Spare tire solution - after upsizing my OEM tires (1 Viewer)

[claytondc]

Hi, all! First post here, so please be gentle with the newbie

I've done a lot of research on the spare tire topic here, and on other sites. This is by far my favorite forum, so I decided to register and start to attend some of the discussions around here. I have just acquired a new (to me!) 2017 GX460, and I did some basic modifications: a roof box; a skinny roof rack, side by side with the roof box; the little device that closes windows and fold external mirrors (this is a Base model); a bunch of stickers; and... new BFG KO2 tires on 275/65/R18 (OEM rims), or 32.1 inches total size. I LOVED the tires, so much better than the OEM ones.

Now I have to deal with the spare-with-a-different-size issue.

I've seem the spare carrier solutions recommended here, but I had a (probably crazy?) idea that I wanted to throw in here so the experts can chime in: what if, I keep the OEM spare (265/60R18, or 30.52 inches) and, in case I need to use it, I add snow chains to it? The spare is for emergencies only, and I will be careful to limit the speed while on it. The difference between the spare and the new KO2's is 1.4 inches, and I guess a snow chain would make the tire at least one inch bigger (my total guess here, though)???

Comments? What am I missing? Is it just a stupid idea, and I should suck it up and carry a same-size spare?

Also, for context, the rig is mostly for weekend and day trips. No plans for cross-continent adventures (for now), or rock crawling. I do plan to do some camping on remote areas, though.

All comments are welcome. And feel free to call (the idea) stupid

C

 

[Rednexus]

I would just spring for a same-sized spare. You can probably find one at a used tire shop for <$75. I paid $40 mounted for a 20% tread 265/70R17.

 

[URJ150L]

Full size spare and kdss spacers to make it fit

 

[Washingtontaco]

Absolutely buy a same size spare. Look on Offer Up or CL. The last thing you will want is drivetrain issues trying to save a few bucks.

 

[claytondc]

Full size spare and kdss spacers to make it fit

Hi, URJ150L! My car has no KDSS, but I'm assuming the spacers might have a play, anyway? Not sure how it will work. Can you point me to some previous discussion on this? I'd be VERY interested in a solution to keep a same size spare under the car, in its proper location.

 

[Rednexus]

I would remove one of your 32" wheels/tires and see if it fits. If it fits, you can then find a good used spare. A 32" spare fit under my 470 with no issues.

 

[URJ150L]

You got kdss… buy this and your spare will fit

KDSS Spacer Kit

If you’re lifted, and have wheeled, you have undoubtedly encountered some kdss lean. In the 6 years of working with my 2005 GX470 sport with kdss,...

www.treatyoakoffroad.com

Basically it will lower your sway bar to make room for a larger spare tire

 

[claytondc]

You got kdss… buy this and your spare will fit

KDSS Spacer Kit

If you’re lifted, and have wheeled, you have undoubtedly encountered some kdss lean. In the 6 years of working with my 2005 GX470 sport with kdss,...

www.treatyoakoffroad.com

Basically it will lower your sway bar to make room for a larger spare tire

Thanks, a lot! It looks like they are restocking now and should start to deliver before the end of the year. Also, oops on the KDSS. I've learned that ALL GX460 have it. Thanks for the clarification.

 

[r2m]

If you do some searches, I've posted this a couple of times on MUD.
In short: DO NOT USE AN UNDER/OVER (different size) SIZED SPARE, EVER!!!
GX's are ALL-wheel drive which means there is torque going to any one of 4 tires all the time.
If you mount a different size tire you WILL wind up your drive train!

Very short story that's been told before here on MUD.
Wife and I had an all-wheel drive Toyota Previa minivan. Had a flat, used a different size spare. Wound up the drive train. $3,000 + repair bill.
Fortunately it was still under warranty and Toyota picked up the bill.
It may not happen in a mile or two and I don't recall how far we went when we wrecked our van, but it happened.

You would probably be better off with a couple cans of inflation sealant.

So do as you please, but consider yourself forewarned.

 

[claytondc]

If you do some searches, I've posted this a couple of times on MUD.
In short: DO NOT USE AN UNDER/OVER (different size) SIZED SPARE, EVER!!!
GX's are ALL-wheel drive which means there is torque going to any one of 4 tires all the time.
If you mount a different size tire you WILL wind up your drive train!

Very short story that's been told before here on MUD.
Wife and I had an all-wheel drive Toyota Previa minivan. Had a flat, used a different size spare. Wound up the drive train. $3,000 + repair bill.
Fortunately it was still under warranty and Toyota picked up the bill.
It may not happen in a mile or two and I don't recall how far we went when we wrecked our van, but it happened.

You would probably be better off with a couple cans of inflation sealant.

So do as you please, but consider yourself forewarned.

Thanks, Richard! I've seem your original post on the incident. I understand the risks, and that's why I was planning to (try to) make the spare the same size of the other tires, with the snow chain. Still, for now, it looks like the KDSS spacer is actually a better idea. I already have a tire fix kit, and I might consider to carry the inflation sealant cans, too.

 

[orangerock]

Will the KDSS spacer allow a 33" tire to fit underneath?

 

[Rednexus]

It looks like the Previa had a viscous coupling in the center diff, which is actually a similar approach as a MT Subaru. For those vehicles, running a significantly different-sized spare may result in the fluid in the viscous coupling getting "cooked" due to more sustained slip and therefore heat than the system was designed for, as all of the slip is taken up by the fluid (rather than a mechanical system).

The GX is a bit different as it has a Torsen center diff, which, when unlocked, doesn't use a viscous coupling and instead operates more like an open diff and allows for quite a bit of mechanical slip between the axles. In an emergency situation, I would personally be just fine driving a GX several miles with a different sized spare, with the center diff unlocked, at a slow speed, back to civilization and getting the tire fixed. Since the front and rear of a GX are unlocked, it basically has three differentials allowing slip (center, rear, and front), so it seems unlikely that significant damage would occur with a different sized tire, as the entire system is always accommodating different speeds at different tires/axles and front to rear (think about A-TRAC, which will look up a tire without traction completely, while allowing the other one to spin).

That being said, it there is always some residual risk of driveline damage, and having to hitch a ride back to town or try to find a proper-sized replacement tire in the middle or nowhere might be difficult. If you can fit a full-sized spare, always go that route. It makes it easier to just swap out the wheel/tire and get it fixed later on.

 

[Banandalorian]

Are your upsized tires too big to fit in the OEM spare location? Or are you just trying to save a buck?

My tires don't fit in the OEM spare tub. For everyday driving, my spare lives in my garage and I have a can of fix-a-flat in the GX. If I'm going far away and/or off road, I strap the upsized spare to my roof rack. I'll get some kind of swingout carrier in the future but I'm not messing with mismatched tire diameters.

 

[r2m]

In an emergency situation, I would personally be just fine driving a GX several miles with a different sized spare, with the center diff unlocked, at a slow speed, back to civilization and getting the tire fixed. Since the front and rear of a GX are unlocked, it basically has three differentials allowing slip (center, rear, and front), so it seems unlikely that significant damage would occur with a different sized tire, as the entire system is always accommodating different speeds at different tires/axles and front to rear (think about A-TRAC, which will look up a tire without traction completely, while allowing the other one to spin).

That being said, it there is always some residual risk of driveline damage, and having to hitch a ride back to town or try to find a proper-sized replacement tire in the middle or nowhere might be difficult. If you can fit a full-sized spare, always go that route. It makes it easier to just swap out the wheel/tire and get it fixed later on.

You hit upon an interesting point Rednexus. If you are out in the boonies, assuming dirt/gravel roads, you can drive as far and as long as you want on miss-matched tire sizes, so long as the surface you're driving on is loose and the tires have the ability to "catch up" (unwind). That's why one should never use locking hubs and L4 on pavement, the tires don't have the ability to scrub off the extra rotations.
Hope that made sense.

 

[URJ150L]

Will the KDSS spacer allow a 33" tire to fit underneath?

Possibly… I plan to check with the spare off my Tacoma. I currently have a 31.6 up in there and it looks like there’s about a little over an inch of extra space with the spacers… the Tacoma spare is 32.7 so if it does fit, I suspect it’ll be tight just like how the 31.6 was before the spacers.

 

[claytondc]

Are your upsized tires too big to fit in the OEM spare location? Or are you just trying to save a buck?

My tires don't fit in the OEM spare tub. For everyday driving, my spare lives in my garage and I have a can of fix-a-flat in the GX. If I'm going far away and/or off road, I strap the upsized spare to my roof rack. I'll get some kind of swingout carrier in the future but I'm not messing with mismatched tire diameters.

The correct size spare won't fit under the GX. I still have the OEM size tire there, but I need to fix it soon. My alternatives seem to be: [1] the KDSS spacer mod (investigating now); [2] the same you're doing (spare at home, and on the roof rack for trips); [3] swing out hitch spare carrier (effective, but kinda expensive);

 

[Jstawgn]

Torsen are different than viscous that lock up with speed differential. No issue to use slightly smaller spare tire.

I got 255/75R17 spare which is same 32.1" as what you run. This is on GX470 with KDSS.and 2" lift. Any thicker and it would not slip above the KDSS bar. GX460 KDSS are a bit wider and should accommodate slightly bigger spare.
I do have to jack up the frame to make it easier to position the tire. When the axle drop it moves forward a bit and makes it easier to position the tire.

 

[URJ150L]

It looks like the Previa had a viscous coupling in the center diff, which is actually a similar approach as a MT Subaru. For those vehicles, running a significantly different-sized spare may result in the fluid in the viscous coupling getting "cooked" due to more sustained slip and therefore heat than the system was designed for, as all of the slip is taken up by the fluid (rather than a mechanical system).

The GX is a bit different as it has a Torsen center diff, which, when unlocked, doesn't use a viscous coupling and instead operates more like an open diff and allows for quite a bit of mechanical slip between the axles. In an emergency situation, I would personally be just fine driving a GX several miles with a different sized spare, with the center diff unlocked, at a slow speed, back to civilization and getting the tire fixed. Since the front and rear of a GX are unlocked, it basically has three differentials allowing slip (center, rear, and front), so it seems unlikely that significant damage would occur with a different sized tire, as the entire system is always accommodating different speeds at different tires/axles and front to rear (think about A-TRAC, which will look up a tire without traction completely, while allowing the other one to spin).

That being said, it there is always some residual risk of driveline damage, and having to hitch a ride back to town or try to find a proper-sized replacement tire in the middle or nowhere might be difficult. If you can fit a full-sized spare, always go that route. It makes it easier to just swap out the wheel/tire and get it fixed later on.

I will add that the wife’s nx 300 is equipped from factory with a spare that is 1.2 inches smaller than the other tires…

As far as the Previa goes, r2m should’ve never got rid of it… mid engine, RWD, supercharged, chase lounge interior:

 

[Rednexus]

I will add that the wife’s nx 300 is equipped from factory with a spare that is 1.2 inches smaller than the other tires…

As far as the Previa goes, r2m should’ve never got rid of it… mid engine, RWD, supercharged, chase lounge interior:

My wife wants a new hybrid Highlander, but I'm suggested a few times that she get a Previa or JDM Hi-Ace instead for the family hauler. Needless to say it hasn't been received well .

 

[r2m]

I will add that the wife’s nx 300 is equipped from factory with a spare that is 1.2 inches smaller than the other tires…

As far as the Previa goes, r2m should’ve never got rid of it… mid engine, RWD, supercharged, chase lounge interior:

Truth be told, we LOVED that van! We had to special order it because we wanted the all-wheel drive, color and seat layout that we wanted and there was nothing in the entire state CA or even Nevada. I lowered it a wee bit, and mounted 17" wheels with 45 series low profile (all season) tires. It looked and handled awesome! Just not a lot of power, but it worked. I would have done the super charger, but the option for both super charger and all-wheel drive was not available. We needed the all-wheel drive over power on account of spending a lot of time in Lake Tahoe in the winter.
BUT, I had to replace the starter once and that was a headache! Had to remove the drivers seat, access all the bolts with 12" long 1/4 drive extensions from both under the van and inside AND I had to use my air ratchet for one bolt because there was absolutely no space for a ratchet to swing back and forth.
Then it turns out that mid year Toyota decided to change starters on the Previa so I had to go back and exchange the new starter I just purchased for another.

Now in a deep announcers voice from the 1950's...
"We will now return you to the normally scheduled OP."