Is This Glass-Point Tire Damage?

I just had the original all-seasons swapped back onto the Mini's stock wheels after running RE71Rs for a couple of summers.

I'm looking at the odd "cracked" thing going on with some of the tread blocks, and wondering whether this is actual, serious damage from rolling on them on chilly mornings/evenings. I was DDing them all autocross season, though I only made a half dozen events over the two summers.

To be clear, they were swapped out for winter tires seasonally.

This is giving me pause as I ponder tires for the MGB... I won't be driving it often in conditions where 200TW tires would feel sketchy, but if I have to actually let the car sit 'til it's over 40, that's rather more limiting...

I was really hoping the fun car could make do with one set of tires for autocross, track days, and street use.

Bump for another chance for my awkwardly-titled question. Probably sounds like I'm wondering whether I drove over broken bottles...

https://www.tirerack.com/tires/tiretech/techpage.jsp?techid=30

Don't know the answer, but interested in the conclusion as autox season has started here and it goes below freezing here at night.

How cold have they gotten? 

FWIW, I haven't seen that on 200tw I've let freeze but those are all near bald tires used for storage that don't see much driving.

For what it is worth, I had my car sitting on Star specs for something like six years, plenty of sub-freezing nights in the driveway though I had snow tires on the car in the winter. I never had anything that looks like that although the tires were not regularly used for any Motorsports, just a few Auto crosses over the years

In reply to Run_Away :

They've gotten down into the thirties, I'm pretty sure, but not by much; I probably mounted them in April and took them off in October, and our overnight lows don't usually get too far below 40 in that range, IIRC. I did jump in the car and drive (just in-town commuting) on plenty of those 40-ish degree mornings, and I guess it's entirely possible that some were down in the 30s.

I just went back and looked at October of last year and April of this year (no data for April last year) as the coldest months I'd have had the tires on, and 40 is about as low as it got.

In reply to ebonyandivory :

I don't think that's what this looks like. It's isolated to the tread blocks; the sidewalls look dandy, and they're nowhere near old enough to be showing that sort of age-checking you see on old tires. They don't have the look of being dried out at all.

I bought these tires two years ago, and have a DOT date code indicating they were molded in late 2016 (the 43rd week).

In reply to irish44j :

This is similar use; I DDed them with a few autocrosses April-October 2017/18. They were stored in the house over the winter.

I hate to potentially threadjack myself, but I can't find the recent article where GRM compared an R-comp, and 200 TW tire, and some Very High Performance summer tire one notch less aggressive than that... Anybody recall a more specific title, have a link, etc?

IIRC the 200TW tire landed much closer to the R-comp than the more general use tire, which bums me out with regard to dialing my tire selection one notch less aggressive and hoping to be able to autocross effectively on that tire.

All the more reason to be curious whether the funny reaction of my Bridgestones really is a sign that I can't get away with just 200 TWs all the time.