tire Pressure
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More Turbo
Joined: Nov 2004
Posts: 590
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From: in the woods of Maine!
tire Pressure
I have some 36" TSL SX's on my 78 Bronco. I was wondering how many lbs pressure I should be running, it's goin' to be a daily driver that I will hammer through the trails every other day on my way home, or for some weekend fun.
Butt-Head
Joined: Apr 2004
Posts: 9,455
Likes: 2,938
From: Reed Point, MT
Actually, one of the 4x4 rags had a big article on this one time. The process they had was extremely lengthy, but it really makes sense if you think about it. I used this method on my bohemoth's Ground Hawgs. If you want to hear wierdness, I came up with the max. tire p.s.i. on the front which is 30 p.s.i., and 15 p.s.i. in the rear. It all comes down to vehicle weight. My pickup weighs 9075 lbs. according to the transfer station scale and over 68% of the wieght is on the front axle, hence the pressure difference. I am a firm believer in this method as I have over 16K highway miles on the Hawgs and three of them still look new at roughly 90% tread life. The last one is a special-case issue not related to pressure.
The trick involves clean pavement (newer blacktop works best), some of that sidewalk chalk (the BIG ones), and lots of time. First, air up the tires to max. PSI. Color about a six-inch wide path across the tread of the tires and move the pickup forward until the chalk contacts the pavement. Examine how much of the tread actually contacted the road. You'll probably notice that (on a pickup), the front tires put down more of a contact patch at max. psi than the rears.
Let some air out of each of the tires until you get the biggest contact patch with the highest air pressure possible. You'll notice the difference more with super-wide tires....I'm dreading doing the 49's
.
Hope it helps,
Cody
The trick involves clean pavement (newer blacktop works best), some of that sidewalk chalk (the BIG ones), and lots of time. First, air up the tires to max. PSI. Color about a six-inch wide path across the tread of the tires and move the pickup forward until the chalk contacts the pavement. Examine how much of the tread actually contacted the road. You'll probably notice that (on a pickup), the front tires put down more of a contact patch at max. psi than the rears.
Let some air out of each of the tires until you get the biggest contact patch with the highest air pressure possible. You'll notice the difference more with super-wide tires....I'm dreading doing the 49's
.Hope it helps,
Cody
Senior User
Joined: Jan 2002
Posts: 377
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yep, definately the best way to do it, except i just eyeball it. let air out until i think it looks like it is riding correctly. has to be better then when i bout my tires and they had 45lbs in them. Now i run 18 in rear and 25 up front
Post Fiend
Joined: Jul 2003
Posts: 11,945
Likes: 3
From: Spokane, WA
That's really interesting Cody. I never would have thought of doing that by measuring the contact patch. Something new to try PLUS I get to play with chalk. 
I guess once you know what pressure should be in them it wouldn't be a big deail to air down for offroad driving since you'll know exactly what to air them to when you're done.
I guess once you know what pressure should be in them it wouldn't be a big deail to air down for offroad driving since you'll know exactly what to air them to when you're done.
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