Guys-

Got a call this morning from my mechanic stating my pretty new front tires are chunking at the outside edge (Michelin Pilot Sport 4S). He is suggesting adjustable roll bars.
Question: Should I get them now, or wait to consult with my NASA instructor next month at NCM, to see if my driving style is to blame?

Background: Last summer at around my 6th HPDE I decided to get new tires. When I went to Mid-Ohio I noticed the front outside edges were getting roasted, especially the left. Back home my mechanic suggested a sport alignment, basically some negative camber. I do think that helped, as the events I went to later that year it seemed the car was pushing less. What I don't know is whether the current tire condition is due to only the wear BEFORE the negative camber was added, OR ALSO after the negative camber was added. In other words, I'm not sure whether the problem was fixed by the new alignment, or if my driving style is still to blame. With imperfect information, and not a lot of racetrack experience, its hard for me to make a wise choice. I know I don't want to throw new equipment at a problem if the real issue is a driving technique problem.

Not sure what to do, so I ask the community of pros. Here are a couple photos I took last year on my phone. I think both come from the front tires, but the one that is not zoomed in may be the front right. i also noticed some "feathering" at the back end of the blocks (towards the rear of the vehicle when looking at them from this view - that I am guessing comes from hard braking.

All comments welcome!

Jeff

 

What are your new camber settings?

Assuming the new settings are somewhat reasonable, I would personally mark the sidewalls at your next event. After a session (or less) I would check on tire rollover and start increasing pressures a bit (to get you through the event) to get the tire off the outside edge before it cords.

If the tire rollover is with the current settings, consider a more aggressive alignment to prevent new tires from getting ruined as well as tweaking your driving style to better prevent understeer on turn-in. Watch your steering wheel inputs and if adding a touch of steering does not immediately change your direction than you are sliding and rolling the tire over most likely. Try to trail brake a touch or brake a bit deeper into the braking zones to slow the car down a bit more so you can reach the apex consistently with less understeer. IANADC so take with a grain of salt....

 

The 4S tires have soft sidewalls and if you're going to track you can get better tires which will allow you to air down more w/o rolling the edge.
It also looks like you need some GT3 LCA's to get more negative camber and a good track alignment. Sway bars are nice but do the LCA's first.
You are currently just putting too much load on the outer edge of the tire. More nagative camber will dial that in.

 

Im going to lean towards driving style and not enough negative camber, until you get a "proper" amount of camber up front you're going to burn through front tires. Im not sure what the max camber on stock suspension parts is but a set of quality camber plates like these Elephant Racing ones will get your fronts in to the -2 range. Their design allows for more adjustment than other plates out there.
https://www.elephantracing.com/porsc...lates-for-991/

As a reference but not a apples to apples comparison, a couple years ago I ran the Continental Extreme Contact Sport (copy of the 4S with same tread pattern and wear rating) for 24 days while I was in the Blue(intermediate solo) run group, half those days were at Lime Rock which eats front left tires. Difference was I had camber plates on my 2600 lb '98 Boxster set to -2.6 in front -2.2 rear with stock sway bars at the time but with PSS9 shocks and springs. I never went out cold below 27 lbs front and usually bled down to 32 after first session. At day 12 I swapped the tires left to right and that's it. Results below are of front left outer edge when I retired them..

 

Frankly, those tires don't look chunked to me. Sure there is outer wear, but my definition of chunking includes chunks of tread missing, hence the name "chunking" - I've seen a lot worse than this.

As Oldmiss540 was alluding too, be careful not to overdrive the front tires. It may be that as you pick up speed and confidence that you are pushing the front end more than you may think.

My gut feeling is ask your instructor about it. In the end, I suspect the "fix" will be both suspension and nut behind the wheel mods - but you always want to check the nut behind the wheel first.

-Mike

 

Consider getting a pyrometer as well. When you get new tires take temps across the tire. Do this in the pit lane before they cool down too much. Ideally you want even temp readings across the tire. If the outer edge is hotter then you'll know right away without waiting to see if the tire wears unevenly.

 

As above, those tires aren't chunked at all--mine look like that all the time (stock suspension w/ fwd) and then eventually they get flipped on the rim for further use.

Don't know your front camber but if you have anything approaching -2 your tires shouldn't look like that. Again, as above, you're a newish driver and I suggest you get some (i.e. lots of) seat time with good coaching so you don't keep frying the outer edges like that--gets 'spensive You're letting the front end of the car do all the work in the turns resulting in what you now have. I would also try simple stuff like adjusting your pressures first before you start replacing parts.

Gary

 

Alignment is negative 2 degrees front and back.

 

THANK YOU for all of the excellent feedback! My plan is to replace the two front tires now, and talk to my NASA instructor next month at NCM for his or her advice on my driving and this issue.

Jeff

 

Agree with Gbuff here. I don't see the "chunking", unless I don't know what chunking means.

That being said, tire pressures, temps, and smoothness come to mind when I see tires like that.

Spend the money on instruction and ask for help in the paddock re: tire pressures and temps.

You could be rolling over on the tire shoulders from either starting pressures too low or, on the opposite end, getting them to hot by starting with pressures too high. My guess is "too low" and not turning in smoothly before they're up to temp.

Camber could indeed be playing a role as well, but at your level of driving, I am leaning towards getting smoother and setting the pressures better at the beginning of each session.

I too made rookie mistakes when I first started tracking, and the tires did indeed get very expensive.

Once I got smoother, and learned how to set pressures correctly depending on the day, the weather, and the track, things got a lot better.

You got some really good advice above in this thread. Take it to heart.

Good luck and be safe...

 

PS4S don’t like roll over and need more pressure I usually start at 32 psi and shoot for 38 psi hot. They don’t hold up to track use as well as the older MPSS, which about as good as the PS4S in the dry, but the PS4S is a better wet tire.

Peter

 

I also found that the new PS4S tended to have more edge wear than the MPSS on my 09 Boxster at Summit Point, WV. As a good a tire as the PS4S is, its still a street tire you can drive on the track. I pretty much wore off the outer 1/4, could barely see thread line, but never corded. I put on Elephant adjustable LCAs with -2 camber and swapped the tires from left to right. Bob's Radial in Silver Springs, MD said they flipped a set of PS4S and ran the "rain grove" side as the outer with no adverse handling or tire wear. That's a pretty extreme solution for edge wear

Bought a 2013 BS to replace the 09 and have put on 18" wheels and Hankook RS4s to replace the OEM 20s and PZeros. Putting on the elephant adjustable LCAs next week and will put -2,5 camber in the front. That's about as much negative camber I think I can do and still drive to and from the track. I might go -3.0 later in the year if I still see too much left edge wear. IMO negative camber, tire pressure and driving style effect the outer edge, but on a clockwise track the left front will wear. I plan on flipping the RS4s half way through the DE year.

 

Adjustable roll bars have nothing to do with anything I have seen here. Neither does driving style. Those suggestions do not make any sense to me at all.

And instructors are not always the best advisors for things like this.

I suggest joining the PCA and hanging out with folks that know what they are talking about. If you are in CHI, then you are not far away from Kelly Moss in Madison. If you cannot find a wise group of experienced advisors easily in the CHI area, I suggest contacting KMR for a recommendation. They likely know some of the best resources for your kind of Porsche around your area.

What I see in this thread suggests you are dealing with folks that may not have the best type of experience to help you. Or worse, far from it.

For what it is worth, I have been at this for 30 years and have been in Norcal since 1991. I grew up in MKE. On a business trip back there in 1994 Jeff and David Stone at KMR allowed me to visit with them for 4 hours on a Saturday. On a Saturday! Gracious!

They were running 965's in IMSA at the time along with a potent 968 in Firehawk. David is no longer with us, but I am pretty sure that Jeff is.

I suggest that you find your way to folks with the proper experience. Not many hang out here.

As an example, I see Elephant Racing Products mentioned here. I have known them for years. They are not racers. Far from it. No real connection with the fat part of curve of the Porsche performance driving and/or racing scene here locally. They do make some great and important products. I am happy to share illustrative stories... one of my young friends just left there after about a year. He may have sold parts to some of you folks.

Ira at Tarrett is more informed, and he gets help and advice from Cary Eisenlohr and others. Cary is... well famous. Experienced, accomplished and expert.

 

The only way to solve the problem is with adjustable lower control arms, The front will max out at 1.0-1.5 negative camber in stock form you need to get it to 2.0 to 2.5

 

I added OE GT3 LCA's to my C2S, I got them from Tarett, and my mechanic dialed them in at -2. That and swapping to a better dual purpose tire with firmer sidewalls helped.
Pilot4S is a fantastic street tire for spirited roads but on track you can overdrive them pretty quickly. When you get to that point, look into the Hankook RS4. I've been running them on my gt3 as a do it all tire and have been very impressed.