What kind of tire damage is this?

Found these cracks appearing on the outer shoulder of the tires, couldn't find anything in tire damage pictorial guides that matches. It goes about 1/5th way around the tire. Should I be worried?

Tread separation due to wear, due to poor alignment or excessive cornering loads?????

Nothing to worry about until 30 seconds befor the tread Flys off..

All speculation on my part. I am sure if tou ask a shop they will say replace. 

Might drive on it cautiously myself, but you not want anyone else in the car.

You have worn through the outer belt of rubber that has all the stamped tread design and are starting to see the carcass underneath.  

What is the car used for? What car and what alignment settings?

Toyobaru, dual-use weekend & track car, front camber changed from 0 to ~-2.6deg and lowered 1.4" (which brings the rear camber to maybe -2deg) but otherwise stock alignment.

Was hoping to get 1 track night, 1 autocross, and 1 drive to Florida on these before putting on some new Conti ECFs I ordered...I do have spare Firehawk 500s I could mount up but the track night is directly after work today...

Plenty of life left - not seeing the threads yet. 

(This is my last job where the branch manager got paid extra on controlling expenses so he tightened up and spent the least possible he had too.  F450 POS box truck that I notified 2 people we needed to replace - crickets)

GameboyRMH said:

Toyobaru, dual-use weekend & track car, front camber changed from 0 to ~-2.6deg and lowered 1.4" (which brings the rear camber to maybe -2deg) but otherwise stock alignment.

What pyrometer readings have you gotten? Were they read immediately upon exiting the track?

I do have one set of pyrometer readings taken immediately after coming off track, unfortunately in a clipboard I just packed away into the car...but tire temps (measured with a probe-type) were around 110F and pretty even across the tread, slightly higher than some readings I've got after autocross runs. These tires did chunk a bit on the last track day though.

I had a tire that looked like that from rubbing. It was cut by the inner fender lip. 

Totally possible, I was running this tire on the front when I found out the hard way that I had too much compression travel for this wheel size. It's on the rear now and bump stop spacers are installed on the front.

GameboyRMH said:

I do have one set of pyrometer readings taken immediately after coming off track, unfortunately in a clipboard I just packed away into the car...but tire temps (measured with a probe-type) were around 110F and pretty even across the tread, slightly higher than some readings I've got after autocross runs. These tires did chunk a bit on the last track day though.

measured with a probe-type - good

around 110F - as I recall from my street tire days that seems pretty cool like they had cooled off some.

pretty even across the tread - normally that would be good BUT given the picture it may be from cooling off.

These tires did chunk a bit on the last track day though. - not a good sign plus the wear

Was hoping to get 1 track night, 1 autocross, and 1 drive to Florida - if it were me the autoX but not the other 2. High speed tire failures are not as fun as they might sound. Maybe put the rears up front?

I can't tell if I think that's actual damage or not, but either way it looks like it's time to flip the tires if you hope to get much more life out of them.

I would say those are roasty-toasty and done. Looks to me like cracking due to heat. If the tires chunked on the last outing that to me is the final clue. There are a finite number of heat cycles in any given tire. I think you've probably gotten what you can out of these.

In your position, I wouldn't put myself on the track with those tires. In some places I'm not sure they'd pass tech. 

Racebrick said:

I had a tire that looked like that from rubbing. It was cut by the inner fender lip. 

Same. 

These are PS4Ses which are asymmetrical but non-directional, so they can't be flipped inside-to-outside. Right now this tire is on the rear. I will watch this tire like a hawk and see how it goes, track night entry is at the gate so if there are any signs of worsening and I can back out and mount up the Indy 500s...

In reply to Racebrick :

yep, looks like it was scored radially. probably tire hit body on a big compression. also explains why it is only part of the circumference.

GameboyRMH said:

These are PS4Ses which are asymmetrical but non-directional, so they can't be flipped inside-to-outside. Right now this tire is on the rear. I will watch this tire like a hawk and see how it goes, track night entry is at the gate so if there are any signs of worsening and I can back out and mount up the Indy 500s...

Didn't pay enough attention and thought they were A052s from the photos. Seems like there's some compound differences across the tire so flipping might actually be a bad idea. In that case I'd probably just rotate it to the back and run it as is until it dies, while keeping an eye on that seam.

Didn't have any trouble with the tire, the crack/cut became harder to find after each session, I might've worn it down or melted it shut