Problems caused by different tire sizes?

It's been a very frustrating year with my 98 AWD mountaineeer in the shop more often than not. I posted awhile ago about getting much lower gas mileage and followed the advice given, but haven't been able to check my mileage since my car has been in the shop constantly.:frown:

Yesterday I get a call from my mechanic who said he just noticed my tires are different sizes, fronts are 235 & rear are 225 and he feels this may have caused some of my recent problems. My receipt for my tires indicates that I purchased 4 P235/75R15 tires 2/2006 from PepBoys and at the same time I paid for balancing and alignment. My mechanic says no way could they actually have done an alignment since the tires are different sizes. Is this true?

I'm hoping to get some facts so that when I go back to PepBoys they will honor my receipt & put the tires I paid for on my car.

I have spent thousands of dollars in repairs in the past year, some of which may be connected this tire issue (per my mechanic).

I would like to find out if:

The abs sensor I had to replace 6 months after getting these tires may have been damaged due to the tire sizes being different.

When the abs sensor was replaced I was told my brakes were completely worn and needed to be replaced (again!) even though they had all been replaced the previous year.

Next my transfer case had to be replaced.

Then my front axle had to be replaced.

My mechanic can not seem to get the axle squared away it's been back to the shop 4 times since he replaced it....and now he thinks the tires being different sizes may be part of the problem.

One thing I noticed right away after getting my tires replaced is that they were very noisy...could the noise be due to the size difference?

I've been searching but really haven't found any facts about problems caused by different size tires on AWD vehicles.

yes that is the reason for the noise.

what is the other numbers on the 225 tires ?

if it is 235/75 in fornt and 225/70 in rear that could be very bad.

if it is 225/75 and 235/75 that wouldnt be so bad but it is still not good.

if you bought four someone screwed up and you should get 4 new ones not just 2. being different circumfrences is very bad on an awd.

Thanks for responding Greg.
I don't know about the other numbers yet as my car is still in the shop & I hope to pick it up later today. The mechanic only mentioned the first #'s to me when he called.
I will be sure to check all the numbers when I pick up my car.

And likewise, if it was 235/70 on one end and 225/75 on the other, it may not be an issue (although you still didn't get what you paid for and your speedometer/odometer would be off.

The different tire diameters would not have an effect on the ABS sensor.

If you have traction control or AdvancTrac, different tire sizes could cause excessive brake wear. If you do not have any form of traction control, the different tire sizes would not accelerate brake wear.

The different tire sizes could certainly lead to transfer case wear/damage. If the tires were installed a month or more before the transfer case failed, I would certainly pursue having PepBoys pay for the damage.

With AWD, the transfer case is attempting to turn the front axle at the same speed as the rear axle. The different tire diameters would fight this, causing wear on the transfer case as well as at least the ring and pinion gears for the front.

To really have a case, you'd need to understand what part of the transfer case and front differential failed.

I agree that PepBoys should replace all four tires rather than just the tires that are of the wrong size. The AWD could accelerate the wear on all four tires.

-Rod

Rod,

I checked all the tires when I picked up my car and only the 235 & 225 #'s were different the rest of the numbers were the same.

I checked with my mechanic & he said the transfer case failed due to broken gears.

I called my local PepBoys where I had purchased the tires & the manager told me to bring it in along with all my repair receipts. He told me that the ABS, the transfer case & the front axle could have all been damaged by the difference in tire ratio. :nono: Everyone there was wonderful & actually thanked me for bringing in my car & giving them a chance to make amends.:)

They replaced all 4 tires for me & also did an alignment (everything I had originally purchased). They kept copies of all my receipts to be sent to corporate & they said they noted that the wrong tires HAD been put onthe car & that I would hear from their district manager next week.

Trust me I double checked the tires before I drove away:grinno: and what a difference I could feel! The car no longer felt like it was bucking & no more tire noise. I can now tell that my front shocks are "soft" so I guess I'll have to look into that next...does it ever end?
Hope springs eternal so I'm hoping the shocks just need to be adjusted (if there is even such a thing):rolleyes:

Great, sounds like you found a decent PepBoys, it's just too bad the mistake happened in the first place. Glad to hear they seem to be treating you right. I hope it continues for you (but it won't in the case of shock "adjustment" -- no such thing).

-Rod