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Old 12-14-2010, 08:18 PM   #1
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tire psi?

I'm currently running 305-70/16 bfg's ta ko's... I'm just curious if my psi is correct?97 tj. 4.0... I'm running 40 psi now. Should I change it from winter to summer... 4 inch ome susp. Lift. It does ride kinda tight. Any info would be greatly appreciated....

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Old 12-14-2010, 08:25 PM   #2
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In run 28 in my 285's might want to try lowering that a bit....,

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Old 12-14-2010, 08:33 PM   #3
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I run 26-27 psi on my 33s. 40psi is WAY TOO MUCH!!!!
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Old 12-14-2010, 08:42 PM   #4
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Look at the PSI rating on the inside of your door. The ratings are assigned based on the vehicles weight not tire size so it doesn't matter that you have larger than stock tires.
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Old 12-14-2010, 11:44 PM   #5
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The best way I have found to ascertain the best pressure for your highway or city driving needs is to mark the entire tread surface of each tire with a piece of sidewalk chalk. Then alter the pressure untill it is all evenly worn off. If it's only worn in the center you have too much pressure in the tire.

I have found for my 33" MTZ's 20-21 PSI is the best for highway use.
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Old 12-14-2010, 11:46 PM   #6
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Quote:
Originally Posted by chamblin
The best way I have found to ascertain the best pressure for your highway or city driving needs is to mark the entire tread surface of each tire with a piece of sidewalk chalk. Then alter the pressure untill it is all evenly worn off. If it's only worn in the center you have too much pressure in the tire.

I have found for my 33" MTZ's 20-21 PSI is the best for highway use.
Does that hurt mpg alot?
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Old 12-15-2010, 12:21 AM   #7
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yea that seems abit low, i run 28 in my 33's a/ts on the road and low 20s offfroad
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Old 12-15-2010, 12:37 AM   #8
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I run 11-12 psi offroad and 26-27 on road on 33s MTs
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Old 12-15-2010, 12:41 AM   #9
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Alot also depends on the load rating a E tire is stiffer than a D so you want a lower PSI than in a D. My retreads are a BFG AT carcass that's D rated so I could probably go lower than I do but my round trip to work is 92 miles all hwy speeds, at 28 they are wearing even but I still have a nice ride. You just have to fiddle with it to get it right for you. That said I wouldn't run mine at 20, I think it would be a little squishy on curves and such esp as soft as the BFG sidewalls seem to be. Now an E rated MTR might be fine at 20 with the Kevlar, I know the 31's I had in the MTR were stiff as hell at 30 PSI!
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Old 12-15-2010, 01:57 AM   #10
Knows a couple things...

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If you're running 40 psi because you see 40 psi molded onto the tire's sidewall, that's a common error a lot of people make. The pressure molded onto a tire's sidewall is on the tire's maximum safe air pressure to be used ONLY when the tire is carrying its maximum possible load. Since most of our tires are carrying nowhere near their limits, usually only about 50% of that max limit, you'd never use the air pressure molded onto the sidewall.

Your 305/70/R16 tire is roughly equivilent to a 33" tire and a good air pressure for it would be 26 to perhaps 28 if you're taking a long highway trip and want to maximize fuel economy... certainly no more than that.

The air pressure shown in owner's manuals and on the door jambs only apply to the specific tire sizes those pressures are for which are also shown on the label. Generally speaking, the larger the tire, the less air pressure you need to run in it with a given vehicle weight.

Too much air pressure in a tire causes all kinds of problems... too stiff of a ride, vibration, uneven tire wear, and even a higher likelihood of tire damage should the tire hit something.
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Old 12-15-2010, 05:56 AM   #11
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Thank you all very much for the advice... I guess I'm gonna be taking some air outta my tires as soon as I get off work today. Lol... So honestly, is it better to lower the psi in my tires say, after I have been driving it for awhile. Or should I let the tires sit before I lower the psi.. I have heard people say before that you should set your tire pressures on a warm tire"after it's been driven" thanks again...
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Old 12-15-2010, 08:18 AM   #12
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Cold I think. Because the psi will increase when they warm up. Thus, if you adjust them when they're warm, when they are cold they'll be really low. And you'd be running low every time you took a short trip.








But, that may be the most ridiculous bunch of hooey I ever threw out there.... Makes sense to me on this cold, icky, most definitely blond morning tho'...
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Old 12-15-2010, 09:19 AM   #13
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Thanks infernogirl. I was thinking the same thing as doing it as a cold tire.
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Old 12-15-2010, 10:38 AM   #14
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Yep...pretty sure tire pressures are rated cold and not warm unless they say otherwise. So if it's recommended you fill them to 28 psi...then you should fill them to 28 psi while cold.
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Old 12-16-2010, 07:26 AM   #15
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Well I lowered all my tires down to 28 psi. All I can say is WOW!!! It diffently made a 100% difference... I remember when I would change lanes on the interstate and you know how there is a seperation in the asphalt between the lanes. The groove where the layed asplhalt beside the other asphalt. Well it used to kinda grab the jeep and kinda sling shot me a little. It doesn't do that anymore either. I hope y'all understand what I was talking about. It's early in the morning and that was the best way I could describe it.... Lmbo :-). Have a great day WF!!!! Thanks everyone...
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Old 12-16-2010, 09:42 PM   #16
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Does that hurt mpg alot?
Not really. Of course if I ran them at 40 I would probably see a significant gain I imagine. But I really don't drive my Jeep much on the highway nor is mileage really something I think about with the Jeep.
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Old 12-16-2010, 10:34 PM   #17
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Not really. Of course if I ran them at 40 I would probably see a significant gain I imagine. But I really don't drive my Jeep much on the highway nor is mileage really something I think about with the Jeep.
Wish i could say the same thing But then again you know going into it how low of mpg jeeps get so i guess its all good.
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Old 12-18-2010, 09:54 PM   #18
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Look at the PSI rating on the inside of your door. The ratings are assigned based on the vehicles weight not tire size so it doesn't matter that you have larger than stock tires.
Wrong. Try again.

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