Air Pressure in 33's

[jsfrmsj]

For those of you with 33's, what PSI are you running?

I've done a search and found a lot of conflicting information. I know, I should just do the chalk test, but I'm just curious what other guys are running.

When I bought them, they were pumped up to 40 PSI, the max on the tire says 65 PSI.

I deflated them to 35 PSI.

 

[smdk2500]

What are you doing with the truck? Street driving, 4 wheeling. I ran all sorts of different tire pressures. If I was in sand I ran 5-8 psi. In mud I ran what the tire called for. For street driving I ran 20ish.

 

[jsfrmsj]

When I go in the sand I air down, with stock tires I did 15 psi.

I mostly do street driving, but I do hit the trails regularly. The trails are usually dirt, gravel, sometimes mud, with 6-8 inch rocks.

I also go to Lake Tahoe yearly which can see some moderate to light snow.

I never aired down for the trails and the snow with stock tires. Any help you guys have for pressure with 33's in the different scenarios is appreciated.

 

[east302]

I ran 33-psi in the front and 29 on the back on a K1500 with 285/75/16 BFGs. I’d guess that’s about a 33” tire. Tread wear has been fine, and that’s been since 2012 and around 30k miles.

 

[blacksport]

i thought he meant 33 in wheels LOL
i was thinking he had rubber-bands for tires

 

[east302]

Lol, I’m sure someone’s got them somewhere

 

[jdla140]

I've had my 33" mud grapplers on 2 different sets of wheels now.

One set was 8" wide, I kept the tires at less than 30 PSI at all times on those wheels. The other set is 10" wide, I keep them closer to 60 on those wheels.

It depends the width of your wheels and the weight of your truck. If you do some searching you can find how to check contact patch to find the right pressure.

 

[jsfrmsj]

I should probably get a signature sooner or later haha

I've got a K1500 Suburban coming in at 6k lbs give or take a couple hundred.

The tires are 33x12.5r16.5LT, they are E rated tires so they're good for towing which I do here and there.

The rims are 10 inches wide.

Again, I know I can do the chalk test. I'm just curious what other guys are running for their psi.

For those of you that ran 20 ish PSI, isn't that kind of low given the weight of a fullsize?

 

[smdk2500]

I didn't think it was to low. But different strokes for different folks. Im sure that it effected tire life. The truck i ran that low of pressure on wasn't a gmt-400 though. It was a late 70s f150 with a big block and they didn't seem to squish to much in the front. And just a FYI i wouldn't run much less then 10psi on those 16.5 rims unless you've got some sort of beadlock. Ive seen lots of guys running low air pressure with no bead locks on a 16.5 and they hit something and next thing they know they have lost the bead and have a flat.

 

[jsfrmsj]

So I did a little math today. I found an equation that says "Tire Weight / Tire Pressure = Load Rating per PSI".

The tires that I have indicate a max load rating of 3,525 lbs at 65 PSI. So, 3,525/65=54.23 lbs of load capacity per PSI.

According to the label on the door jam, the suburban has Gross Axle Wheel Rating of 3,925 lbs in the front. Which is 1,962.5 lbs per tire. 1,962.5/54.23 = 36.18 PSI

4,000 lbs for the rear, 2,000 per tire. 2,000/54.23 = 36.88 PSI.

All of which is to say that if the truck were completely maxed out as far as weight is concerned, I'd be safe with 37 PSI.