Spring Rates for the Track

[mwagner10702]

Looking for guidance on spring rates from those of you who track their NSX. I currently have 8k front and 6k rear springs (Swift) and feel like they are a little on the soft side.

My car has MCS 2WR dampers and 21mm and 17.5mm sway bars. 17x8 (215/40R17) front and 18x10 (265/35R18) rear wheel / tire setup. Ran A052's this track season and liked them. Thinking of moving to Nankang AR-1's for next year.

Ride quality is of lower concern to me than overall handling at the track (more important). The MCS dampers can handle pretty high spring rates and still provide a compliant ride on surface streets.

Please feel free to comment on configurations you have personally run on your car - preferably on the track. I'd rather not get into hypotheticals about this "should" work scenarios.

Finally, what's the best way to get additional negative camber in both the front and rear of the car?

Thanks in advance.

Mark

 

[docjohn]

the comptech pro kit was 1200/800 lb/in....

 

[Ponyboy]

I've had the Comptech Pro on my car for years and years and years and love them. You may have to line up a kidney transplant on the street, even a bumpy track, but on the track they're amazing providing they have enough tire. I run Falken 660s in 235/40-17 and 285/30-18 sizes and bladed sways set on full soft up front and full hard in back. 2.5 degrees camber all around. Maybe I'm not driving too hard but there doesn't seem to be too much tire roll to warrant more camber. Stock toe and rake settings. No aero outside of a vented hood (without duct) and the stock NSX rear wing (no diffusor).

Car feels mostly neutral but with a little understeer on corner entry. Loads and loads of mechanical grip.

@docjohn - I am almost certain the Comptech Pro uses 1000k front and 600lb rear Eibach springs with Koni 3012 shocks. I'm too comfortable on the couch and my TV program to get up and check the car (if I remember it's listed on each spring). Will check tomorrow.

 

[asylum]

No straightforward answer. Damper settings also have a big influence. I am not a big fan of very hard front springs as there is not a lot of weight in the front of the NSX. Especially when you begin to put it on diet.

I would go with a good set of adjustable coilovers and sway bars. try to find a comfortable setting for your driving style. Harder is not always better. Must be adjusted to the grip potential of the tires. Camber too. Tire wear (or better, temperature) across the section can be a good indicator of the rightness of the settings.

For camber, on a lowered car, you will have far enough negative rear, even with slicks. If you have really sticky tires, perhaps you cannot get enough negative front and you will need excentric front camber bushings.

 

[Honcho]

I tracked for years on the 10/8 combo with my BC suspension. I found it to be quite good. I have driven a Comptech Pro equipped NSX and, man, it is HARSH. But it is sublime on the circuit.

For negative camber, the best solution by far is Thom's camber correction kit for the rear upper control arms. Might be hard to find a set though. You may want to reach out to @titaniumdave, who may have a solution as well.

 

[RYU]

I hesitate answering questions like these because what might be perfect for me is, at best, a ballpark guess for yours. Here i'll go anyway.

Some disclaimers:
* I have the full Type R "downforce" kit (underbody, hood duct, R wing, etc) which really means zero lift not any real positive downforce like a GT wing or a divingboard splitter. Obviously these will make a huge difference in your optimal spring rates
* I'm running the Dali Racing front "track" sway bar (It's the one below their stiffest "Trophy" bar). Running Type S rear bar. Again, sway bars make a noticeable setup difference
* I'm usually on 200UHP cheater tires but never any true Hoosier level R comps (e.g. Yoko AD08R, Maxxis RC-1, Falken RT660, etc)
* I'm also on factory NSX valved JRZ RS Pros
* When I removed my CTSC it noticeably changed the balance at the limit where i'd need to swap from about 1k softer/stiffer to get back to baseline. I'm now on ITBs which is even lighter than the factory NSX intake manifold

Here's from stiff to soft
Stiffest setup i've tried = 14k/12k - NOPE... my dampers didn't have enough range in the current valving to cope. It was just wrong... I'd run this setup if I could revalve or had significant downforce. The cool part about this setup was it used so little suspension travel so I could really slam the car and still drive it like an asshole.

Next Stiffest = 12k/9k - this is acceptable and had good balance with my sway bar setup if I moved my front sway bar setting to the middle stiffest. This gave a more or less neutral feel. However, the happy spot of my JRZs were topped out on the compression valving. I wanted about 2-3 clicks more firm to really give me a track by track adjustability. This was borderline ok for my bumpy canyon roads. The JRZs were good enough to cope but I can tell I was giving up max grip for agility.

Next Softer = 10k/8k which is basically NA2 Type R stock setup. The rears I bounced around between 8k or 7k because I have them on hand anyway. 8k provided the best balance where 7k would just be understeery enough to be annoying and i'd need to add too much rear rebound in the dampers to upset the frequency of bounce between the front and rear on bigger bumps (like the front would oscilate differently then the rear). I like to optimize for ride as well as under/oversteer when I can. It's always a compromise.

Current Softest Setup = 9k/7k My current setup is pretty much retired from any track duty. My favorite canyon roads near my house are off camber, bumpy, and the asphalt moves around due to the soft soil underneath it. Reminds me of shit Brittish B roads. It's my current happy place given the compromises. It's a bit too soft but the damper settings are able to compensate. It feels especially good here since I just had the JRZs rebuilt and damping is super firm and accurate again. The one annoyance with this setup is I needed to raise up my car to make use of the damping and suspension travel. It's likely too slow for track work but keep in mind... KW V3 ships stock with 6k/6k. I can't even imagine running something that soft but evidently lots of people love it.....

The last two settings fell in the middle enough of the JRZ stock damping range to make adjustments in the damper firmness meaningful.

 

[RYU]

I meant to also add here for any new guys reading, that the amount of rake makes a noticeable difference in our NSXs. I'm usually balancing between the front of the car being between 3/8-1/8" lower. It looks best at 1/4" with most tire combinations but for neutral handling I like only 1/8" rake the best. With too much front rake the initial turn-in is sharp but the rear is too willing to come around (i.e. trailbraking), however not having enough rake causes excessive front end push/understeer when applying throttle early coming out of a turn. So it's really going to be based on your personal driving preferrence. You can mitigate much of this wanted or unwanted behavior with damper settings (if you have good dampers with lots of usable range) and of course, sway bars and springs rates.

 

[aniladitya]

How bad is stock NSX on track? How much of a lap time difference do we get with these setups without any engine mods?

 

[Honcho]

How bad is stock NSX on track? How much of a lap time difference do we get with these setups without any engine mods?

The stock NSX is fantastic on the track (assuming a healthy suspension- most are very old/tired at this point). All you really need are good brake pads and fluid. Here's Scuderia AlphaTauri F1 driver Pierre Gasly ripping around in a bone stock 91 NSX. This shows what the stock car is truly capable of. No normal person could drive this fast, but it shows the car is quite capable, even 30 years later.

The skill of the driver matters more for lap times than any particular suspension setup. A pro driver in a stock NSX can run circles around a novice in a fully-built track car. Suspension mods expand the envelope of the car's performance potential, but driver skill is how you tap into it. That said, anecdotally I've seen most quality suspension mods yield 1-3 seconds less per lap for an average driver.

 

[aniladitya]

Thank you! I just want this answer recorded from some one who knows these cars well. I drive a bone stock 91 NSX and a head to toe modified supercharged Miata. I love driving NSX any day.