With help from the forum, I've decided to upgrade tires just a bit. Still deciding between 265s and 285s (up from 255).

The 265s have a diameter of 31.7 compared to the 285s of 32.8. Against the original 255s diameter of 30.1. So the 265s would raise the truck height about 3/4 inch; the 285s about 1.25 inch.

What's the functional advantage of one vs the other?

What are the relative impact on performance (rear diff is 3.55)?

Is it correct to assume the effect on the speedometer accuracy is a function of tire circumference? So that the 265s would be off by about 11% and the 385s off by around 19%? And that would be the speedo/odo reading slow, yes?

To get it to read correctly after the change, would it require the computer to be reprogrammed, or replaced? Or just do the math in my head and drive at a slower indicated speed than I would otherwise, knowing that I'm really going faster?

Anything else I need to make sure I'm aware of before I do this?

Thanks, and sorry for the dumb questions, but when it comes to this, I am dumb.

Bruce

 

Also, the stock 16 in wheels are 7 inches wide, correct? How much backspacing does it have? would I need new wheels to go with 285s if the recommended wheel width is 7.5-9"?

 

Dont know what the stock 16" wheel size is.

The warrantee on the sticker states the the tire must be mounted on "approved" rims. That would not be the case with the 285 tire.

But....

There is no reason that you could not do that, they will work.

I put a 315 on an unapproved 7 1/2" rim. I measured the tires in they're natural state, unmounted, and the bead to bead dimension was 8".....

So if warrantee is an issue for you, then stick with 265's.

285's feel the wheel well with more tire, thus look better...

 

I went from the little stockers to 285/75/16's... 265's weren't even a consideration.


What size are stockers? The speedo will read 5.7% slower between 255/75/16's and 285/75/16's...

 

Stock tires are 255/70R16.

I know that 285s will fit on the stock 16x7 wheels, but that's outside of the range spec'd by GY, and warranty coverage is somewhat of an issue.

I don't really wanna spend at least $600 for 4 wheels on top of the $220 +/- for each tire.

I always lean towards functionality over form. "Works great" always trumps "Looks great" for me.

 

im running 285/75/16 bfgs on my stock rims and its worked out fine. my speedo is off by about 10-12 mph at highway speeds so i just use my gps to get me a more accurate speed. but for the 99+ you can use a programmer to fix that issue.

 

Or... you can take your truck into the dealership if it's a 99+ and have the dealership recalibrate your speedometer.