10-28-2005, 11:47 AM
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#1
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Join Date: Apr 2005
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Tire Pressure
hey,
Ive had my wranglers on for about 4 months now. When i bought the tires the guy told me to run 40 Psi all around..because i went from P265/70/16 to LT265/75/16's , also went from a standard load range (P to LT 10 ply) do you think is a good idea or nay? or just personal prefernce?
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10-28-2005, 12:23 PM
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#2
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somebody correct me if im wrong, but i really dont think you need to run that high of psi in your tires. you went from a p to a lt tire with stronger sidewalls. they probably say you could put a max of 65 psi or so, but it doesnt mean you should.
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10-28-2005, 12:50 PM
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#3
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wow 40??
i run 30-32 in my mt/rs...
a friend runs around 25-28 in his bfg ko's...
id say 40 is too much.
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11-08-2005, 01:28 AM
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#4
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More psi info
I have the same question, Kramer. I just bought a set of BFG All-Terrain T/A KO's. They are LT265/70R16/D, the same size as my originals, only LT's instead of P's. The manager at Discount Tire told me to keep them at 45 psi because they were "rated 65 psi max" and would run too hot at lower psi. The tech who checked my allignment after the purchase was from another garage, and he agreed with the store manager. The tech said to keep at least 40 psi in them or else they might separate from the rim if I turned sharply at highway speeds! He didn't even mention the heat issue.
However, several 4x4er's I have talked to since the purchase, including a service writer at the local T-dealership, say I will prematurely wear out the center of the tire at those pressures. I performed the "chalk test" to test the warning about uneven wear. I drew a thick white chalk line across my left front tire and drove my Runner straight ahead about 40 yards at 2-3 mph and then checked the line. The center was almost worn off while the lugs on the outside edges were barely touched. I dropped the pressure all around to 36 psi and repeated the test and discovered nearly uniform wearing. The 36 psi was with warm tires. When I checked the test pressure the next morning with cold tires, they were 33 psi. So indeed, there is evidence to suggest 40-45 psi could cause your tires to wear unevenly.
What I don't know about is the separation of tire and rim during high speed cornering nor the heat issue at highway speeds. I have not been able to find anyone in person or on the net who has heard of a problem when the pressure is 28-35 psi, no matter what tire, except maybe the old Firestones in summertime Texas. Even guys with large mudders on tiny lifted older Tacos run at 35 psi or less on the highway and drive as fast as their little 4-bangers will scoot with big boots. I called BFG customer service and they won't answer any questions because their chart doesn't show my size tire being recommended for a 4Runner. Legalities, I assume.
Selecting the correct highway pressure for any tire seems to be a matter of adjusting to the load, and you know you have the right psi for the load when the tire wears nearly uniformly on its available surface (the chalk test). I think I'm gonna run 32 cold psi on the highway with my KO's, which I really like by-the-way. (They crawled through some fairly deep north slope snow with a fresh covering southwest of Pikes Peak last Saturday morning without the slightest slip nor a bit of tire damage--there were plenty of rock and ledge surprises under the snow.)
On the other hand, if the Discount Tire manager is correct about 45 psi for highway safety on 65 psi max. LT tires, someone needs to speak up ASAP and present the evidence.
2000 SR5 5spd V6 with optional 16" wheels. No mods yet.
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11-08-2005, 10:52 AM
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#5
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i performed a little test with pressure last friday when i went up to connticut to pick up my buddy at qunnipiac..Had 40 psi in all the tires put em down to 35...infeact i didnt de-bead the tire nor lose any tread (still at 12/32nd) all around. i dont know why they told me to run so high with E's. my tires got so cupped from 40 psi =/
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'04 4Runner SR5-Weathertech mats/putco raingaurds/silverstar ultras/surco Safari rack/4 hella 500's/550's/Cornfed 3 inch/spidertraxx/285/70R17 cooper ATR's/JVC R800/cobra CB/black taillights/Axe and Shovel Adapter/Hi lift adapter and jack/Stubbs HDSKO sliders/FJ steelies
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11-08-2005, 04:47 PM
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#6
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Re: More psi info
Quote:
Originally posted by RockyMtRunner
The manager at Discount Tire told me...The tech said...I performed the "chalk test"
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With litigation out of control, you always have to wonder if undue caution motivates anyone speaking in an official capacity. It creates a seemingly unmanageable number of uncertainties so I think you simply have to go with the one piece of reliable information you have until better info presents itself. Treadwear, period.
My LT KOs are wearing well at cold 34.
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11-08-2005, 05:01 PM
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#7
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i did the same change, at 40 psi the centers did get a bit more wear. BUT at 32 psi i got 2-3 worse mpg. I think i'll go with better economy for a while.
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11-13-2005, 11:06 PM
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#8
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I've been experiment with tires pressures lately as well; I run LT265/70R16 (stock size) BFG All-Terrain TA/KO's on my '97 SR5 and like the poster, I heard/read somewhere that lower pressures can be bad news on LT tires, which are designed for higher pressures.
I'd run 32k with no problems for some time, but I experiment and went all the way up to 48psi (!) and discovered after about a week that there was no point in the murderous ride. I dropped down to about 38psi, and have since found that about 35-36psi cold gives an acceptable ride, is only 4psi above Toyota's spec for the OEM Goodyears, and shouldn't result in any uneven wear (hopefully).
Running about 35psi cold, I got nearly 21mpg on a weekend trip to Vermont; I can live with that for an engine with 152k/mi & all the power I need right now.
Loaded & towing, I might air up to 44psi or so, but otherwise I'm staying mid-30s, then maybe dropping to around 30psi in deep snow...
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Last edited by bmanning; 11-13-2005 at 11:11 PM.
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