Mismatched Tire Sizes with Center Diff.

[travestyevp]

Guys,
Have a quick question about running different tire sizes at the same time.
Picture this, got all new 285/60/18 Offroad tires on some steelies and you have a blow out. Now you have to run the spare which is the original tire size 265? Does this hurt the diffs (center/rear)? Coming from DSMs and EVOs this is very ill advised. Break hard parts....

In short, when buying new tires, must you replace your spare tire also. I know you "should", but is the size match required?. Or could I shuffle tires around move a front to the back and use the undersized tire on the open front diff and just not lock the center diff? Does the CD ever attempt to lock without the button pressed? Is the center diff always open?

With a VCD found in DSM and older WRXs you will burn up the fluid. With a clutch plate diff you will burn up plates, and torsens are gear so bad news there.

What we got for must haves?
TIA
EVO

 

[OregonLC]

There are no clutch plates in either the front, rear, or center. They're conventional differentials, so you'll have increased wear but you won't immediately 'burn up' anything. However, it's never advised to run staggered sizes. Just as important as highway safety is the ability to get back off the trail. You can definitely fit 33's in the OE spare location. 34+ can fit too with some minor rework, although there has to be a practical limit to what the spare hoist can take as well as the incumberence on ground clearance.

The auto center lock is year dependent. Search for "Pin 7 mod".

I run all 5 full size and do a 5-tire rotation.

 

[krom]

Will a full size 33" spare fit with a trailer hitch installed? I currently have a 255/70/18 spare and it looks like the tire is close to touching the back of the hitch. Is it possible to mount the spare a little more forward? Also found this link helpful

https://forum.ih8mud.com/100-series-cruisers/82135-does-285-75-16-fit-spare-tire-holder.html

 

[OregonLC]

You can fit up to a 34.5" tire under there. Done it with a little resorting of things. However, I wouldn't recommend it. That's a lot to ask of the factory winch and the larger spares can weigh up to 2x what OEM does. Plus the impact on ground clearance...

 

[krom]

Is that 34.5" with the factory hitch? Thanks.

 

[OregonLC]

Yep, 295/70 R18 NTG on Tundra rims with an OEM hitch. IIRC the hitch wasn't the issue, it's the little bracket thingies which you have to either flip around or remove. It's been a while, but it will be obvious when you're under there.