37's on 20's on Rap, Can I use 37 on 17 as a Spare???

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Bozz

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Have (4) 37's running on 20-inch rims on truck.

Have had an IMPOSSIBLE time finding a matching wheel (not particularly the brand, model or style....just the exact size, width, offset, bolt pattern, etc.) for a spare.

Currently have original spare mounted under truck, 35-inch, which recently came to my attention that that would be useless as a spare while running 37's. Never even paid attention to the spare, been running for just under 3 years without so much as having need to put air in my tires (Cooper Discoverer STT Pro). They have held at 41lbs for almost 3 years! o_O

I have the original 17-inch rims that came on the Raptor, plus the spare rim and tire (whatever that rim size is).

I have looked at this from all possible angles and don't see a problem, just wanted a few more eyes on this before doing it...

Putting a 37-inch tire on a 17-inch rim (for a spare) will still have the same overall diameter of a 37-inch tire on a 20-inch rim. Still 37 inches. (obviously it would be a 37 for a 17-inch rim, not trying to put a 37r20 on a 17)

Shouldn't be a problem. For a spare. For a short-term use, get out of trouble situation, get back to town until getting one of the 37/20 tires fixed/replaced.

Anyone see a problem with this?

Wouldn't be concerned about a spare at all, but going on a long-distance off-road event far from home and don't need to be stranded waiting for a new tire or new wheel.
 

MDJAK

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37s clear the opening on a Gen2? Did you have to do any trimming?
 

jdm_sixtwo

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They’re on a gen1. I’d measure first because I’ve had 35x1250 r17s and 35x1250 r20s and the r20s were about an inch larger in diameter, probably because the wheel doesn’t compress, and there’s less tire to compress or something.
 

HORN HIGH ACES

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Have (4) 37's running on 20-inch rims on truck.

Have had an IMPOSSIBLE time finding a matching wheel (not particularly the brand, model or style....just the exact size, width, offset, bolt pattern, etc.) for a spare.

Currently have original spare mounted under truck, 35-inch, which recently came to my attention that that would be useless as a spare while running 37's. Never even paid attention to the spare, been running for just under 3 years without so much as having need to put air in my tires (Cooper Discoverer STT Pro). They have held at 41lbs for almost 3 years! o_O

I have the original 17-inch rims that came on the Raptor, plus the spare rim and tire (whatever that rim size is).

I have looked at this from all possible angles and don't see a problem, just wanted a few more eyes on this before doing it...

Putting a 37-inch tire on a 17-inch rim (for a spare) will still have the same overall diameter of a 37-inch tire on a 20-inch rim. Still 37 inches. (obviously it would be a 37 for a 17-inch rim, not trying to put a 37r20 on a 17)

Shouldn't be a problem. For a spare. For a short-term use, get out of trouble situation, get back to town until getting one of the 37/20 tires fixed/replaced.

Anyone see a problem with this?

Wouldn't be concerned about a spare at all, but going on a long-distance off-road event far from home and don't need to be stranded waiting for a new tire or new wheel.

You should be good unless you have aftermarket UCAs (typically require 0 offset) or a big brake kit (17s might not clear the caliper).

The OEM sytle lug nuts are intended to be used with the OEM wheels. I assume the lug nuts where changed with the new wheels so it's not ideal to use them with an OEM spare. Throw 6 (or 7) OEM lug nuts in your truck and you should be set. For a spare, 17" vs 20" wheel diameter makes no difference if the tire diameter is the same.
 
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Bozz

Bozz

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You should be good unless you have aftermarket UCAs (typically require 0 offset) or a big brake kit (17s might not clear the caliper).

The OEM sytle lug nuts are intended to be used with the OEM wheels. I assume the lug nuts where changed with the new wheels so it's not ideal to use them with an OEM spare. Throw 6 (or 7) OEM lug nuts in your truck and you should be set. For a spare, 17" vs 20" wheel diameter makes no difference if the tire diameter is the same.
Not sure if the original owner reused the lug nuts on the 20's when changing from the 17's or not. The truck came with both sets of wheels, but only the lug nuts that were on the 20's mounted to the truck.
 

HORN HIGH ACES

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Not sure if the original owner reused the lug nuts on the 20's when changing from the 17's or not. The truck came with both sets of wheels, but only the lug nuts that were on the 20's mounted to the truck.

Most people change to a spline style lug with aftermarket wheels. And maybe those are okay on OEM wheels, but not always the other way around? You could do some digging from old posts or maybe someone else can chime in, but you are guaranteed to be good if you use OEM lugs with the OEM spare.
 
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