[aardvarcus]

Tall skinny tires have many advantages both on-road and off-road, but they can have some disadvantages too. I have found that other features of a tire (tread pattern, sipes, compound, etcetera) are much more important than size. Also width should be considered in the context of vehicle weight and other factors.

Selection in some of these odd sizes is a big one. I wanted to get a set of the 255/85R16’s for their 33”+ diameter, but the only choices are mud terrains, or all terrains that look a lot more like mud terrains than anything else. Ended up going with 255/85R16 Cooper Discoverers, thinking they were all terrain, but they are definitely on the mud terrain side of the all-terrain spectrum.

Put them on my 2001 4x4 Chevy 2500HD, absolutely hated how they did on road. (Note truck probably weighs 7000lbs.) Swapped over to Michelin LTX M/S2 285/70R17’s, I love them on the road, and so far they have performed better than you would think off-road.

Next my 1991 Chevy 2500LD 4x4 got the 255/85R16 Cooper tires. It handled ok on-road with the tires, since this truck is probably only 4500lbs, but panic stops would send me spinning and/or into other lanes. The brakes weren’t the best, but the truck wouldn’t ever do this with the 265/75R16 Uniroyal Laredos that I had on another set of wheels and swapped back and forth.

Since I got my 2005 Tacoma, I moved the 255/85R16 Cooper tires onto a spare set of Tacoma rims, but got a set of 235/85R16 Michelin LTX M/S2 for daily driving. Love the Michelins, truck is very confident and planted on bad road conditions. Will plow through standing water on the road from torrential downpours just fine. I recently did a swapout to do some offroading, so I had the coopers on the Tacoma for a few days. I didn’t push them on road, since I already knew what to expect, but they performed ok. They handled the offroading with ease, but honestly my DD Michelins would have done ok for what I did, since there wasn’t any mud or extreme terrain.

Now for the MPG.

My next fill up for the tacoma, which was ½ DD tires and ½ Offroad tires on mostly highway was 25.1 MPG, which compared to similar tanks that included similar offroading done with the DD tires (26.8 MPG used as reference), implies that the off-road tires would have accounted for a 3.4 MPG loss for half the trip (23.4).

I had observed roughly a 3 MPG difference between the two tire sets on my 1991 Chevy, using only on road highway driving comparisons. (14 vs 17)

I saw no MPG difference between the two tire sets on my 2001 Chevy, probably because the disadvantages of the mud terrain type tread pattern were offset by the extreme weight of the new wheels and tires. Roughly 20lb wheels and 35lb tires versus 30 lb wheels and 55 lb tires is a big difference. Also when you are only getting 11-14 anyway, differences are hard to discern.

The moral of the story is: I don’t care how cool it is, I hate driving with mud terrains on pavement. Period.

Edit: Oh, and all the numbers have been adjusted for differences in diameter.