Replacing SUV tire(s)

There are a few vehicles that a difference in size of any of the tires will confuse the ABS system resulting in a bad situation when braking. Yours may or may not be one of them but, it may be that the Sears shop has chosen not to go there on any of them whether or not the vehicle is one that can be compromised with unmatched tires.

Lugnut

"lugnut" wrote

That's the standard "cover your ass" policy. Everyone knows that whoever touched the car last is responsible for anything that happens to it.

The transfer case could blow up next week, and who gets blamed, the customer who drove on the undersized spare for who knows how long ("It was working fine when I brought it to the shop"), or the Sears store that put on a slightly larger (new) tire?

On Mon, 02 Oct 2006 10:40:33 GMT, "MasterBlaster" touched the car last is responsible for anything that happens to it.

Unfortunately, too many people think the small donut spare is for use until they have the next flat at which time they will take care of it. Meanwhile who knows whether or not they know how to use their powertrain properly under what conditions. You are correct. It is a CYA policy and I don't know that I can blame them with today's litigation climate. I think the proper way to handle this would be to have the info written on a work order releasing the vendor from any liability for damage to the drivetrain if it comes in with a mismatched tire if that is their problem. That will not preclude thier ability to sue the vendor if it can be shown that the failure and resulting damages were a result of failure to complete the work with reasonable care using standard industry practices. Let the customer decide from there. The fact is that you can have tire diameters mismatched as much as you would get between tread depths just because of inflation differences and, probably, over half the vehicles on the road at any given time have improperly inflated tires to one degree or another.

Lugnut

If your vehicle came with a 'silly spare', then you can normally put slightly different tires on it and get away with it or at least change two on the same axle and be safe.

If it came with a full sized spare, then you need to ask the manufacturer or read the owners manual to see if you have a locked or limited slip diff or a all time 4x4 that can be wrecked with a mis match.

The don't 'normally' put donuts or 'silly spares' on vehicle that can be destroyed that way.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail >

driving with a 44" tall tire and a 30" tall tire IS hard on the diff. but, driving with a 30" and a 30.1" tall tire isn't exactly tearing up anything... measure your new tires, I bet the circumference isn't the same.

If anything tho, you want the tires on an axle to be roughly the same for grip - think of stopping in the snow with one bald tire and one snow tire.

I would have had them change one pair of tires so they were the same and then kept the old tire as a spare.

No need to get 4 tires.

And yes, this was a CYA policy by them.

I've had non-stock sized tires mounted on my truck by mentioning upfront that I knew they were nonstock and they wrote that on the work order and then mounted them without any grief.

Ray

Don't most (or all) modern AWD or all-time-4WD vehicles have the 'third diff' between the front diff and rear diff, thus resulting in:

1) Every wheel can turn at its own whimsical speed with no drivetrain damage or funky handling. 2) A relative compromise to the "All Wheel Drive" concept under certain conditions (but still better in say, snow/slush/heavy rain compared to 2WD if you don't do something stupid)

3) There is no 3.

4) Didn't Jeep 'pioneer' this sort of thing many many many many years ago?

-phaeton

What was your vehicle? What size was your doughnut tire? If driving around with different size tires was likely to damage the 4WD system, then the vehicle manufacturer would have included a spare with the same OD.

There is an interesting thing about radial tires that comes in to play. The OD of the tire has only a secondary affect on the rolling radius (the dimension that affect the number of revolutions per mile). The tread sections act more like a tank tread than the outside diameter of a solid wheel. The actual rolling radius is mostly dependent on the radius of the steel belt instead of the outside diameter of the tread. For instance, a Michelin CrossTerrain P235R16 Tire has an outside diameter of 29". If this was a hard wheel with a 29" diameter, it would take 695.4 revolutions of the wheel to go one mile. According to the Michelin specs, the actual number of revolutions per mile is 720 (at 45 mph - speed is a factor because it changes the tire diameter slightly). 720 revolutions per mile gives you an effective diameter of 28". This is close to the diameter of the steel belt inside the rubber. This diameter of the steel belt is not effected by wearing the tread down. There is some slight change in rolling diameter as the tread is worn away, but not to the extent the outside diameter change would indicate. In the case of the Michelin P235R16 tires, the tread depth, was 10/32. Even if the effective rolling diameter was decreased from 29" to

28.4" (new to bald), the theoretical number of revolutions per mile would have only changed from 695.4 to 710.1. Any system that can't handle 15 revolutions in a mile is already defective. Going around corners is a more significant difference than that. And in actual fact the difference in effective rolling diameter between the new tire and the old tire (assuming the same brand, size, and type) was probably more like 5 revolutions per mile and probably less.

I think it was justifiable to replace two tires (the bad one and the other one on the same axle). Replacing four was totally unnecessary. And didn't warning bells go off when this tire store forced you to buy four tires since

18 months earlier you had already just replaced two of the four?

Ed

I like to by tires at Sam's Club (decent price, decent workers mounting the tires, no attempt to sell me shocks, brakes, a new air freshener, etc.). Unfortunately they have adopted a very strict policy on replacement tires. They will only sell you tires that are the same size, type, and rating as tires that the vehicle manufacturer offered on the vehicle. This was a pain in the rear when I needed new tires for my Saturn Vue. They had nothing in the OEM size at all. When I suggested that a slightly larger tire was just fine, they said, nope, it is not in the book. They wouldn't even let me sign a statement saying I understood there were not liable because of the non-standard size. My Vue didn't even have ABS, so any arguments about the tire size screwing up the ABS did not apply. You can circumvent this by taking in the rims (without the car), but that is a pain as well and eliminates the free rotation and balancing you normally get.

Ed

Some places STILL won't do that though. You tell them "yes I know what I'm doing, yes I understand the 'risks', and yes I understand that you don't want to be liable. Write it on the work order, I'll sign it, and you will be 100% free and clear if I go out and kill a school bus full of kids"....

But they just won't do it. I dunno. Maybe it's because in this 'litigatious climate' the lawyers have found ways around that. I know that in some states you legally cannot put rotors and drums back on the car if they're under spec (too thin, that is). That's got to be a hard sell to the customer sometimes..."yes we turned them. But now they're too thin and I can't put them back on."

But the fact is, all the bitching and moaning by the customer and all the signed documents won't save you- you get a hefty fine whether they crash and die or whether they come back in at the end of the week and have you do it right.

-phaeton

Most SUV and many light duty trucks (F150, Tundra, etc) come form the factory with P series tires (often with extra load P series tires). There is nothing wrong with using P series tires on trucks and SUVs as long as 1) you de-rate the load rating by 10%, and 2) understand that the tires cannot standup to off-road hazards as well as LT tires. In may cases the P Series tires are a better choice for SUVs than LT tires because the sidewall are not as heavy and do not build up as much heat at high speed as LT tires. For a given load rating, an LT tire requires a significantly higher pressure to prevent flexing and heat build up. The higher pressure and the stiffer sidewall can make for a very stiff ride with no improvement in safety. Now if you are going to spend a lot of time on gravel roads, or off roading, the heavier carcass of an LT tire can be a real advantage. However, if you go to a tire store with a strict policy of replacing tires only with the OEM size and type, they cannot sell you LT tires for many SUVs. And if they do sell you an LT tire for vehicle that came with P Series tires, they need to tell you to adjust your inflation pressures upwards by 3 or more psi to prevent heat build-up. How many tire monkies know to do that? Many of them either over inflate the tires by blindly assuming the max pressure listed on the tire's sidewall is the correct pressure, or they apply the P series pressure on the vehicle's decal to the LT tires - also a bad idea.

Ed

Yes, Jeep called it a quadratrac I believe. They now have a slectrac that acts similar.

That is what I was implying with the use of a silly spare.

If you have a 'part time' 4x4 with a locking center diff or if you have limited slip or a locker in the axle diffs, or some ABS systems you need to match the tires, otherwise....

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06 (More Off Road album links at bottom of the view page)

also, the width of the rim affects the shape of the mounted tire as well. I have a pair 235/60R-15 BFG mounted on a 7" wheel and on an 8" wheel for my race car. You can see the difference - the tire on the 8" wheel is shorter and wider even though unmounted they're the same.

Hmm... that just gave me an idea for stagger for next year...

I've ran into that as well, which is why I was surprised that it was Canadian Tire that did it for me without all the extras. And they've done it twice in two years - once for my Jimmy, once for my pickup. Although, I wish they would have pulled the drums on my pickup... it wasn't until months later I discovered the nasty oil seal leakage... I might have even let them fix it. Oh well, normally people complain about mechanics being pushy...

Ray (fwiw, stock tires for the Jimmy 205/75-15 -> replacement tires I chose were 235/75-15 which were stock size for the later ones. The pickup went from a 245/75-16 to a 265/75-16 which was also a stock size, just the largest stock size.)

I know. Which is why I own a pickup truck for delivering wheels and tires to be mounted for my race car with a minimum of fuss by the tire store.

And it's also why I patronize certain places and don't go back to places that don't work for me.

That said, I understand why some places won't install non-stock tires, especially undersized tires, because people are cheap. I've seen quite a few pickups with 3000 pounds of bricks in the back and what looks like

10 year old 205/75-15's with 10 psi in them squirming down the highway.

Ok, I went back to day and spent an hour there "speaking" with the on-duty assistant manager as well as the auto center manager. Originally the assistant said it was my fault, that I could have, at the time, just declined everything and chose not to have anything done. Well as I was there to get a flat fixed that was not my intention, although I suppose I could have.

What I really liked was when he said that if I bring the car back with the 4 new tires (wife has the car now) then he would gladly replace all

4 tires with my 4 old tires and refund my money. He still had my 4 old tires as they had not been picked up for recycling yet. Actually he'd put the donut back on where the flat was. He was actually serious when he said that but I said that it was an unacceptable solution and was quite surprised Sears would do such a thing.

They then said that it was Sears policy for all 4WD cars to not mount new tires if you don't purchase all 4 of them new from Sears. When I asked to see this in writing they flipped through there 'Ops and RMDS" binder and could not find anything. I pointed out that there is nothing prominently displayed in the area that a customer could see that this was supposedly their policy. After a few minutes they said they remember seeing something to the effect about the 'policy' on their intranet. Again I said, I as a customer have no access to Sears intranet and it wouldn't matter anyway - it should be displayed on a wall somewhere so that a customer can see/read it and not just take it at face value from a Sears technician. They were unable to produce this mystery document from their intranet. The Auto Center Manager did agree that it should be clearly available for a customer to see and read (I'm surprised he even agreed about this).

In any event, I called my local Mercedes repair center and asked them about the 4WD issue and what they do/recommend when only 1 tire is bad. He said that they recommend replacing tires in pairs on the same axle. Which is what I offered to Sears yesterday and they declined to do that.

The Auto Center Manager took me aside and said that if I show him the owners manual or he can chat with the MB technician about replacing tires in pairs (and not all 4) then he really owes me some money. At this point it sounds like he would refund the two tires (and associated balancing and disposal fees) and still let me keep the tires.

Walter

ray wrote:

Sears has gone into Damage Control Mode.

IOW, you still haven't a dollar to buy a cup of coffee with, do you? No...I didn't think so.

What you want is 2 new tires on the axle that had the original defective tire, and your *original* tires back on the other axle.

And, a refund of the difference in price between the 4 tires they shoved down your throat, and the 2 you should have gotten to begin with.

Lg

Yes, that is what I want - or even to keep the new tires and still get the refund, as the service manager implied :)

By the way, the new tires have a tread depth, according to the sales receipt, of 11. What does 11 translate to in inches?

Thanks, Walter

Lawrence Glickman wrote:

Watch what they do, not what they say. Believe it when you see it. Maybe he is trying to buy his way out of trouble. Maybe he knows he screwed the pooch, and is going to give you a deal to keep his head off the corporate chopping block. Anyhow, don't spend your money until you have it in your hands.

I dunno. Not a tire man myself. somebody here knows though, you can bet your life on it.

Lg

Wow. If he's serious, I'd probably take him up on it right until he was ready to hand over the cash and then I'd thank him for doing the right thing and just sell my old tires in the buy & sell.

Ray