What tire pressure to use.

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platypusREX

platypusREX

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I looked in the owners manual and the specs. are for the old school bias ply tire.

What is the proper tire pressure for a modern day tire? It doesn't say on the side wall. It just 50 psi max @ 1900 llbs. I have 31 in them right now.

Any suggestions?
Thanks
Antoine
 
I run 30-33 highway

12-14 offroad
 
I'm with ya. 30-32 on road 15-18 on the trail.
 
Years ago Armstrong tires published a PSI chart based on vehicle weight . Their Norseman tire ( now a Dick Cepek Fun Country ) in a 31" tire on an FJ40 was optimal at 27 PSI highway. Off road 12~18.
The lower tire pressures will promote tread separation so save the 12 PSI for when you really need it.
Nowadays the advertised pressures are generic and conservative in the manufacturers best interests
 
I had the same question myself for road-running. However, it was answered at a very recent wheel balance when I noted that the tyre shop inflated them to 32 psi. I'm guessing this is a conservative highway pressure.
 
I run my 12.5 x 33's 30 psi here in the PI on the road just to keep a grip as they stay wet a lot. On the Expressway 32 psi. Off road 18-20 psi. A friend of mine has a troopy and he runs the same.
 
N one has mentioned this yet but with the rear empty I always drop the pressure a a few psi in the back. My truck is more than happy loose traction back there first with a panic stop since the rear brake bias is so strong. And I check every new set of tires with a cheapo tire thermometer to get the temps even across the surface. That is how I ended up running less in the rear. Each make tire will be a bit different but 30 or ther about worked out well for my 235/85r16 bfg all terrains with around 27 in the rear unloaded. Fully loaded (my bj 44 is a half ton truck) I had the rear much higher than the fronts. I want to say about 37 or so.


Pete
 
4wd Toyota Owner just had good article about figuring out what tire pressure to run. Basically, you over inflate your tires and rub chalk on the tread. Then you roll it back and forth while adjusting the tire pressure until you get the chalk to wear off evenly. I have not tried it and the process seems it may take some time, but if it is that important to you it seems like this would be the most accurate way to dial in the pressures.
 
It definitely depends on the setup and the chaulk method is a good way to dial it in. I just got a set of 33x10.5 BFGs and have found that I need to run them around 40psi or they feel very soft and unstable. If I am running my 36" bias ply I run around 20-25 psi.

Eric
 
Just remember that your hot tire pressures will be the ones to check. If you do the chalk method be sure to do it with hot tires as cold pressures will be much lower.


Pete
 
General rule of thumb is 1 psi for every 100 pounds of rig weight, start there, and then use the chalk method to dial it in. You can also spray some water in a line and drive over it to see the tread pattern. This will get you in the ballpark. Given our trucks aren't exactly modern, I eyeball it and then leave it at that.
 
Monty231 said:
4wd Toyota Owner just had good article about figuring out what tire pressure to run. Basically, you over inflate your tires and rub chalk on the tread. Then you roll it back and forth while adjusting the tire pressure until you get the chalk to wear off evenly. I have not tried it and the process seems it may take some time, but if it is that important to you it seems like this would be the most accurate way to dial in the pressures.
Click to expand...

pavieSD said:
General rule of thumb is 1 psi for every 100 pounds of rig weight, start there, and then use the chalk method to dial it in. You can also spray some water in a line and drive over it to see the tread pattern. This will get you in the ballpark. Given our trucks aren't exactly modern, I eyeball it and then leave it at that.
Click to expand...

/\ These ideas...
What I have heard is that you must set the pressure for the unique tire/vehicle combo for optimal results.
So you drive through a little bit of water, just enough to wet the face of the tread and then study the foot print it leaves on the dry pavement to see how much contact you have. Decrease pressure until you have full contact, and then drop another 3 PSI.
 
My highway inflation meathod is simular to the chalk and water meathod. Drive through dirt than drive on asphalt, see if the whole tread width is touching the ground, add or subtract air to get full contact. Airing down is simpler, air down till you get a good sidewall buldge. Then try to remember YOUR own inflation pressures. This can be done without a tire gauge.
 
Years ago I did the chalk trick for Winston Fun & Muds (33x12.5-15 on 10" wheels) and ended up with 21 psi front and 17 psi rear; that was for a FJ40 SBC with hardtop on. Ran great on the streets and highways and only air'd down if traction became an issue off-road.
 
Isn't it hard to turn the steering wheel when it is low?
 
Grab the cage and rock till it looks right, works with or without a load, am I the only one?;)
 
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