Replacing rear tires only - ruin transmission??

Hey folks....

I went in to Big O (always chuckle at the namehttp://veganfreakradio.com/o-face.jpg) Tires today to have a couple new tires put on my 2002 CRV which I've owned for about a month.

The salesman had a look at all four tires and, with a grave expression, said "your car is 4-wheel drive and must have the exact same size, brand, and age of tires on all four wheels. The tread depth can differ no more than 2/32 from tire to tire otherwise transmission damage can result."

I thought he was joking at first. But he was very serious.

The front tires are maybe 25% worn, if that and I am getting a similar kind of tire tread (all weather) and the exact same size.

I acted as if I gave some serious thought to his (implied) suggestion but told him to just put two new tires on the back. He replied "Well.... I'll do it but you'll have to sign a waiver saying you just brought the wheels in coz we cain't be held responsible when your transmission goes out."

I did a precursory search prior to posting this and couldn't find anything about tires causing transmission damage. Is there any truth to what he is saying? If so, the transmission is probably already toast because the two tires replaced were almost bald.

Comments?

While he was close, what he probably meant was that the rear differential would have issues from the difference in the tires. That is the downside of AWD vehicles that they don't tell you.

While he was close, what he probably meant was that the rear differential would have issues from the difference in the tires. That is the downside of AWD vehicles that they don't tell you.

Any link or reference to this? I find it difficult to believe that the exact same size tire but different amounts of wear would affect the drive train of a vehicle.

i've read and heard of different sizes from back to front or front to back will wreck your tranny.
but not exact same size but different tread wear, then again - anything is possible.

Hey folks....

I went in to Big O (always chuckle at the namehttp://veganfreakradio.com/o-face.jpg) Tires today to have a couple new tires put on my 2002 CRV which I've owned for about a month.

The salesman had a look at all four tires and, with a grave expression, said "your car is 4-wheel drive and must have the exact same size, brand, and age of tires on all four wheels. The tread depth can differ no more than 2/32 from tire to tire otherwise transmission damage can result."

I thought he was joking at first. But he was very serious.

The front tires are maybe 25% worn, if that and I am getting a similar kind of tire tread (all weather) and the exact same size.

I acted as if I gave some serious thought to his (implied) suggestion but told him to just put two new tires on the back. He replied "Well.... I'll do it but you'll have to sign a waiver saying you just brought the wheels in coz we cain't be held responsible when your transmission goes out."

I did a precursory search prior to posting this and couldn't find anything about tires causing transmission damage. Is there any truth to what he is saying? If so, the transmission is probably already toast because the two tires replaced were almost bald.

Comments?

NONSENSE. I seriously doubt it, otherwise you would have to replace tires continuously. Don't believe everything you hear.

If your V is FWD, of course you can run different size tires front to rear. It's bad practice for handling reasons and because of the ABS and VSA (Gen 2.5 and 3 only) systems, but it will not harm your drive line. For AWD Vs (RT4WD) it's a different story. The rear pump in the RT4WD System is 2.5% larger than the front pump to allow for the different wheel speeds in turns, particularly tight turns and normal slip rates under acceleration. If larger tires (rolling radius) are installed on the rear axle they will turn slower than the front wheels and this will be additive to any wheel speed differences in turns and under acceleration. At some point, the RT4WD System will start to engage as if the front wheels were loosing traction (turning faster than the rear wheels). In high traction conditions (clear, dry, paved surface) this will lead to torque buildups between the front and rear axles leading to clutch pack wear and higher than normal rear differential component wear.

If, on the other hand, larger tires (rolling radius) are installed on the front axle, the risk for RT4WD damage is lessened but you still run the risk of complications due to wheel speed differences and the ABS/VSA systems. In slippery conditions the RT4WD System will also be slower to react, possibly causing problems.

In short, installing different size tires (even due to larger differences in tread wear) can be problematic in newer cars. That is why regular tire rotations are emphasized in owner's manuals and technical literature. For the OP: If it's simply a moderate difference in tread wear, that's normal and OK, but be careful about the differences in rolling radius between different tire manufacturers even for the SAME SIZE tires. We have seen reports of note worthy differences in tire diameters for the same size and model tires from the same manufacturer but different model years.

In short, installing different size tires (even due to larger differences in tread wear) can be problematic in newer cars. That is why regular tire rotations are emphasized in owner's manuals and technical literature. For the OP: If it's simply a moderate difference in tread wear, that's normal and OK, but be careful about the differences in rolling radius between different tire manufacturers even for the SAME SIZE tires. We have seen reports of note worthy differences in tire diameters for the same size and model tires from the same manufacturer but different model years.

Thank you for your kind and informative reply. The tires are different brands and the new ones went in back.

I found these instructions to measure rolling radius - do you recommend I do this?:

Here’s a simple way to measure the effective rolling radius. First of all make a mark on your tire’s sidewall at the center of the contact patch and also mark the ground at this spot. Lightly move the car forward so that the tire makes one complete revolution and the mark on the sidewall is again at the center of the contact patch. Now make another mark on the ground at this point. Finally measure the distance between the two marks on the ground in inches and divide that number by 3.14. That would be your Effective Tire Diameter. You don’t need to worry about being accurate to the last 1/100th of an inch. Being within a quarter of an inch or so it’s close enough.

Also, I take it from your reply that I should put the newer tires in the front.

Thanks!

Thank you for your kind and informative reply. The tires are different brands and the new ones went in back.

I found these instructions to measure rolling radius - do you recommend I do this?:

Here’s a simple way to measure the effective rolling radius. First of all make a mark on your tire’s sidewall at the center of the contact patch and also mark the ground at this spot. Lightly move the car forward so that the tire makes one complete revolution and the mark on the sidewall is again at the center of the contact patch. Now make another mark on the ground at this point. Finally measure the distance between the two marks on the ground in inches and divide that number by 3.14. That would be your Effective Tire Diameter. You don’t need to worry about being accurate to the last 1/100th of an inch. Being within a quarter of an inch or so it’s close enough.

Also, I take it from your reply that I should put the newer tires in the front.

Thanks!

The method is as good as any. Really all you need is a number for comparison. Rolling Radius, Effective Tire Diameter, Inflated Circumference, Revolutions per Mile are all just numbers used for comparisons between tires. If you can, it might be worth the extra time and effort to be sure you are not more than the 2 or 3% (difference) recommended (just to be sure you haven't stumbled on one of the bigger differences between manufacturers).

Your comment about putting the new tires up front is right on.:) The front tires take the lion's share of all tractive, cornering and braking loads and will wear faster anyway. Putting them up front will also minimize your drive line issues, if any.