Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

Different tire sizes installed on same axle in front and in back, i.e. same size on driver side v. Different size on Passenger side

Help! Is this dangerous? What are possible current/future mechanical problems resulting from installation and running 900 miles of two different size tires on same axle in front and in back? I.e.: same size of tires on front and back of one side of car, and a smaller set installed on the other side of car. Its already pulling and needs alignment. Installer says it’s fine to drive car until two more tires come in?!?!. Car is not AWD or 4WD.

If I HAD to run two different sizes I’d put both larger sizes on the front and the smaller sizes on the rear assuming it’s a car and not a truck. It may appear to need an alignment simply because of how the tires are now oriented. How soon are the new tires coming in?

Well I can’t say anything for sure without knowing how much difference there is in size between the left and right tires. Do you know the sizes? But I don’t think you’re in for any kind of damage or wear.

I can’t help but ask how you ended up with 2 different sizes left and right.

Do your differential a favor and put the same size tires on the front wheels.


Yep, get the same size tires on the same axles. What are the exact tire sizes? There could still be a problem with the ABS, if the difference is too great.

A clue as to tire size would help people give more accurate answers.

1 Like

At the risk of asking a question that the OP would rather not answer, I just have to ask:
Who made the decision to put non-matching tires on each axle, instead of installing the same size tires on the front, and the other (matching) size on the rear?

If it was a tire shop or a mechanic, I REALLY hope that the OP never returns to that place of business, as they clearly have no clue about what they are doing.


I assume you’re asking if you did any damage, since you already drove 900 miles.

Given this car is not AWD/4WD and given you had the same size tires on the front, then I would not worry about it at all. If it were me, I’d continue driving it until your new tires came in.

Not that I’d recommend this, but for much of the first decade that I had a license (years ago), my cars almost always had different size tires on them. The reason was because I worked gas stations and would grab any old tire that had some tread left and that fit my rims and would run it on my car. Oftentimes they were very different sizes. I never had a problem.

1 Like

The auto shop that installed the tires somehow installed two different size sets on the vehicle without realizing it. They are the ones saying it is OK to keep driving until they get two more tires in to make four matching tires. It was another auto shop that caught the error when it was brought in for alignment (probably started pulling because of running it for so long on mismatched tire sizes??)

Except the front tires are different sizes

Sorry I missed that.
What is the size of each of the two tires?

Please don’t tell us that the front was aligned with mismatched tires still on the front.

As referred above, there’s a piece of the transmission in your Corolla called the “differential”. Part of its job is to compensate for variations in front wheel rotation speed, left vs right. That only happens when making turns though, provided the tire sizes are the same. So the gear gadgets it uses to do that aren’t very robust, as they are seldom in motion. So the problem is that if the tire sizes aren’t the same on the front, those seldom-used gears in the differential are now constantly in motion. And will eventually wear out from overuse, at which point you’re looking at an expensive repair bill. How many miles of driving on different tire sizes will cause that, hard to say. But the fewer the better if you want to keep the contents of your wallet intact.

Thankfully the alignment techs did not align the vehicle, they are the ones that actually found the problem.

What size tires are we talking about here?

I’m not sure if the sizes of each tire off the top of my head. I did read somewhere about the differential issue, and I read about potential problems with braking fast and spinning as a result of tire size difference. Hence my questions to you all about safety and any additional mechanical problems resulting from running mismatched tires. I appreciate any and all feedback, thank you so much.

Before writing another word, I’d go remove the wheels and match the front tires and the rear tires, putting the same size on the opposite sides of each end of the car. You’ll be doing yourself a big favor. The car will handle better, brake evenly, and you’ll prevent the excess wear on the mechanicals described so well by George.

And yes, different size tires on the left side than the right size could absolutely be dangerous in an emergency handling or braking situation. They could cause you to crash… maybe even into the front end of e Freightliner. Without knowing the actual tire sizes, It’s not possible to guess HOW dangerous, but if it was causing pulling to one side it was definitely too much of a difference.

And don’t forget; after they replace the two off sized tires they owe you a four wheel alignment. I would have it done elsewhere and give them the receipt for compensation. Write a concise and comprehensive letter of complaint stating the problem, that they sent you on your way with an unsafe pulling to one side, uneven braking, and that you no longer trust them to do an alignment and that you expect to be compensated for a four wheel alignment at a competent shop. Emphasize the safety issue, mention a formal complaint to the state attorney general’s office of consumer protection, and I’ll bet they’ll be happy to reimburse you for the alignment.

Don’t worry, you should be find between now and Monday when you get them replaced. Don’t worry about the differential, it is not going to wear out in a short period of time.