Spare Tire One Inch Smaller

[Go Hogs!]

Appreciate the responses. I will pick up a used tire of the same size and brand on eBay for the spare. I will not take the risk.

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[2nd 392]

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.

I stand corrected— my 95 PU that has had no issues doing this 27 years doesn’t have all the computerized systems to make a mess of it.

 

[Reinen]

I stand corrected— my 95 PU that has had no issues doing this 27 years doesn’t have all the computerized systems to make a mess of it.

Yup, modern technology and jerry rigging are not friends.

 

[Apexcars]

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)

Wouldn’t this be just like rotating 5 tires and then keeping the least worn as the spare? You would have to buy 4 but each tire should last longer anyway and offset the cost by not having to replace as often.

 

[XJ-99]

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)

Hopefully you will never have to replace a flat, but you never know when you might. On my first Jeep, I had a tire shred on a back road in the middle of Montana, miles from the closest paved road. I was so glad I replaced the donut with a full-size spare.

 

[J0E]

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.

I've run a 31" spare on the front with 37's all around. Like others say, put it on the front then in 2 Hi no differential to worry about. I have 4 full size spares at home.

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

LOL

Get the full size fixed ASAP. Don't go over 65 MPH.

Hopefully you will never have to replace a flat, but you never know when you might. On my first Jeep, I had a tire shred on a back road in the middle of Montana, miles from the closest paved road. I was so glad I replaced the donut with a full-size spare.

Ha, I need to get a donut for my Leaf. Leaf's and many new cars don't come with a spare, not even a donut. For sure you need a real tire where you were at. I don't take the leaf off road much.

 

[SDE]

Isn’t it the same as only rotating 4 tires (like my dealer recommended, and like many of us probably do) and eventually needing to use the unworn spare?

After just a year and 12K miles, my spare has a noticeably larger thread as the 4 tires wear out.

 

[BXFXJeep]

 

[Headbarcode]

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.

Every time I see this question asked, I can't help but envision spiking the ball at the 5 yard line. I'll never see the justification in doing so. All it takes is a little more effort to erase any wiggle room to debate.

 

[YJdude]

A 1" smaller spare beats no spare.
Don't let anyone talk you into the dumbest thing since angry grills: the "spare tire delete" aka STD.

 

[roaniecowpony]

A bunch of mamby pamby, worry wart, the sky is falling, BS.

Using a Toyo AT3 as the tire du jour for this discussion smaller tire theoretically goes around 628.6 revolutions per mile. The larger tire goes around 607.8 revolutions over the same mile. That's about 21 revolutions per minute difference at 60 mph, or 1 revolution in 3 seconds, or about the speed of a hot dog on the roller cooker in 7Eleven. I'm pretty sure the spider gears can handle that for quite a long while. ABS is looking for a locked wheel and it doesn't even come into play until you get deep in the binders (but we all knew that).

Yeah, I wouldn't retrace Route 66 across the country like that, but you know many a down and out drifter has done exactly that. Get over it. Nothing here to worry about for spare that may see a few hundred miles, if any.

 

[Smoke Showing]

Wouldn’t the same be true if you use a virgin spare to replace a well worn A/T or M/T when you have a flat? The spare is the oddball because it’s now bigger. This is another reason to use the rule of 5’s: 5 matching tires/5 tire rotation/5 thousand miles. I used to be that person who didn’t rotate tires unless I saw uneven wear. I was young and dumb, I have actually paid a $10 disposal fee on brand new spares when I changed brands and sizes. 4 people like me and the mechanic gets himself new tires and a tank of gas. I wonder how much I paid for blinker fluid too?

 

[Bleda2002]

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.

No issue if you put it on the front right and stay out of 4wd. With the fad on that side, from a mechanical stand point it won't matter one bit as it's only connected to the outer axle shaft and won't even turn the spider gears.

 

[azwjowner]

Every time I see this question asked, I can't help but envision spiking the ball at the 5 yard line. I'll never see the justification in doing so. All it takes is a little more effort to erase any wiggle room to debate.

Especially since you can buy the cheapest used tire with only a bit of tread left. It's only for emergency use.

 

[Headbarcode]

Especially since you can buy the cheapest used tire with only a bit of tread left. It's only for emergency use.

The only difference between 5 and 4 tire rotations is how much is spent on one given occasion. Over time and multiple sets of tires, the total cost evens out.

The benefits of 5 tire rotations done every 5k miles, are maximizing the time and mileage between replacement and always having a spare of known condition and comparable worn size to the 4 on the ground. A secondary benefit is only needing 1 jack during the whole process, because the spare is dropped first and there's always a loose one waiting to go on until finally making it around to hanging the new spare.

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