How to measure tread on tires
02-08-2006, 08:06 AM
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Re: How to measure tread on tires (civicsareslow)
There are two ways: in 32nds of an inch, and in percent of treadlife.
To measure in 32nds of an inch, check the depth between the tread blocks. I recently got a free card at a Discount Tire location that makes it REALLY easy to see. Otherwise, you'll have to find a ruler or something that allows you to take a measurement with an accuracy of 1/32 of an inch. (If someone tells you a tread depth in millimeters, you can multiply that by 1.26 to give you the number of 32nds of an inch.)
To measure percent of treadlife, here's how I do it: I look up the specs for the tire, either on the manufacturer's website or on the website of a dealer like the Tire Rack, to find the tread depth when new. This is not the same for all tires. Most street tires are around 10/32" (some are 9/32", some are 11/32"). Winter tires are more than that, track tires are less than that (even before shaving, which some dealers do upon request). I assume that the tires will be replaced when the treadwear indicator bars are flat across, which happens at 2/32". I then interpolate to pro-rate the wear between those two figures. For example, if a tire's tread is 10/32" deep when new, and it gets tossed at 2/32", then each 1/32" represents one eighth (12.5 percent) of its life; if the tread depth is at 8/32", then it has 75 percent tread life remaining.
To measure in 32nds of an inch, check the depth between the tread blocks. I recently got a free card at a Discount Tire location that makes it REALLY easy to see. Otherwise, you'll have to find a ruler or something that allows you to take a measurement with an accuracy of 1/32 of an inch. (If someone tells you a tread depth in millimeters, you can multiply that by 1.26 to give you the number of 32nds of an inch.)
To measure percent of treadlife, here's how I do it: I look up the specs for the tire, either on the manufacturer's website or on the website of a dealer like the Tire Rack, to find the tread depth when new. This is not the same for all tires. Most street tires are around 10/32" (some are 9/32", some are 11/32"). Winter tires are more than that, track tires are less than that (even before shaving, which some dealers do upon request). I assume that the tires will be replaced when the treadwear indicator bars are flat across, which happens at 2/32". I then interpolate to pro-rate the wear between those two figures. For example, if a tire's tread is 10/32" deep when new, and it gets tossed at 2/32", then each 1/32" represents one eighth (12.5 percent) of its life; if the tread depth is at 8/32", then it has 75 percent tread life remaining.
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