BT17R

The new-to-me FJ-80 I bought has different brands of tires on the front and rear axles, but are all of the correct size. The tread design and all the ratings are essentially identical, too. The vehicle tracks well, no pulling or wandering.

However, after checking the tirerack.com site, I found that the Michelin LTX's have a 5% slower rotational speed than the Dunlop Rovers on the front axle. Given that the rig has AWD with a viscous center diff, should I be concerned that the center coupling is being overworked? The Tire Rack Land Cruiser expert said "no worries" and to not lose any sleep over it. He also said that just buying two tires to match wouldn't do any good because of the mismatched remaining tread depth and they should be replaced in sets of four.

Currently, all four tires have 90% tread remaining, so I'd like to keep them. Would, say, inflating the Rovers 4-5 psi more than the LTX's to increase rolling radius and lower revs per mile closer to the Michelins be an effective band-aid (observing max inflation pressures)?

I'd like to minimize expenses on the Crusher. I'm already planning on shelling out serious ducats on all fluid change outs (engine, tranny, all diffs and x-fer case, coolant) to synthetics, a major tuneup plus belts and hoses (what I routinely do to any "new" used vehicle), and tires weren't supposed to be part of the program. Thanks in advance for your advice!

bulldog-yota

I'm not familiar with the FJ80, but are you sure it has a viscious center diff like an Audi quattro? I thought it just had a plain good ol normal center diff, in which case you should be fine.

If so I would refer to the owners and service manual to see what it says, but I know Audi and SUbaru as examples do not recommend having different tires. On the SUbi's I believe their is even a disconnect plug if you change to the space saver spare. In short for a viscious diff it is not recommended to have different size tires, as the diff uses the fluid coupling for torque tranfer. Think like an auto torque converter that never locks while pulling heavy loads, it heats up.

X-AWDriver

I think it would be ok since you don't drive around in 4wd all the time and you're not AWD.

EDGE

I think your safe running in 2wd but even if your in AWD I would guess the truck would not have a problem being that the 4 wheels are pretty much even tread wear and similar tires, you could always buy 2 tires to match the front or rear and trade the other 2 in for a discount or someone here.

I know with Audi if you need 1 new tire you have to shell out for 4 new 1's and Chrysler is the same but they just make POS, I've know people who had problems with the AWD system with identical tires on all 4s turning was the problem

Either way I think your fine, the previous owner probably ran that way for the life of it but how the hell does a tire turn 5% slower, is it heavier or does it just stick to the ground, maybe thats just from a start not from aroll

BT17R

FJ-80 is permanent AWD 4X4 with viscous center diff and locker, plus lockers f/r. The Tire Rack site shows that the tires on it now, all OEM size but different brands f/r, have a 5% revs/mile difference. Previous owner just stuck those on, so no long-term history yet. Ah well, I'll probably just go with what's on there, it came with a driveline warranty just in case. Thanks.

X-AWDriver

AWD? Then definetly stick with the same type.

its2slo

what size are they? we could trade if they are 31x10.50r15's
i got a nice set of ltx's that will never fit my truck again after this summer

My99

FJ 80's are full time AWD, not 4x4. I wouldn't worry about the difference. Just put the taller tires on the front end, there's more weight up there and with the cornering and braking, they'll wear down faster.

BT17R

its2slo, sorry, they're 16's.

My99, not to split hairs, but why isn't it a 4X4 w/AWD? It's actually a more versatile, but similar setup to the Gen IV 4Runner. It has full-time 4Hi, 4Lo, transfer case with PTO, locking center, front and rear diffs. Isn't that a 4X4, or should it be called something else? I'm no 4X4 authority, but an FJ-80 seems to cover the bases and more, and the design was carried over to the FJ-100.

My99

Oops... didn't mean to say you didn't have 4x4. Just wanted to clear up that it was full time AWD, not full time 4x4, there is a difference. I'm not sure on your model, but some of the early 80's had a lockable center diff for high range. I believe in yours, you're only in true 4x4 (locked center diff) when in low range but I may be wrong. I also think there's a mod you can do to be able to lock your center diff at will with the touch of a button if you so desire. Hop on www.ih8mud.com Those guys are fairly knowledgeable, although some think a little *too* highly of the landcruisers.

I love 80's, was gonna get one if I could find a decent one. Unfortunately this 4runner was too good of a deal to pass up

BT17R

Kyle, no problemo. My 80 has the center locker that can be engaged with a button in 4Hi, and automatically engages in 4Lo. The f/r diffs can be engaged in 4Lo only (makes sense) in the sequence of R/F+R with a switch.

Yeah, ih8mud site is a good tech reference. They, and about half the world, are Land Cruiser fanatics, that's for sure. The other half are 4Runner fanatics with some misguided Rover/Jeep/D-C fanatics thrown in.

I admit to being a Land Cruiser fanatic, though. This is my seventh, and second 80 series. Nothing else comes close to my needs except the current 4th Gen 4Runner that in many ways surpasses the FJ-100, IMHO. The upcoming FJ-110 series is overdue, and should be something if you don't mind getting a mortgage on a motor vehicle.

Woodbert

Isn't that the truth. The LC series here are gawd awful expensive. The 70 series starts at $30K base, Prado starts at $40K base with the full LC 100 being $50K base for new models.

Realistically, to walk out the door with a 100 series, the minimum cost would be $60K.

Bob- The first thing I thought when I saw the picture of your truck was, "needs bigger tires."

BT17R

So true. I have a solution in the works, stay tuned. Lots more choices in 16" tires, I'm finding.

its2slo

what size are they, just out of curiosity. btw my friend was running 33's on one of those stock.

BT17R

OEM is 275/70-16. There's an amazing array of substitutes available.