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PSI for 33x10.50 on 15x7

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Old 02-25-2007, 06:05 PM
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PSI for 33x10.50 on 15x7

I haven't been able to get my tires to fully touch 100% of the tread since putting them on my truck about 2K miles ago. I am running around 26psi right now, but the edges still aren't touching. Does anyone have any suggestion about how low to go to make them touch or if it's even a problem as long as I keep everything rotated?

Thanks in Advanced
Chris
Old 02-25-2007, 06:07 PM
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35 PSI minimun. 26 is wayyyy too low
Old 02-25-2007, 06:28 PM
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32-35psi on warm tires
Old 02-26-2007, 06:13 AM
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How does putting a higher PSI in the tires help put more of the tread down?
Old 02-26-2007, 06:30 AM
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Originally Posted by 91ToyTrck
How does putting a higher PSI in the tires help put more of the tread down?
I'm not quite sure on your question, but I would like to no. I do no that 26psi is to low.
Old 02-26-2007, 06:55 AM
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I run between 35-40 on the road. The 33x10.50's are rated up to 50 psi.
Old 02-26-2007, 07:02 AM
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The way I've always understood it if a tire is underinflated it will cup pulling the center of the tread away from the road resulting in more wear on the outside while if its overinflated it will bulge in the center causing more wear in the center.
Old 02-26-2007, 11:46 AM
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That was always the case in the old bias-ply days, but not necessarily true with radials since the belt structure behind the tread is so much stiffer.

With the price of gas these days, I'm MUCH more worried about fuel economy than tread life, and would certainly want to be on the "overinflated" side more than the underinflated side...
Old 02-26-2007, 12:01 PM
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On 15x6 rims, I run anywhere from 20-50 psi in mine. Usually 20-30 around town and 30-50 on the highway:
- http://www.4crawler.com/Diesel/Tires...roperInflation

I get a flat contact patch in the low 20's, but usually lift the edges up a bit w/ higher pressures. This does increase center tread wear on the road, but off-road, the outsides tend to get chewed up more, so it all evens out over time.

Last edited by 4Crawler; 02-26-2007 at 12:05 PM.
Old 02-26-2007, 12:09 PM
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Chaulk line method to find the best pressure for YOUR rig.
Old 02-26-2007, 01:15 PM
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Thanks for the quick replies. I'm going to shoot them up to 35psi for a while and see how that works out. I can always add larger rims or lower the pressure down later.
Old 02-27-2007, 07:35 AM
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the edges are going to get eaten up with 26. i would suggest 35-40.
Old 02-27-2007, 08:05 AM
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Originally Posted by 91ToyTrck
How does putting a higher PSI in the tires help put more of the tread down?
It dosen't. If you want to have all of your tread touching the ground, drop more pressure. The problem with running a 10.5 on a 7" rim is that the side walls are being pulled in so you may have to go as low as 15psi before all your tread is on the ground. I would try just letting the air out of one of your tires slowly and see how far you really have to go to get it where you want it. The more air you put in it, the more the center of the tire's tread is going to push out. this will make your actual tread come up on the sides.
Old 02-27-2007, 11:24 AM
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I'm going to try a few different options. I guess I might have to break down and buy some 15x8s, but I love my SR5 rims. I really like how the tires are stiill in the fenderwells and don't rub when I turn the wheel.

The main vote is between 30-40spi right? I'm going to start at 35psi as soon as I get her running again.
Old 02-27-2007, 11:55 AM
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Here is what you do to find the best pressure, take the max pressure and subtract about 5-8psi and fill it around there.

Take some sidewalk chalk and draw a line right across the thread, get in and drive about 50 ft and dont turn. Get out and check to see where the chalk wore away. If you have the correct pressure your chalk will be worn away the same, if to little the sides will wear away and to much the center wears away.

This is the best method around, do not, I repeat do not listen to any yo-yo about putting in the stock pressures-those are for the stinking stock tires and stock tire size! I cannot stress this enough, I keep seeing people suggest this!
Old 02-27-2007, 02:13 PM
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I would never put the stock tire air pressure in my 33s. That would be crazy and just not smart. I know (from reading) that to low air pressure kills your gas mileage. My truck is my DD, so some kind of gas mileage is important.
Old 02-27-2007, 05:20 PM
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10.5's should be just fine on 7" rims
Old 03-01-2007, 04:34 AM
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I run 33"x12.5" MT's on my factory 15x7's @ 30lbs and they are fairly flat...
Old 03-01-2007, 07:34 AM
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i run 20-25psi on mine
Old 03-01-2007, 07:54 AM
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Wink Tire Pressure

I used to work at a upper end tire place and they always ran 32-35psi over the road....No less than 26-28psi off-road (for traction - but that is only for a few hours wheelin') and pretty much never over 36-38psi. I have 33.5 x 10.5 and I keep right at 35psi. Im getting 15 MPG with mixed freeway and around town driving...
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