[Shiny]

My son had two tires punctured by vandals. Tire store told him he needed to replace all 4 to avoid damage to AWD (2010 Jeep GC), presumably caused by significantly mismatched radius. So he bought 4, being told the wear on the two "good" tires was significant enough they would not make it safely through the winter.

Subsequently, insurance claim was filed and my son was told by adjuster they don't agree all 4 were needed. Adjuster apparently said "Jeep recommends but doesn't require..."

Should he argue?

How?

Thanks for opinions, facts, or experience.

[Chris65LeMans]

As much as I hate insurance companies, tire stores have become pretty bad these days, too.

It will all depend on what state he's in. (Insurance laws vary by state.)

[marxjunk]

i see this all the time..they shave the new tires to the same diameter as old if they replace 1 or 2...around here theres several shops that do it..pretty cheap..never done it myself..so i dont know the all details...

[Shiny]

Thanks for the thoughts. Agree every tire company online recommends replacing all 4 with AWD but I'm not having luck finding allowable radius and/or circumference difference for a Jeep GC. I'll call a dealer tomorrow and see if Jeep provides any "quantitative" guidance.

Sad to me an adjuster is arguing 200 bucks when minor fender-bender claims can cost thousands. Is lost customer confidence worth a month's payment when they get to keep the other 11 months? If they will go after $200 for this, what would they do if he needed them!!

[Shiny]

Originally Posted by marxjunk

i see this all the time..they shave the new tires to the same diameter as old if they replace 1 or 2...around here theres several shops that do it..pretty cheap..never done it myself..so i dont know the all details...

Thanks.. I read about that online also. I will have to find out how worn his old ones were but the tire store assertion was he'd need new tires for winter anyway.. suggests they were worn too much for shaving the new ones to make sense.

[chevymad]

Recently worked on a Subaru that had mismatched wear on the tires. Subaru's spec for the mismatch is any difference greater then 1/4" in circumference needs to have the tires changed. It won't take much wear to make a 1/4" difference when you're talking circumference.

[Shiny]

Originally Posted by chevymad

Recently worked on a Subaru that had mismatched wear on the tires. Subaru's spec for the mismatch is any difference greater then 1/4" in circumference needs to have the tires changed. It won't take much wear to make a 1/4" difference when you're talking circumference.

Thank you. Will try to find out if Jeep has a similar spec. Agree 1/4" in circumference isn't much. Makes me wonder if a few psi difference in air pressure will have the same effect.

[Sirrotica]

I found this discussion about AWD cars, and tire circumference. It may, or may not, help your situation out:

https://www.eng-tips.com/viewthread.cfm?qid=292105

!/4 inch of circumference is pretty insignificant in the overall scheme of things. Driving on a space saver tire for 50 miles isn't prohibited on an AWD vehicle. The argument against this is that a shorter tire will tell the ECM that the tire is slipping, commanding the torque split to the axle with the shorter tire. will it damage the driveline? Some have an opinion it will, and others say it's probably not going to cause major problems.

If you aren't having any luck with the adjuster, I'd ask to speak to a senior supervisor within the company. I just went through this with a metal roof claim and was getting nowhere with the recent college graduate with the new diploma that thought that diploma made her smarter than myself. They also don't give the adjusters any leeway to make a decision that may raise the amount of the estimate, effectively tying their hands to help the customer. A senior supervisor is the only way the estimate can be over ridden.

You might also try to ask the insurance company to say in writing if you have any driveline failures connected with tires of circumference differences, that they will stand the damages due to their insistence of not replacing all 4 tires. If there is still new car warranty left will their actions void the remaining warranty? That would make them assume the responsibility of voiding the warranty. This was how I got my other roof panels replaced, the roof has a 40 year warranty, but not replacing the flattened corrugated panels voided the factory warranty, making the insurance company liable for any rusting of the roof in the future.

Good luck with your fight..........

[lemansboy70]

I had a flat on my 2018 Subaru Outback. They would only replace the tire after shaving it to match the rest.

[Shiny]

Thanks Sirrotica! Very useful.

You too lemansboy70. I appreciate the experience. The tire stores don't want the liability, that's clear.

And as Sirrotica shared, the insurance company isn't going to be liable for a differential or clutch failure in the driveline so they don't care.

I like the warranty angle. The car is out of warranty but it's a good tactic to ask both Jeep and to negotiate with the insurance.

[Chief of the 60's]

Think of it this way..... Would you run 2 different size tires on the back of a GTO with posi? It's much worse with AWD.

[necdb3]

I ran a Lincoln/Mercury dealer Service Dept about 15 years ago and we used to run into that a lot. it would take out the viscous clutch on the Mountaineers by the 2 axles spinning at different rates. As mentioned, the tires need to be the same diameter however you decide to accomplish that. Replace 4 or shave the new, shave the new seems insane to me, it's a waste.

[Chief of the 60's]

I owned an AWD Pontiac 6000. The "engineers" at GM thought it was a great idea to put a space-saver spare in the car that was a bit smaller than the tires that were on the car. Yep, awesome idea! Until I got a flat. Could not go above 20mph without the car shaking like a leaf. Gotta love those "engineers".

[jerry455]

Tires are cheaper than drive line components. I would never shave tires, if there is that much of a difference then the others probably need to be replaced.

['ol Pinion head]

A good used tire jockey is what you need if you want to replace with what were destroyed with same size used. One who moves a ton of used tires to used tire shops.

[Stuart]

Originally Posted by Sirrotica

!/4 inch of circumference is pretty insignificant in the overall scheme of things. Driving on a space saver tire for 50 miles isn't prohibited on an AWD vehicle. The argument against this is that a shorter tire will tell the ECM that the tire is slipping, commanding the torque split to the axle with the shorter tire. will it damage the driveline? Some have an opinion it will, and others say it's probably not going to cause major problems.

It all depends on how much wear there is on the existing tires, and what is the maximum difference allowed for that model Jeep. Driving 50 miles on a spare is one thing, driving 30,000 miles or more on a set of mismatched tires may be another.

[Radman]

Originally Posted by Chief of the 60's

I owned an AWD Pontiac 6000. The "engineers" at GM thought it was a great idea to put a space-saver spare in the car that was a bit smaller than the tires that were on the car. Yep, awesome idea! Until I got a flat. Could not go above 20mph without the car shaking like a leaf. Gotta love those "engineers".

Probably wasn't the engineers idea. More likely a front office bean counter.

[Sirrotica]

I'm going to approach this problem with some common sense, and mathematics, as well as real world experience.

I/4 inch of circumference difference is less than 1% on, you can easily get that much difference just by inflation pressure differential.

On an 88 inch circumference tire (28 inches tall) that is .3%, 1/3 of 1% should be well within engineering limits.

BTW, on my dirt track cars we ran usually 3 inches of stagger on the rear axle, commonly with GM posi. I ran the same 70 GTO 8.2 rear axle for 5 years with zero problems. Differentials aren't that sensitive that a little bit of mismatch side to side that would cause a problem, I logged 100s of laps in 5 years on a used 8.2 unit with a minimum of 3 inches of tire stagger

How many times have you seen a open rear axle car spin one wheel for 150 feet? Does the differential expire? The speedometer reading at 50 MPH during a open rear axle burnout means the RR wheel is nearly going 100 MPH, the left is barely turning.

If you've ever driven a 4X4 on dry asphalt in 4 wheel drive as soon as you turn a corner it binds up because the front axle and the rear axle are turning at different rates while cornering. There is no differential in the transfer case.

I owned a 73 Jeep with Quadra Trac and even with 4 matched tires the differential unit wore out. When mine did I replaced it with a standard in/out part time transfer case. I also worked on a customers 77 Jeep with Quadra Trac and replaced the center differential because it had worn out, again with matched tires front to rear. It's not uncommon for the middle differential to wear out, with matched tires. Under 70,000 miles on that 77 Jeep the unit was worn out and not rebuildable.

If the AWD system is going to wear out with .3% differential in tire size, you better never turn a corner on a dry road because I can tell you just turning a corner you're probably at a minimum of 25% differential in wheel speed between the front and rear axles because of the different arcs the wheels are taking executing a turn. That .3% tire mismatch is pretty insignificant compared to 25% while rounding a corner.

In the article I linked to previously, a gentleman said if he locked the center differential on his AWD with 4 matched tires, he could only push it straight ahead by hand a few feet before the wrap up in the axles would stop him from pushing it by hand. 4 matched tires is still causing a driveline wrap up, by unlocking the differential will let the middle differential equalize the slight difference, hence the name differential.

AWD has always had a problem wearing out the transfer case differential, especially in Jeeps and AMC vehicles. I suspect it will continue as long as people steer their cars to go around corners. Putting the problem onto very minor tire circumference mismatch is a cop out by the manufacturers for bad engineering from the get go.

Having already owned a AWD vehicle, as well as servicing customers AWD vehicles (AMC eagles were also another trouble prone AWD vehicle) I don't believe I'd go looking for another one. Jeeps been building AWD vehicles for nearly 50 years (1973 they debuted Quadra Trac), they should have gotten their engineering better than it is by now.

Battle on.

[Mike Davis]

I am a Jeep Fan.
I had a 2010 Jeep Commander Hemi AWD (same platform as the GC). I had a tire get cut down on a forestry road. Tires had approx 15K miles on them. Changed 1 tire on the rear and it tripped the service 4wd light and at times the Anti lock brake light. Purchased another to match the other side of the rear and reset light. About 2 weeks later the service 4wd light came back on. The actuator went out. Coincidence? Maybe. I bought 2 more tires and no problems after that.
The Jeep AWD system is very sensitive. They use electronic limited slip diffs and have a brake lock differential. It does not care how fast the tires turn just they are turning the same speed. This is tied into the electronic stability control as well.

My newer Rubicon is very picky with tire size and rotations.

Here is a good article on the ESC, BLD and ELSD system.
https://blog.fcanorthamerica.com/200...rol-explained/

[Shiny]

Thanks all.

I called the local Jeep dealer. Service guy didn't want to deal with me, tossed me to parts guy. Parts guy tried, but could not find an allowable size difference.

My insurance agent didn't know any hard and fast rules.

Mike's comments about sensors and potential for failure of ABS and ESC suggests my son could make a safety argument.

End of the day, he did the right thing and bought 4 new tires. I told him he didn't lose 4 new tires. Given they are a wear item, the adjustor could reasonably argue a pro-rated loss.

I hope he continues to assert for a better settlement on principal, but seems tough to find a Chrysler/Jeep rule that he can point to...