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Help interpreting weird Goodyear tire size?

I have a 99 Dodge Durango and need to replace the tires, but the Goodyears on the vehicle now are marked "31x10.5R15LT". Evidently this is an optional tire size, the standard for this model being 235/75R15.

I understand the latter nomenclature; 235mm width, 75% of that for sidewall height, and 15" rim. But what does 31x10.5 mean, and what's the equivalent tire specified in the more usual way? Goodyear and a few others sell some tires marked this way, but the selection is small, and I'd like to be able to cross reference it.

Thanks, J

Reply to
JHD
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Reply to
Shep

Those tire sizes are the 'old' way of measuring them.

The 31" is the unloaded height of the tire on the stock rim a 10.5" wide tire is supposed to fit on according to the chart at Goodyear. Likely a

7" or maybe an 8" wide rim.

The 10.5" is the width of the tire at the fattest part of the sidewall again on the proper rim size.

Just a note, the sidewall width does not normally correspond exactly to the 'tread' width. I 'think' the 31x10.5 Goodyears have 'about' a

10.25" wide tread.

I 'know' my 33x9.5's have a 7.5" tread with the 9.5" sidewall width and the last pair of 31x10.5's I had measured 10.25" at the tread but they were MudKings, not Goodyears. Every maker is slightly different.

Our 235/75R15 BFG's measure 8.5" on the tread.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail >
Reply to
Mike Romain

Those are Light Truck tires. 31 inches in diameter, 10.5 width at the sidewalls, R = Radial 15 inch rim width, Light Truck

If those are what was on that vehicle from the factory (check the door tag to be sure) then you almost have to buy that size. Metric sizing would be close to 325/75/15 and those are not real common.

Reply to
Steve W.

"Steve W." wrote

Really? In my metric system, 10.5 inches is 266.7mm. That would be about a 265/75-15, or 255/80-15.

Reply to
MasterBlaster

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