12.00-20 psi

[USN_Green_Addict]

I just got some 12.00-20 tires put on. What's the best way to figure out the correct PSI?

 

[tobyS]

So you are running them as singles?

 

[USN_Green_Addict]

So you are running them as singles?

Yes

 

[montaillou]

The manufacturer will have recommended PSI in their catalog. If the tires aren't made anymore, old catalogs are easy to find with a web search, though very old ones, 10+ years get harder to find. Or, find a tire similar and see what they recommend for that. For instance, look at the 12R20 XZL here: http://www.thebox.fr/Michelin/XFORCEMILITAR040416.pdf

 

[williamh]

I gotta say I had the same question when I put on my tires , they were used but are at 98% I looked around and couldn’t find crap. I have the basically the same tires and I’m running 70psi all the way around , they are rated for 120psi for maximum load , driving on a flat surface after driving on dirt I noticed the rear tires show they may be a little over pressurized due to not 100% contact with the pavement , dirt still on the outside of the tread I haven’t lowered the pressure yet but thinking of dropping down to 60. I was running 50 with my original tires but was doing 60/40 on/off road , i was more concerned about over stressing the sidewalks by running them too low of pressure , I've only put about 500 mi on them since install , my biggest issue with it now is it wants to wander all over the road when it’s uneven and I didn’t have that issue before going to radial tires. I did flip the hubs and are running M135 rims that have the proper offset for running as singles. Front tires don’t have that issue

 

[cattlerepairman]

The front end geometry is set up for bias ply tires. You will want to first measure (and, if needed, adjust) toe-in. Typically, with bias ply, toe in is set at 1/4 inch toe in. You will want to turn that to zero. Then road test and see whether manners improved. If it is better, but still bad, read up on the modification to the front spring perches. Gringeltaube has good graphics.

In a w/w/ truck, the front axle is close to max weight even with the truck empty. Radials will want around 70-85 psi front tire pressure. If you are empty and the rear axles are very lively and bouncy, check your dog bone ends and trunnion for play. Radials will amplify existing issues in this department. Swapping in the upgraded heavy duty dog bone ends (Heim joints) did more for calming the rear end than anything else I had done. Empty, I run my radials as low as 55 psi. This is not on the manufacturer's chart (because they do not make charts for people that drive their truck around for fun, without carrying a load). Side wall flex is minimal on the empty truck at 55 psi.

Your results will vary; you may need to experiment a bit.

 

[USN_Green_Addict]

The front end geometry is set up for bias ply tires. You will want to first measure (and, if needed, adjust) toe-in. Typically, with bias ply, toe in is set at 1/4 inch toe in. You will want to turn that to zero. Then road test and see whether manners improved. If it is better, but still bad, read up on the modification to the front spring perches. Gringeltaube has good graphics.

In a w/w/ truck, the front axle is close to max weight even with the truck empty. Radials will want around 70-85 psi front tire pressure. If you are empty and the rear axles are very lively and bouncy, check your dog bone ends and trunnion for play. Radials will amplify existing issues in this department. Swapping in the upgraded heavy duty dog bone ends (Heim joints) did more for calming the rear end than anything else I had done. Empty, I run my radials as low as 55 psi. This is not on the manufacturer's chart (because they do not make charts for people that drive their truck around for fun, without carrying a load). Side wall flex is minimal on the empty truck at 55 psi.

Your results will vary; you may need to experiment a bit.

I appreciate the information, I'm thinking about doing an alignment after I swap out the tierod ends. My dog bone ends are only a year old. I mostly run mine empty.