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jp467 05-22-2011 11:30 PM

Tire Pressure and Balance
 
I have about 2200 miles on my Overland now and I love it. I have been playing witIh the tire pressure to find that perfect pressure. I know they recommend 36 cold with the 20 inch tires. I have been finding With the warmer weather that 36 quickly goes to 38 or 39 when driving on the highway. I have found this thing seems to have the perfect ride and handling when the pressure is around 36 hot rather than cold. When it gets up to 38 and 39 the tires seem to bounce alot over rough pavement and there is alot of that around here. Another thing I have noticed is I have a very slight vibration in the steering wheel only at 70 mph and when I say slight I mean slight sometimes it's not even there. So I am looking for some opinions on that. When I take it for the first oil change should I have to dealer balance them? Should I have them road force Balanced( not sure if my dealer does this). If I have them balanced I am going to have those weight on the outside of the wheel instead of glued inside. One other question I have for Overland owners. When I am going very slow over rough pavement sometime I will feel what almost feels like a clunk in the steerling wheel with no noise. It seems to be just when the left front wheel hits the bumps. It is only once in a while and again is very slight. Has anyone with an overland felt anything like this? Thanks

Red G8R 05-23-2011 08:08 AM

Re: Tire Pressure and Balance
 
First, I haven't experienced anything like yours with my Overland but it does sound like a balance problem. Factory balanced tires are usually perfect but I guess it's possible to be off. Road Force balancing should still be able to keep the weights hidden and I would never accept outside weights on any alloy rim.
All tire recommended pressures are cold pressures and are expected to go up with use. Starting at 36 psi cold, I would expect up to 40 psi hot or more but likewise the tires should be more pliable at higher temps and smoothness shouldn't change that much.
Having said that, my winter tires are 18" Blizzaks and are recommended to run them at 33psi but they feel so hard compared to the 20" Forteras at 36psi. I was so happy to get back on the Forteras after the winter.

Bmwister 05-23-2011 11:44 AM

Re: Tire Pressure and Balance
 
Quote:

Originally Posted by jp467 (Post 419090)
Another thing I have noticed is I have a very slight vibration in the steering wheel only at 70 mph and when I say slight I mean slight sometimes it's not even there. So I am looking for some opinions on that.

Many tires, even the best ones, often have small imperfections that are amplified under higher tire pressures especially in low-profile sizes; it is these small imperfections that can cause slight vibrations. Obviously, higher tire pressures will also transmit road imperfections more readily so do not rule out the road as a cause. Roads can have their own repeating texture frequencies that can be sensed as wheel vibration.

I run 33psi cold for the 20" stock wheels and tires and see 35-36psi heated up. That feels best for for myself for ride comfort/handling. That said, I do run 36psi cold when loaded for a trip and/or towing. But, for my big old derriere, 33psi cold is working well and there is no unusual wear after many thousands of miles.

MikeD 05-23-2011 12:47 PM

Re: Tire Pressure and Balance
 
Quote:

Originally Posted by jp467 (Post 419090)
So I One other question I have for Overland owners. When I am going very slow over rough pavement sometime I will feel what almost feels like a clunk in the steering wheel with no noise. It seems to be just when the left front wheel hits the bumps. It is only once in a while and again is very slight. Has anyone with an overland felt anything like this? Thanks


I have the same issue with the clunk, almost like the steering wheel is a little loose, it doesn't happen often but I do notice it when it does.

Lingohocken 05-23-2011 01:13 PM

Re: Tire Pressure and Balance
 
Fill with nitrogen and the pressure should remain relatively constant regardless of temperature.

JayB 05-23-2011 01:19 PM

Re: Tire Pressure and Balance
 
Quote:

Originally Posted by Lingohocken (Post 419314)
Fill with nitrogen and the pressure should remain relatively constant regardless of temperature.

Sure.... if by "relatively" you mean it will vary constantly with the ideal gas laws... then yes ;)

Red G8R 05-23-2011 04:41 PM

Re: Tire Pressure and Balance
 
Quote:

Originally Posted by Lingohocken (Post 419314)
Fill with nitrogen and the pressure should remain relatively constant regardless of temperature.

That's a great suggestion.

jp467 05-23-2011 06:38 PM

Re: Tire Pressure and Balance
 
Quote:

Originally Posted by MikeD (Post 419299)
I have the same issue with the clunk, almost like the steering wheel is a little loose, it doesn't happen often but I do notice it when it does.


Have you had this checked out?

Andrew Klossner 05-23-2011 07:06 PM

Re: Tire Pressure and Balance
 
Quote:

Originally Posted by Red G8R (Post 419425)
That's a great suggestion.

Is that tongue in cheek? As JayB pointed out, nitrogen expands with temperature at exactly the same rate as any other gas.

The reason to use straight nitrogen instead of an atmospheric 80-20 nitrogen/oxygen mix is to reduce the amount the tires deflate over time due to oxygen escaping the system. Unbiased studies, like this one, suggest that the effect is slight and not worth the expense, compared with monitoring your tire pressure and inflating as necessary. There are also claims that a dry nitrogen load with low water vapor is beneficial.

shamus 05-23-2011 11:35 PM

Re: Tire Pressure and Balance
 
dealer used nitrogen in mine and tires flucuate from 36 to 41

Lingohocken 05-23-2011 11:42 PM

Re: Tire Pressure and Balance
 
Quote:

Originally Posted by Andrew Klossner (Post 419556)
Is that tongue in cheek? As JayB pointed out, nitrogen expands with temperature at exactly the same rate as any other gas.

The reason to use straight nitrogen instead of an atmospheric 80-20 nitrogen/oxygen mix is to reduce the amount the tires deflate over time due to oxygen escaping the system. Unbiased studies, like this one, suggest that the effect is slight and not worth the expense, compared with monitoring your tire pressure and inflating as necessary. There are also claims that a dry nitrogen load with low water vapor is beneficial.

And, yes, there are endless opinions on this (see for example the comments to the above link: http://news.consumerreports.org/cars...en-tires-.html). Yer pays yer money, yer takes yer choices, and guys I trust say their firsthand experience is diminished change in pressure with ambient temperature or friction from driving. That said, the impact could be due to the lack of moisture in nitrogen filling systems.

mjw930 05-24-2011 09:06 AM

Re: Tire Pressure and Balance
 
I had similar issues with the stock Goodyear's, slight vibration between 68 - 74 mph and a generally sloppy feeling when under inflated and a "bouncy" feeling when over inflated. I had them rebalanced and that helped but it was still not optimal.

I replaced them with Michelin Latitude Tour HP's running 36/36 nominal cold pressure. The ride is as close to perfect as you could ever expect on this platform. I see an average 2 lb increase when hot (Florida 90+ degrees at highway speeds). When towing I set them to 38/42 cold and over 2500 miles it worked perfectly, adding the additional stiffness needed to resist sway while not negatively impacting ride comfort.

So, part of your issues are the brand of tire IMHO. It's not something Jeep will correct for you, aside from re-balancing or replacement with the same tire if one is deemed to be out of round. If it really bothers you, like it did me, then you can replace them but be prepared to spend over $1000 to get a really good tire.

As for nitrogen, it's mainly something that came from racing where inert gasses have been used for decades to stabilize pressures. It's not so much the removal of oxygen that helps but the removal of moisture. Line dryers help but as long as you have hydrogen and oxygen in the mix the pressure fluctuations as you get close to the boiling point of water will drive you nuts on the track. Nitrogen eliminated the water issue so pressures can be managed in a more linear fashion as the tire temp rises. For street tires it's a waste of time and money IMHO.


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