What is your tread depth before changing tires (mm)?

I have about 9,000 miles on my summer tires- Michelin Pilot "sport" PS2. (We've been using winter tires for 5 mo / year.) The dealer service department told me that I should be changing the tires soon, but I can probably stretch it out another season.

My husband told me we should be able to drive to ~4mm. Replacement tire websites suggest 30% wear from new.

I've seen a bunch of posts on changing after different mileages (6-25K miles) and years (6 mo -4 years), but nobody is really commenting on tread-depth, which seems like it should be the primary factor.

Last night, we did the coin test and confirmed that the rear tires are wearing down a little faster than the fronts. We have 5-6mm left. I also learned that the rears started with less tread than the fronts when new ( 6.35mm vs 7.15mm)

Yesterday I drove a twisty road with lots of standing water...and the traction still seems really good. Full control. No slip at all. (Was super fun, too. Big grins)

Historical data points on tread-depth are appreciated.

 

depending on how good your alignment is and how much negative camber you are running the inside edge of the rear tires will cord long before the tread is gone so it is imperative to observe closely the inside edges...I just took off a set of rear PS-2 tires on my street wheels and the tread was still good but the inside edge was completey corded...I'm sure my alignment is more agressive than yours but your wear pattern will be similar

 

Hi Chuck -

What does it mean to "cord"? Is this akin to a frayed rope or a de-lamination?

Thanks in advance.

 

It means you can see the silver metal belts (or cords).

You will know it when you see it.

 

they say a pic is worth more than a bunch of words...you can see there is a lot of tread left but the cord is visible along the inside edge (bottom of top tire)

 

that is a pretty aggressive alignment Chuck. Your tires look almost new on the outside edge. I find the shoulders of the PS2's are pretty quick to wear.

 

I do have a track alignment and I do drive aggresively....these ps2's also have seen some track duty due to my mpsc's giving up the ghost mid weekend...the outside edge you can see is on a front...the outside of the rears is not as good

 

MPSC! Time to improve your tires for the track!

 

Yep, just replaced my PS2's and there was just a tiny hint of cord on the inside edge. Still pretty healthy on the outsides but not as radical as yours. That tells me I got my $ worth out of those tires.

Kinda like when the check to the undertaker bounces.

 

You can buy an inexpensive tire tread gauge at an auto parts store that will quantitatively measure your tread, which will give you a better idea of your wear rate than a penny. Mine measures in 32nds of an inch. Here's an excerpt from www.consumerreports.org:

Tires are considered bald when one or more of their grooves reaches 2/32 of an inch deep, compared with about 10/32 of an inch for new tires (tread wear is usually measured in 1/32-inch increments). Manufacturers have made bald tires easier to spot by placing a series of molded horizontal bars at the base of the grooves. The bars become flush with surrounding tread when wear reduces a groove's depth to 2/32 of an inch. That's also the point where tires will flunk a state safety inspection—and where tread must be worn for you to collect on a tire's tread-wear warranty.
Unfortunately, 2/32 of an inch may be too late if you drive in rain or snow. Based on our tests of new and half-tread-depth tires, you may want to consider shopping for new ones on your car or truck closer to the 4/32-inch groove depth.

 

Great thread.

Legally work is when the wear bars on a tire are worn down as to be level with the tread. This happens at 2/32nds of an inch. At 4/32nds they will be pretty sketchy.

Chuck's right. It's very difficult to see inside tire wear on these cars. You have to get them on a lift, or basically lay down and go under them to see it. If you get your tires to the point they cord, you have gone wayyyy too long on them. 12-15k is normal life - no matter you put on them.

If you have any questions on tires, please do some reading at our tech section, or call me! Thanks.

 

Damon,

I thought the wear bars are the little steel belts in the tires

 

once i hit 3/32 or about 3mm, i will look at replacement.

you will start to hydroplane at that point, especially on the rear in a decline ramp.

 

When you get down to the belts, consider them "maypops"...

They may pop, they may not.

Oh and watch you hands- handle those suckers with gloves because those belts will rip your hands to shreds if they have been compromised, and they probably will once they start showing themselves substantially.

 

If you can confirm you have 5-6mm left with a gauge and no excessive wear (pics above are excellent)....then you can stretch the life out until the end of the Fall. Get your snow tires mounted a little earlier than normal, then get brand new Summer tires mounted in the Spring.

Just be careful driving through puddles as your tires wear down. These tires are so wide, that the water really needs those treaded grooves to maintain traction.