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Spare tire question

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Rgpracer

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Evening all. I have a Friend that has a 2018 Laramie with 20" tires but, spare is an 18".
You can't run an 18" and a 20" on the rear.....we both pull campers and going to be taking ling trips in 2022. Is his option if a flat on the rear to.....move tire from front to rear, put spare on front or just buy an extra 20" and throw in bed??
He has had truck for a year and never thought to check until lately, found out that it's an 18".
Will a 20" fit in place of the 18" spare.....is there enough room? He says that the 18" fits VERY snuggly.

Thanks
Ray
 
Rgpracer said:
Evening all. I have a Friend that has a 2018 Laramie with 20" tires but, spare is an 18".You can't run an 18" and a 20" on the rear.....we both pull campers and going to be taking ling trips in 2022. Is his option if a flat on the rear to.....move tire from front to rear, put spare on front or just buy an extra 20" and throw in bed??
He has had truck for a year and never thought to check until lately, found out that it's an 18".
Will a 20" fit in place of the 18" spare.....is there enough room? He says that the 18" fits VERY snuggly.

Thanks
Ray
Click to expand...
The tire is the same size the rim size does not matter it wont have any affect having the 20 and 18 on the rear they are both the same tire diameter…
 
H3LZSN1P3R said:
The tire is the same size the rim size does not matter it wont have any affect having the 20 and 18 on the rear they are both the same tire diameter…
Click to expand...
REALLY???
The roll out is the same on the 18" and 20" tires?
 
Rgpracer said:
Evening all. I have a Friend that has a 2018 Laramie with 20" tires but, spare is an 18".
You can't run an 18" and a 20" on the rear.....we both pull campers and going to be taking ling trips in 2022. Is his option if a flat on the rear to.....move tire from front to rear, put spare on front or just buy an extra 20" and throw in bed??
He has had truck for a year and never thought to check until lately, found out that it's an 18".
Will a 20" fit in place of the 18" spare.....is there enough room? He says that the 18" fits VERY snuggly.

Thanks
Ray
Click to expand...

The 18" wheel fits snugly because the tire size diameter is approximately the same as the 20"

Factory 20 were usually 285/60R20, spare 275/70R18. They are within 0.9% or 6+ revs/mile form each other. With some wear on the 20", they will be close to dead on the same.

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Tire size is the same. Numbering system is different as the rim dia is different
Metric numbering is confusing.
First numbers is tire width in mm. Second number is raito of side wall to width. Then you have to double that number as you have the side wall width above and below the rim. Then add in the rim dia.
 
I'll try to simplify this using non-metric tire size... a 35×12.50×18 is the same diameter as a 35×12.50×20.
Simply put, the wheel size is inconsequential as long as the tire has the same diameter.
 
Not surprising considering they quit teaching practical math 20 years ago! SMH
 
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