Please help settle an argument over tire size

M1165A1

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Friend is replacing his 16.5" 24 bolt beadlocks on an M1151 with 17" rims (the new tires are also 37s).

He is too cheap to buy a 5th matching rim/tire to carry on his Rhino and plans to carry one of the original beadlocks as a spare.

We are now having a row about whether that will damage the differential, hub, transfer case or what else.

Anyone have a view on mixing wheel sizes, even short term?
 

AtlantaSBR

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As long as the tires are the same diameter, I wouldn’t think it would matter too much in an emergency situation until you can get a new tire.
 

osteo16

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Emergency situation and short distance might be ok.. Never can be sure same tire dimensions are equal even if stated so.. Ive had 37' tires measure anywhere from 35 1/2'' to 37 1/2".... will kill your diff eventually..
 

springer1981

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Measure the circumferance of the tires, if they are the same or very close it will be fine. Different tire manufactures can size tires differently and call them the same. Example, a 37" tire might be 36.5" at one manufacture and 37.4" at another. The 36.5" has a circumference of 114.6" while a 37.4" is 117.4" That's almost a 3" per revolution difference. To put that into perspective that's a 45' difference per mile of travel.

Short distances probably wouldn't hurt it and on dirt where nothing will bind it wouldn't hurt it. On pavement it would do some damage or accelerated wear to something.
 

Coug

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short term/low speed it shouldn't be a major issue.
High speed or long distance will cause extra heat/wear in the differentials and the transfer case, which is just asking for premature failure.

Even if the outer diameter is identical, different brands of tires and even different load ratings of the same tire series have different rolling characteristics, and can lead to issues if the vehicle is operated on them excessively, but if you keep in mind it's only a temporary solution (and not a permanent temporary solution) I don't see why not.

It's always best to have 4 identical tires, but there is a little wiggle room. Plus if the vehicle isn't loaded heavy it helps as well.
 

Coug

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Also to add, why would you want a 160 lb tire/wheel as your spare? If nothing else he should buy a cheap rim and tire that weighs in at half of that for a spare.
 

Action

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Isn't the diff designed to let one wheel spin faster or slower than the other (on the same diff) ?
Wouldn't a 1/2" shorter tire have the same effect as turning?
I am not talking about 4 HI or 4 LO.
 

HUNvee

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If he sells the four old wheels as a set, it gets more for him to buy the fifth new wheel from it.
IMO
 

TOBASH

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Maybe you just need to find new (and smarter) friends.

(Always best to match outer diameters on spares, but the unmatched lateral offsets will also create driveability issues).
 

microjeep

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I would never intentionally run or recommend using a different size spare but think of this, I live in the north Georgia Mountains and there are very few straights long as a 1/2 mile. That would mean one tire is constantly running faster than the other. I've often pondered if this would shorten the life of a limited slip diff? Just food for thought.
 
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