Thread: Tread depth
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#7: 01-18-2013, 07:02 AM
 Norm Peterson
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Originally Posted by computersoc View Post
After almost 21k miles, I have 7/32 to 7.5/32 on each tire. I think one is a little above 7/32, two are around 7.25/32 and the other is a little under 7.5/32, is that ok for wear since they're all different?
They're all within 0.02", which is about as good as you can expect unless you go out of your way to find tire pressures and alignment specs that work best for you in your specific driving.

Measure at least three positions across the tread (inside, mid, outside) and see how close to even they are.

Is being around 7/32 normal or good after appx. 21k miles? My driving is mostly highway.
Exactly what tires do you have? Not only do various tires have vastly different treadwear ratings, there is also at least 2/32 variation in the tread depth that they start out with. IOW, I can't tell if you've worn only 2 or 3/32nds off them (about 35% worn from a 10/32 tire) or if it's been closer to 5/32 that's already gone (50% worn from 12/32). Estimates based on keeping them down to 2/32".

50% worn @ 21000 miles sounds about right for 350 - 400 treadwear tires.

How many 32nds can I run them down to until they need to be replaced? I think law in my state is 2/32, but I'm not sure what traction, handling, or feel will be like at that. My guess is that is too low?
For upstate NY, I'd have put on a set of dedicated winter tires and not be concerned yet.

For "3-season" purposes, if you've got some reasonably current wet autocross experience under your belt you probably can go all the way to the wear bars (2/32). If not, start your tire-shopping once you drop below 5/32 so you'll be able to make your tire decision at leisure instead of in haste under time pressure.


Last edited by Norm Peterson; 01-18-2013 at 07:10 AM..