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Spare Tire One Inch Smaller

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If one upgraded their 255/70/18 Sport Altitude tires to 275/70/18 and left the 255 on as the spare for emergency use only, would there be an issue with this setup as long as 4WD wasn't used? The difference when the tires are new would be 1 inch, and that difference would continue to shrink as the tires on the ground aged.
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JJ_WA

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Like this? New version of the space saver tire. "They" will be a little lop-sided if there's a flat. ~

Jeep Wrangler JL Spare Tire One Inch Smaller Lifted jee
 
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I said an inch difference, not a foot....ha.


Like this? New version of the space saver tire. "They" will be a little lop-sided if there's a flat. ~

Jeep Wrangler JL Spare Tire One Inch Smaller Lifted jee
 

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If one upgraded their 255/70/18 Sport Altitude tires to 275/70/18 and left the 255 on as the spare for emergency use only, would there be an issue with this setup as long as 4WD wasn't used? The difference when the tires are new would be 1 inch, and that difference would continue to shrink as the tires on the ground aged.
Doable, (not recommended) if no engaged lockers or LSD, put the spare on the front , repair ASAP. I do this on my PU because the tires are too big for the spare spot.
 
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Just save up till you can afford one more tire. The difference of 1" isn't the problem, it is the revolutions per mile that tire will need to achieve to keep up with the other three. This increased revolution will create excessive heat. There are also the numerous electronics that will have to compensate (ABS, etc) for the fact that one tire is moving considerably fast than all three other tires.

For instance the 255 tire is rotating 629 times per mile, where as the 275 is covering the same distance with 609 rotations.

If you needed it in an emergency pinch where you weren't going to go a considerable distance or speed, you're probably fine. But if you need it for a long haul, I wound't personally do it.
 

JEEP4U

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Not recommended. Do not let your dealer see that. They could void your warranty.

Probably will Illuminate a dash light.......different wheel speeds. Will produce additional heat in the differentials and transfer case........due to slipping.
 

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If it's just for an emergency drive if/when you get a flat, I see no issue with this. Any modern car that even has a spare will have a space-saver that's smaller than the stock diameter. Totally fine for limping the car home or to a shop to get a replacement. Those little donut tires are much more than a 1" difference too.

No dealer would see your slightly smaller tire and void your warranty any faster than they'd void someone's warranty pulling in on a donut space saver spare (which is to say, they wouldn't).

Though be ready for eagle-eyed Jeepers to point and laugh at your expense, I expect. It's not exactly the classiest look to have a mismatched spare on the back of your Wrangler. Thing is, is it really that hard to save up another $250-300 and buy a 5th tire? Remember, the tire isn't going to go unused; you rotate it in with the other 4, extending the time between tire replacements. And if you're expecting to at some point get a flat and swap it in anyway ...
 
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If it's just for an emergency drive if/when you get a flat, I see no issue with this. Most cars that have a spare (fewer and fewer even have them!) have a spare that's smaller than the stock diameter. Totally fine for limping the car home or to a shop to get a replacement. No dealer would see that and void your warranty any faster than they'd void someone's warranty pulling in on a donut space saver spare (which is to say, they wouldn't).

Though be ready for eagle-eyed Jeepers to point and laugh at your expense, I expect. It's not exactly the classiest look to have a mismatched spare on the back of your Wrangler.
At my age and after owning 9 Jeeps, those eagle-eyed jeepers don't bother me much. I would keep a cover over the spare to trip them up.... ha
 

azwjowner

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If it's just for an emergency drive if/when you get a flat, I see no issue with this. Any modern car that even has a spare will have a space-saver that's smaller than the stock diameter. Totally fine for limping the car home or to a shop to get a replacement. Those little donut tires are much more than a 1" difference too.

No dealer would see your slightly smaller tire and void your warranty any faster than they'd void someone's warranty pulling in on a donut space saver spare (which is to say, they wouldn't).

Though be ready for eagle-eyed Jeepers to point and laugh at your expense, I expect. It's not exactly the classiest look to have a mismatched spare on the back of your Wrangler.
I would follow the same limitations that those space saver spares have -- no more than 50 MPH, no more than 50 miles. So you don't overheat the spider gears.
 

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If it's just for an emergency drive if/when you get a flat, I see no issue with this. Any modern car that even has a spare will have a space-saver that's smaller than the stock diameter. Totally fine for limping the car home or to a shop to get a replacement. Those little donut tires are much more than a 1" difference too.

No dealer would see your slightly smaller tire and void your warranty any faster than they'd void someone's warranty pulling in on a donut space saver spare (which is to say, they wouldn't).

Though be ready for eagle-eyed Jeepers to point and laugh at your expense, I expect. It's not exactly the classiest look to have a mismatched spare on the back of your Wrangler. Thing is, is it really that hard to save up another $250-300 and buy a 5th tire? Remember, the tire isn't going to go unused; you rotate it in with the other 4, extending the time between tire replacements. And if you're expecting to at some point get a flat and swap it in anyway ...
On my other Jeeps I have only rotated 4 and then when time for the first replacement bought the exact same tire and only bought 3 and used the "original" spare as the 4th tire and put the best of the worn tires on as the spare. Come to think of it, in 40 years of driving, I have never used a spare tire to replace a flat....(knock on wood)
 

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Like this? New version of the space saver tire. "They" will be a little lop-sided if there's a flat. ~

Jeep Wrangler JL Spare Tire One Inch Smaller Lifted jee
Nope, that's my Jeep with 37s and the 33 spare.... I took it off because it just looked silly. Hope I don't get a flat!
 

Reinen

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Don't do it. You'll freak out the Jeep if you use the spare.

The wheel speed sensors will constantly think the smaller tire is slipping and losing traction because its rotation speed will be slightly faster than the other tires. Then all sorts of unnecessary alarms and restrictions will kick in.

You're far better off getting the right sized spare and doing a 5 tire rotation.
 

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great way to destroy your differential running 2 different size tires on the same axle, not to mention unsafe
 

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Don't do it. You'll freak out the Jeep if you use the spare.

The wheel speed sensors will constantly think the smaller tire is slipping and losing traction because its rotation speed will be slightly faster than the other tires. Then all sorts of unnecessary alarms and restrictions will kick in.

You're far better off getting the right sized spare and doing a 5 tire rotation.
Oh that's a good point. I'm not used to vehicles with fancy computers. He probably should just get the same size tire.
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