tire pressure suggestions

[K5dreamer]

Hey all, im running 33x12.5 - R15 goodyear wrangler MT/R's on my 86 blazer 4x4. and was wondering what yall would reccomend for tire pressure. right now im running around 32 psi, but i keep reading about guys running like 70-90 psi, which i thought was dually terrirory. this is my first truck so im a bit confused. i wouldnt mind running a bit higher pressure on the tires for better mileage, but i dont want to over air and blow the tire.

Thanks for any input.

 

[ryan22re]

32 is probably where you want to be. If your tires are a C load range or even D range, the max psi would be around 60 PSI, more like 44-50. The max pressure for your tires should be printed on the sidewall somewhere.

If the tires start to wear on the edges and not the center, the pressure it too low. If the tires wear in the center they are overinflated. You may try changing the air pressure in the tires to see how it changes the ride and handling to suit your driving style.

 

[southernspeed]

Yeah, as ryan says. I run between 30 and 35 on my 35" BFG m/ts on the road.

 

[Randy92782]

i wanted to know this also. my tires are 35 14.50's on 10" wide wheels. they ride fine but i have to run around 10lbs of air in em to get them to wear evenly. i need wider wheels i guess but it's only temperary now. just afraid imma run the tire off the bead

 

[K5dreamer]

thanks all, i had thought i was in the right, but i was reading reviews about guys running those high pressures in the mt/r's and was very confused.

 

[Blue85]

First of all, forget about the fact that 90% of passener cars run 30-32psi all year round regardless of load. For one thing, they don't all do it right. Secondly, once you start swapping tire sizes, the factory recommendations are irrelevant and you have to re-evaluate the correct presssure.

In theory, the pressure should depend on the weight. The tire has a max pressure and a max weight stamped on the sidewall. These two numbers go together, meaning you only run that much pressure with that much weight. The 2nd data point is 0 PSI @ 0 lbs. For all weights in-between, just interpolate to get the right pressure.

The bigger your tires, the less pressure you need. Remember that PSI = lbs/sq. in. If your vehicle doesn't get heavier, but the surface of the contact patch grows, that means less PSI required.

In the end you will still probably tweak it based on performance. Some run extra pressure for improved fuel economy. Some run less for a smoother ride. Personally I try to run what gives the most even tire wear.


I think 32 psi will be a little high for 33" tires. I wouldn't be surprised if 28 is a better number. Maybe more in the front and less in the back.

 

[Greg72]

Blue has is right.....

Look at the max pressure and max weight ratings on the sidewall... then do a little math.

My K5 weighs about 5000Lbs (~1250Lbs per tire)....with my 38" Swampers and the data on the sidewall, I calculated a "street" tire pressure of only 17 PSI.

Tire wear is perfectly even at that pressure, and the tires don't overheat.

 

[gmc4cw]

tire wear takes to long to tell you that the tires are over or under inflated. I run 28 in the rear and 30 in the front of my truck. I bump them all up to 40 for towing.

 

[6.2Blazer]

thanks all, i had thought i was in the right, but i was reading reviews about guys running those high pressures in the mt/r's and was very confused.

Just because it's an MT/R doesn't mean they all take the same pressure. Something like a 245/75R16 E rated tire is probably rated for a max. of 80 psi and 3,000 lbs. The 33x12.50 is only rated for 35 psi and 2,500 lbs.

With that said 32 psi is probably a little on the high side for these tires because that basically gives the tires the capability of supporting 9,000+ lbs.

 

[bear76]

I have never heard a better explaination of where to set my PSI.

Thanks.