Chris C.

All:

Who is running the Sport Cups on their 993s on the track? With what suspension settings, tire pressures, and results?

Two weekends ago I left a PCA DE at Road Atlanta convinced that I had finally worn out my stock Boge shocks.

My car normally jacks weight from left front to right rear in hard right hand turns, exascerbated with elevation changes (turns 1, 9 and 12 at Road Atlanta). This is the same "wallowing" described by many on this Board with stock and m030 suspensions. Most times it is not reassuring but manageable (turn 12 is the Big B*** turn at Road A!).

Well, throw the Sport Cups into the equation (running at 32.5 to 35 psi hot), and the car is now heaving violently in those same situations, best described as feeling like completely undamped spring motion.

I am running stock suspension settings on the US m033 shocks at 42K miles.

A good friend and Rennlister has now had the very same experience in the same locations on Road A with new Sport Cups on his 95 993 with the OEM RS suspension and alignment.

Did we both get a bad batch of tires (purchased in the last 3 weeks from Tire Rack)? What are we missing in terms of setting up the car to use these tires? Tire Rack and Michelin imply that these tires are made to run with less neg camber than Hoosiers.

BTW, other than this odd behavior, the tires grip like stink!

TIA for any input or suggestions. I have a call in to Michelin tech support for help.

Viken

If I understand you correctly, you are convinced that your shocks are worn. At 42k miles, they ought to be. Mine gave me the same feelings at 20k miles on the track. As to the Pilot Sport Cups, I would have to guess their somewhat strange behavior is likely due to the lack of damping. It is quite possible that these tires are much more sensitive to lack of damping or alignment settings. I strongly suggest you get yourself at least a new set of shocks and a slightly more aggressive alignment if you want to continue driving on the track.

Chris C.

Viken:

[quote] I strongly suggest you get yourself at least a new set of shocks and a slightly more aggressive alignment if you want to continue driving on the track. <hr></blockquote>

I am doing so in the next 2 weeks, installing either H&R or PSS-9 coilovers.

I was convinced it was *only* my worn shocks before someone else experienced the same reaction on a car that has recently run better than 1:42s on Kumhos at Road A with the RS coilovers with none of this drama.

Changing to coilovers and a more aggressive alignment, it seems, will not cure this dynamic in itself.

I am looking for advice/data points here from 993ers with more experience with these tires.

I have talked with several guys running them on 944s with no problems, but I am sure the rear weight bias is at play here.

Viken

Chris,

As I had posted once before, a friend, who is an experienced driver, ran these tires on a 996 Carrera 4 with a slightly modified suspension. The car performed extremely well on the track and the tires were surprisingly good for the street. I guess what I am trying to say is that the rear weight bias may not be the issue.

SundayDriver

Chris,

First, it sounds like your shocks are bad, though I experienced the wollowing on my C2 with only 13k miles. I think it is an inherent unstable mode of the 993 and is exacerbated with worn shocks.

Second, your hot pressues are quite a bit lower than what I have run at the track, though I have never run the Pilots. Hopefully others can chime in with experience with those particular tires, but I can tell you what would happen with Hoosiers, P-Zero C's or Kuhmo's at those pressures. For all those tires, you would experience a 'mushy' turn-in at anything under 40 HOT. (I assume by hot you mean measured as soon as you come off the track.) That mushy feeling would likely also feel like a delayed settling of the car as the tires started to finally bite.

Finally, I don't know what camber you are running, but it anywhere close to stock, it is not enough for any of those tires to work - especially with the body roll from stock suspension (I assume, but do not know, that the camber gain in the stock suspension does not exceed the body roll). Hoosiers and P-Zero C's seem to like 4+ deg camber while the Kuhmos appeared to work very well at 2 deg. That was all with full coil over suspension and less roll than stock.

Chris C.

Guys:

Good points, all. I am wondering if there is a bad couple of tires here, since I've heard nothing but glowing reviews about these tires.

Viken: I know the tires were designed for PCA and Porsche, so I'd hope they were designed for the 911's rear wieght bias. I was only suggesting that experiences with these tires on 944s might may not be applicable.

I have experienced 4 different 993s wallowing in turn 12 at Road A. I wonder if your friend's 996 c4 just hasn't hit that particular combination of forces, or just shifts weight better than our 993s...my car is very stable at a lot of places on the track.

Mark: from all reports (including Michelin) these tires work best at 32-25 psi hot...defined by me as hot pit temps. I am going to get a pyrometer for track tuning.

I agree the shocks are one of the problems, and I will remove that variable first.

Still hoping for some input from others running these tires.

George Helser

Chris C.,

I am running Sport Cups, stock size (225/40 ZR18 & 265/35 ZR18 ) on stock 18” Factory Tech wheels.
It is a 1997 993 C2 coupe
- Stock M030 USA shocks & sway bars
- H&R Stage 2 springs (lowering 1.4” front & 1.3” rear)

ALIGNMENT
---------------------------------------------
FRONT L R
Camber -1 deg 35’ | -1 deg 32’
Toe +05’ | +05’
Castor +5 deg 33’ | +5 deg 50’

REAR
Camber -1 deg 51’ | -1 deg 51’
Toe +15’ | +14’
Castor +7 deg 20’ | +7 deg 20’
Set Kinematic toe to minimum

Based on recommendations here on the forum I tried lower than standard tire pressure the first time at the track (Firebird in Phoenix). Starting with 34/40 PSI cold, the tires were wearing a little too far down the sidewalls. I went back to the stock 36/44 PSI cold.

I am very happy with the Sport Cups with all the above as well as with the stock alignment. They are very stable and grip well.

Good luck!

Regards,
George
In sunny Arizona

P.S. With the above alignment settings the car steers more like a 911SC when on a road with depressed tracks and the car wants to steer L/R by itself if you don’t have your hands on the wheel.

Joe@Fabspeed

The Michelin SportCups need several hard heat cycles to "come-in". A good day or 2 and they get faster every time 'out'. You must scrub these tires alot and they get faster....if you expect to go out abd be "fast like you did on brandnew Hoosiers" you be "spooked"! Michelins get faster as you put more heatcycles on them...its counterintuitive trust me.

I dont know about your M030 wearing out but I would follow Vikens advice. M030 is so soft when its new and most likely probably shot @42,000 miles and you are probably driving your 993 real hard at Road Atlanta and your skills are stronger than a new M030 suspensioned 993 can handle especially at a rollercoaster track like Road Atlanta.

Get the Bilsteins and double spring it and youll never have a suspension problem and have lots of grins as you pass your buddies.

IMichelin advice:
start out at 26psi front cold and 25 psi cold rear and try to get to 34psi hot. Jump out of the car after several hotlaps and get your hotpressures and see where you are at and then adjust accordingly.

You dont need alot of camber in the sportcups. If you race then must get Sportcups HOT to get grip. Start swerving left and right on your way down pitlane and on the track to get heat in the tires. When they get hot they are great.

Sportcups last seemingly forever and are a great street & track tire. If you have unlimited $$$ and several sets of wheels and like sprint races only--- and you are prepared can change wheels with new Hoosiers several times a weekend.....I personally think the Hoosiers are faster.

However if you are Sprint racing or lapping with over 20minute duration the "Michelins dont go away like the Hoosiers" they just keep on sticking and get better and you will catch the Hoosier racers. In an Enduro, Trackmaster weekend, or at a weekend with Open track time (Run till you drop)..........you be much happier on the Michelins and if it rains you had better be on Michelin Sportcups or you'll wreck on Hoosiers.
Have a great day.
Joe Fab

Anir

Joe,

I'm currently running P-Zero C's, but plan to try the Michelin Cups next time around. Thank you for a very informative post.

Chris C.

Thanks Joe...I agree with your assessment of the Cups, but have no experience on Hoosiers against which to compare. My tires took 1.5 20 mins run sessions to begin to grip, but show no wear at all after 8 sessions. They run best at 3.5/32 according to Michelin (shipped at 6/32)

I'll let Hank post his wheel rate theory, since I don't understand it

but I think we learned this weekend that Michelin Cups are incredible R tires, but need even lower pressures when run on 993s with non-race suspensions (read: springs in the 200-600 lb arena) to avoid the dreaded pitching and wallowing.

You are close with your pressure suggestion...seems the tire really behaves (and matches the dampeners) at 26-28 psi HOT.

I will check with Michelin this week to be sure that this is acceptable given their construction, but the way they respond at 32 psi clearly is *not* acceptable, IMnsHO!

Hopefully Hank will provide more details later tonight.

Greg Fishman

Here is a post from the email list, that Bill Gregory posted.
I posted the same info I recieved directly from one of the Michelin engineers.


"Bill, the Pilot Sport Cup needs to run with HOT pressure in a range of
32 - 35 PSI - so cold would need to begin at approximately 7 PSI lower
(to allow for pressure increase). Your first run session should be to
determine your pressure build from cold to hot (with the hot range
again at the 32 - 35 PSI range). At the conclusion of the first run
session, adjust pressures as required to achieve the hot pressure and
begin to tune for handling adjusting one end at a time by 2 PSI (so you
can feel the affect of the changes in oversteer / understeer).

The traditional front-to-rear split of factory recommendations is out the
window for track applications and you may end-up with cold something
like RF 25, LF 26, RR 24, LR 25 and that's OK. Pyrometer reading
have a very wide range of acceptability for the Pilot Sport Cup at 160 -
220 F - and should be the last thing that you fine-tune.

A couple of things to remember, tire pressure is affected by ambient
temperature by 1 PSI for each 10 degrees of ambient change. The
wheel sizes for your tire sizes is a range of 7.0 - 8.5 for the front and
8.5 - 10.0 for the rear and wider is better."

Joe@Fabspeed

I would have posted more Michelin tire data I received from Michelin BUT it in my car's glove box at the shop. I am basically paraphrasing Michelin info from memory as best as I can.

Yes you want around 34degrees hot all around so yes as Bill Gregory and Greg Fishman mentioned you will have .5 - 1lb increments around the car.

But the real bonus that gets me pumped is that for street & track racers is that we now have a longlasting fast, steel belted DOT racetire thats as "fast as Hoosiers" (sic) but allows all of us to drive to work and race in the rain too.

Other facts: all you need is up to 2.5degrees maximum camber. Therefore, you dont need nor want wild 4 degrees negative camber like Hoosiers.

I have 2.25 degrees front and like 2 rear and the car has 20+ heatcycles and the about 300miles of street driving and some chassis dyno pulls. The last track time was like 4+ hours at Watkins Glen with the final 90minutes being an Enduro.

These tires are so good that I am seriuos and happy to report that I will run them again at Mosport in the sprint race and 1.5hour Enduro. If all goes well perhaps 1-2 sets of tires is all I may need per driving season-- and thats street & track!!!

Hank Cohn

Guys:

This is a long read - This is just my experience at Road Atlanta this weekend on Michelin Pilot Sport Cups (MPSC). I am not a tire or suspension expert by any means, but I feel that I do have a solid theoretical and practical understanding of some of the basic suspension concepts and I have raced several 911s with good results – all podium finishes with several class wins. On to the story….

Other than the rain Saturday morning, it was hot and sunny at Road Atlanta this weekend. The temperature read out in the truck said that it was 94 degrees when I left the track around 6:00 PM Sunday. I had been to Road Atlanta two weeks prior to this event with exactly the same car BUT with 17” stock cup wheels with 225 and 255 Kumho V700 Victoracers. As an aside, I think these are great tires for DEs and possibly even racing given their price, performance and durability.

I just bought a set of stock OEM 18” hollow spoke turbo twist 8” and 10” wheels for my narrow body ’95 993 for track wheels. I mounted 225 and 265 full depth MPSC tires from tire rack. I had driven with Chris C. two weeks prior and was stunned by how atrociously his car handled with the same tires. Given all the discussions on this board that addressed the worn stock shocks and struts, I assumed that Chris C. had bad shocks as the symptoms felt, to me, like completely undamped spring motion. Specifically, Chris C’s car was violently rocking from the left front to the right rear.

My car has OEM RS shocks, springs, monoball tops and adjustable (RS) sway bars (front and rear) set at RS ride height with RS alignment settings. Granted, my shocks are 7 years old but they have been sitting in my work shop unused for the past 4 years. I am not ruling out the possibility that they are bad, but we did test them by hand (not on a shock dyno) before installing them.

I started with hot pressures of 31 and 33 using nitrogen which equates to 25 and 27 cold starting pressures. My car performed exactly like Chris C’s had two weeks prior. After checking my suspension, I discovered that the rear sway bar had a lot of preload. I fixed that problem at the track and will scale the car later this week and recheck the sway bars and corner balance at that time.

I started reducing hot tire pressures and the problem started to lessen. After several warm up laps, I would run two laps, pit hot, check temperatures and reduce pressures even more. The temps were a pretty consistent 140 to 155 degrees on each tire. Ultimately I settled on 26 and 28 PSI hot. I didn’t want to reduce pressures further without talking with a Michelin engineer. The rocking motion was significantly reduced and lap times came down considerably. We started at 1:47s and ended up at 1:43s. In cooler weather, the same car on the aforementioned Kumhos turned 1:41s. I believe the hot weather can account for the two seconds, maybe more.

Once we fix whatever is wrong with the car or figure out the proper tire pressures, the tires will be great. Like others have said, the grip is incredible. We were given a 50 minute session on Saturday and a 40 minute session on Sunday in addition to the three regular 20 minute sessions both days. I put a total of three hours and 30 minutes of track time on the tires and they look like I just scrubbed them for an initial heat cycle. I feel that you could easily get three DE events out of the tires if not four or five or, perhaps, even more.

I realize there are a lot of loose variables associated with my experience, but there are two factors that must be considered. First, the car handled beautifully just two weeks before on the Kumhos and, second, my experience is exactly like Chris C’s with the identical wheel/tire combination. I will report my findings later this week regarding car setup and any anomalous suspension metrics. Hopefully, I or someone else will have had a chance to talk with a Michelin guy too.

Sorry for the long read, but hopefully someone will find something useful or interesting in this tome,

Hank