is AWD effected by upsizing tire

[Tenderfoot]

2005 merc Mtn.
Plans to add larger than OEM tires on OEM rims, found out sizes via the Search (thanks' to all). however I'm not going with the Max size that fits on stock, going with most likely P245/70 R17 to maintain same width but taller tire (since it doesn't look like much more width will fit or will be very very close)..plus I don't want it to look to funny being max size on stock height. Of course not rulling out a few other sizes. (my chart).

245 65 R17 OEM
255 65 R17 slightly wider and slightly taller
265 65 R17 wider and taller
245 70 R17 OEM width and taller ( I like thise size )
255 70 R17 slightly wider and taller
265 70 R17 Max wider and taller

I do most tire comparisons on Wheelsmaster.com

My main query is, is their any effect other than Speedo when upsizing the tire with AWD ? The '05 Merc. Mountaineer in question is always in AWD unlike the Explorer counterparts. I had some tire shop guy tell me it was a big deal blah blah blah today (goodyear tire place) and I think he was full of crap as to problems with ABS and AWD. However thought I'd bounce that off ya'll since it may have come up but I couldn't find the answer since most tire related questions were only dealing with max size and examples were explorers w/o AWD full time. BTW, the tire shop guy said "no way will you get a 70's series on a Mountaineer"..I left.

secondary question is if I upsize my tires, will an upsized spare fit under ? anyone upsize their spare as well (AWD should be upsized to match but I'm not sure if taller sizes fit under rearend ?

 

[EasyRhino]

As long as all four of your tires are the same circumference as each other, you should be okay.

 

[eXcali]

Most ppl put their oversized spares either on the roof or inside the back. There are some mods ppl have done for a swing out Wrangler style rack for the back hatch.

 

[XCAMP]

Hey are your rims 17 or 16? My explorer came with stock 235/70/16 and went up to a 245/70/16 with no effect on anything. I actually think my mpg went up a little but that's probably because the old tires were worn.

If you go up to like a 265, you will probably run into problems. I wish I had put on a 255 instead of 245.

 

[jrford]

AWD here, i went with the full size spare, i even went so far as getting a stock rim to match the others, which will enable me to do a 5 tire rotation. If you go taller, it should be OK, i think there was 15-20mm extra clearance for the spare. Also with 5 tires and say you have a blow out with 40k on them, the mismatched tire will affect the AWD and burn it up well before its time. With 5 tires in rotation i can drop to 4 or as someone also suggested you could get a new one and have it shaved to the right circumfrence. Anything over 1/2 inch difference in diameter i heard was bad.

Watch on going wider as the clearance between the top of the tire and steering knuckle was only 10mm with the 245's, the 255 would have been 5mm closer. . .thats not enoough room imo. . 70series, i never really looked into.

I stuck with the 245/65-17 Michelin LTX A/T 2. . . .great so far, but i have yet to try them in the snow which was the main reason i got them.

 

[Tenderfoot]

AWD here, i went with the full size spare, i even went so far as getting a stock rim to match the others, which will enable me to do a 5 tire rotation. If you go taller, it should be OK, i think there was 15-20mm extra clearance for the spare. Also with 5 tires and say you have a blow out with 40k on them, the mismatched tire will affect the AWD and burn it up well before its time. With 5 tires in rotation i can drop to 4 or as someone also suggested you could get a new one and have it shaved to the right circumfrence. Anything over 1/2 inch difference in diameter i heard was bad.

Watch on going wider as the clearance between the top of the tire and steering knuckle was only 10mm with the 245's, the 255 would have been 5mm closer. . .thats not enoough room imo. . 70series, i never really looked into.

I stuck with the 245/65-17 Michelin LTX A/T 2. . . .great so far, but i have yet to try them in the snow which was the main reason i got them.

Thanks for the tips, I was curious on how people are fitting the wider tires, that's why I'm going with same width as OEM but taller, since I don't see much room between inside of tire and that A-Arm/suspension..wonder if the Mercury Mountaineer rim is offset different than Explorers (assuming some Explorers had 17" rim OEM option).

That sux I might have to buy a spare for sure, since the current spare I have is unused (never put in rotation), but seems I'd have too for AWD..dang.

So now I'm questioning my choice...now I'm thinking
245-65
255-65
245-70

 

[1_v8_merc]

I have a 2004 Mountaineer, v8 AWD.

My stock tires were 235/70/r16 i believe.

I upgraded to 245/75/r16

I bought BFG M/T's too,lol, so i was concerned with the sidewall nubs hitting my wheel-wells or steering or whatever.

But it clears perfect.
I could have upgraded to 265's no problem i believe, but for SOME REASON my Rear-Left step-guard sticks out extra far in the rear tire area, so it prevented me from going any larger than my current size.


My MPG went down pretty good since getting mud terrains on too.
But the traction increase is UNREAL!
It feels like a ####ing tank compared to stock tires.


The users manual DOES tell you to NOT go above your Stock tire size.
(every vehicle tells you this anyways....really nothing to do with AWD. They tell you this for pure liability reasons....thats all)

However I've had bigger tires for probably almost 2 years, not a hitch wrong.
The AWD systems are VERY strong and dependable from what i've read and heard....they are MEANT to be run in AWD for their entire lifetime, so they were designed stronger.

(there was a guy on here that ran a 400hp AWD Mountaineer, and never had a problem with his AWD system.)

If you are concerned with clearance issues, you need to look up the conversion charts, and get out and measure your actual wheel clearance.
I did this, and as long as your math is correct, you're good.
Although some tire manufactures tend to make tires alittle bit bigger or smaller than the advertised size.....i KEEP hearing this from people, but NEVER seen it myself in person.

 

[jrford]

OP is talking 17"s. A 16" 265 might work but no way on a 17" unless you increasee the offset, or add a spacer.
Mounties are the same size. . .

You don't have to get a 5th tire, if you keep the spare and say have a blow out at 40k on the tires and with the unused spare you can get home or to a tire shop but i wouldn't go much further. . .then you could buy the same tire and have them shave it down to the right size, or in other words, add 40k to the new tire using some lathe device. .
I added the 5th rim/tire for about $100 on the used rim and $200 for the tire, its a little expensive but whats $300 after you spend $800 seesh, tires are expensive now, the last set of LTX A/T i got about 70k on only 4, with 5 i hope these will last the rest of the trucks life. . .

 

[Layinhp]

OP is talking 17"s. A 16" 265 might work but no way on a 17" unless you increasee the offset, or add a spacer.
Mounties are the same size. . .

You don't have to get a 5th tire, if you keep the spare and say have a blow out at 40k on the tires and with the unused spare you can get home or to a tire shop but i wouldn't go much further. . .then you could buy the same tire and have them shave it down to the right size, or in other words, add 40k to the new tire using some lathe device. .
I added the 5th rim/tire for about $100 on the used rim and $200 for the tire, its a little expensive but whats $300 after you spend $800 seesh, tires are expensive now, the last set of LTX A/T i got about 70k on only 4, with 5 i hope these will last the rest of the trucks life. . .

i wouldnt try it unless you dont like seeing your 4x4 parts fly out from under your truck, a good way to distroy alot of parts

if its awd it will register the different speed and try and kick in the awd mode and your 4x4 system is fighting itself which normaly equals broken parts

 

[kbviper]

Went to 265/65 17

My 2004 Explorer XLT came with 245/65 17 tires. I just put a set of agressive winter 265/65 17 tires on and no apparent problems. No rubbing, truck runs fine. According to a tire website they should have raised the truck about an inch the the speedo will be off about 3 kms at 100 km/hr (reading slow)