Laertes

Went out on Hoosier R6 for the first time on my .2RS (235/35-19 and 325/30-19) and had some behavior I hadn't expected, and would love some input from the masses.

Car is set up with full monoball suspension but stock springs/dampers. Can't remember what the sway bar settings are off the top of my head.

Went out at 30 psi, monitored to keep at 38psi hot.

Car is set up for Trofeos, so lots of camber (-3.2 front, -2.7 back).

As expected, the grip levels were mostly way better than the Trofeos; however, I had a terrible time with the stability control going crazy very late in the corner, past apex when I had just a little steering lock on but was at full throttle. Grip at turn in, at, and immediately after apex was great, and the issue didn't appear to be due to too abrupt throttle application (i.e. power oversteer) as it occurred quite a ways after the apex, and also only on higher speed corners and not on 2 gear hairpins and such. Entry and midcorner grip were great, but at the very end of the corner just before the wheel was completely straight (essentially at the exit cone) the stability control would kick in and pull throttle, completely killing the corner. I've never had any issue like this with the Trofeos, and since it was my first time with the Hoosiers I was actually being pretty conservative, so I'm pretty sure it wasn't an issue of me overdriving the tires as I was driving them pretty close to how I did the Trofeos (supported by data). Also, my lap times were about the same as on the Trofeos, which I know are a fast tire but I would have expected more.

Yes, I know the solution is to turn off the stability control. I do normally drive without it; however, any time I make a change to the system (e.g. new suspension settings or tires) I turn it back on just as a safety net in case the behavior of the car changes in an unexpected way. So I look at the PSM intervention as an indicator that I was losing late corner grip, something I'd never seen before on any other tire (either with stability control on or off) unless they were completely gone and I was messing around, and then the oversteer always came at apex when I went to the throttle, not past the apex at exit as was the case here.

Anybody else had this issue? Do I have too much camber and am thus up on the inside of the tires once lateral g's diminish at the end of the corner, causing a smaller contact patch and thus less traction? Is my rear bar too stiff? I don't think this is just because I was being a knucklehead and getting on the throttle too aggressively as I wasn't driving any different than I normally do on the Trofeos and I think the R6s should have better grip at exit than the Trofeos, not less.

Thoughts?

Spyerx

stock diff?

Laertes

Good question. No; Guard 40/60.

24Chromium

Gotta ask why are you driving with the DSC & TSC on when you've "graduated" to Hoosiers?

Laertes

Like I said in my original message, I only left the nannies on because I wanted to safely explore the limits of the new setup without risking a high speed off if something should be drastically different than what I was expecting. I'm not crazy or wealthy enough to make a major change and just charge in and hope nothing bad happens.

FWIW, I'm very comfortable running the car with all nannies off. My post wasn't to complain about the behavior of the stability control; it was to ask why I'm losing late corner grip. The stability control merely gave me definitive reproducible and unequivocal evidence that was occurring.

Laguna_Dude

Any issues with ABS during hard braking? generally that is from tire ratio too off from stock. that might be issue with stability control as well. I have never run with stability and traction control on.. so i don't know if i would have had the same issues. I would simply turn it off and slowly built up to speed with new setup, changes, etc. I believe stability control calculated steering angle vs. throttle, etc.. so maybe the system felt you had too much steering to be full throttle. Are you letting the car track out naturally or are you steering the car out of turns? It is also probably calibrated to stock, street tires and the high level of grip from R6's is throwing it off.

Laertes

Car is tracking out naturally, most steering done early in corner to allow earlier throttle application.

The car was also getting a little squirrelly under braking too, and I did get into the ABS occasionally whereas I nearly never have in the past. You're theory is interesting; maybe it wasn't that the car was losing traction; maybe it was that the stability control was freaking out and kicking in due to dissatisfaction with the tire diameters. I guess I'll just go out with the nannies off and see what happens.....

KaiB

FWIW, I see 38 psi hot and think this may be worth looking at.

My car is 2500# driven and I can't get away with anything over 34 - which is already greasy.

If your 38 psi hot was taken after a cool down lap and back in the pits, I would certainly think about dropping pressure (as you may have been running at 40). Again, FWIW, I run at 32psi hot - a true hot pit hot pressure, not back in the parking troughs.

The fact that you were a bit niddly under braking suggests this may be true...but remember that the R6 does indeed get a bit vague under braking at the limit of adhesion.

Izzone

I'm with Kai

On my antique..yes different car..first thing in morning I go out at 19 psi left and 20 psi right

Bring them up to temp very slow..or u May split tire

Aim for 29 -30 hot..gt3 was same hot pressure

Anything more and they are greasy

Once dialed in u should be able to drive without the nanny firing..but smooth

mmuller

I run 38 hot with Hoosiers on my 6GT3 Trackcar and find the grip is actually pretty good all the way through about 28 HC. From there they slowy degrade and I can get 32-35 HC out them before the slip becomes greater than 2-3seconds a lap at a place like Watkins Glen. It will still do flat 2:05's on 30 HC tires.

I had run them through a range of pressures when I first got them and found the best stick/longevity at 38 hot.

My take on the Stobility kicking in is grip level. The Hoosier provides a substantially higher grip level, beyond what the psychics of the oem ECU can handle. Once outside its parameters, it cuts in. It doesn't know more grip is better. This is also for example one of the contributors of ice mode in modern Porsche's, running cars with tires that have a higher grip level the the oem psychics model can deal with. Cayman's suffer this cronicly without any intervention of some kind. Turn them off completely and you will see there is no sudden loss of grip requiring intervention by the driver or computer. I have seen this and experienced it myself in my own 7GT3RS's

daedton

FWIW when I tracked my 11 RS on Hoosiers I never went about 30 hot. Always started at about 21F and 21R depending on temps outside. Loved them like that. Had great wear and stickiness. I think 38 hot is WAY too high.

11 Cup
11 RS
98 993 Cup
98 C2S
71 911T
77 911S

mmuller

This is from the Hoosier R6/A6 spec sheet -

TIRE PRESSuRE RECOmmENdATIONS FOR COmPETITION
Traditionally, Hoosier tires have often required higher pressures than other brands. This has changed with the A6/R6.
Roadrace/track applications
VEhICLE SIzE RECOmmENdEd hOT PRESSuRE COLd PRESSuRE
1800-2200 LBS. 30-33+. 22-27
2200-2600 LBS. 31-34+ 23-28
2600-3000 LBS. 33-37+. 23-28
OVER 3000 LBS. 34-39+. 23-29

+Higher pressures will improve the performance capability but will require a more sensitive feel to take advantage of the increase.


https://www.hoosiertire.com/pdfs/tctR6_A6.pdf

My experience with R6's would mirror these suggested specs

996FLT6

I'm at 36 hot with my 6. As I increased hoo hoo's felt better. Started at 28 hot which is what I run on kuhmo v710- r6 felt sloshy. Then 32 hot better but still sloshy then 36. Tried 42 but was sliding bit too much. I think 36-38 hot is a good zone for r6. Mike

tcsracing1

22psi cold all the way around for me.

flyingpenguin

Don't have definite answer as to what is causing this, but chiming in at least trying to help narrow it down.

From what I can find online, the tire diameters of the R6's and Pirelli Trofeos for the sizes indicated are very similar, or at least the ratio between front and back. That would exclude TC being thrown off by mismatched tires diameters.

Also, plotting a graph with lateral G-Force, going from turn-in to apex to track-out, you'd expect a spike somewhere around the apex, not at the very end towards track-out. Never seen TC kick in because of high lateral loads, so this makes the theory of R6's having grip levels beyond what the oem ECU can handle implausible, and even more so in the situation that you describe (at the end of track out).

It's obvious that something is throwing off the TC unit, so suggest to start looking at input sensors. Maybe a piece of track rubber got caught in one of the wheel speed (ABS) sensors?

Curious to hear what you find.