One tire blows out and tire shop wants to change all four!!!
 

Have to vent out....
Was out of town and one of the tires on my sister’s SUV (Acura MDX) blow out (big nail/iron piece went through it on HW). All four tires were replaced recently and have less than 10K miles. I figured we can change just the rear two but the shop guy says he will do all four or none! Well, we were out of town and were in a fix. I really don’t understand this concept. Costco, discount tires etc same game…they say that the 4WD drive lines will break apart if they just change the rear two. MDX is a mechanical device and not CD changer, so really? The tires wear out unevenly anyway and certainly the roads are not even to exert equal pressure on all four tire at all give time. Any thoughts?

Many modern AWD systems need all four tires to be very close, generally 1/4" circumference is the spec given. I know on Subarus with automatics (since they have the computer controlled clutch pack for rear output) if the tires are much beyond that spec they will buck every now and then as the computer applies the clutch pack. The mechanical ones can overheat the viscous clutch, leading to permanent torque bind since over time with that heat the viscous fluid can polymerize into a solid.
As far as replacing all four, that's a CYA move by the tire dealer. If they sell you one or two then the transfer clutch blows, they can be held liable.
Hopefully you kept the old tires? Take a tape and wrap it around the center of an old one, then do the same with one of the new ones. If there's more than 1/4" difference, then sell the old tires and move on. If not, maybe call the district manager for the store you went to and make sure they properly train the store staff so this doesn't happen again.

Moved from General Non-Automotive Discussion. :-tap

I am kind of surprised and alarmed at this thread. I had no idea you woud have to replace even two tires at a time, much less all four. The wife drives an Audi quatro. I like how it hugs the road like white on rice. However I do find it annoying that if you back up with the wheels cut to one side it's like I'm driving my Ford 4wd with the front wheels in lockl.

It made me sick that we ended paying $890 for four new tire installed. I guess this is probably the reason I stay away from all these automatic-luxury stuff. I have changed front tires on my dually before leaving the rear as-is. Same thing on my Jeep as well.
BTW, I got the old tires home...

They took advantage of you and knew you were not coming back, as simple as that.. Were they AAA rated?

What's done is done. I would study the owner's manual and or call the car dealer to get the true story. The tire shop may have very well been in the rights to force you into a complete tire change.

The question would be for me,

Is there a road hazard policy that would cover or help cover this type of a situation? Afterall, the cars drive train requires four tires of equal diameter.

Tim

I'll more or less repeat but AWD, not to be confused with 4wd, require all 4 tires to be very close to the same. The tranny's do not like much a a size difference or they will torpedo. Off hand I have no idea if the car in question is AWD but I assume it is and if the tires would have been out of spec with a new one then the proper decision was made. You also have to realize after the Ford/Firestone/Explorer/moron non tire pressure checking owners lawsuit, companies have to be scared to death to leave any decision making up to consumers as they will sue the hell out of anyone they can for their own mistakes.

I've also heard of tire shops, when replacing only 2 tires on a FWD car, putting the new tires on the back only. They won't put them on the front for the same fears.

Wow, after reading this thread, I'm not sure I ever want to buy a newer model AWD vehicle of any kind...

The closest I came to this was with a couple of AMC Eagles - a 1980 with an NP119 t-case and a 1984 with an NP129... Both cars had to run the same size tires all the way around so as not to wear out the viscous coupler in the t-case prematurely but I've never heard of any other issue with them other than the coupler can wear out and not work like it should...

Sounds like these newer AWD's are much more finicky about such things...

I just recently put tires on my Expy and the tire manager and I were talking away. According his corporate people, the reasoning behind placing the new tires on the rear of a front driver is the rear of the car has very little drive control. The newer tires are supposed to help prevent the back end from fishtailing and coming around.

I'm not so sure I agree with them 100%.

I was considering an AWD Edge as my replacement for the Expy in the future, not anymore.

Tim

IIRC, you can swap the full time case out of the Eagle for an NP208, and have a regular 2wd/4wd system.
The problem isn't limited to the newer ones alone. Subaru has been using this same system since 86 in their turbo models with automatic transmission. The one I have will buck noticeably if the tires are not matched.

The 119 is a full-time case. The 129 has a vacuum-actuated front-axle disconnect. AMC also used a 128 which, I believe, is open-ended and was only used for 1 year ('85). The Jeep NP229 is a direct bolt-in for the 129 - just have to drill a hole down by one of the driver's seat rails for the hi/lo lever to stick through...

They are kinda neat cars. The weekend mail delivery person here uses one, and honestly that's the only AMC product I'd even really consider buying (I have had very bad experiences with an FSJ and an XJ Cherokee).

Funny you should mention the XJ - The Eagle was a an experiment that AMC performed to see whether or not a vehicle with a unibody could hold up to the 4WD - It was the predecessor to the XJ (YJ?) Wrangler. The AMC 258 inline 6 is, more or less, still in use today in the form of the Jeep 4.0 liter - Swapping parts between the 258 and the 4.0 can produce a 4.6 liter stroker...

I was on the AMC List for a while and can probably tell you anything you need to know about the Eagle... I even wrote up an article on how to bypass the MCU - You can still find that writeup here: http://www.skidmore.edu/~pdwyer/amc/eagle/bypass.htm - Somewhere around here, I have parts microfiche for the 80-87 Eagles...

OK, now that I've taken this thread wwwaaaayyyy off-topic, I'll leave now :)

FWIW

I had a 1998 3/4 ton Chevrolet 4WD that I bought new in 97. I cut a sidewall and replaced the rear two tires. After that it was difficult engaging/disengaging 4 High or 4 Low. Took it to a reputable shop and the explained it was the mismatched tires - they replaced the front two and the problem went away.

what problems did you have with the xj? I had a 92,and it was the most reliable vehicle I have ever owned,and I lifted it,put bigger tires on it and abused the heck out of it off and on road.