Spare Tire Modifications

[Greg B]

In preparation for my Slee rear bumper without a tire carrier, I crawled under the 100 this week end to look at the current spare mount. I was looking at what it would take to get the spare higher up under the 100. There are three areas that need to be addressed.

The first area is the front rail that pushes against the tire. It is mounted to the cross member in front of the spare tire. This was simple. I unbolted it and flipped it over and bolted it back on. It didn’t really matter much though as the tire rests against the cross member now and doesn’t hit the rail. The cross member is smooth so I don’t expect it to damage the spare any more than the rail would.

[Greg B]

The second step is to address the rear bar that the tire rests against. This was also simple. This bar just needs to be tilted upwards on its existing mounts to gain the clearance you need. (Pic 1) To do this, I took off the 4 bolts that hold it on. I then took a drill and wallowed out the top holes so the bolts had more room when the mount pivoted. (Pic 2) Then I added three washers in between the frame and the mounting flange on each of the bottom two bolts. These washers act as a shim. (Pic 3) Then add the top bolts and tighten everything down. This will pivot the bar upward almost touching the body of the 100.

[Greg B]

The last area to deal with is the cross member that holds the spare tire winch. It is held on with 2 bolts on each side. (Pic 1) Remove the 4 bolts and leave the cross member lying on the mounting bracket. Next, you must create some 1 ½ inch spacers. I used a steel half inch pipe and cut into 4 sections. I then filed down the rough edges and primed and painted them. Then I added the spacers in between the cross member and the mounting bracket. I used new 8mm x 1.25 x 60 mm hex head bolts to secure the cross member. (Pic 2)

[Greg B]

These three modifications allowed me to raise the tire further up in the spare tire well. It moved the front of the tire up another inch and allowed the rear to go up another 1 ½ inches. Overall, I am really happy with the new height. Between the narrower size of the 255x85 spare tire and these modifications, the spare hangs down over two inches less than before. This will definitely help with clearance as I plan to keep the tire under there after the Slee bumper is fitted to the 100. Here are a couple final pics of the spare after the modifications are done.

[hoser]

Great write-up. I thought about doing the same thing but abandoned the idea when I couldn't find a suitable 35x9.5-16 tire. 255/85-16 is much easier to find.

[macneill]

That looks great, and simple. Nice job. May consider doing that when I get my new rear bumper on.

[dclee]

Nice job Greg! I'd be all over this mod, if I didn't plan on sticking an OEM subtank up above the spare...

[rockclmbr]

Hey Greg,

Very nice idea and write-up. I only have a 285/75R16 Nitto spare but I would still like to get more ground clearance since I don't and probably won't add a swingout rear tire carrier. I will be doing this soon too. Thanks for the post.

Re: Raising the crossmember-

1. I know that doesn't really add much strength especially compared to the already stout frame on the 100. But, I'm wary of the idea of using SS tubing for a spacer. That doesn't look very strong to me. I'd opt for a block of steel joining the two holes if possible. Like I said, I doubt it adds that much strength anyways and probably isn't a big deal.

[rockclmbr]

One more thing-

How does raising the tire up affect the way the tire is loaded/unloaded with the little winch and extension bar for raising/lowering it? Does it still engage without rubbing?


Thx!

[SINCITY100]

Nice job stuffing that tire up in there...you can barely see it now from the rear !

You will love that new bumper !

[hoser]

Originally Posted by rockclmbr

1. I know that doesn't really add much strength especially compared to the already stout frame on the 100. But, I'm wary of the idea of using SS tubing for a spacer. That doesn't look very strong to me. I'd opt for a block of steel joining the two holes if possible.

They've been doing a similiar mod to this on the FZJ80's for a long time. Some people have even used a stack of washers as spacers. But a block would be nicer.

[Landpimp]

yup, great mod, did it on my 80 many many moons ago, hadn't checked the 100 to see if it was the same, looks close enough, thanks

Originally Posted by hoser

They've been doing a similiar mod to this on the FZJ80's for a long time. Some people have even used a stack of washers as spacers. But a block would be nicer.

[Greg B]

Originally Posted by rockclmbr

Hey Greg,

Very nice idea and write-up. I only have a 285/75R16 Nitto spare but I would still like to get more ground clearance since I don't and probably won't add a swingout rear tire carrier. I will be doing this soon too. Thanks for the post.

Re: Raising the crossmember-

1. I know that doesn't really add much strength especially compared to the already stout frame on the 100. But, I'm wary of the idea of using SS tubing for a spacer. That doesn't look very strong to me. I'd opt for a block of steel joining the two holes if possible. Like I said, I doubt it adds that much strength anyways and probably isn't a big deal.

I used a pretty heavy pipe to make the spacers. There's no way they will collapse with the amount of weight they are holding. The brackets are thinner than the spacers, if too much weight gets put on them they would probably fail before the spacers. If you're really worried about it though, you could use blocks, spacers, washers, etc. I'll post back if it ever fails.

[Greg B]

Originally Posted by rockclmbr

One more thing-

How does raising the tire up affect the way the tire is loaded/unloaded with the little winch and extension bar for raising/lowering it? Does it still engage without rubbing?

When you tilt the rear bar (Step 2) upwards, it will not be in the way of the winch. I can still put the crank bar through the bumper and it goes into the winch mouth just fine. If you went any higher though, you probably couldn't get the crank bar into the winch mouth through the stock bumper.

[EL_3grab]

I have the SUB tank .. I think I cant do this mod .. thanks any way ..

[ZJ2UZJ100]

Nice write-up. Great idea!

[FirstToy]

Gregb,
with the VSC you can't use a different size spare with the 4 larger tires. Is there a contingincy plan for this?

[dclee]

Originally Posted by FirstToy

Gregb,
with the VSC you can't use a different size spare with the 4 larger tires. Is there a contingincy plan for this?

All that matters for the driveline is that the rolling diameters are the same, tire width doesn't really matter (yeah yeah, different rolling resistance and all that, but I don't see that making much of a difference in this scenario). Going purely by the "+ One" formula, his stock tire (I assume on a 16" wheel) is 33.4" in diameter. The 255, because of the higher aspect ratio of 85%, comes out to 33.1" in diameter. IMHO he should be fine to run this tire with only a 0.3" difference.

[FirstToy]

That's pretty close then, but maybe do a test run. (Remember that one guy who had his VSC kick in during higher speed turns b/c one rr tire was worn out)

but .3" sounds inconsequential. I thought it was a larger difference

[SINCITY100]

Originally Posted by dclee

All that matters for the driveline is that the rolling diameters are the same, tire width doesn't really matter (yeah yeah, different rolling resistance and all that, but I don't see that making much of a difference in this scenario). Going purely by the "+ One" formula, his stock tire (I assume on a 16" wheel) is 33.4" in diameter. The 255, because of the higher aspect ratio of 85%, comes out to 33.1" in diameter. IMHO he should be fine to run this tire with only a 0.3" difference.

I agree with DCLEE (Hey, that kinda rhymes !)

The VSC will operate normally, even if one tire is MUCH lower in pressure than the rest..as long as it is within a "reasonable" diameter of the other 3 tires (dont know how much "reasonable" actually is) but it (VSC) seems to be pretty understanding, even when your running with one tire that is almost flat

[Greg B]

Originally Posted by FirstToy

Gregb,
with the VSC you can't use a different size spare with the 4 larger tires. Is there a contingincy plan for this?

I realize Derek and SinCity already answered most of this, but I'd like to clarify a little bit. First off, the BFG website lists the 295 AT's diameter as 33.2 inches and the 255 MT's diameter as 33.3 inches. Once the two are mounted, they measure within 1/16 of an inch of each other from the ground to the bottom edge of the wheel. Both tires had 35 lbs of air pressure in them. Width doesn't play a part in this situation.

As for rear world usage, I did drive it around on Sunday and had no issues with any ABS feature throughout the drive.

[spressomon]

Good thinking Greg on your spare tire mod: What a wealth of resources we have here on 'daMUD!

[Greg B]

Thanks Spresso and others for all the compliments! Hopefully it will help some others if they decide to go this route.

By the way, I ordered my Slee rear bumper without the tire carrier yesterday. I'll have it painted and installed within a couple of weeks. Gotta get this rig ready for Moab!

[e9999]

nice writeup, I'll put it in the FAQ.

I did something similar on the 80. In that case it only lifted the front of the tire because of some obstacle in the rear. The winch had to be lowered and is less easy to operate than before, though. So this one may be better.

Main concern I have, though, is that the mod may give a false sense of security. Aside from the unexpected encounter with an obstacle during "normal" driving, for which a couple of inches may save the day, I have pretty much concluded that I don't want to leave the spare under there when wheeling. Given that it seems that I am dragging my tail everywhere, it just takes a small rock to slash a $200 tire. Not good. Now I just remove the spare and bring it up.

[Greg B]

Originally Posted by e9999

nice writeup, I'll put it in the FAQ.

Thanks!

Originally Posted by e9999

Main concern I have, though, is that the mod may give a false sense of security. Aside from the unexpected encounter with an obstacle during "normal" driving, for which a couple of inches may save the day, I have pretty much concluded that I don't want to leave the spare under there when wheeling. Given that it seems that I am dragging my tail everywhere, it just takes a small rock to slash a $200 tire. Not good. Now I just remove the spare and bring it up.

I see you're point on the false sense of security. You definitely have to watch the tire when dropping off ledges.

However, I've got a plan for this too. My intention from the beginning was to add a Slee Rear bumper without a tire carrier and then do this mod to raise the spare. My goal is to get the spare as high as possible because I plan to build a skid plate to protect the spare. I need the Slee bumper on though to build the skid plate as I plan on connecting the two for strength.

But, this is a new topic for a different thread. (coming soon )

By the way, if one did this mod and left the factory tow hitch on, one could easily build a basic skid that covers the spare. A spacer/bracket could be attached to the frame or tow hitch or both to support the skid plate.

[Kneel]

Originally Posted by hoser

Great write-up. I thought about doing the same thing but abandoned the idea when I couldn't find a suitable 35x9.5-16 tire. 255/85-16 is much easier to find.

Have you seen the Interco SSR 35x10.5R16? It has a 9" tread width and 10.5" center section width. They are quite tame on road. I wouldn't use it as a primary tire as you'd only get 25k out of them. But for a spare...