Tire hardness
 

I just bought a tire durameter. It measures hardness.

I read somewhere that Michelin pilot super sports start life with a Ha hardness of 72. For comparison, my chunking, heat cycled out set were about 80.

My old NT01 set that have just lost their thread pattern were 61.

A used set of Federal race tires I just purchased were a little disappointing 72.

But I have no experience with these test or numbers.

Anyone taking pressures, temps AND harness that can share some wisdom?

I found very little value in the measure, since you're just pressing a spring into a soft material there's so many variables I could get a 10 point swing based on how I pressed the durometer into the rubber (super quick vs super slow). You could also take some rock hard tires that have sat over the winter, go heat cycle/scrub them and they'd get five points softer.

It'd be invaluable if you had to pick out some unlabeled tires from a stock or you get to pick a cart at the local rental place, with enough careful notes and experiences with a certain compound you might be able to predict some characteristics, but I'm not sure the duro adds a lot more to the notes. idk been a long time since I played with one consistently.

Played with one in the past at a test and tune and a couple of sets of the same model tire (2 brand new sets and 1 used set of shaved 195/50/15 Toyo R1R's). I couldn't identify a relationship between durometer reading and grip numbers in our data and what showed up on the clock.

Thanks for both replies. Unfortunately,you seem to confirm what I've been worried about.

Since I can't carry more than one additional set of tires to the track, this year, I've driven on what were suppose to be dedicated rain tires on perfectly dry days.

I had hoped that hardness could be consistently measured so I could predict when tires become useless as rain tires BEFORE I needed them.

I have a durometer tester in the trailer and variety of R7s and A7s and set of federals. Let me do some measurings and see how different...

1 heat cycle r7 = 64
Sticker A7 = 62
7 cycle A7 = 58
10 cycle R7 = 64
Brand new E-Range trailer tire = 66
3k mile trailer tire = 70
2 session Fz201S = 66
20k Yokohama Geolander = 78


The FZ, even though it’s the “soft” compound just means is 40tw instead of 100tw and like the r7, you should expect the fz to get faster with heat.

I would be curious to test hardness with heat.

So you are one of the many people that think MPSS are good track tires?
Lol lol lol lol.
Then wonder why they get chunky. Nice.

Durometer doesn't have all that much effect on grip, just it's hardness. It seems obvious that soft tires are grippier, but that's much more dependent on the compound rather than the duro.

Do you post anything other shitting on a 10 year old tire that's out of production?

OP didn't even say they were good

It's my life's mission to trash talk those tires till I die.

And pointing out when people should have just bought a Civic.

I’ve found the measurements helpful when repeated on the same tire set over months+.
It pretty much just puts a number on what seemed obvious, but I use it anyway. My new RE71s started at ~65. They’re useless now after 150 autocross runs and now read ~85 with essentially no grip.
Snow tires tend to be 50s. Summer performance tires are mid 60s to 70 when new.

Just my $0.02 though.