The SKINNY on skinny tires

How much are you lifted?

 

Im not lifted. I went with this size specifically because i read these fit without needing a lift

 

These trucks are kinda weird. On some you can get away with no lift no problem yet on another it'll rub lke crazy.

 

A lot depends on the alignment and how much caster. Those with more caster will have less rubbing. Also, the wheels (back spacing and offset) make a huge difference.

 

True even in stock configuration all that plays into effect

 

Question I am going to with 315 75 16 Ko2 they 34s under 35s I am running 285 75 16 rn would I have to regear or will be ok?

 

Regear if you don't want it to be a complete dog and have to rev out to get it moving

 

I read through this but don't understand what the OEM tires have to do with anything.

 

I'd heat that up and move it if possible. If not, nip & tuck.

 

Pretty much, yeah. If you have a perfectly flat, smooth surface. A parking lot is good.

 

This ^^^ FTW.

 

If he's rubbing in the front and not the back either they are too wide or he has too much caster. Knowing there is no lift would lead me to believe there was no reason for an alignment with max caster. So I am going with too wide.

Post the size again @-_- tumbleweed -_-

 

So the gist of it from my understanding is this:

Your truck was designed for tires with a specific load capacity, the combined rating of which is higher than the GVWR of the truck (5600lbs truck, tires let's say 8000lbs). I'm sure this is a designed safety factor for overloaded vehicles and dynamic driving conditions.

Basically you want to equal the OEM tire load rating with your new tires. If the combined rating of your OEM tires is 8000lbs (4x2000lbs), you wouldn't want to inflate your new tires to a psi that only supports 6000lbs, even tho this is over what your truck "should" weigh.

So, generally speaking what allows LT tires to carry more weight is that they can handle higher pressures. At 35psi a c-load/d-load/e-load have the SAME weight rating, and the same size tire in P-metric is actually rated for MORE weight at the same psi.

If you look towards the end of that PDF, it has charts of almost every tire size and load, and I'm pretty sure these ratings are regulated so it should be consistent across brands. If your OEM tire has 2000lbs rated capacity per tire, you find your new tire size and load range on the chart. Then you figure out at what psi the new tire is rated for at least 2000lbs, and there you go.

That's the issue with certain LT tires on our trucks, they need to be run at a psi high enough to equal the weight rating, which may be uncomfortably stiff. Running them below this pressure could lead to overheating and failure of the tire.

 

Example:
My truck came with P245/75/16 and a recommended cold PSI of 32.
Looking at that size and psi on the chart gives a load rating of 2,172lbs because it's a P-metric on a truck it gets de-rated by a factor of 1.1, so it's actual rating is 1,975lbs.

My summer tires are Cooper discover AT3, LT265/75/16 C-load. Looking at the LT chart, the load ratings in that size are as follows:

35psi - 1,910lbs
40psi - 2,100lbs
45psi - 2,280lbs

So I'd need to run somewhere around 36psi to match the load rating of my OEM tires. Now let's say I stuck with stock size (245/75/16) but in a LT:

35psi - 1,700lbs
40psi - 1,870lbs
45psi - 2,030lbs

Here I would need to run at almost 45psi to maintain proper weight capacity. Most common LT sizes will meet weight rating at 35psi, but it's important to check.

 

Pete,
First, thank you for taking the time to go into detail like this. I appreciate it, and I'm sure others do as well.

I'm an information junkie, so this is great reading. When I was younger information like this was the farthest thing from my mind. Even though I was an enthusiast back then we just listened to what other people said and followed what they did, no questions asked. This was long before we all had a computer and the Interwebs in our pockets.

Your information sounds solid, thank you.

It's going to force me to dig deeper for more though. Not with the intent to discredit that info, rather, I'd like to tell you you're 100% correct.



My mind has been stimulated

 

Thanks. I did give the front inner fender a little snipping, i haven't had a chance to test it out yet but hopefully thats all thats needed

They are maxxis bighorn 255/85/16s on stock OR rims. They measure to 33.3' tall and 10.3" wide

 

How many of you guys had to regear?

 

I haven’t nor so I want to. As long s I stay with the 255’ or maybe 285/70/17’s I won’t have to

 

Ok I'm about to pull the trigger on some and definitely don't want to regear .. like ever

 

I'm in a 3rd Gen with 255/80/17 ST MAXX and I have plenty of power (no need to regear). You, having a 4.0 rather than a 3.5 should not have any issues.