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!

 

[pacofortacos]

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.

For yours, if your spare is a 17" wheel (which most are) a new 285/70/17 is about identical to a used 275/60/R20 tire in diameter. The spare wheel is a bit narrow for that tire but it's a spare and I would prefer a normal tire spare - even if less than ideal. (The narrow wheel will hurt handling to a degree but that's it).

That's the setup I have with my 17" spare wheel and my 275/60/R20 tires. New 20" is 33", new 285/70/17 is 32.7", so it ends up being perfect for my used 20's.

 

[JayLeonard]

I guess I’m more ****. When I had my 17 1500 bighorn, I searched locally and was able to find a single 20 inch aluminum wheel for cheap that matched the stock ones. Mounted a tire on it, cranked it up under the truck and threw the oem temp setup in the dumpster.

 

[PA Ram]

I guess I’m more ****. When I had my 17 1500 bighorn, I searched locally and was able to find a single 20 inch aluminum wheel for cheap that matched the stock ones. Mounted a tire on it, cranked it up under the truck and threw the oem temp setup in the dumpster.

This is exactly what I wanted to do! Now to just find a single rim as I do not want to buy a set even if cheap since I need one.

 

[Wild one]

I guess I’m more ****. When I had my 17 1500 bighorn, I searched locally and was able to find a single 20 inch aluminum wheel for cheap that matched the stock ones. Mounted a tire on it, cranked it up under the truck and threw the oem temp setup in the dumpster.

Curious on what factory aluminium 20" rim for a 1500 you found, that allowed you to get the hook to go through it's center hole.I've got a few differant factory 20" aluminium rims,and none of them will accept the hook for the spare tire assembly to fit through the center hole,so you can wind it up under the truck

 

[PA Ram]

Curious on what factory aluminium 20" rim for a 1500 you found, that allowed you to get the hook to go through it's center hole.I've got a few differant factory 20" aluminium rims,and none of them will accept the hook for the spare tire assembly to fit through the center hole,so you can wind it up under the truck

This ^^^ I was just looking on ebay for same stock rims and the holes are probably way to small for the tire holder to fit through Could maybe change the holder to something custom that works with stock center hole. That's a project for spring/summer unless I get my truck in my son-in-laws shop to replace/fix manifold, replace front struts with rough country lifted struts and replace front sway bar since mine has a crack. Those are all my winter projects since his shop has heated floors and is huge since he is a diesel mechanic for his families paving business working on big ass dump trucks and what not.

 

[JayLeonard]

Curious on what factory aluminium 20" rim for a 1500 you found, that allowed you to get the hook to go through it's center hole.I've got a few differant factory 20" aluminium rims,and none of them will accept the hook for the spare tire assembly to fit through the center hole,so you can wind it up under the truck

I had to modify the piece so it would fit thru the hole. Was not difficult, nothing my 4 inch makita couldn’t handle. The pia was holding it and grinding it under the truck because it had to stay attached to the cable.

 

[Wild one]

I had to modify the piece so it would fit thru the hole. Was not difficult, nothing my 4 inch makita couldn’t handle. The pia was holding it and grinding it under the truck because it had to stay attached to the cable.

I'd be scared to cut it down that much,that it'd fit threw the center hole on a factory aluminium wheel. My luck it'd give out,drop the spare on the highway,where it'd proceed to go through somebodies windshield,and then they'd sue me,lol.
I've looked at doing that,but there's not enough meat left in my opinion to properly support a full size 20" rim/tire combo,so i passed on cutting the retainer that much

 

[JayLeonard]

I'd be scared to cut it down that much,that it'd fit threw the center hole on a factory aluminium wheel. My luck it'd give out,drop the spare on the highway,where it'd proceed to go through somebodies windshield,and then they'd sue me,lol.
I've looked at doing that,but there's not enough meat left in my opinion to properly support a full size 20" rim/tire combo,so i passed on cutting the retainer that much

In MY opinion there was plenty of material left. I thought initially of making a slotted piece of flat steel to act like a washer above the narrowed “foot” or whatever it’s called but decided it wasn’t necessary. Again that was MY opinion using my 40 years of engineering experience.

 

[Wild one]

In MY opinion there was plenty of material left. I thought initially of making a slotted piece of flat steel to act like a washer above the narrowed “foot” or whatever it’s called but decided it wasn’t necessary. Again that was MY opinion using my 40 years of engineering experience.

Yea i looked at cutting a washer out of a piece of 3/16" plate,but didn't want to waste that much steel,and that was several years ago,before the price of steel went through the roof,lol

 

[PA Ram]

I had to modify the piece so it would fit thru the hole. Was not difficult, nothing my 4 inch makita couldn’t handle. The pia was holding it and grinding it under the truck because it had to stay attached to the cable.

That was what I was wondering without looking at mine. If it was possible to remove the end piece and swap something else on there. I might do the same and just make it small enough to fit and then maybe adding something once through to make surface area bigger. Once I do this I have zero intentions of putting a temp space under there anyways.