2nd Gen Setup GR86 - STR - 7/9K springs?
 

17x9 Apex ARC8 on RE71RS
Front sway Perrin 22MM
Stock rear sway
RCE Tarmac 2s (400lb/in -> 7k all four corners)
Catback Borla Type S

Usually run tire pressure at 30/31 psi hot. Front camber is between -4/-5 degrees with Vorshlog plates. Toe out on the front and toe in on the rear, no caster adjustments available.

I want to change my rear springs to 9k and keep 7k up front. Seems that most of the top national autox guys seem to like more spring rate in the rear, like running 7/9. But still 7/9 is what the fast guys are running in autox.

Any opinions here? I know I’ll lose to ND1/2s but at least worth trying to get the best setup with what I have.


Sent from my iPhone using Tapatalk

I'm still in DS with my first gen, but I've been doing some heavy research on spring rates, coilover options, etc. as I'm planning on an STX build in the near future.

Spring rates come down to what you want the car to do - be neutral, oversteer, understeer, etc.

A lot of the top guys want higher spring rates in the rear to increase rotation. Which is great if that's what you want and how you drive. You do want some rotation in the rear... but of course, if it doesn't fit your driving style, then don't just do it because all the cool kids are.

How much experience/events do you have on the current setup and do you need more rear rotation?

STX in a gen 1 correct? I thought you couldn’t build an STX gen 2 build.


Sent from my iPhone using Tapatalk

The chassis setup between the two is nearly identical for STX or STR, IME.


I've got 6k/9k springs, running the Karcepts front bar (the bigger one) around the middle (lower on asphalt, higher on concrete) and a little bit of positive rake (hub to fender)


-4.9 front camber, -2.5 rear camber. Zero front toe, ~3/16" total rear toe-in.




Running equal spring rates all around is just... not ideal. You then need a really small front bar or a big rear bar to make it work well. The math supports the idea of running more rear spring, motion ratios are a thing :)

I'm running 6k/9k springs on my Gen1 and it feels so much better than the 6k/7k setup I had before.

I went RCE SS-2 coilovers on my '23 with standard 7k front springs with 9k rears (in place of the 7k rear springs that came with them). This based on my old '17 suffering mid-corner understeer with 4.4kg front and 5.3 kg rear springs. I did *not* want to go with a "square" spring setup, which of course greatly biases stiffness to the front.

I have a few events with this setup, really like it as far as handling balance! Kind of a non-standard car tho, I added tons of ballast to remain in my time-trialling class. Competition weight 3107 lb. :cry:, with spare tire from my '17 in the trunk along with 120 lb. (!) of ballast, distribution is 51.5 front 48.5 rear. So I'm relatively a lot less front-biased than most...

6k/7k mk1 here, gotten good feedback so far, I’m convinced with talent car can take top pax as it sits. I am curious about trying 8k or 9k rear but I think I’m leaving it alone for the rest of this year unless someone wants to trade for the extra 7k swift springs I’ve got in the garage. Also make sure your dampers can handle the spring you put on it.

Lots of ways to skin the cat, bumpstops, damping, swaybars, lsd, alignment, ride heights, will all play a role in how it handles and where you end up setup wise. My advice is when cornering the car should feel like both outside wheels have the same amount of grip, that they load up equally and reach/exceed the limit of grip in unison. Last Saturday I struggled hard, I changed the front bar but hadn’t changed the rear to match, Sunday was way better after I went back to my old baseline.

You can absolutely put some 9k springs on the rear of SS2s or T2s, it can work really well. :)

Indeed! And you see a lot of very different and strong preferences from various suspension tuners. Even rates from 949 racing and I think Strano and sometimes CSG, stiffer fronts from MCA in Australia, stiffer rears from a lot of the newer more focused tuners, and so on. And for track cars big rear wings are a lot more common these days which certainly makes stiffer rear rates a good idea. You can make arguments about flat ride vs sucky front mcpherson struts, and both are important with plenty of nuance and details to sort.

We are actually flexible...but primarily spec even rates on our kits as standard. One reason for that is because out of the box with minimal supporting mods, it just works really well for people with a wider range of goals. And it's easy to drive and set up for most people. It's harder to screw up the driving and the overall set up.

And so we also do custom kits, almost all of which use stiffer rear rates because the type of driver that wants a more custom set up is the type that will benefit from stiffer rears. But plenty of experienced and fast people are still using the standard rates too.

Our new 3 ways do come with slightly stiffer rears as standard, but of course we can customize them.

For my car (street only at the moment) I'm on 5k/6k right now with 3 ways and stock bars and it's mega fun and comfortable. It would easily be faster with just adding a bigger front bar, or just switching to 6k front rates, or just switching to stiffer rear rates...whatever..as long as the rest of the car was set up well but I'm just having a good time and this works really well for my uses.

- Andrew

Sounds good. Plan is to try 9k out back and keep the stock 7k springs up front. Looking to get less under steer for autocross. It does tend to under steer more than desired on a 7k setup on all four corners (aka square).

Any problem with mixing the stock RCE (Eibach?) springs up front and Swift out back? Do I need to replace the helper springs out back with Swift?


Sent from my iPhone using Tapatalk

No issue mixing spring manufacturers and you can keep the helpers that you have too.

- Andrew