Question:

Tyre wear and when to replace

by Guest3283  |  earlier

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We have 40k miles on Goodyear assurance triplet red, 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 are 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.
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 are not 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 cant (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.

With regards to mixing the old tires and new ones. Since it is front wheel drive (with traction control), wouldnt 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 wouldnt that mean they wouldnt want to move the left rear tire into the right front position? It sounds like Tread wear 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? Doesnt the good traction on the other tires compensate for it?

 Tags: replace, tyre, wear

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1 ANSWERS

  1. Tom Reeds

    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:

    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.

     

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