It’s not clear to me reading material about tread wear depth how tread wear pattern may affect tire replacement.
It generally states to replace when the wear indicators are exposed (flush with tread) or when less than 2/32" with the penny test. But is that applicable for when any one of the tread grooves meet that criteria or when all the grooves meet that criteria?
Say for example I have some car alignment problem etc. and one side of tires are nearly worn but the other 2/3 (middle and other side) of tire is still good. That seems a bit wasteful if have to replace under that circumstance.
Also, if the set of tires were bought new and reached this (one sided) wear state before the full/max tire life rating (mileage/year), would the prorated discount generally apply or not (because they’ll just say your car has problems that wore out the tires)?
Short answer is yes the tire needs to be replaced. The long answer is fix the alignment problem and you won’t have to worry about this. And no the tire will not get prorated because of the alignment problem.
“But is that applicable for when any one of the tread grooves meet that criteria or when all the grooves meet that criteria?”
That criterion is met when any part of the tread is flush with the wear indicators.
You need to replace your tires.
"Also, if the set of tires were bought new and reached this (one sided) wear state before the full/max tire life rating (mileage/year), would the prorated discount generally apply or not (because they’ll just say your car has problems that wore out the tires)? "
Failure to do needed wheel alignment falls within the category of owner negligence, and no warranty (be it on tires, or an appliance, or even the car itself) will cover repairs that result from owner negligence. If you read the details of the treadwear warranty, I can guarantee that it includes some verbiage regarding wheel alignment being necessary in order to keep that warranty in effect.
Uneven wear happens for a reason. Usually it simply needs an alignment. sometimes there’s a chassis problem. Either way, the tires need to be replaced and the cause of the uneven wear diagnosed and corrected.
By the way, 2/32" (the wear bars) are a LEGAL limit. At that level tires are becoming unable to clear heavy rain on the roads. Personally, I don’t consider 2/32" to be safe in wet regions, such as Washington State or Oregon. I change mine when the wear bars become obvious, rather than waiting until the tread reaches them. It’s cheap insurance against sliding off an exit ramp. Note that this is just one man’s opinion. The amount of money you save by letting them go all the way to the wear bars is minuscule.
+1 to mountainbike’s comment.
Tires that are significantly worn are not somehow perfectly safe up until the wear indicators are obvious, and then suddenly unsafe once those bars appear. It’s not an “all or nothing” situation, but is actually a matter of losing traction gradually over the life of the tire’s tread.
Tires progressively lose wet traction as the tread wears, until the point where they reach the minimum legal tread depth and they have to be replaced. The prudent driver who wants to be able to maintain control of his car on wet roads, and who wants to be able to stop quickly in an emergency situation won’t wait until his tires reach the minimum legal tread depth.
The only thing I will add to the already great comments is that quite often by the time a tire is worn down to the bars dry rot may also be setting in.
Dry rot can lead to a blowout just as easily as other factors.
The roads for the most part in OK suck and have poor drainage; usually due to repeated heavy farm and oil field equipment traffic. I can’t stand skating around on thin tires that won’t displace much water.
texases is correct as usual. Fix the alignment issue and then replace the tires.
While it may depend upon the vendor, as a rule of thumb tire warranties should not apply to problems caused by worn suspension/steering parts and/or alignment.
If it’s the outside edges of the tires that are worn this would mean excessive positive camber or too much toe-in. Or both.
If the inner edges are worn that means excessive negative camber or too much toe-out. Or both.
