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Old 11-03-2012, 02:44 PM
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Tire Pressure Questions

It seems that the factory recommended tire pressure is 37 for our GCs, or at least mine (hemi with 20s). And I notice the ride is firm and a little lower pressure would certainly help. I've always run about 32 in my cars in the past and so 37 seems high. And one morning when it was cold one sensor went off for being low tire pressure at 35.

I also just got some slightly larger tires (275/55/20) and was curious if running the pressure this high would cause premature wear by 'ballooning' the tire, specially considering I'm running the stock rims and these tires are a tad wide for them.

So- what is everyone on here running for pressure and what are the results?
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Old 11-03-2012, 04:34 PM
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Re: Tire Pressure Questions

Get some kids sidewalk chalk, make a line across your tires. Drive just far enough to rotate the tires a couple of times and check your chalk lines. The chalk should be worn off even across the tread. If the middle is gone, to much tire pressure. If the outsides are gone, not enough. I run 32 psi in my wife's 275/55/20 Silent Armor and the same on my JK. They're both 5000lb vehicles. 40 psi in my 3/4 ton pickup empty, 60 if hauling anything.
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Old 11-03-2012, 06:59 PM
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Re: Tire Pressure Questions

What about the tpms going off?
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Old 11-03-2012, 08:49 PM
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Re: Tire Pressure Questions

You need to run at least 36 in the OEM GY to keep them from vibrating. Many here run 40 psi with even tire wear. I try to keep mine around 36, which is the 2011 recommended pressure, perhaps 38. The newer tires are designed to run with a bit more pressure to reduce rolling resistance and increase mpg. They ride "softer" with QL.

How do you know the TPMS went off at 35psi? That is higher than it is suppose to. The alert usually gets set down around 29psi, it may take 35 or 36 psi to reset the alert once it is triggered. That's TPMS sensor psi, the number displayed in the EVIC, which may be off from an accurate tire gauge.

Your brand of larger tires may have a stiffer sidewall which will contribute to the firm ride.
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Old 11-03-2012, 09:54 PM
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Re: Tire Pressure Questions

Quote:
Originally Posted by ColdCase View Post
You need to run at least 36 in the OEM GY to keep them from vibrating. Many here run 40 psi with even tire wear. I try to keep mine around 36, which is the 2011 recommended pressure, perhaps 38. The newer tires are designed to run with a bit more pressure to reduce rolling resistance and increase mpg. They ride "softer" with QL.

How do you know the TPMS went off at 35psi? That is higher than it is suppose to. The alert usually gets set down around 29psi, it may take 35 or 36 psi to reset the alert once it is triggered. That's TPMS sensor psi, the number displayed in the EVIC, which may be off from an accurate tire gauge.

Your brand of larger tires may have a stiffer sidewall which will contribute to the firm ride.
The ride was firm with the factory tires too. I guess I was just used to the one from my WJ. As for the tire pressure it could be going off because of variation too. It displayed a message on the evic. It was at :35 (checked with a gauge and indicated the same) while the others were at 37. I think the most important is to do the chalk test.
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Old 11-04-2012, 10:38 AM
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Re: Tire Pressure Questions

What do you mean by variation? If you have a warning going off at 35psi, you have a defect in the TPMS.

Our KK tires are typically set to 34 cold 60 degree weather. If I don't adjust for winter use, I notice that when the tires gets cold overnight in 30 degree weather, the tire pressure will drop enough to set the alert after you drive off. By the time I stop and check tire pressure, the tires have warmed up enough to indicate like 32 psi. (A visual tire check is part of my pre-flight checklist so I would notice a really low or flat tire).

Ride is subjective, to some its firm, to others its just right.

With the current belting design, the chalk test will not likely provide reliable results, or may be misleading, as both a dangerously low or high tire will have near the same contact patch across the tread.
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Old 11-05-2012, 08:53 AM
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Re: Tire Pressure Questions

Quote:
Originally Posted by ColdCase View Post
What do you mean by variation? If you have a warning going off at 35psi, you have a defect in the TPMS.

Our KK tires are typically set to 34 cold 60 degree weather. If I don't adjust for winter use, I notice that when the tires gets cold overnight in 30 degree weather, the tire pressure will drop enough to set the alert after you drive off. By the time I stop and check tire pressure, the tires have warmed up enough to indicate like 32 psi. (A visual tire check is part of my pre-flight checklist so I would notice a really low or flat tire).

Ride is subjective, to some its firm, to others its just right.

With the current belting design, the chalk test will not likely provide reliable results, or may be misleading, as both a dangerously low or high tire will have near the same contact patch across the tread.
By variation- I mean the variation between the tires. One was 35 the other 3 were 37. I'm curious if this also sets it off.
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Old 11-05-2012, 10:29 AM
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Re: Tire Pressure Questions

No the pressure variation does not set the alert, only a low pressure reading.
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