Dissimilar tires

What are the measurements of each tire. You will find numbers like 235

Yes, but probably with good reason.

You can go to a truck tire shop or a retread shop and have the tire shaved down so it matches the others. Kinda a waste of rubber, but that will mean you don't need 3 new ones right away.

The dealer is likely right on the potential for problems, some 4x4 systems are really picky about matching rotations when under power.

Mike

Okay, probably a bad idea.

Is it? What are the numbers? If it is indeed the wrong size, you have trouble.

At LEAST replace tires in pairs for God's sake. And use the right size.

--scott

John D'Errico wrote: (96 Subaru outback wagon 187k Miles)

A repair shop replaced a flat tire 10,000 miles ago. Our Subaru dealer claims that this tire is 1 inch larger in circumference than the rest, and that this will cause problems in the drive train.

Is this a problem or is he just trying to sell us a new set of tires? ______________________________________________________

A 1-inch circumference error is a 0.159-inch radius error.

In a 2WD vehicle, non-matching tire diameters on the drive axle will cause the differential gears to work continuously instead of just when turning, and there could be some steering pull from the different tire torques applied. Both effects are minor, and cars have operated reliably for years with mismatched tires.

In 4WD vehicles one mismatched tire could put unwanted strain on interconnecting gearboxes. Call the Subaru dealer back and ask the manager exactly why the mismatched tires cause drive train problems in your car, then make an informed decision.

Good luck.

Rodan.

Mike Romain wrote in news: snipped-for-privacy@sympatico.ca:

My mechanic tells me you can't shave tires that have been used. Once they've been used, little pieces of grit get stuck in the tread, which tears up the machine's cutting blades.

Well, your dealer is right. Especially if your wagon is an AWD vehicle.

On a GM vehicle with auto 4x4 or AWD, the factory spec is that all the tires should be within 3mm tread depth of each other. Otherwise, you will experience problems with the drivetrain eventually.

Ian

When going down this thread, I was hoping that someone would point out the wisdom of replacing tires in axle pairs. In bad weather, it can be darn near suicide, in some cases, not to do it.

Running one tire on an differential driven axle set that is significantly different in circumference than the other, is heap bad medicine.

Sounds like a new set of tires this year instead of next spring.

Thanks, John

You likely have a viscous coupling in your AWD transaxle. (assuming Subaru=AWD in most cases)

If this coupling fails from being run with dissimilar tire diameters, you will pay a whopping price for a new unit.

I would be more upset at the incompetent sack that put a wrong size or wrongly-marked-from-factory tire on your car. That is, unless he only had that size and told you the dangers first but you OKed the replacement anyway.

Toyota MDT in MO

Hey, I guess you are the expert then!...Feel free to run your AWD vehicle with a worn tire....I could care less! The more of you that do this type of thing, the more work there is for me.

Ian

Technically, you would have to quibble over 4 silly millimeters. Anyhoo, the fact is that the wheel/tire assembly was rotating one extra inch per revolution verses the other tires. Hmm, where does all of that friction go? cough!::viscous coupling:::cough!

Toyota MDT in MO