QuestionQUESTION: We have 40k miles on goodyear assurance tripletred, for a toyota sienna minivan. They come with an 80k mileage warranty. One of the reasons we picked these tires was for the good snow rating on tirerack.com, since we live in New England, but they seem to have lost some their snow performance since we originally purchased them.
Our tire shop recently measured the tread depth at the outer, center, and inner edges of each tire and found the following (in order,):
front left: 5/32, 5/32, 5/32
front right: 5/32, 4/32, 3/32
rear left: 6/32, 6/32, 6/32
rear right: 5/32, 5/32, 4/32
We're trying to understand what level of wear tells us it is time to replace the tires. Also, if only one edge of one tire is worn down to that level, does it mean it is time to replace all of them? Does being in a snowy area affect the answer?
FYI, the tire shop says goodyear will only apply their warranty when a tire is down to 2/32, which I would think was unsafe...
Thanks,
Jim
ANSWER: Jim,
Let's deal with the mileage warranty issue first.
Mileage warranties aren't a promise that the tire will get the mileage specified - in your case, 80,000 miles. That would be a guarantee. A warranty is merely a promise that if you fail to get the mileage specified that you will be compensated per the provisions of the warranty - and that is usually in the form of a reduced cost for the next set of identical tires - same size and pattern - and if not available, something comparable from the same manufacturer (or however the warranty states it).
Be aware that there are provisions in the warranty that must be met. Usually these are that the tires must be rotated regularly and that the wear must be even across the face of the tread - which is not the case here. The reason tires don't wear evenly across the face of the tread is almost 100% because of alignment problems.
Take a look at the RF tread depths. There is a 2/32nds of an inch difference from the outside to the inside. This means that the RF position has a camber and/or caster issue - assuming that tire has been in that position a long time.
I should point out that the RR position also shows the same wear pattern, but to a lesser degree. This would indicate to me the rotation pattern used was front to back and not an "X" pattern that is usually specified by the vehicle manufacturer. The rotation pattern itself is not of importance relative to the warranty. I am merely pointing this out for diagnostic reasons.
There is usually a provision in the warranty that states that the tires have to reach 2/32nds of an inch - the legal minimum - for the mileage warranty to be in effect. However, it is common for tire shops to honor a mileage warranty if you get close - say 3 or 4 /32nds tread depth remaining.
Please note that for the purposes of mileage warranty, the entire set is taken as a group.
Put together, the tires would not be covered by the mileage warranty - both because of the uneven wear and the tire really aren't close even for the tire shop to "make a case" with Goodyear.
Now let's tackle the issue of snow traction.
As tires wear, their ability to generate traction in adverse conditions degrades. This is not only true for snow - and snow related conditions - but also for wet conditions. There is a lot of hard data available which backs this up.
Remember, the traction of a tire was not guaranteed, nor was it warranted - and in particular the loss of traction is something that is the result of the laws of Physics and well beyond the control of the manufacturer.
Unfortunately, there isn't a "point" at which this degradation can be stated to become "unsafe". The traction vs tread depth curve is smooth and continuous, but it is true that traction degrades faster as you approach 2/32nds of an inch tread depth.
Clearly, you are feeling the loss of traction due to the wear - but this is to be expected. Also clearly, the RF tire - where the wear is down to 3/32nds - is adversely affecting this.
Also clearly, you feel you have to do something about this. Please note that there is a legal position that says that if you are aware of a situation you have do what you can to "mitigate the damage". This means that now that you are aware of the situation, you can not claim negligence on the part of either the tire shop or Goodyear if something bad happens.
Taken as a whole - regardless of the "safety" issue - you have a dilemma: The tires aren't warrantable and there is a traction issue.
I suggest you appeal to the tire shop. They have the ability to make their own rules - which the manufacturer can't (The manufacturer has to treat everyone the same or they have "fair trade" issues with the government)
Since you appear to have an alignment problem, suggest that you are willing to pay for an alignment and 50% of the cost of 2 tires. Use the left side tires on the front and put the new tires on the rear. Hopefully the tire shop will see this as a reasonable compromise.
(BTW, common negotiation tactics say to start at a point lower than you are willing to accept, so I would start by offering to pay for the alignment with the tires being free and let the tire shop offer 50%.)
---------- FOLLOW-UP ----------
QUESTION: Barry,
Thanks for your detailed reply and suggestions. I get the feeling that my comment about warranties may have offended you, and that was certainly not my intention. I have no interest in pursuing legal action. I just want to replace my tires at the right time, without making a huge dent in my wallet. I also wouldn't ask anyone to violate the laws of physics, although I'd be impressed if they had that ability...
With regards to rotation, the tire shop (a local chain of approx 5 stores) says that they only "rotate" tires front to back. It was unclear as to whether that is what they do for ALL tires, or just for the goodyear assurance tripletred.
With regards to mixing the old tires and new ones:
-since it's front wheel drive (with traction control), wouldn't we want the new ones on the front?
-Is it ok to mix old and new tires? How bad would it be to have one tire at 5/32. another tire at 6/32, and then two new ones?
-what is the logic that leads them to only rotate front to back, and wouldn't that mean they wouldn't want to move the left rear tire into the right front position?
It sounds like treadwear vs traction is a non-linear curve, with the loss of traction worsening at a more rapid rate as you approach the lower tread depths. However, is there a rule of thumb (threshold or range) as to when to replace, especially in snow country?
Also, how many bad edges (e.g., inner/outer/middle) do you need on how many tires in order to have a significant loss in traction? Doesn't the good traction on the other tires compensate for it?
Since this followup was so wordy, I promise not to ask any more questions...
Regards,
Jim
AnswerJim,
I spent a good deal of my first response to you dealing with warranty because this area is not well understood by the average consumer and I wanted to clear up some misconceptions.
Many tire shops still fall back on the old "Front - to - Back" rotation pattern that was used in the early days of radial tires. There's nothing really wrong with that, it's just that a "Modified X" is a better pattern - allowing all the tires to see all positions.
It is a common misconception that the best tires should go on the front. You want the best tire to go on the rear so that you will not spin out - which is basically not recoverable. Here's a link that shows this:
http://www.youtube.com/watch?v=P7_wPfcomQU
Tread wear vs traction (wet and snow) is not linear and gets worse faster as the tire wears.
Rule of thumb? Well, there isn't a good consensus within the tire industry, but for all season and high performance tires, 4/32nds seems to becoming an accepted limit. Winter tires has gotten the same attention, but many feel that 5/32nds is a good number.
The traction on a car is only as good as the worst tire. The coefficient of sliding friction is much lower than rolling friction. One odd tire will tend to make the vehicle pivot around that odd tire - regardless of whether the tire is good or bad.
I hope this answers your question, but don't be afraid to ask more.
