Sachs PP Shock & Eibach Spring Combo - Roll Center Correction?
 

Hello all,

I am planning on doing a Sachs PP strut w/ an Eibach Sportline spring combination, and have been reading that drops less than 1.5" do not need roll center correction.

In theory, if the body of the car is lowered any amount, the distance between the roll center & center of gravity will be increased, hence increasing body roll. So wouldn't a 1.5" drop from the Sportline kit (or even 1.0" drop from the pro-kit) essentially require roll-center correction to minimize body roll?

Looking forward to your responses, & thank you in advance for your insight.

I would recommend Eibach Pro kit over Sportline springs if you're sticking with Eibach springs.

The roll center kit would improve geometry, but the lack of bump travel from the 1.5 inch drop is a much bigger concern.

- Andrew

If you want to go lower than an inch, look into the Bilstein dampers. The b8 is made for spring drops and will be much better suited to being low than an essentially factory one.

Thank you for everyone's responses so far; I was really happy to get a response from @Racecomp Engineering too!

I will be sticking with the Eibach Pro-Kit plan then in that case. I am trying to achieve the best "handling" so far for the least amount of money & mods so that I can spend on an angle kit & tires.

I have heard good things about the 2017 PP Sachs shocks, but ultimately, I know nothing about how to pair dampers and springs.

If I were to look at for example, a performance spec sheet for springs and dampers, what is the typical procedure in determining a good matching pair? In other words, what characteristics of the strut am I trying to pair with the spring rate?

Also, what are your opinions on the Pro-Kit spring & Sachs PP strut combination?

Another member posted about the TRD springs on sale.
http://www.ft86club.com/forums/showthread.php?t=135704

I just installed the PP Sachs and am going to order the springs tomorrow since it’s payday for me. $180 shipped is a pretty good price and most people say that the TRD are rebranded pro kits. I dont know how much I believe that, but enough people on here agree they are the same.

It's rare to find technical data for shocks, but this thread talks a little about what to look for in a shock dyno. I need to fix the picture links though.
https://www.ft86club.com/forums/showthread.php?t=81062

The optimumG link in that thread can get you into the weeds if you want to nerd out.

Pro-kit with Sachs PP struts is a pretty good combo. I prefer our RCE Yellow springs (duh!) but the Pro-kits are one of the only other springs we sell.

Are you planning on tracking or autocrossing your car?

- Andrew

Hey there, yes the TRD springs/Eibach pro-kit is what I am seeking. I believe it is cheaper to find them as a pair rather than buying them separate, so I'm trying to wait around for a deal to snag, haha.


@Racecomp Engineering Thank you for the reference! I plan to have the car set up as stock as possible for drifting prior to adding more complex modifications. I read in another post (I may have also misunderstood it) that to keep the "oversteering" characteristic of this car, a lower (softer? maybe referring to struts?) spring rate is preferred, hence my choice of the pro-kit, because I believe the RCE yellows are both 4.5k front and rear, which is more oriented towards grip? Otherwise I would have gone RCE yellows for their reputation in performance and their willingness to help the community.

Please correct me if I am wrong, and feel free to provide any insight in regards to spring rates and its effect on oversteer/understeer as I am trying to achieve an oversteer bias. Thanks so much for everyone's insight so far!

I've got a set of tS revalved PP dampers and STi springs that'll improve handling over what you're currently looking at!

$450-470 shipped depending on location in CONUS

For your uses yes the pro-kits may be a better option.

For me a good stage 0 is good alignment, rear whiteline diff inserts, rear whiteline subframe bushings. Add perrin steering lockdown for feel if you like. Obviously choose the right tires for your application. You might try that before even going to springs. This assumes you have good condition shocks.

- Andrew

Would you recommend the steering lockdown bushings by themselves, for someone wanting better steering but without the nvh of the other bushings (subframe/diff inserts)?

I like the steering lock down. No real drawbacks, can be used on an otherwise stock car. Fairly cheap and a nice "feel" upgrade which for me is important especially with steering.

- Andrew

Noted. Whiteline bushings are also at the top of my list, and I have 102k miles on my current shocks, but they don't feel like they're out yet (I probably can't even tell between worn and not unworn).

Hope I'm not asking too much, but is there an explanation as to why a lower spring rate would be geared towards oversteer, and vice versa, why a higher spring rate would induce more grip? Or is that just a fallacy?

x_hawker: worth noting, lower (or higher) spring rate where, at front or at rear? Usually it's about changing it on one end to change grip bias, no?

I went a slightly different route, replacing my steering rack bushings altogether, but with the same purpose/result. I'd definitely recommend this generally, although be aware it may result in some wheel vibration when idling (especially if combined with other things to stiffen the chassis). Makes a huge difference in steering feel and only improves with increased front caster.


Realistically, before even worrying about lowering the car or anything else with the suspension, the first two things everyone should do as RCE pointed out is get a good alignment (which may require replacing parts to enable necessary adjustment) and tires. Those two things alone make a massive difference in how the car drives.