jakermc

Last week I completed heat cycles #14-17 at Homestead Motor Speedway and I continue to like this tire more and more. Specifically, now that the tread has worn down, they are more consistent and the peaky-ness is now very minor. In fact, they are incredibly consistent over the course of the day and the throughout a particular run, Why? With a shallower tread depth there is less tread movement (or squirm, as I usually refer to it) and it's the tread squirm that causes heat and pressure to rise in the tire, As heat and pressure rise past a certain point, performance degrades. So now the tire is able to stay in the sweet spot longer without falling off.

Some data to back this up The last run of the day, heat cycle 17, logged a fast lap of 1:38.4 and an average lap of 1:38.6 across 10 laps. So it's running within 0.1 of its time when new but with greater consistency and with a lower average lap time. (these are runs at about 85% of capability, appropriate for a HPDE environment when you want to be certain you can drive your car home LOL). The fast lap for 3 of the 4 sessions run that day still happened in Lap 2, so the peak still exists, but the fall off is now inconsequential.

The implications of this is that I believe this tire would benefit from shaving if you want to achieve the best laps times and sacrifice longevity. With regards to the latter, I am now at the wear bars and believe I can squeak out 3-4 more cycles in the dry, at which point I think I will see cords. I would not run this tire in the wet in their current state. So expect about 5 days of use in a normal HPDE type environment.

4 Point 0

I’ve been a huge advocate of CR-S since they came out.

Nankang learnt a lot from the AR-1. I think they should have called the CR-S the AR-2. Its a more refined and improved AR-1. AR-1 is horrendously noisy and they are undersized, but they take a beating and are cheap as chips.

Now I’ve had CR-S, I’d never run AR-1 again ever.

Tread depth. I’m with you there.
Cup2 vs Cup2-R. The three things that make Cup2-R far superior are

1. Much Stiffer sidewall
2. Much narrower rain grooves
3. Very shallow shaved tread.

With all of that said, I wish they would make a Cup3.

The cup3 would have the Cup2-R stiffer sidewall, and its narrow rain grooves, however it would have a tread depth either in between the two or as much as the normal cup2.

That would make it a great all round track tyre.

Cuo2-R are too expensive to run all the time, and because of lack of tread they don’t last very long.

The ideal track day tyre would be a combination of the two.

CR-S isn’t far off those specs.

jakermc

@4 Point 0 Tell me more about the Cup2 R as I have not tested on that yet. How do lap times compare to the CRSv2? How many useful heat cycles have you gotten from them?

IRunalot

That is a really nice lap time for Homestead!

4 Point 0

Cup2-R is faster by about 2 seconds on a 60 second track.
When you are ready for PB’s, cup2-R is the tyre of choice.
Faster than Goodyear Eagle F1 Supersport RS as well.
In my opinion, its the fastest non slick tyre. I

I usually get 4 x half day, track days from them. We do open pit lane.

I’d get twice that from CR-S.

jakermc

Last week I ran heat cycles 18 – 20 on the Nankang CRSv2. On the first session, I quickly realized the tires can given up their grip. In particular, lots of oversteer mid corner when transitioning to throttle. Also, braking zones were sketchy, very inconsistent and taking longer to stop. Very modest lap times, about 1 second off my previous runs at Homestead.

Then something funny happened. My good friend in a 991 GT3 posted a time quicker than me. Then I went to the grid with a 992 GT3 in front of me and a 781 GT4RS behind me. My competitive juices got turned on for the first time in a while. I went out hard, wanting to keep pace with the GT3 and not give up time to the GT4. I drove at speeds horribly inappropriate for the tires on the car. They screamed and yelled and slid, but never unpredictably so. I can work with that. I had to stay very dialed in to catch each oversteer and react to unpredictable braking, but the playful nature of the car made it fun, and fun is fast!

Who would think that tires that look like this:



Would produce times that look like this (note both the overall speed and the consistency over 10 laps):

Cycle 19


Cycle 20



The consistency was the result of the tread wearing down to nothing. Without the tread squirm, they settled in a steady pressure and temp, so less variables to manage over the course of a session. Sure, I’ve been faster before on other tires, but I have never been this quick on cords. Love the Nankangs!

Now the bad news. Nankangs are currently in a tariff dispute with US Customs and all product is on hold at the ports. Containers have been there for about 7 weeks now, I believe, with no end date in site. My plan to stock the tire for my customers is on hold, and as a result, I will be testing other options in the mean time.

Next week I will make my first runs on the Dunlop Sport Maxx Race 2 N2, the newest offering from Dunlop that was developed for the GT3/GT3 RS. Quick observation versus the Nankang, they have a more rounded shoulder that results in about ½” smaller tread width when mounted on the rim. Of course this is in a static environment, so how they flex on track really determines how much rubber hits the road during corning. They are rated as 80TW, but that is nonsense as manufacturers play with those numbers for marketing and other reasons. The stop watch will tell us more …..

enzotcat

I'll be interested in your opinion on the Dunlops - that's what I currently have on my car. I don't know if they're N2 or a previous rev, and the car is in the shop so I can't go and check. In any event, to me they seemed ultimately slower than the Cup 2, but with a more gradual drop-off in performance during a session.

jakermc

The N2 is supposed to be a big step-up in performance, so very curious which version you have. Please report back when you are able to.

Their reputation for a gradual drop-off is what attracted me to them over my other consideration for testing, the Cup 2 R. Things are about to start getting hot here in S. Florida, so going to save the Cup 2 R for the end of the year and cooler temps.

PorscheAddict

Great thread. Are you still running stock SPASM with H&R springs and DSC? What's current alignment?

jakermc

Correct, everything is stock except for the H&R springs and the addition of the DSC controller to the stock components. The current alignment is posted in message #107 of this thread.

Current Achilles heel is the lack of front camber. I suspect I may give in and change the control arms to correct this, but I am trying very hard to resist the temptation as I really want to push the limits of the stock components to show just how capable the car is without hardware changes.

Keeping with the ethos of the car, DSC tuning is absolutely in its future. Once I have new rubber on, I'll be ready to lock down on the changes needed. Although most track tuning happens on the slow speed rebound and compression, there is a big compression at the apex of T10 at Homestead and lots of bumps throughout T17 at Sebring, both of which keep me from WOT as quickly as I'd like. I believe these are both considered high speed events and there are big gains available in both corners if I can get this right. @IRunalot has probably done more DSC testing on the 991.2 chassis than anyone on the planet, so I will work with him on the fine tuning.

IRunalot

Just let me know when you want to hit Homestead and I'll take a day off and meet you there and we will do some tuning.

I fixed the my rear end braking issue(way more rear rebound control) I had last time you drove the car and am ~10 files or so past that point. I need to get on the track to make a few more track based high speed changes which I obviously can't do on the street.. The car is much more planted and playful now.

Do you know what your spring rates you are running?

enzotcat

I just checked my Tire Rack invoice for the tires - they're supposed to be N2, and my bet is they are because I tend to check that kind of thing. That said, I'll let you know when I get the car back next week.

4 Point 0

You have corded the tyre with loads of tread left.

The last time i did that was to a TrofeoR when i was on 75/150 spring rate/

By changing the front to 100 made me 100/150 and adding more neg camber, I can get the tyres smooth before cording.

I see a number of issues at play.

Too much toe
Not enough camber
Not enough front spring rate (possibly not enough rear as well) But clearly front to back ratio is off for tracking.
Too much rubber deflection. (Need more spherical bearings)

When your geometry is right, not only do you go much faster, but your tyre wear is far more even.

My point being, near stock setup is no where near good enough to track. You just prematurely burn up consumables at ridiculous rates.

jakermc

Looks in the picture are a little deceiving. The entire tire is at the wear bar and the tire went 20 heat cycles. So tread or not, they were done. This is an absolutely acceptable rate of degradation for the purpose and mission of this car. Remember, my intent is not to build the ultimate track animal as your build is. It's meant to show that with minimal changes and a good driver who is able to adapt to conditions, you can lap as fast or faster than most GT cars you will share the track with.

Here is the current Garmin Catalyst leaderboard for 2024 at Homestead. The Top 12 is made up of 9 Porsche GT cars, 2 fully build race cars, and me in the Carrera T. I'm in 9th place, the 3 cars immediately ahead of me and 3 cars immediately behind me are all GT3s. This was the mission, and I am still getting faster with the little tweaks to the set-up and my driving style that I am making.




Toe - I am running modest toe out (-0.03), a change I made halfway through the tire's life. Prior to the change the wear was perfectly even. After the change, the inside edge wore more aggressively. I decided the change was worth the trade-off as lap times did drop. The correct set-up to optimize speed and the set-up to optimize wear are not always the same. I think I found my happy place. For my customers, I explain the pros and cons to them and let them decide how they want to manage that trade-off.

Camber - Absolutely limited by stock components. Might decide to address this in the future.

Spring rates - Agreed, but not changing. Not in the car's mission at the moment. instead I will play with the DSC controller and work on rebound and compression rates of the shock

Rubber deflection - Agreed, but not in the mission for this car

enzotcat

Confirmed in person - they are N2 spec. Car isn't back yet, but I thought it felt lonely so I went to visit it at the shop 🤣