OK, so even Consumer Reports recommends checking tire wear with a quarter. As you all know, if the tread doesn’t at least touch the top of George Washington’s head, the tire needs to be replaced.
The problem is that different quarter designs have different distances to the top of George’s head. A plain old 1982 Liberty quarter has less distance to the top of Mr. Washington’s head than the new state quarters. I’m even wondering if the tire industry lobby didn’t grease some pols in DC to get the distance increased so they could sell more tires.
Trust the wear bars that are in the tire’s treads to signal when the tire is worn out. It’s not an exact science anyway, I mean, it’s not like the tire suddenly transforms from perfectly safe to use to too hazardus to drive on at that precise wear point.
The state vehicle inspection stations don’t use quarters to check your tire tread depth anyway, they use a gauge meant for measuring tire tread depth.
The rule I learned is to use a penny, the distance from the edge to the top of Lincoln’s head is 2/32 the legal limit in my state. Actually I wouldn’t want to head into winter or on a road trip on less than 4/32 .
My vote is with CapriRacer. I had to buy a tire depth gauge many years ago when I became a state vehicle inspector because the state required that the depth in 32nds on all 4 tires be checked and noted on the inspection certificate.
In OK the minimum was 2/32 and in my opinion I think that tires should probably be replaced before they really get that thin, especially if the car sees a lot of high speed driving and out of town use.
You should also keep in mind that if tires are aged and tread depth is very shallow that dry rot could also be a problem. That’s yet another reason to replace them. (Even if the tread depth is more than adequate.)
However I run winter tires which lets me run well worn all-season tires in the spring and sometimes right to fall. I feel like I get an extra 5k-15k out of tires that most people throw out.
IMHO thread depth gauges are the most accurate way to monitor depth…however if your tires are so worn down that you have to monitor them with a thread gauge, you should be shopping for new tires. I know tires are getting expensive (I just bought some), however they’re one of the most critical safety items on your car, and it’s worth throwing away a few bucks worth of “unused” tread to ensure that when the heavy rains hit you won’t get it a wreck. A wreck is far more expensive than a set of even the best tires.
When your tires get to a level where the wear bars become obvious, start shopping. Your life and the lives of your loved ones are at stake.
Think of the cost this way: if you get 60,000 miles out of your $600 set of tires and you replace them while they still have 2,000 left before the wear bars, you’ve thrown away 1/30th of your tread. That’s 1/30th of $600…$20 thrown away, to ensure that you have good traction when the roads get bad. To me that’s really cheap insurance against an accident.
If those 60,000 mile $600 set of tires started with 10/32 of tread and you replace them at 4/32 instead of the legal 2/32 you’ve thrown away 1/4th of your tread: $75.
Still a reasonable insurance against inclement weather IMHO.
This is about worst case. Some tires have more than 10/32 and 3/32 would still be 50% better than the legal limit.
Actually this is the best time of the year to buy new tires. I don’t like to buy new tires in the summer or especially at the beginning of summer. The extra tread depth of new tires means more heat build up. I’d rather have the new thread in the late fall or early winter where I’m likely to need it the most and when the tires will be cooler as they get broken in.
While I don’t have a problem with wearing set of tires all the way to the legal limit, or a little beyond, if I feel I can’t make it to next fall, then I’m getting the new tires now. If I can, then I 'll get them next fall.