ProjectMcFly

I apologize in advance for the n00bility of this question...but I want to confirm a few things about changes in tire size and the spare wheel.

I've got an AWD Subaru as my daily, and I know that the car is especially temperamental to running mismatched tires. My truck is my first foray into the shift into 4wd setup, so I want to make sure I've got all my facts right.

I've currently got a matched set of Uniroyals in 235/75-15, fitted by the previous owner, which I realize is slightly wider than the OEM size of 225/75-15.

I'm planning on going up to BFG KOs in 31x10.5-15 mounted on a set of 15x8 Cragars (wheels already purchased).

So my question is in regards to the spare tire. I'm hoping to get an oversand permit for a weekend down Cape Cod this summer and one of the things that's part of the inspection is the spare wheel that has to be full size.

So my question lies in both the physical size of the spare wheel and then tire selection.

I'm currently running a 15x6 wheel, and I know the spare is 15x6. I'm reading that the largest tire that most manufacturers recommend on a 6" wide wheel is a 225 series tire. Using that logic, I'm already exceeding the wheel width with the 235 tire (makes me wonder who mounted those tires on the wheels for the previous owner.)

To mount a 31x10.5 tire, I will have to pick up a larger rim, correct? I suppose another 15x8 Cragar won't be that expensive, but could I run either a 7 or 7.5" wheel (if I found a single wheel cheaper)

Then it comes to tires. I found this thread here:

https://www.yotatech.com/forums/f116...e-brand-92613/

That talks about running mismatched tires and that under low grip circumstances (and 2WD mounted on the front wheels) mismatched tires are not too bad. Given the cost of the BFGs ever increasing, I was planning on picking up a good used 31" tire at a used tire dealer and using that as my spare, will I run into any issues for occasional use? I will obviously take some time to go through and find a good one that hasn't expired datewise.

I know that again on my DD, if the tires are not within something like 2/32nds of an inch treadwise, it can wreck the diffs.

I'm planning on only using the spare as needed (obviously) and have no illusions of locking it in 4WD unless I blow a tire on the trail and need something to limp out. However, given that I need a proper size spare for the oversand permit, I'm just trying to find something cost effective.

Sorry if this is really dumb...I've done some searching, but I haven't found a solid answer about the spare. I've found threads about fitting a 31" spare under the bed, unjamming a busted winch, etc, etc.

Thanks in advance.

dropzone

iTrader: (6)

you can run a 31.10.50 on a 7" Rim

no you should not have any issues with a used 31" Tire as a spare.
The spare should fit in the existing location easily

ProjectMcFly

Excellent. That's exactly what I wanted to hear. So now I'll just have to find a cheap wheel to mount a cheap spare on.

I appreciate the help.

thurlo76

my father has all stock rims and he just bought all my 31x10.5x15s and had them all mounted on 6 in rims they are fine

HawkStrong16

31x10.50x15 is the second stock option for our trucks(according to tire rack.com) And as far as I know the rim size is the same. So you should be fine to just get your 4 BFGs and find a used 31 for a spare you'll be fine with stock rims

BoredOutnJackdUp

i got 1 black steel 15x8 with a 35 inch bfg with has a piece of madrone
through the side wall i would be more than willing to give you if you lived close?

ProjectMcFly

I always thought the 31s were mounted on the alloys, which were 15x7. I could be wrong about that.

I appreciate the offer, but I am in MA, so shipping would be a killer. I found a generic Cragar 15x7 on summit for under $50 shipped, so that should work fine.

mt_goat

My truck came stock with a 31" spare, I now have a 33" spare in the same spot. It hung down a little farther until I modified the carrier some. I have pics of that if anyone wants to see it. I could probably fit a 35" in there now.

tlrskunk

^ pics of this would be interesting to see as fitting a 35 under the truck sounds insane. even a 33 is nuts

mt_goat

I moved the center attachment about half as much as I lengthen the arms forward.









I now have a narrower spare to help ground clearance but its still a 33" mud-t, just 10.50 instead of 12.50.

tlrskunk

Do you have a side view pic that shows how much a 1250 hangs down from under there? That is what i was really wondering was how much ground clearance you lost back there and if you ever actually felt it was a problem. I was contemplating running a different gas tank back there and eliminate the stock tank to not have it hang up on stuff.

RustBucket

iTrader: (1)

I have a 33x10.5 MFG mud under my 88 4Runner. I didn't modify the mounts at all and it fits okay. My exhaust pipe gets real close so I stuffed a piece of exhaust gasket material between it and the tire.

mt_goat

This is with the 12.50:



I never noticed it hitting on anything but I have lots of clearance anyway. Obviously the 10.50 is better clearance, I need to take some new pics.

4Crawler

iTrader: (3)

I can fit a 33x9.50 or 10.50 spare under my '85. I find I need to pull the tire back as far as I can to keep it clear of the e-brake hardware on the axle and also need to take a little time to make sure the shackle bolts are lined up with the voids in the tread so they don't hit as the suspension flexes. I do have a spare gas tank above the spare so the tire hangs down ~4" lower than normal:


Have heard of folks running 35" spares by deflating and collapsing the tire with a ratchet strap. Basically makes the tire more of a square shape as you pull the tread in. Of course, you need a good on-board air system to air up the tire if you need to use it as it is flat to begin with.

Stuwy123

iTrader: (1)

I ran with my spare tire in the bed for a long time. It just got really annoying to shift it around all the time.
So I put it in the stock location. 33 x 12.5 on 15x10 rim. It's wide.
The truck looks like a big arsed bumble bee with the big spare hanging back there.
I want a swing out spare tire carrier on the tail gate.

angrybob

This interests me because I am considering the same thing with a 285/70R17 MT-R (about 11" wide). The PO had a custom exhaust installed with the tail pipe exiting the back of the truck, not behind the left rear wheel. The tail pipe is inboard of the leaf sring and in the way of the tire. I'll move the pipe if I know it will work. How close to your shackles is the tire. I have 6" rear shackles on it and it looks like it will be a tight fit. I do have a 1" body lift though so that will help some.

Have you hit the tire while wheeling?

I'll know more tomorrow as a buddy from work has an '86 4Runner. We are going to try and fit it on his rig.

4Crawler

iTrader: (3)

With a 1" body lift (at the time), I was able to run the exhaust up and over the frame for a side exit:
- http://www.4crawler.com/4x4/CheapTricks/TailPipe.shtml

This was before when I went through the spring:


But later went between the frame and body (2" ID pipe). Have run that way for about 13 years now w/o issue, running a stainless steel flex pipe.

angrybob

Outstanding! I can't believe I missed it on your site. After all, I have done about half a dozen or so 'cheap tricks' already