I'm not going to "do" anything "with the numbers"...I just wanted some real world measurements off a mounted tire on a Rubi rim for information's sake...a "few millimeters" isn't going to open a rift in the universe, I just wanted the measurements if someone could send...jeez, if someone wanted the measurements on a Cooper Discoverer STT 33x12.50/17, I would walk outside, measure the blasted thing, and send them the measurements...

KM, not the KM2.

Gary

 

It says its dimensions on the Cooper web site, and on the sidewall....so no one would probably ask you though.

 

Hi Gary,
why don´t you look on the bfgoodrichtires.com site? They tell you on the data sheet what`ll to be expected on different rims .... that should be exact enough

 

SteelblueJK,

Thanks, I did look at that, and it shows the specs for that tire (at least for a KM2, which I would suppose would be close enough) on an 8.5" rim, but I was wondering if those measurements might be different, however slight, on a 7.5" rim, which the stock Rubicon rim is...

Gary

 

Lets put it this way...making the rim an inch narrower will not change the size of the tire enough for someone going outside with a tape measure and measuring it to tell the difference.



Just use the published numbers...it will save you a lot of hassle, and work for you.

For an LT tire, the rule of thumb is around 0.1" of section width for each 1/2" of narrower rim (Narrower rim means a narrower section width)...so your one inch narrower rim would have roughly 0.2", or about 5 mm difference, not observable, and too small for a tape measure to reliably pick up, given how hard it is to measure section width, etc. (+/- 2%)

For a smaller tire, its closer to 0.2"/inch....and for low profile racing tires, its almost 0.3"/inch (Less than 50 series, etc).

The diameter won't change for a steel belted radial tire, as the belts dictate the diameter.

The tread width won't change, as that's also dictated by the belts/mold, not by the rim.

Hopefully, you'll be able to imagine what the tire will look like on the different rim size now (The same)

 

I hope this helps some what. I don't have MT but I have AT the same size 285/70/17 on 17x8 rims. They measure 32" x 11" and the tread width is 9" at 35psi. The spare tire measures 32.33". I thought they would measure taller but they don't.

 

Wings fan,

Thank you. I appreciate your doing what I asked although you didn't have to.

TEEJ felt the need to continue to send me instructions on how to use the manufacturer's published information, in spite of my repeated posts about knowing what he was saying, just needing measurements off a real mounted tire. The measurements on my Cooper STT tires mounted do not match the published info on Cooper's site, so I knew they were different, however slight. I'm not using the measurements for any great decisions, just wanted to know how they vary from stock mounted BFG tires.

Thank you providing what I asked for.

Gary

 

Cooper is Cooper and BFG is BFG - I would trust BFG and their published data, as TEEJ said.

Sorry, i´m german and don´t know the american tire market but BFG has the very best name in Off Road tires in Germany ...