Tire Tread Depth
 

I bought a tire tread depth gauge today to keep track of how bad autocrossing is tearing up my tires and I have a question...

Front and rear tires are measuring at 5/32. Tires were new when I bought the car, and I have put about 12k miles on it since then ( including 3 autocrosses ).

I believe that new most tires are at 10/32 so wear seems pretty good considering the mileage.

Can I wait until 2/32 to replace the tires ( I don't drive the car in the rain or snow ) or will I need to replace them sooner ?

Thanks,

Nick

Ok, first of all, you got 12K out of a set of REARS? Amazing!!

As to tread depth, you will notice a loss of wet weather traction as the tire wears, but if you dont drive it in the wet you can go all the way to the wear bars (and some would argue beyond).

Patrick

nick, bring that thing on sunday, i bet i have like 1/32 LOL

on my old car i drove untill i heard the threads swinging around in the tire well..bad idea.
tire blew few days later....

your tires looked really good last time i saw them, i was actually looking at them (dont tell ur car i was checking out your tires ;) )

Hi,

One thing to bear in mind is that on many Tires, wear is not linear. I have found this to be especially true of Dunlops, Pirellis, and BF Goodrich.

You may have used only 5/32s for 12k mi., but the Tires may be all in by 13 or 14k mi.

I had a set of Dunlops on my Esprit a few years ago (GREAT Tires btw), anyway, they showed only 3/32s wear in 10k mi., but were at the wear bars by 12k mi.

I don't know what the Tread Gauge cost you, but here's a way to gauge tread depth that costs you nothing:

• Take a Penny and insert it into several tread grooves in the tire (Lincoln facing you and going into the tread head first). If any part of Lincoln's head is not exposed by the tread, you have more than 2/32" of tread depth remaining.
  
  Now, take the same Penny, reverse it, and insert it into several tread grooves in the tire. If the top of the Lincoln Memorial is always covered by the tread, you have at least 6/32" of tread depth remaining.
  
  Finally, take a Quarter, and place it, Washington facing you, head first, into several tread grooves in the tire. If any part of Washington's head is not exposed, you have more than 4/32" of tread depth remaining.

Now, you can also use the same methods and with a fine line Sharpie, mark the coins prior to an event and set them aside. After the event, using the same coins, test the tread depth again and place another mark on the coin. Check the distance between marks to determine your Tire usage for the event. Hope this helps...

Happy Motoring!... Jim'99

Jim,
thx for that.
i knew about the 1st method, linclons head... didnt know about the other 2.
sweet

I've got 16.7K+ miles on my original Contis and they are just approaching wear bars now (rear tread varies from being at "E Pluribus" and "Unum" on the back side of a penny, still plenty to go). This is after 1 autocross and 5 DE days where they were not babied. I drive with vigor on regular roads as well. Would probably go with another set of SportContacts if they are still available... I'm very pleased with how these have lasted - only the outer edges show any real residual wear from the track events despite the "black curds" developed on the inner treads during the event.

Great info...thanks!!!

Anywhere near 3/32nds in to 2/32nds in should be replaced because not only is it worn down but the rubber compound is going bad at that point.

FYI: remember to always measure it at the lowest point on your tread contact patch where the most wear is at.

New tires for the Porsche are 8MM.

That actually depends on tire manufacturers. Some tires vary from 8mm-9.50-10 mm (9/32 - 10/32nd of an inch) of tire depth. Major OE supplier to Porsches would be Michelin and Bridgestones and they range from the Michelin Pilots to the Bridgestone RE960 or RE040, each brand and model having varying tire tread depths when new.

Anyway, when tire depth goes lower (sometimes bridgestons have the Uni-t and dual layer technologies to curb breakdown of the effectiveness of the rubber) the rubber compound is exposed to heat and other elements which causes a reduction of tire 'stickiness' or effectivness of grip which results in the factory and repair shop standard of replacing tires when reaching 3/32nds of an inch.

8MM on Continental and Michelin OEM tires on the Box. At least that is what they were a few years ago.