How many Miles + - does the grip last with New Tires?

I installed front and rear Pirelli Diablo Rosso II's yesterday,
had 10k on my rear Pirelli Angel and probably 4500mile on
the front Rosso II.

So...... a tad bit disturbing this am, disturbing
morphing into, 'nice'..... however the bike
DOES NOT turn well at all, which circles me back
to the operative; Disturbing.
I routinely do some quick shallow lane changes
when no one is on the road, and this am, given
very typical weather/conditions here, I
was taken back on how hard it was to change
directions at 50mph the bike felt like the
rotational inertia ( which makes some sense to me
given there is more rubber on these new tires)
was making the bike much harder to turn in in corners
and those lane changes I referred to, like the gyro
action is holding be back and almost as if there
is some braking action in play, though of course
I wasn't touching brakes.
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1. When does the excellent grip of tires like my
new set start to lose grip, is the compound markedly
different when we wear off 3/16'' of the new rubber,
1/8'' etc? More grip for that first layer of rubber
than underneath?
2. The grip feels really nice though and these tires
only have about 15 miles now, def not broken in,
on one hand I DON'T like the hard turn in action,
on the other hand, I'm really digging the nice grip,
but would like to get a 'grip' on roughly when
that grip will go away, as I realize its a very
gradual change and will be hard to gauge it, I'm thinking
that if I can get an idea of when that grip layer
is gone, when to expect it, I might just change
to a new set even though there is a ton or miles
left, and save them for burnouts etc.

I haven't ever noticed a change in grip but I have always changed tires before or shortly after seeing the outer compound was worn away. You will see a spot on the tire where the outer layer has worn away. There will be a roughened edge around this spot. It will happen on the center of the tread if you wear the tires most riding with the bike straight up and down (not cornering). This is the inner carcass of the tire showing and it is probably an eighth inch thick or maybe less. I tried to measure it with a makeshift calipers once and the carcass was alarmingly thin. Most of your sipes around the rest of the tire will probably be worn pretty shallow by the time a spot revealing the carcass shows up.

I don't think tire wear changes up to this point. The spot with the carcass showing through will probably have a lot less grip but it's usually on the center of the tread and usually a pretty small spot about an inch long. If you change tires when any spot measures the minimum tread depth, you probably will never see any places that have worn through to the carcass.

Age will affect tire grip. A tire that's a few years old probably is less grippy than a new one even if the old tire has little wear.

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You will see a spot on the tire where the outer layer has worn away. There will be a roughened edge around this spot. It will happen on the center of the tread if you wear the tires most riding with the bike straight up and down (not cornering). This is the inner carcass of the tire showing and it is probably an eighth inch thick or maybe less. I tried to measure it with a makeshift calipers once and the carcass was alarmingly thin.

Thanks,
I had a light colored flat-spot about an inch and a half wide
on the rear Angel that I put about 10k miles on, lots
of straight line riding with friends to those
promise-lands of twisties, and a lot of
quick start practicing here locally.
The flat spot was there for couple to a few weeks,
then last week I was alarmed to see steel belt
and ordered both front and rear Rosso II's.
I guess that is the carcass you're
referring to , the flat spot, not the steel belt,
which is probably beyond carcass I would guess.
So now I figure when that lighter colored flat spot
shows in the center and the wear bars are mostly gone,
time to re-tread up.
These are the low end Diablo Rosso's, and as I say,
I'm quite impressed with the grip, and hope it lasts
but there's that slow turn in feel, it might also be
the psi I'm running, I've got 30lbs in it, the
tire shop accidentally put in 50psi both tires,
which is really odd, cause he said he put 35 psi
in them and I said, yeah, that's great.
I'd been running 28 on the last rosso II front, and
28 on the rear Angel. The bike was pretty agile
and now , kind of disturbingly slow at turn in,
as mentioned, but in a couple of test sweeps, the
stability felt impressive, which I guess is my
top priority. Along the issue of slow turn-in
and feeling like brakes almost coming on just
changing lanes quickly, I'm wondering if I might be
better off with a bit more psi for awhile, it
wasn't hot this am, so that's not an issue,
I might mess around with that psi a bit
and see what I see.

I had a light colored flat-spot about an inch and a half wide
on the rear Angel that I put about 10k miles on, lots
of straight line riding with friends to those
promise-lands of twisties, and a lot of
quick start practicing here locally.

I've never seen the whitish inner carcass in real life. I have seen pics of the outer compound worn away and there are spots of wear that have a pattern of fine white lines in a diagonal pattern. I think that might be after the outer compound is worn away and then wear to the carcass reveals the cords (possibly some kind of fiber). I tell you, I've removed a few worn tires. I've placed a finger on the outside spot wear I see the carcass exposed and another finger inside the tire at the same spot. It feels as though my finger on each hand is extremely close. I didn't have a large enough calipers to reach around the tire from the inside to the outside so I made a calipers. LOL it was made out of wood taped together but I was careful. I marked the calipers position with a pencil before removing them from the tire. The measurement was about an eighth inch. Something is telling me it might have been even less. I never saw cords though.

I guess that is the carcass you're
referring to , the flat spot, not the steel belt,
which is probably beyond carcass I would guess.

Yes, I guess I might describe the carcass I've seen peeking through the outer compound as a flat spot. When I've seen it, its always been a pretty small spot but running a finger ver it, Im sure I'd feel a definite change from round to flat.

If you saw strands of steel, that's extreme. You were already riding on almost nothing and then wore the tire to half of nothing.

So now I figure when that lighter colored flat spot
shows in the center and the wear bars are mostly gone,
time to re-tread up.

LOL I would re-tread up before you see any spot. I'd rely on the wear bars of the tire or use a tread depth measuring tool to determine when a tire is used up.

I'm quite impressed with the grip, and hope it lasts
but there's that slow turn in feel, it might also be
the psi I'm running, I've got 30lbs in it

30 psi seems like it should be adequate for any tire. Maybe you have a softer compound closer to the edge of the tread and you feel it grabbing the road harder.

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30 psi seems like it should be adequate for any tire. Maybe you have a softer compound closer to the edge of the tread and you feel it grabbing the road harder.

I ran about 32 to 34 psi front and back this am, seemed
like it was a bit better.
I'll be paying more attention to the wear bars.

The only difference i have ever really felt with tire pressure is a "stretchy" feeling in low speed handling with low psi. I tip the bike in and the bike tips in more than it should...and it's not the bike, I can feel it's the tires stretching. The Pirellis I've used don't seem to do this even with extremely low psi. These Pirelli tires have been very aggressive street/sport tires or full on slicks though. On the street, I don't think I corner faster with low tire pressure but I feel a lot more comfortable pushing it than I would with normal tire pressure.

Higher than normal tire pressure, I feel the bumps more but no difference in cornering grip. I presume higher than normal tire pressure increases the life of the tire but have heard otherwise.

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The only difference i have ever really felt with tire pressure is a "stretchy" feeling in low speed handling with low psi.

'Stretchy'
Good descriptive, I think that's about how I felt,
a good and not so good feeling at one time.
When you say 'carcass of the tire' what exactly
would that be, is that pretty much anything left
of the tire after reaching the wear bars?
If I have this more or less right, when we've
hit the wear bars, we are into a different
compound of the tire?
So, if that's the case this is an important
issue imv, one that I've never heard anyone
cover, had I known this, if the case, I would
have had a much better understanding of what
kind of condition my rear tire (especially) was
in and what it meant in terms of practical performance.
One aspect of tires that has
had me confused up to this point is
that some people tell me that a slick is
always going to have a better grip,
but that has apparently nothing to do
with a tire that has become a slick from wear,
and everything to do with a racing slick, one designed
as a racing slick.

When you say 'carcass of the tire' what exactly
would that be,

The carcass is the layer below the compound. The compound has good gripping properties. The carcass is the foundation of the tire and I imagine it's a lot harder than the compound...and a lot thinner.

If I have this more or less right, when we've
hit the wear bars, we are into a different
compound of the tire?

No, not quite. The wear bars are there to tell you when you're almost through the compound. I'm sure you could go to the bottom of the sipes and you're still on compound. The problem with that is that tires never wear evenly. There's bound to be a spot or two that has worn more from hard braking or some other reason. You can be at the bottom of the sipes but one spot is worn past that right to the carcass. The carcass is a different kind of rubber than the compound but more importantly, it's very thin. It's susceptible to a puncture or a blowout.

One aspect of tires that has
had me confused up to this point is
that some people tell me that a slick is
always going to have a better grip,
but that has apparently nothing to do
with a tire that has become a slick from wear

If you can get a slick from wearing a DOT tire perfectly evenly and without exposing the carcass, I guess that's the same as a slick. As far as grip goes, I can't tell the difference between a slick and a DOT tire. I use slicks because they look cool. I suspect I'd need to have a lot more skill to appreciate the improved grip of having constant rubber against the road. For street riding, I'm sure sipes provide better grip for more conditions than slicks do. Sipes push dust and water out of the way so the tire maintains contact with the road. Slicks are for track conditions, of course. I had always done my best to ride on the street under conditions that were as close to track riding as possible. If I see the road is wet or dusty, I'm sure going to be extra careful on slicks. In any case, I don't try to push my bikes as hard as I can no matter what tires I have. I don't want to find out at what point I'll lose traction. ...maybe I would on a track beater but not my perfect street bikes.

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I have a better understanding now, good analysis,
thanks.