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Full Time AWD (Limited and Platinum) Spare Tire Question

JR_Ontario

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Hi group,

Does the full time AWD system require all 4 tires to have precisely the same diameter as each other? I ask in case I replace the factory wheels / tires with a different size, and need to use the full size spare for any reason.

Thanks in advance!
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fur_runner

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Yes, you'll need to match them. If you don't, it puts a lot of stress and heat into the diffs
 

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it really sucks if you get a flat/etc and its non fixable, you pretty much have to replace all 4 tires.

but thats the price you pay for being in the big leagues of FT4WD

awd is technically different since most awd are fwd then kick in the rear drive as needed or brake those wheels that are spinning to simulate 4wd

on a side note, i never rotate my tires since the tires usually wear evenly due to being FT4WD (and if you DONT drive like a madman all the time)
 
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JR_Ontario

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Thanks everyone for the feedback.....

When shopping for snow tires, it looks like 265/65/18 are within 0.3% of the 20" full size spare.

Assume that is "close enough" for a short trip with the spare tire in case of a flat?

2025 4runner 6th gen Full Time AWD (Limited and Platinum) Spare Tire Question Screenshot 2025-08-27 102413
 

fur_runner

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Yeah, the issue isn't binary like a light switch. Basically the bigger the difference in circumference, the more differential action the diffs are putting up with all the time. They are designed to do that (its right there in the name) but it does build up heat with a large difference for a long time. Would being a little off be a problem? No not at all. I mean, think about what happens if all your tires aren't at the exact same air pressure. Or what happens when you go around turns.

What matters is that it isn't off by a LOT, and that you don't drive on it like that for a long time or with the diffs locked (can't imagine that scenario, but just don't do it.) Your example is only off by 2 rotations per mile, you'll be fine
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