Odd size spare

[Art_in_CO]

Picked up a 2019 1500 Laramie last week. The mounted tires are the correct original size - 275/65-18. But the spare is a size that's not even available anymore - 245/70-18.

An online tire calculator shows the 275/65-18 at 629 revs/mile and the 245/70-18 at 641 revs/mile. That's a difference of 1.87%.

Would it be ok to use that odd size spare if necessary or should I replace the spare with the correct size?

Thanks.

 

[Travelin Ram]

You could get that much size difference just from tread wear. Irrelevant for short term use.

I wouldn’t go cross country with it on the rear if there’s an LSD in there.

Is it from the factory, or an old tire swapped in? Check the date code.

 

[GTyankee]

art
go to this website
USE ALL CAPITAL LETTERS

it will tell you how your truck left the factory

FCA RAM

fcagroup.my.site.com

 

[brian42]

Rule of thumb is not more than 5% difference in circumference between the opposing sides of a differential so no worries for temporary use.

I'm very OCD about those kinds of things so every rear flat I've had on a truck I've put the spare on the front then taken the front tire and put it on the back to match sides...but that's just me.

 

[GTyankee]

Using an under sized spare tire & where to put it
different shops are in conflict

If a Temporary/Compact Spare tire is used in a driven-wheel position, any differences in tire revolutions per mile require the vehicle's driveline to compensate continuously, increasing heat, wear and the possibility of failure. This is especially true for four-wheel and all-wheel drive vehicles, as well as any vehicle equipped with a limited-slip differential.
many vehicle manufacturers recommend using Temporary/Compact Spare tires only in non-driven-wheel positions.

 

[pacofortacos]

Honestly, I would remove the 245 and put a used (about 1/2 to 3/4 tread) 275/65-18 tire on the spare rim and call it a day.

 

[caulk04]

That's a factory spare, totally normal. It's a temporary tire, not intended to be used for any real length of time. Like the 'donut' tires that many of us are used to seeing they have less tread and are made of a softer rubber to maintain similar traction as a fullsize tire.

If it's in good condition, check it's pressure or carry a pump and forget about it.

 

[PA Ram]

Honestly, I would remove the 245 and put a used (about 1/2 to 3/4 tread) 275/65-18 tire on the spare rim and call it a day.

That's a great idea, I never even looked at my spare until I installed load lifter airbags and had to drop my spare. It's in good condition and I checked inflation. When I swap out for new tires I will probably get the same tires unless I go to 35's. I have Cooper Discoverer AT3 XLT 275x60/R20 I'd feel much safer having one of those tires even if worn for a spare.

 

[Wild one]

Picked up a 2019 1500 Laramie last week. The mounted tires are the correct original size - 275/65-18. But the spare is a size that's not even available anymore - 245/70-18.

An online tire calculator shows the 275/65-18 at 629 revs/mile and the 245/70-18 at 641 revs/mile. That's a difference of 1.87%.

Would it be ok to use that odd size spare if necessary or should I replace the spare with the correct size?

Thanks.

I have a brand new matching spare if you want another one,lol A few guys have used the temporary spare as front runners at the dragstrip,but that's pushing it a bit in my opinion

 

[Black-Wolf]

art
go to this website
USE ALL CAPITAL LETTERS

it will tell you how your truck left the factory

FCA RAM

fcagroup.my.site.com

Awesome!