Kosts Krazy Suspension Thread...

[Kostamojen]

Originally Posted by redlined600

Maybe you aren't giving all the information, but my obvious question is why not use shorter springs? Are you running out of shock travel? It looks like you have plenty of room on the shock body for adjustment.

I don't want short travel, I want long travel up front. Short springs also means stiffer rates. Also, with the stock camber plates I ran out of adjustment because I had to lower it so much the springs actually lost compression at full droop, and pre-loading the springs more meant the car got REALLY high (stock ride height) to get it at acceptable pre-load.



Anyway, My basic suspension philosophy for this car right now is this:

Stiff front swaybar, Softer/taller front springs...
Soft rear swaybar, Stiffer/shorter rear springs...
More quality dampening (shocks) less reliance on stiff springs (IE over-sprung)

The rear suspension isn't capable of a lot of travel, unlike the fronts (Pretty common information bout the design of the Subaru rear subframe they use in this car plus the Imprezas/Foresters) and with the rear suspension unless you are running an expensive clutch pack rear diff, needs as much independence as possible to keep the wheels on the ground (as I learned running the stiffer rear bar).


Some more background information... I used to have a '95 Impreza that was fully built suspension wise with EVERY single bushing in that car being replaced/upgraded (a couple of them took trial and error to reduce NVH) granted I had crummy coilovers for awhile that were over-sprung (Megan Racing, I had one of the first sets for the GC's) that car also had a front Helical diff and a rear viscous which made it VERY grippy and weighed about the same as the twins since I was running it N/A (EJ25 running about 180hp with mods).

With that car, it was all about swaybars being almost even front/back and spring rates being almost even front/back. But that car had a Macpherson rear as well as front so it had a lot more travel in the rear than the BRZ does but wasn't multilink and had static camber. That car was OK to lift a rear tire because it didn't cause snap oversteer with the diffs I was running and I actually run rather mild swaybars for that car and focused more on using suspension settings to adjust the cars handling balance, but I did have to go through a couple swaybars to get that car right too.

[Wepeel]

What is the spring rate in the front? Also, make sure you double and triple check the math on coil bind vs. damper/bumpstop travel. If you're using spacers to get the desired height with additional travel (perch threaded higher than without spacer) then you may start getting into coil bind territory depending on the setup. Especially since it's a somewhat customized setup.

[Kostamojen]

Did some freeway driving today with the current setup, wasn't that happy with the ride quality... I think the camber plates have compromised the ride enough to where the daily driving quality has gone from "acceptable" to "not comfortable".

As mentioned, I've had coilovers before and have experienced this, and I do personally think a lot of it has to do with the compromise of going from a suspension designed for street use which uses bushings in places to a coilover type suspension with full metal-on-metal bearings instead of bushings for camber plates (and even more so when you start swapping out suspension joints for bearings instead of bushings).


So right now, I'm thinking of three possibilities on what to do next:


1) The all-out route: Go with 6" springs up front instead of 7" and up the spring rate from the ~225 now to ~275 or higher. Swap out the rear stock Bilstein springs for linear springs and go with Raceng rear tophats and go with ~350 6" springs. This would be an all-in approach and probably sacrifice any possibility at good ride quality...

2) The reverse-route: Try the 6" 275 springs up front but with the Group-N tophats instead of the camber plates and see if I can get the ride height OK with the shorter springs. This would be the least expensive option to try and get the car to where I want it with having linear coilover springs with good shocks and keep the Group-N/STI tophats to maintain a good ride quality as well...

3) The start-over route: Sell what I have now, go for Bilstein B8 shocks with either RCE Tarmac springs or another lowering spring that doesn't have even front/rear rates but still are nice and stiff, and use the Group-N/STI mounts. This would be risky with wheel clearance and expensive buying a whole new setup, and lose any height adjustability, but would probably be a good all-around setup...

[MeisterR]

So your main goal is comfortable daily driving, as well as good performance for the odd AutoX event, is that correct?

Do you have any regulation limitation?

Jerrick

[Kostamojen]

Originally Posted by MeisterR

So your main goal is comfortable daily driving, as well as good performance for the odd AutoX event, is that correct?

Do you have any regulation limitation?

Jerrick

No I'm not shooting for a specific class, that was early last year I was aiming for STX lol

I only do local events and not entire seasons, so specific class rules aren't a big deal. Eventually I'm thinking CARB legal supercharger too which would be SM of course.

As for "comfort" stiff is perfectly acceptable, but harsh is not. Harsh being vibrations and sharp hits from small bumps/imperfections in the road. Once upon a time I could daily drive a harsh car but maybe not so much now.

[Norville Rogers]

What a mess.

Did you at least swap the mild steel washers for stainless?

[Ro_Ja]

Originally Posted by Kostamojen

Did some freeway driving today with the current setup, wasn't that happy with the ride quality... I think the camber plates have compromised the ride enough to where the daily driving quality has gone from "acceptable" to "not comfortable".

As mentioned, I've had coilovers before and have experienced this, and I do personally think a lot of it has to do with the compromise of going from a suspension designed for street use which uses bushings in places to a coilover type suspension with full metal-on-metal bearings instead of bushings for camber plates (and even more so when you start swapping out suspension joints for bearings instead of bushings).

I've only had one other car with coilovers in my life, and those reused the stock rubber top hats, and that seemed acceptable to me. They were quiet, but I think most of my grumbling of NVH came from the coilovers themselves and all the shit they made rattle and creak in the car since they were stiff and overdamped. My passengers would always complain, haha. But, the rates themselves seemed pretty good (I just looked up rates, and holy balls, they were much stiffer than I thought) and that car was decently balanced and could carry itself through corners very well. But, those were the days when I was young and stuck out the uncomfortable ride because I didn't care and didn't have money to play with my suspension–I just wanted the lowered look back then.

On the FRS, I currently have the the OTS B14s and HVT camber plates (stock rear rubber mounts, and all factory bushings). Unfortunately, I installed both at the same time, so I don't have the experience between stock upper mounts and the HVTs, but trying to compare it to my experience in my old car, the solid mounts do add a little bit of NVH, but it doesn't sound as bad as what you're experiencing in your FRS. I think my complaints about the B14s mainly stem from the soft progressive rates and the slightly underdamped(?) valving.

So right now, I'm thinking of three possibilities on what to do next:

1) The all-out route: Go with 6" springs up front instead of 7" and up the spring rate from the ~225 now to ~275 or higher. Swap out the rear stock Bilstein springs for linear springs and go with Raceng rear tophats and go with ~350 6" springs. This would be an all-in approach and probably sacrifice any possibility at good ride quality...

2) The reverse-route: Try the 6" 275 springs up front but with the Group-N tophats instead of the camber plates and see if I can get the ride height OK with the shorter springs. This would be the least expensive option to try and get the car to where I want it with having linear coilover springs with good shocks and keep the Group-N/STI tophats to maintain a good ride quality as well...

3) The start-over route: Sell what I have now, go for Bilstein B8 shocks with either RCE Tarmac springs or another lowering spring that doesn't have even front/rear rates but still are nice and stiff, and use the Group-N/STI mounts. This would be risky with wheel clearance and expensive buying a whole new setup, and lose any height adjustability, but would probably be a good all-around setup...

I can't tell you how many times I've considered the "start over" option on my car. Half of me wants to tear into the B14s, the other half wants to walk away from them and just get B6s (revalved) and a set of Swift Spec Rs. I never plan to run anything larger than the 17x8/225s I currently have, and I have no desire or need for the corner balancing capability, so there isn't really a reason why I should have coilovers in the first place. Looking back, I guess I only bought them because the B6/B8s weren't out yet and I wanted Bilstein suspension (for reasons of decent-to-good quality and rebuilding/service). What I want to avoid with building the B14s is having to continually play with spring rates. I don't really have the time to constantly be testing and switching springs (and revalving if necessary). I am slightly interested in the RCE spec B14s coming soon, but I'm turned off by the even F/R rates.

[redlined600]

Are you sure that even with the increased travel top hats you aren't hitting the bumpstops with springs that soft?

[Kostamojen]

Originally Posted by Norville Rogers

What a mess.

Did you at least swap the mild steel washers for stainless?

Didnt run with the washers, pretty much just took the photos and thats it, and they were stainless.

[Kostamojen]

Originally Posted by redlined600

Are you sure that even with the increased travel top hats you aren't hitting the bumpstops with springs that soft?

Maybe on speedbumps, but ill find out if they have issues with hard turns during the autox this upcoming weekend. FYI 225 isnt thst soft, the progressive stock springs on these B15's max out around there.


I'm thinking right now ill order some 6" ~275lbs front springs to try. Should I run helper springs though?

[strat61caster]

fwiw I didn't experience any significant increase in NVH with my camber plates (Raceseng) aside from a minor rubbing of the spring perch at full lock over bumpy pavement (shit parking lot). The stock top hats are remarkably stiff compared to the other bushes on the car.

Originally Posted by Kostamojen

I'm thinking right now ill order some 6" ~275lbs front springs to try. Should I run helper springs though?

I think so, I could use helpers on my 8" springs up front right now, but I'm not going super low because I'm prioritizing maintaining suspension geometry.

But why are you doing this? To go lower?

I won't try and pontificate about the bumpstop as I don't have a great understanding of the reality of all the variables at play yet.

But I will say this, it sounds like you can technically go lower on the fronts but don't because you want to have the springs pre-loaded. I say go max low in the front, yeah springs will be free but it's just a test, if that's too low you might be able to use the springs you have now and just add helpers. Note that if it's harsh because of the bump stop, changing spring rate will only have a minimal impact on comfort up front unless you alter the bump stop again.

If you slam it and still want to go lower (and are ok with the harshness if the bump stop is in play) then you'll need to get a shorter spring and I would say helpers are a must.

[Kostamojen]

Originally Posted by strat61caster

fwiw I didn't experience any significant increase in NVH with my camber plates (Raceseng) aside from a minor rubbing of the spring perch at full lock over bumpy pavement (shit parking lot). The stock top hats are remarkably stiff compared to the other bushes on the car.



I think so, I could use helpers on my 8" springs up front right now, but I'm not going super low because I'm prioritizing maintaining suspension geometry.

But why are you doing this? To go lower?

I won't try and pontificate about the bumpstop as I don't have a great understanding of the reality of all the variables at play yet.

But I will say this, it sounds like you can technically go lower on the fronts but don't because you want to have the springs pre-loaded. I say go max low in the front, yeah springs will be free but it's just a test, if that's too low you might be able to use the springs you have now and just add helpers. Note that if it's harsh because of the bump stop, changing spring rate will only have a minimal impact on comfort up front unless you alter the bump stop again.

If you slam it and still want to go lower (and are ok with the harshness if the bump stop is in play) then you'll need to get a shorter spring and I would say helpers are a must.

What I want is the comfort of the Group-N tophats I had, but without the issue of them raising the car so crazy high with the linear springs. With these 7" springs and those tophats, it sat at stock height with the springs barely pre-loaded (and also note, it drove great like that). I solved that by running the Ground Control camber plates, but now its uncomfortable.

I do think the spring rates are a tad soft now, so thats why the 6" springs instead but with stiffer rates. The question is if they need helper springs and which helper springs to go with.


FWIW, I'm very sensitive to changes in suspension. I've been able to notice specific differences with all sorts of parts, from individual bushings to fender braces and strut bars, and of course spring rates. Shocks I'm probably not too familiar with identifying rebound/dampening isolation but thats due to lack of experience with adjustable shocks... I have had single-adjustable shocks before and was able to dial those in (coilovers and those old AGX shocks for Imprezas).

[Kostamojen]

I'm looking into the springs now, and here are a couple pics of some options:



I'm thinking 280's for the front with the 6" spring, 336 is probably too much. That was what I was actually thinking for the rears if I go with the "all out" option, run those with Raceng rear 1" tophats.

But if I go with helper springs, I have NO IDEA which ones I would pick! I'm starting to research methods for calculating helper springs, but I'm starting from zero on this so any input is appreciated:

[langjai23]

i think i have the 6 inch swift springs with helper springs/thrust plates sitting in a box in my garage. let me check the part numbers on them i cant remember if they are 6k or 7k springs. if you are interested i can make you a deal on them.