Optimal ride height for track setup
 

Looking for thoughts on how far to drop from stock height for track setup for ideal CG.

I am installing Bilstein B16 PSS10 on 2014 Sport where a professional race shop will be performing the setup. I am just looking to see what amount of drop those of you with track experience recommend.

Key input:
- Track experience 25+ days
- 75% Track Use / 25% Weekend Driver (I do drive it to track - 150 Miles)
- RS4 275/40/18 square
- SPL Upper Control Arms
- Hotchkins Front and Rear Bars
- No Aero
- Current Camber is -2.75...but expect it will go to -3.x

I'm literally getting rs4 in that size put on Monday. How do you like them?

I never found an answer when I was looking this up and from what I can see and measure, you don't have to worry about going so low that the roll centers end up below the road surface.

I'm at 26.5" from floor to bottom of fender. If you are on ots Bilstein you will probably need to run on the higher side around 27" or more to avoid bottoming out the chassis on the pavement on common road imperfections.

Edit: I am on 275/40/18 yokohama ao52

Been looking for these two posts on and off for the longest time, finally found them again. May find some of the stuff useful regarding BGTV8’s rationale on trying not to lower the car too much.

http://www.the370z.com/track-autocro...ml#post3100179

http://www.the370z.com/brakes-suspen...ml#post3776914

The Z does not have a linear camber curve in the rear. How can I explain this. This is just an example. Say you have your camber set at -1. Squat the rear inch, camber goes to -2. Squat 2 inches, camber goes to -3. In the Z, squat 1 inch, camber is -2. Squat 2 inches, camber is now -3.5. Also, the lower the rear. The more non linear the camber curve becomes. Lower the Z by 1 inch. Camber at -1. Squat 1 inch, camber is now -2.25. Squat 2 inches, camber now at -3.75. I don't know what the exact numbers are. But that's the way is was explained to me from AM Perf.

I don’t think this is related to height - in those two linked threads, there was a lot of talk about curing oversteer in those race cars. I noticed those cars had TRUE TYPE coilovers running heavy springs in rear...


Since those threads we discussed how true type required a different spring rate from divorced type. I wonder if those drivers would have solved their issues by going softer in rear accordingly

From my experience, going to low will cause understeer. I try not to go too extreme on dropping the ride height. It does help on tighter corner tracks.

Thanks for the replies...I just looking to see how much you track guys have dropped...1/2", 1", 1.25", etc and feel good about where you are.

Brendan - I am currently sitting at 27 3/8" on 18" wheels with stock dampers.

Rusty - I expect the suspension shop would set the appropriate Camber settings given the final lowered stance...would't they? I will remind them of the non-linear camber rate on squat.

Sharad - I have no need to go "real" low...this is not for looks...it is for performance. Hence my question as to what ride height seems to be working for those who track?

I do not have any understeer problems today (at Square and -2.75 camber)....my objectives are to be fully planted, car control (increase confidence on high speed turns) and address excessive outer tire wear.

It’s specifically BG’s response. It’s about the part where he discussed lowering CG via smaller diameter wheel + tire vs lowering via spring, leading to benefits on keeping a longer suspension stroke (also see how second post mentions lowering too much via spring messes up the roll center), and how he managed the gain in rear toe-OUT under braking (makes the rear end wander) during braking. Add what Rusty said, sort of finicky nature of camber change.

It’s not so much directly related. Just somewhat related.

I have been told that the rear camber issue can be fixed but it is expensive. Requires totally modifying the rear subframe and pickup points. I never got into the details of it but I may later on.

That's what i was told too. That to correct it, Some of the pivot points have to be move. It's not cheap and involving lots of engineering.

Yeap, I think MA-Motorsports can do it. Brian is the one that told me.

I wouldn't run any lower than two inches. Nismo stock is 28" floor to the finder well. There always trade offs. If you run a splitter you want to get as low as possible without causing issues. I run 26" front and 26.5" rear.

Sent from my SM-G965U using Tapatalk

The other thing about going too low. You are no longer in the middle of your shock/coil-over stroke. You are now closer to the bump stops. If you are riding on the bump stops in a turn and hit a bump. You don't have any travel to absorb the bump. Something not good is going to happen. The next thing is if hard on the brakes before a turn. You use up your travel and are on the bump stops. You hit a bump, guess what happens next. This may be one of the reasons for ice mode. Something to think about.

If you have a proper thread-into-body coilover, don’t worry about travel within your suspension components. The biggest problem is that lowering our double wishbone fronts causes unwanted alignment changes and limits suspension travel from the front upper control arm to the strut tower.

At stock height, the upper control arm will sit nearly perpendicular to the front knuckle; therefore, the camber/toe doesn’t not change a lot through compression/extension. Lower the car 1-2 inches, now that upper control arm sits at a 30-45 degree angle upwards. With the same amount of compression/extension, the camber/toe will change drastically more. Over bumps, the car will be easy to unsettle because your tire contact patch is diminishing.

Ideally, you would shorten knuckles and get full SPL arms to eliminate this unpredictability (similar idea for the rear to prevent unpredictable oversteer from camber/toe changes when lowered), but that’s a lot of $$$ and work to support a simple mod.

Basically the closer the ride height to stock, the better your car will handle. The alignment benefits really outweigh the slim benefits from low COG. Driver confidence is key. A low bucket seat will also help.

My '14 Nismo height and damping settings.
 

I have a 2014 Nismo. For my FA510s I run 27 1/4 in the front and 27 1/2 in the back. Rides just fine on street and track lowered to these measurements. I set the damping to 14 front and 10 in the back for the track and 4/4 for the street. I like the ride softer on the street anything more than 14F/10R the car seems unsettled at speed when at the track.

Just my experience.

You have to set the car up the way you like it and for the tracks you run on. A smooth track with few bumps you want to increase stiffness and bumpy tracks you decrease stiffness as a general rule. I am running with a big wing in the rear and a five inch splitter up front which changes the dynamics for suspension setup. It is a game of trade offs as all cars have limitations. It is just about how much money you want spend on getting them as perfect as you can for your driving style and ability. Many of the best pro drivers will tell you for handling performance you pretty much can't beat a Miata that is well setup and from my experience that is a true statement.

Sent from my SM-G965U using Tapatalk

The Bilstein B16's are a thread-into-body coilover...as such, I assume I will not have to worry about compression travel distance and any pre-mature bumpstop strikes. Is my understanding correct?

I already have installed the SPL Upper Control arm. Will that help with any of the geometry concerns of lowering that you guys have brought up?

I will defer to my Suspension Track Shop (Miata Race Shop)...but I would not look to drop any more than 30mm. Given than I am already at 27 3/8" stock....I would drop to ~ 26 1/4" worse case.

Still looking for everyone's input...as I take it to the shop on Wed morning.

So I have found a solution for lowering the front as has been suggested by Rusty, Spooler and vq37818. They are $500 for the set.https://uploads.tapatalk-cdn.com/202...4300c0b77c.jpghttps://uploads.tapatalk-cdn.com/202...b8dc070d88.jpg

Sent from my SM-G965U using Tapatalk

Are those nightlrkr's?

Who???:icon14:

Here it is

http://www.the370z.com/brakes-suspen...-knuckles.html

In short, he took the stock ones, chopped and shortened them, then welded the two ends back together. Looks like good quality, but the thought of it snapping is scary.

An old timer here did snap an OEM one during a tight curve, car was totaled as a result. Hard for me to shake that thought every time I think about nightlrkr’s knuckle, no matter how much I wanted it.

:iagree:

LOL...I don't know how I missed that thread and to Jar's question that is him. He has sold a number of sets and I have yet to hear any issues granted track session is just getting geared up. I read the whole thread and I follow him on Instagram and from what I see he is legit. He responded to all my questions quickly and in real time.

Lastly, everything we do once we start modifying the car adds a level of risk. Leaving it stock is risky when you are tracking it. Hell ask a manufacture what does off road use mean for a 4x4 truck and they will tell you it is for maintained dirt roads, rain and mud and snow on paved or those maintained dirt roads. Everything we do at the track is about comfort level of the risk we are willing to take.

At some point I hope to dig up my balls again and buy a set.

I think I am going to do it to optimize my aero setup. May the force be with me!!!

Down force.

Go big or go home!!!:p

Optimal ride height for track setup
 

Exactly. I’ve been meaning buying a set of those knuckles for months. He told me that the knuckles correct camber by a degree, so gonna wait until I buy some SPL FUCAs.

You can lessen the effect of that exponential camber change by adjusting the arms close to 0 degrees, but you will lose the contact patch (positive camber) on extension. I would just lower to the 26 1/4” and get a feel for the car. It’s all subjective, you may not be bothered by it at your limits.

This was my greatest worry. Putting a cast suspension component through another heat-cycle will make it extremely brittle. He really pushes his car on the track on I’ve yet to hear any bad stories. He’s been testing them for a while before he began to openly sell, so I would assume that he trusts the product enough...

Try it, but it might be too low. I've never hit the bump stops with my coils so I have my dampers set up to give me as much droop as possible. Lack of down travel can make a car handle as badly as a weird camber curve or hitting bump stops.

If you're not sure you can try setting up the damper up for maximum length and desired ride height. Take off the wheel and support the the control arm so that the damper and spring are compressed and you should be able to see how much travel you have before bump stops or coil bind.

Bilstein B16 PSS10 are installed...here is where I landed on ride height and track alignment specs

- Lowered 26mm Front / 10mm Rear; Rake 1/8”
- Camber: -3.55(F); -2.88 (R)
- Caster: 5.17(L); 5.41(R)
- Total Toe: .06 (F); .18(R)
- Corner Balance: Left 51.5%; Rear 45.1%; Cross 50.1%

Looks good except your rear camber seems high, I think -2.2 would be a good match for your front camber, if you want your car to response quicker, front toe would be better to be 0 or negative (as most alignment sheets shows toe out as negative)

Agreed!

Sent from my SM-G965U using Tapatalk

Just measured mine and it’s 25.5” with 275/35R18 (inch smaller than OE), is that too low?

On the street you are going to be hating life. I ran mine at that ride height the last time I was at ZDAYZ. I was on Toyo 295 30 18 square. My camber was -3.3 front and -2.2 rear. The handling was spot on. Turn in was quick and she was nimble. The down side is there are some sharp turns with quick rises and I would bottom out on them. When got home I had two rivets left on my Zspeed undertray and there was a small hole was forming on the undertray. Conversely getting in an out of parking areas and gas stations were a pain. If she is 80% track car go for it. I am looking at 26 up front and 26.5 rear.

Sent from my SM-G965U using Tapatalk

time for an air cup system for the parking area part

I agree with my esteemed colleague Hotrodz. That low and your chassis will be limiting your suspension from doing it's job and it will be a pain on the street.

This would be nice

https://www.instagram.com/p/CAQYXNTn...d=myg48eavt9gy

https://www.instagram.com/p/CAQYXNTn...d=7u9e3wngy9pv