to do with it then that article above is all bull****? and the person who showed it to me it fixed his death wobble problem. defiantly from the front btw.

i've had this problem for months now. in the past year or so i replaced all TRE's, both front wheel bearings, balanced wheels, alignment by someone who specializes in lifted jeeps, adjustable track bar plus checked myself for any play up front (none) and then had my mechanic check as well. the only thing they found was the lock nut on my track bar was loose. i tightened that up when i got home and it seemed to fix the problem for a day or two (which is weird) then the wobble started again, yet that nut was tight.

CJ7-Tim 11-23-2013 10:01 AM

A chalk test will get you to within a few psi of the correct tire pressure for your vehicles and it's modifications.

If you have steering wheel wiggle that comes and goes based entirely on road speed, your have a tire balance, or rim issue. Find an independent tire shop that has a Road Force Balance machine. The tire may need to be turned on the rim to offset a high spot before it will balance correctly. Nearly all retail tire stores are helpless and clueless when dealing with 4x4's and/or diagnostics.

If you have death wobble, you will know it because it is pee your pants scary, and the cure is the same as it always has been, replace all worn out or damaged steering and suspension components and make sure there is no physical damage, excessive wear, loose fasteners, or rust issues with the control arm and track bar mounting points. The info at the link above is total BS.

wilson1010 11-23-2013 11:28 AM

Quote:

Originally Posted by 4x4Jeep (Post 17946458)
thanks. it's defiantly a wobble, much milder version of DW. i've been through everything checked and replaced things that it could be and i also had an alignment and balanced my wheels.

if it has nothing to do with it then that article above is all bull****? and the person who showed it to me it fixed his death wobble problem. defiantly from the front btw.

OK, two things. First, the article you above linked is pure, unadulterated stinking Bull****. Disregard it. It was written by morons. Seriously demented. Contrary to the advice of 99% of the guys here who have millions of off road miles. OK?

Second, you have to decide if you have death wobble or not.

Let me tell you how you will know. If the wobble is there all the time, just mild when you take off, feeling it a little as you get rolling and more significantly at highway speed, you do not have death wobble. Your problem is a drive train component out of balance. Tires, wheels, axles, u joints, diff bearings and/or shafts, etc.

If your rig runs just fine, smooth as can be 95% of the time and just when you think all is going well you hit some potholes or whatnot at 50 mph or so and all Hell breaks loose with your steering wheel shaking your hands and arms like you are having an epileptic fit, you have Death Wobble. Start a new topic, and use the search function before you do.

4x4Jeep 11-23-2013 05:01 PM

not sure why everyone keeps asking if it's death wobble, i clearly state in the first post that it is not death wobble. i've had it in the past due to a bad TRE and wheel bearing, but don't get it now.

imagine death wobble in a less violent, slower way and that's what i'm experiencing. yes it's coming from the front end and i feel it in the steering wheel. in a few months i should be getting new wheels/tires, so if it is a wheel problem i wont be running mine very long.

i want to mention one other thing. this wobble has been happening when i had a steering stabilizer, then one incident off-road it broke which i removed it, and now today i just put a new one on. i took it for a test drive and was able to get up to 60 mph before it started to wobble bad again (previously wobbled at 50). so it seems to have cured it just a little bit.

wilson1010....you mentioned it could be a shaft...one of my front cv boots is opened, been meaning to replace asap, that could cause it?

wilson1010 11-23-2013 05:36 PM

I suppose it could be a worn or bent CV just not bad enough to feel until you get it up to speed. Put the whole front end up in the air and rotate the axles by hand. See how it feels.

350TbiJeep 11-28-2013 11:18 AM

What's a good psi to air up 31x10.5x15 tires on a xj with a 350 in it? I wonder how much different that makes it smoother while driving

wilson1010 11-28-2013 08:34 PM

Quote:

Originally Posted by 350TbiJeep (Post 18089994)
What's a good psi to air up 31x10.5x15 tires on a xj with a 350 in it? I wonder how much different that makes it smoother while driving

There's hardly any difference at all weight wise.

350TbiJeep 11-29-2013 10:21 AM

Quote:

Originally Posted by wilson1010 (Post 18101018)
There's hardly any difference at all weight wise.

But what pressure are you guys running while crawling compared to roading?

wilson1010 11-29-2013 01:59 PM

Quote:

Originally Posted by 350TbiJeep (Post 18109274)
But what pressure are you guys running while crawling compared to roading?

I recommend 12-15 psi for crawling. Very low chance of debeading but double the contact area from a highway psi of 32.


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