"Matching" spare - how different do you go? (2 Viewers)

[re_guderian]

Ever since I stopped running BFG KO's, I haven't had a trail flat, over 17 years and several thousand miles of off road ago, on 4 different Cruisers. I've really only put less than 5 miles at a time on ANY spare, just between my house and the tire shop. I see lots of comments about wanting or "having" to run a matching spare. I'm interested in your actual experiences with this. My last 4 off road vehicles, 80, 2 100's and 460, have been full-time 4WD. Aside from not being able to lock the center diff (or Fr/Rr on an 80, or any other vehicle with axle lockers) I don't see a downside, at least one that justifies the cost and inconvenience of a rear-mounted spare. Differentials are always, well, differentiating, whether turning, accounting for worn tread, or differences in inflation pressure/rolling radius. Anyway, I run the biggest spare that will fit, and call it a day. Also, no 5 tire rotation for me. Thoughts?

 

[Tex68w]

You can trash your driveline on a full-time 4WD system with a tire that isn't the same size as the others. 1/4" of difference probably wouldn't matter but 1/2"+ I would be worried beyond a short distance at slower speeds in a flat/emergency situation. The rule of thumb I have seen on other AWD's is no more than a 5% difference in size. Again, you'll be fine in a pinch but you shouldn't run a different size tire for a prolonged period of time, they are designed to be matching and therefore you should keep a matching spare if at all possible.

 

[r2m]

Ever since I stopped running BFG KO's, I haven't had a trail flat, over 17 years and several thousand miles of off road ago, on 4 different Cruisers. I've really only put less than 5 miles at a time on ANY spare, just between my house and the tire shop. I see lots of comments about wanting or "having" to run a matching spare. I'm interested in your actual experiences with this. My last 4 off road vehicles, 80, 2 100's and 460, have been full-time 4WD. Aside from not being able to lock the center diff (or Fr/Rr on an 80, or any other vehicle with axle lockers) I don't see a downside, at least one that justifies the cost and inconvenience of a rear-mounted spare. Differentials are always, well, differentiating, whether turning, accounting for worn tread, or differences in inflation pressure/rolling radius. Anyway, I run the biggest spare that will fit, and call it a day. Also, no 5 tire rotation for me. Thoughts?

Personal experience that I posted some time ago:

Yet another wheel fitment thread: 17x8.5 wheels 0 offset

Yes, I searched. I am looking at these Method 703 wheels: 703 | Matte Black - https://www.methodracewheels.com/products/703-matte-black?variant=31922243207229 I've seen plenty of 17x8 0 offset, but nothing in 8.5. Should I worry about another .5" in wheel width? And then what size tire are...

forum.ih8mud.com

go to post #12

 

[re_guderian]

I was hoping for some more technical explanations. The All-trac system in the Previa used a viscous coupling center diff, v the Torsen, lockable one in the GX. Full size spare comes with significant negative cost (bumper/carrier), access (garage), and convenience (barn door) implications. I'll keep reading up, but the Torsen in the 100 series never blew up or skipped a beat for short term use with smaller spare. The question is what is the limit of "short term" before you have to drop two grand plus shipping on a rear bumper, and always park outside because now it doesn't fit in the garage, to avoid.... what, exactly?

 

[Tex68w]

Maybe just carry the full size spare when you're going off-road. Throw it in the cargo are or on your rack, not ideal, but keeps you from dealing with the issues you are concerned about. There's always the JW Off-Road spare carrier as well.

 

[jmanscotch]

My personal take on “short term” would be limited to dirt/loose surface only and just off a trail to get access to a tow truck. I wouldn’t be running mismatched on road.

One of the easiest and cost effective solutions that’d fit your needs is placing the spare in the cargo area, either with or without the third row.

I’m in the same rough predicament, minus the garage issues (mine lives outside due to height).

Inside the cargo area robs storage a bit, but a 33” will fit vertical and even easier with the third row removed. You’d have to spend a little working up a system to secure it back there, but that’s about as cheap and easy as it can be done without garage space issues or bumper/spare costs.

For now, I do what Tex recommend: long hauls out of town (for on or off road excursions) I throw the spare either in the cargo area or on the roof rack. For around town, I risk it and know I’ll have to make it work if I get a blow out (patch kit and air present for a slow leak or nail).

If you’re willing to bend on cost considerations, there’s a few options for the hitch mounted carriers for a bit over a grand. Can remove or use only when needed.

 

[Tex68w]

Mine lives in the cargo are 98% of the time and it's a PITA, always robbing me of much needed space. From time to time I'll take it out and leave it in the garage but it never fails as soon as I do I end up needing to go out of town and back in it goes so it just stays in there most of the time to avoid the hassle. I've been waiting for a rear bumper that I like to hit the market in order to finally solve this issue but I might end up giving in and settling for the soon to be released rear bumper from Victory just to be able to finally move on.

 

[r2m]

And there's always the can of green Slime you can keep on hand. It'll take care of most small punctures and should get you to a repair shop, but if you tear a sidewall or a large puncture you're really stuck. Hopfully you wouldn't be out of cell service. In which case you may want to look at the post I started for a mobile cell booster in case of emergency when you're on the fringe of cell service.

 

[Rednexus]

I went through this on my GX after upgrading to 265-70/17s from the OEM 265-65/17s. Not a huge difference (around 1" of height), but enough for concern. I use my GX in some pretty rough/remote areas, so there is always the potential I'd need to have a spare on for 100+ miles, or more if a tire is completely trashed and I have to wait for the tire shop to order a replacement (sidewall cut, as others have mentioned above, which happened to me twice in 10 years of off-roading my old Subaru in particularly rocky areas).

Rather than chance a new transfer case, I visited the local used tire shop and picked up a good used 265-70/17 BFG Long Trail tire for $40 mounted. The OEM spare was 14 years old anyway and therefore questionable, in addition to being the wrong size. $40 is good peace of mind to not have to worry about damaging a transfer case and having a newer spare that can be driven for some distance if needed. Again, from personally having changed several destroyed tires while off-roading (one after dark by a cell phone light), having a good spare is essential for backcountry expeditions.

 

[r2m]

I went through this on my GX after upgrading to 265-70/17s from the OEM 265-65/17s. Not a huge difference (around 1" of height), but enough for concern. I use my GX in some pretty rough/remote areas, so there is always the potential I'd need to have a spare on for 100+ miles, or more if a tire is completely trashed and I have to wait for the tire shop to order a replacement (sidewall cut, as others have mentioned above, which happened to me twice in 10 years of off-roading my old Subaru in particularly rocky areas).

Rather than chance a new transfer case, I visited the local used tire shop and picked up a good used 265-70/17 BFG Long Trail tire for $40 mounted. The OEM spare was 14 years old anyway and therefore questionable, in addition to being the wrong size. $40 is good peace of mind to not have to worry about damaging a transfer case and having a newer spare that can be driven for some distance if needed. Again, from personally having changed several destroyed tires while off-roading (one after dark by a cell phone light), having a good spare is essential for backcountry expeditions.

You noted that the tires you trashed were on your Subaru.
This may make you feel a little more comfortable with your GX, but Subaru's, having smaller rims and smaller size tires, the tires probably have much lighter/thinner sidewalls than heavy all terrain or mud terrain tires. I can easily see how one could tear a Subaru tire, where in the same situation a larger, heavier off road tire would not even feel it. The sidewalls on my LT285/75R17 BFG Mud Terrain TA KM2 at 15 psi, the sidewall is hardly even flexing.

 

[Rednexus]

You noted that the tires you trashed were on your Subaru.
This may make you feel a little more comfortable with your GX, but Subaru's, having smaller rims and smaller size tires, the tires probably have much lighter/thinner sidewalls than heavy all terrain or mud terrain tires. I can easily see how one could tear a Subaru tire, where in the same situation a larger, heavier off road tire would not even feel it. The sidewalls on my LT285/75R17 BFG Mud Terrain TA KM2 at 15 psi, the sidewall is hardly even flexing.

Both the sidewalls I trashed were on Yokohama Geolandar AT-S tires, which were 4-ply AT tires (just like the Wildpeaks on my GX). They were not E-rated LT tires (like your MT's), but I don't run those on my GX either, as I like the lighter weight/better ride and don't tow anything heavy. Also, the Subaru only weighted 3,200 lbs, not 5,200 lbs like a GX.

However, we have some very sharp volcanic rocks around here that are capable to slicing most sidewalls. A larger AT tire will fare better, as would an E-rated 10-ply tire, but no tire is immune from a sidewall slice/puncture. Road debris could also slice a sidewall; other failures could also occur such as losing the bead that may necessitate a putting on a spare.

 

[re_guderian]

I went through this on my GX after upgrading to 265-70/17s from the OEM 265-65/17s. Not a huge difference (around 1" of height), but enough for concern. I use my GX in some pretty rough/remote areas, so there is always the potential I'd need to have a spare on for 100+ miles, or more if a tire is completely trashed and I have to wait for the tire shop to order a replacement (sidewall cut, as others have mentioned above, which happened to me twice in 10 years of off-roading my old Subaru in particularly rocky areas).

Rather than chance a new transfer case, I visited the local used tire shop and picked up a good used 265-70/17 BFG Long Trail tire for $40 mounted. The OEM spare was 14 years old anyway and therefore questionable, in addition to being the wrong size. $40 is good peace of mind to not have to worry about damaging a transfer case and having a newer spare that can be driven for some distance if needed. Again, from personally having changed several destroyed tires while off-roading (one after dark by a cell phone light), having a good spare is essential for backcountry expeditions.

Thanks for the feedback. Assuming your 265/70/17 spare fits under the truck? With/without frame-mounted receiver hitch?

Also, your Subaru had a viscous coupler for the center diff? Much less tolerant of mis-matched tire sizes for long periods than the Torsen geared unit in later Cruisers/GX. Research I've found is that the Torsen unit can handle a 3% difference between Fr/Rr axles. Note that's not 3% difference in tire size, but axle speeds, which would be the average(ish) of the 2 tires on the axle.

I think I'll grab the grinder and an old 255/70/18 and see if there's even a chance it'll fit up under there...

 

[Rednexus]

Thanks for the feedback. Assuming your 265/70/17 spare fits under the truck? With/without frame-mounted receiver hitch?

Also, your Subaru had a viscous coupler for the center diff? Much less tolerant of mis-matched tire sizes for long periods than the Torsen geared unit in later Cruisers/GX. Research I've found is that the Torsen unit can handle a 3% difference between Fr/Rr axles. Note that's not 3% difference in tire size, but axle speeds, which would be the average(ish) of the 2 tires on the axle.

I think I'll grab the grinder and an old 255/70/18 and see if there's even a chance it'll fit up under there...

Yes, it fit under my GX470 with a non-OEM frame-mounted hitch just fine, but I'm not sure about a 460. Folks on here have mentioned partially deflating the spare and using a ratchet strap to make it smaller, perhaps that is an option (although you'd of course need a compressor to use the spare, in addition to needing to fool the TPMS).

My Subie was indeed a 5MT version with the viscous coupling center diff; the factory spec was no more than 1% difference in tire size (which seemed crazy conservative). I actually trashed a tire right before selling it to my neighbor, and put a new tire at ~1.4% difference. She's since put several thousand miles on it without an issue.

For my GX, I browsed Craigslist every now and then for ~6 months looking for a used spare, before calling around to used tire shops and finding one.