So I know dick about cars. I'll get that out there right away. I have a 99 subaru forester I want to sell. However, driving the other night I hit some debris in the road and IZ'ed the sidewall of one tire. I had the road hazard insurance on all 4, but since it went through the sidewall, I had to buy a new tire at a discount. Here's the problem.
The guy at the tire shop was less than helpful overall, but it was a warranty service so I didn't just go elsewhere. He said that the new tire shouldn't pose a problem. The other three tires have run about 30k mi in 18 months. I'm thinking this doesn't sound right. I had hazard insurance on all 4 tires. Am I going to need to replace the other three, and if so, should that be covered on the hazard discount?
Advice/comments welcome.
The other tires weren't damaged...that's what road hazard is for. Just because the tires aren't matched mileage wise is not the tire/insurance companies problem.
You don't need to replace the others until they're worn out.
Quote from: ducpainter on February 14, 2011, 07:01:11 PM
The other tires weren't damaged...that's what road hazard is for. Just because the tires aren't matched mileage wise is not the tire/insurance companies problem.
You don't need to replace the others until they're worn out.
agreed
The sales pitch on the warranty was to cover the set as a set, so it was bothering me that the damage fix was to the isolated problem and not to the set. I guess the sales/service chasm had me worried. But now I'm less worried.
I've heard (and read) on AWD vehicles, mismatching tires can cause problems with the transmission/diff. I went with good tires, so they still have most of their life on them.
From now on I think I'm only going to buy road hazard on one of the four tires. ;D
Quote from: redxblack on February 14, 2011, 07:45:56 PM
From now on I think I'm only going to buy road hazard on one of the four tires. ;D
Tires have a serial # etched. They write that on the warranty.
got a nail gun ??
pop a few nails in the other tyres ;)
Quote from: redxblack on February 14, 2011, 07:45:56 PM
The sales pitch on the warranty was to cover the set as a set, so it was bothering me that the damage fix was to the isolated problem and not to the set. I guess the sales/service chasm had me worried. But now I'm less worried.
I've heard (and read) on AWD vehicles, mismatching tires can cause problems with the transmission/diff. I went with good tires, so they still have most of their life on them.
From now on I think I'm only going to buy road hazard on one of the four tires. ;D
You believed the salesman? :o :o :o
Read the fine print. edit...If in fact the warranty covers the complete set as a set go back and plead your case.
Damage to differentials and transmissions occurs when you run different size/brand tires that are much larger/smaller on the same axle. A slightly worn tire won't cause any issues
I have a Subi as well and have heard about the whole replacing all the tires at once otherwise your diff will explode, or something to that effect. If you are selling the car, I wouldn't worry about this even if it were true.
Quote from: ducpainter on February 15, 2011, 04:20:29 AM
Damage to differentials and transmissions occurs when you run different size/brand tires that are much larger/smaller on the same axle. A slightly worn tire won't cause any issues
Not just on the same axle...
Assuming you're running the same size ring and pinion in both axles, running different sized tires front and rear on a 4wd or awd would not have a good outcome.
That said, I'm in agreement that 30K miles worth of wear on 3 of the tires is nothing to worry about.
I have not looked into this on my Subaru to see what or how in terms of these aspects, but on some AWD cars, the problem lies in the sensors and reading wheel spin/revolutions for to adjust or redirect power to or from (depending on situation) a wheel that is spinning at a different revolution temporarily...continued speed differentials can lead to the transfer cases working at different rates than intended because the computers are telling the vehicle that is has a situation where it needs to correct and the drivetrain suffers a result due to this...this is often the case with AWD/4X4 cars with various formats of electronically aided/controlled traction control, whether it be active or supplimentary...
of course, maybe you should look in your owners manual to see what it says about tire replacement issues in terms of these kinds of things...
I started the same thread a year or two ago! [laugh] Tire guy said I should get 4 new ones when I got a flat with about 15K on my tires. That sounded like overkill, so I just bought 2 instead and put them on the front where they would wear faster. Everything has been fine. [thumbsup]
My truck is an Xterra, so not full time 4WD or AWD.
Quote from: zooom on February 15, 2011, 08:48:21 AM
I have not looked into this on my Subaru to see what or how in terms of these aspects, but on some AWD cars, the problem lies in the sensors and reading wheel spin/revolutions for to adjust or redirect power to or from (depending on situation) a wheel that is spinning at a different revolution temporarily...continued speed differentials can lead to the transfer cases working at different rates than intended because the computers are telling the vehicle that is has a situation where it needs to correct and the drivetrain suffers a result due to this...this is often the case with AWD/4X4 cars with various formats of electronically aided/controlled traction control, whether it be active or supplimentary...
of course, maybe you should look in your owners manual to see what it says about tire replacement issues in terms of these kinds of things...
fwiw, if an 1/8" had worn off the tread depth (pretty extreme scenario for 30K miles) it would cause a .75% difference in wheelspeed for the stock 26" tire height on a 99 Forester.
Quote from: Rameses on February 15, 2011, 09:40:13 AM
fwiw, if an 1/8" had worn off the tread depth (pretty extreme scenario for 30K miles) it would cause a .75% difference in wheelspeed for the stock 26" tire height on a 99 Forester.
okay, now figure at how much different a rate of speed it would spin/turn at and the rate of reading on an ABS sensor for those calculations and why , if it had some format of an electronic stabilization program that uses the ABS sensors as the primary informational point of reference, that would push power around due to those readings....
I say what I did because it doesn't take much to some of the engineers of these programs as far as tolerances/allowances in the algorythim they write for the various computers and modules for to have failures like what I suggest...it is a commonly known thing, like with Volvo's for example with their AWD drivetrain and is laid out explicitly in the owners manual for an owner to see so as to alleviate Volvo of having to pay out of warranty pocket for this occurance.
I went back and checked my math. It's actually a .97% difference.
Anyway, the faster you go, the greater the difference in rotational or linear speed.
So we'll use 85 mph.
At this speed, the larger (new) tire will be spinning at 85.8 mph.
When a 99 Forester is at full lock, it's turning a circle with a 17.7' radius.
With the track width of 57.1", this puts the wheelspeed differential at 53.7%.
If the inside tire is turning 10 mph, the outside tire's turning better than 15 mph.
Far greater difference than the .8 mph at 85.
Without the ABS kicking in.
The only thing that could make a difference is if the computer factors in vehicle speed in regards to how much of a wheelspeed differential to allow.
In order to get a wheelspeed differential of .97% with tires of the same diameter, one would have to drive in a circle roughly 996' in diameter. (I love when things happen to have Ducati-centric numbers in them. :P )
So the question is, how fast could one conceivably travel in a 996' circle without the ABS or AWD circuitry shitting itself? Because driving in a 996' circle is the same as driving with one tire that's worn 1/4" smaller than the other one on the same axle.
I am not a telemtry engineer, nor am I a technology designer, but what I can tell you is that even though the wheel is only spinning that much faster on the outer diameter(based on your calculations), those sensors are reading from the inner hub close to the center of the spinning axis which is now turning at a greater velocity measured in a much smaller increment...one at with the formula of calulation for the computer is now showing a variance like there is a problem it has to somehow compensate for....generally speaking, that outer diameter it is measuring from is maybe in the 2 to 3.5 inch range....
Quote from: zooom on February 15, 2011, 11:57:21 AM
I am not a telemtry engineer, nor am I a technology designer, but what I can tell you is that even though the wheel is only spinning that much faster on the outer diameter(based on your calculations), those sensors are reading from the inner hub close to the center of the spinning axis which is now turning at a greater velocity measured in a much smaller increment...one at with the formula of calulation for the computer is now showing a variance like there is a problem it has to somehow compensate for....generally speaking, that outer diameter it is measuring from is maybe in the 2 to 3.5 inch range....
The rotational difference is going to be the same, in percentage, whether you measure at the tires, hubs, axles where they enter the differential, or the two halves of the differential itself.
But, will the plane take off? ;D
Quote from: redxblack on February 14, 2011, 06:52:30 PM
....I hit some debris in the road and IZ'ed the sidewall of one tire.
[laugh]
Quote from: Speedbag on February 15, 2011, 02:33:49 PM
But, will the plane take off? ;D
I was actually contemplating slipping something about that into one of my posts.
[laugh] [laugh] [laugh]
okay...so...FWIW...I looked in MY owners manual on my 2005 Subaru Baja Turbo and the only thing it says is...
"All four Tires must be the same in terms of manufacturer,brand(tread pattern), construction, degree of wear, speed symbol, load index, and size. Mixing tires of different types, sizes, or degrees of wear can result in damage to the vehicles powertrain....."
now, it does not go on to say anything about parameters or define what is an acceptable difference in "degree of wear"...so take that for what it is worth, but it seems more like a legal sort of warning to cover their ass and give them an out if they chose to use it at some point in terms of getting out of a warranty claim, moreso than anything.
as a side note, refferring back to vehicles with more electronically based active traction oriented controls, as apposed to the passive style moreso used on most cars, I recall there being a tech bulletin when we 1st started seeing angle gear/transfer case failures in 99-02 Volvo XC's due to a tire being of a different size or "degree of wear" and corporate at that point, put out a definition of acceptable wear difference of degree, and I think it was something akin to no more than 3/32's of a difference between tires in wear differentiation.....
and yes...the damn plane will take off!...even after a 620 blew by it at 140mph!
It isn't just the magnitude of difference in wheel speed - it is the variation in wheel speed between all 4 corners - there is a "correct" speed for each wheel based on the speeds of the other 3... If 1 wheel is different than the other 3 by a certain %, it might cause problem, but it would be inpossible to know what the variation limit is.
mitt
Quote from: mitt on February 15, 2011, 05:26:02 PM
It isn't just the magnitude of difference in wheel speed - it is the variation in wheel speed between all 4 corners - there is a "correct" speed for each wheel based on the speeds of the other 3... If 1 wheel is different than the other 3 by a certain %, it might cause problem, but it would be inpossible to know what the variation limit is.
mitt
My guess is that less than 1 percent (in worst case scenario) isn't going to be enough to do it. But that's just a guess.
There's one surefire way to find out though...
redxblack, tell us what happens!! ;D
Quote from: zooom on February 15, 2011, 05:12:20 PM
and yes...the damn plane will take off!...even after a 620 blew by it at 140mph!
[laugh] [laugh] [laugh] [clap]
Quote from: Rameses on February 15, 2011, 07:49:17 PM
There's one surefire way to find out though...
redxblack, tell us what happens!! ;D
[laugh] [laugh] [laugh] [clap]
YOU GOT A DEAL!
I checked my manual and it said the same "degree of wear" line, which is why I was worried about a warranty covering the set. Regardless, the beast is going on CL for CHEAP because I want it gone. It's got 185k and leaks/burns oil. It's a teenager's car/transportation special having outlived its good years. I doubt a newer tire will make/break the sale.
Cheers for the responses! [beer] You lost me with the math. If you were talking history/literature/philosophy, I could hang. Math and cars and I'm floundering.