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My 1997 Honda Accord came with a 115/70/14 donut spare tire. I had to use it for the first time recently, and it is now totally dead and needs to be replaced.

I looked on Ebay and there are a few people selling 115/70/14 Accord donut tires. But there are also a few people selling different sized Accord donut spares that they say will work on a 97 Accord. Those are sized 135/80/15, 125/70/15, and 125/70/14.

Do I have to get a 115/70/14 tire, or will one of those other sized spares work as well?

  • To clarify: when you say "spare tire" you're talking about buying the tire and wheel together? Certainly if you just buy a 15-inch tire and try to install it on your existing 14-inch wheel, it isn't going to work. – Nate Eldredge Mar 30 '15 at 20:55
  • @NateEldredge Yes I meant the tire and wheel together. – pacoverflow Mar 30 '15 at 20:56
  • Note that these tires are larger than your current donut, so they may not fit in your spare tire compartment. – Nate Eldredge Mar 30 '15 at 21:07
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There is a huge pile of information about tire sizing around the internet. I'll attempt to summarize its application here.

Tires have 3 numbers, which work together to describe the tire's size. The first number is the section width, the second number is the sidewall ratio and the third number is the rim diameter.

Section Width

The section width is the width of the tire in millimeters at the largest point. This is important when trying to fit a tire to a rim, but in your case the rim is already matched to the tire so we're good. The number does still matter for us because of what we're calculating.

Sidewall Aspect Ratio

This is the distance from the rim to the tread. It is described as a percentage of the section width, so a 70% sidewall with a 130 section width will be taller than a 70% sidewall with a 110 section width.

Rim Diameter

This is the most obvious of the numbers. It is the rim diameter in inches. Why is the section width in millimeters and the rim diameter in inches? My guess is the same reason many manufactured parts in America are dimensioned in inches, but sometimes they hang out alongside parts manufactured to metric dimensions.

We can use these numbers to (roughly) calculate tire diameter...

Let's start with a standard factory sized '97 Accord tire (yours may vary depending on trim, but it will probably have a similar outer diameter):

185/65R15

185 / 25.4 = 7.283" (Metric to inch conversion)

7.283 * 0.65 = 4.734 (Sidewall height as a percentage of section width)

4.734 * 2 = 9.468 (Double the radius to get diameter)

9.468 + 15 = 24.468 (Sidewalls + rim = outer diameter)

So following the same calculation:

115/70/14 = 20.339

135/80/15 = 23.504

125/70/15 = 21.890

125/70/14 = 20.890

It looks like your other 3 options are between your original spare and your standard tire diameter. As long as they'll fit in the spare tire well any one of them would likely be an adequate spare as long as the bolt pattern matches. I would favor something as close to the standard tire as possible if you know it will fit the tire well.

Please see this link at the Tire Rack for a more detailed explanation of tire sizing.

There is a calculator for tire diameter here.

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    While your information about tire sizing is correct, it isn't so clean when it comes down to the practicality of it. One manufacturer's numbers won't always match anothers. Go to tirerack.com and compare one RPM to another and you will see. – Pᴀᴜʟsᴛᴇʀ2 Mar 31 '15 at 1:48
  • It is practical in this answer, to this question. One is always advised to match tires from left to right, which addresses the small difference in actual diameter from one manufacturer to another (among other things). This question is about the size of a space saver spare, which will never match the tire on the other side. I also said "roughly" on the tire diameter calculation, because it will never be exact. – Lathejockey81 Mar 31 '15 at 9:10
  • Just for reference, a 125/70/15 spare does fit in the tire well. – pacoverflow Dec 9 '15 at 6:09
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tl; dr You can run it, but there is a cost.

You'd need to double check to ensure the rotations per mile (RPM) are almost/nearly the same (if not exactly). If it's off by more than a few percentage, you are going to have a problem with your anti-lock brakes (ABS) throwing codes on you. If you run a mis-matched donut on the front, you will have issues with over-heating your transaxle due to the mismatch of tire sizes. This is due to the differential having to make up the difference in . This will provide extra wear and tear on the differential, especially if it has a posi-traction style differential in it (not sure if Honda even has one, but it is something to consider).

Bottom line - find one which is the same size. You'll be happy doing so and so will your car.

  • My 97 Accord doesn't have ABS. Also, the regular tire size is 15", so wouldn't the 14" donut that came with the car also cause the transaxle to overheat? – pacoverflow Mar 30 '15 at 21:04
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    A donut spare is usually smaller diameter than the standard tires to begin with, so you would have this problem even with the factory-supplied donut, right? That's presumably one of the many reasons why you should only use the donut in emergencies, for short distances at low speeds. Actually, if I read the numbers correctly, the alternatives the OP is considering are actually larger in diameter than the original donut (though still smaller than the standard tires), so they would seem to make this problem better, not worse. – Nate Eldredge Mar 30 '15 at 21:07
  • @NateEldredge indeed, that's why the donut spares always carry a "no more than 50mph for 50 miles" or similar warning, to reduce the risk of damaging the diff... – Nick C Mar 31 '15 at 8:17
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Most donut spares are a smaller diameter than the original tire. If the vehicle has a donut spare this is smaller in diameter then I wouldn't consider it to be a metric of consideration.

My recommendation would be to retain that diameter.

I think the only relevant piece to this is, if you have a greater width of tire, will it fit in the compartment in your trunk?

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