Tire pressures

[CigarPundit]

I’ve been running 34/32 cold. Much higher than that starts to negatively affect the ride quality IMO. Might go a bit lower, if anything.

 

[JohnyPython]

I don’t know why I waited this long to do this. I’m running 38F 34R.

So much more planted in the rear. Feels smoother and the tires have quieted down as well.

 

[JLozano]

Running 38F/34R now, drives much better. Was given those figures at Raptor Assult in July.

 

[Jughead]

Door sticker says 38/38. I'll stick to that.

 

[Winchester30]

Raptor Assault trucks run at 32/28.

 

[jzweedyk]

Tire, pressure and wheel thoughts



It seems to me that there are a lot of questions on tires and wheels. I have never worked in a tire shop, but I have bought a lot of tires, wheeled off-road for over 20 years, belonged to a couple of Jeep clubs and have stayed at a Holiday Inn Express. Here are my thoughts, which are worth what you paid for them.

Wheel size; If you are driving a high performance sports car you want a large wheel for larger brakes and a shorter side wall on the tire (low profile) to give you quick response to steering input. (Very little sidewall flex)

If you are driving an off-road vehicle you want the opposite. A lot of side wall to soak up the irregularities in the trail, and to be able to air down without the wheel coming into contact with the tire tread. Since you also need brakes, the generally best wheel for this is 17 inches. Big enough for good brakes, but small enough for a lot of sidewall on 35”+ tires.

Tires; The size and tread pattern that will be best for you depends on what terrain you are going to be in. Knobby tires will big tread blocks and a lot of void areas are best for mud, as they can not only grip in the mud, but clean out quickly. Tires with small voids will turn into slicks in the mud, and therefore have little traction. Knobby tires can also work well if you are climbing a craggy rock face and need to grab on to the edges of rocks to get traction.

I do a lot of wheeling in Moab which has a lot of “slick rock”, which despite its name is basically sand paper on rock. So, the more rubber you put down (less voids) the greater the traction you will get.

Tread patterns are very personal, so use the one that fits your needs.

Tire size; Generally speaking, bigger is better. The downside to bigger is they are heavier, cost more and put more of a strain on vehicle components. If the tire is big, with a big tire patch, it will test other components, and the weakest link will break. Why is bigger better? The easiest way to understand this is to take it to the extreme. Think of a pebble rolling on cement and coming into contact with an expansion joint. It probably will get stuck and not be able to cross it. Now think of a 40” tire rolling on cement, when it reaches the expansion joint it won’t even slow down. So bigger tires can climb higher obstacles, give you more ground clearance, have a bigger sidewall to absorb shocks and bumps, and cross small “cracks” easily.

Tire Pressure; This is the most misunderstood area of tires. On road follow the vehicle manufacturer instructions. At speed low pressure tires will build heat quickly, and heat is the enemy of tires. Off-road is a different story. What does lower pressure do for you? One, more comfort. The sidewall can flex and absorb shocks better with less pressure. Take a tire inflated to the max and drop it a couple of feet, it will bounce back almost all the way up. Take a tire inflated to 10 psi and drop it, and it will hardly bounce. Two, wrap around obstacles for more grip. Three, increase the tire patch, which is the amount of the tire that is in contact with the ground. This accomplishes three things, one, lowers the pressure per square inch on the ground, which can keep you from sinking into things like sand. Two, gives you more rubber on the ground to increase the chance of getting some traction when climbing an obstacle. Three, lessons the chance of a tire puncture. Again, take it to the extreme. Think of a balloon. If it has hardly any air in it, you can push a pin in quite a way before it will pop. Inflate it to the max and the pin will pop it easily.

So, how low? It depends on several things. First what load range are your tires? C range will have the most flexible sidewalls, and as you go up the alphabet the sidewalls get stiffer. I have bead locks on my Jeep with 39” C range tires. However, the Jeep weighs 6,200 pounds, so if I go much below 10 psi and come down a steep grade where all the weight is on the front the tires will wrinkle up and get too close to the wheel. When I had load range E tires on it, I could go down to 4 psi before they would wrinkle too much. I like C range as it allows the tires to conform to the rocks and get a good grip.

Second what are you going to do? A gravel road will feel better if you drop about 10 pounds from street pressure. For medium trails 18-20 psi can work well. For more serious trails I go down to about 12.

Everyone always worries about blowing a bead. First, if you just had your tires remounted, wait a couple of days. That way the stuff they put on the bead to set them, will have totally dried. Low pressure too quickly may allow the tire to rotate on the rim and change the balance. Second if you are really low 8 – 12 psi, don’t do donuts or try to turn a stuck tire when it is wedged in a rock crevice. With non-bead lock wheels, I have never heard of someone blowing a bead when they had 12+ pounds of air in the tires. You CAN do it, but you will have to work at it. Even with bead locks, most bead locks only work on the outside of the wheel, it can be possible (although unlikely) to blow the inside of the wheel.

To conclude, run the pressure you are comfortable with. Experiment and try different pressures. Buy a good quality HD air compressor. You will pay more for it, but only once. A cheap one you will cuss out every time you use it. The biggest mistake I see on the trails is that most tires have too much air in them. If you are spinning your tires, they may be over inflated.