allroadbryan

How do you measure tread depth on tires? Is there a special device?...

happy allroader

Tread depth is a vertical measurement between the top of the tread rubber to the bottom of the tire's deepest grooves. In the United States, tread depth is measured in 32nds of an inch. Because it is difficult to accurately measure tread depth with a ruler, tread depth is best measured with a tire tread depth gauge. When tires have neared the end of their life, a U.S. Lincoln penny can also be used to confirm the tire's tread depth. If Lincoln's entire head is visible, the tire is worn to approximately 2/32" and is considered legally worn out in most States.

Average new tires used on cars typically start with 10/32" to 11/32" of original tread depth. Dedicated winter tires and light truck tires typically are deeper (for light truck tires, how much deeper depends on the tire's tread type...Highway Rib, Highway All Season, Off Road All Terrain or Off Road Maximum Traction).

As mentioned above, tires are legally "worn out" In most States when they reach 2/32" of remaining tread depth. For example, a typical tire that starts with 10/32" of original tread depth has only 8/32" of useable tread depth. Its useable tread depth is calculated by subtracting a worn out tire's 2/32" from the new tire's original depth of 10/32". The final 2/32" of a tire's tread depth isn't part of the equation when it comes to calculating tread depth percentages because the tire is already legally worn out with just 2/32" of remaining tread depth.

Useable tread depth is calculated by subtracting 2/32" from the tires new tread depth. Then usable tread depth is compared to remaining tread depth in order to calculate tread wear percentages. For example, a tire that started with 10/32" of original tread depth and has worn off 4/32" (down to 6/32" of remaining tread depth) is 50% worn

10/32" original tread depth
-2/32" legally worn out tread depth
8/32" of useable tread depth.

8/32" useable tread depth
-4/32" measured tread depth worn away
4/32" of remaining tread depth (50% of 8/32")

A tire that starts with 10/32" of original tread depth has 12.5% wear for every 1/32" that is worn away, and a tire that starts with 12/32" " of original tread depth, has 10% wear for every 1/32" that is worn away, etc.<ul><li><a href="http://www.tirerack.com/a.jsp?a=AR4&url=%2Ftires-techpage-1%2F148.shtml">Tirerack's article on special tool to measure tire tread depth</a></li></ul>

2002ar

...to be able to safely dispel water and not easily hydroplane in rain. 4/32" for snow tires, too. A U.S. penny is supposed to be 2/32" to the top of Lincoln's head.

Boston Driver

it looks like...

<img src="http://img.alibaba.com/photo/50398029/Tread_Depth_Gauge.jpg">

The metal stick (to the left) goes into the tread channel, and the white hexagonal post (to the right) pops up, and has hash marks for every 32nd of an inch.

<img src="http://www.consumerreports.org/cro/resources/images/cars/tires/dangers-of-worn-tires-204/overview/0301tir005.jpg">

SeeksAR

Hey BD! You trolling allroad forum? Wishing for a little extra cargo space this week?

Boston Driver

...not really "trolling" per se...

Besides, I have always been "Jonesing" for an allroad, but every time I point to an allorad (for my wife) she says that she likes her Honda Pilot. Just the other day, I spotted a Q7 and probed, and she actually said, "Oh, you could buy me one of THOSE!" That was the first time she did not reply with her usual "I-love-my-Pilot-thank-you-very-much" response. We'll see...

girlroad

see the mod god over here Was that sacreligious? Most likely, sorry

Boston Driver

...so her comment about the Q7 was a big suprise for me, as in the past, she shrugged off interest in any of the four-ringer lineup.

That is okay with me. What she WANTS, she will GET, as long as I can write the check.

girlroad

There's a good man...I have one like that too