5.M0NSTER

^This, if you make changes a lot used is definitely the way to go.

I operate on the opposite end of that spectrum. It took me 3 years to decide on suspension, lol.

Also wife not too angry most times. She may get tired of hearing me talk about mods, and pros and cons of each, but the added benefit of that is when I do finally pull the trigger she is almost relieved. Like "finally" haha.

m05fastbackGT

Marty, I'm still debating as to whether or not to change suspensions.. Not so much the parts themselves, but being a PITA to having to uninstall and then reinstall time and time again lol. My wife for the most part has been really supportive over the years and it takes quite a lot to make her angry.. However I also don't want to push my luck either

lsxjunkie

Those whiteline springs will NOT work well with your stock struts. They are 1.3" drop front, 1.7" drop rear, 194lbs front and 174lbs rear.

These are the factory spring rates:

2011-14 Base GT: 123f/156r
2011-14 GT Track Pack: 131f/167r (sits higher than base GT, rear significantly so)
2012-13 Boss 302: 148f/181r (front 3/8" lower than base GT, rear same as base GT, noticeable drop from Track Pack)
2012-13 Boss Laguna Seca: 139f/191r (sits same as Boss 302)
2011-12 GT500 SVT Performance Package: 234f/197r (sits level on a GT, but at front Track Pack height)
2013-14 GT500 SVT Performance Package: 257f/200r (I have not tested these)

Those whiteline springs will bounce, ride like ****, and bottom out your shocks.

I have had the following suspension setups on my car

1. Factory delivered GT Track Pack.

2. 2012 SVTPP shocks and springs. Too stiff on compression, not enough rebound in the front.

3. Boss 302 LS shocks and springs. Too soft in the front, too stiff in the rear, wasn't thrilled with the adjustable shocks, not enough rebound.

4. Boss 302 LS shocks and front spring, Route 66 55D rear spring (170lbs). This was an awesome comfort setup that still handled well, but I wanted more. This is also when I added the Boss rear bar.

5. Koni Yellows with Boss 302 springs. Even with the 148lbs spring, this was still too soft in the front. Also the front sat too low compared to the rear with the additional 1/4" drop you get from the shorter Koni struts. Even zeroing the toe every year the car was still chewing up the insides of my front tires. I won't put camber/caster plates on the car because I don't know/trust anyone around here to set them up correctly and then actually reload the suspension properly to set the toe. The Konis have way more rebound stiffness than I can use on NY roads, but I am glad of the adjustability. This is when I added the BMR Extreme front bar to try to counter the soft front springs, but I still wasn't happy..

6. Current setup. Koni Yellows with 2012 SVTPP front springs, Boss 302 rear springs. Also added J&M Street LCAs, which as increased rear roll stiffness, but not much in the way of harshness. I am mostly happy with this for a daily driver setup, especially for ground clearance. It sits level, about 1/4" lower than the front of a Track Pack due to the Konis, maybe about the same height as a base GT. I currently have the shocks set to 1.5 turns from soft front, .75 turns from soft rear. Any more than that in the rear and the rear wheels will skip over large bumps or extended rough patches in the road. I may dial the rear back down the .5 tomorrow to see if I like that better.


The reason for this Frankenstein suspension setup is that I refuse to lower my car to the point where I have to add an adjustable UCA or Camber/Caster plates. A PHB I'll do, but I don't have the money or the patience to deal with more adjustability for someone to mess up.

I still have the Boss Laguna seca shocks and springs, the Boss 302 front springs, the Route 66 55D rear springs, and my factory track pack stuff sitting in the garage. I probably should have just started with Koni Yellows, P springs, and an adjustable PHB and called it a day 3 years ago, but you live and you learn.

Sorry for the massive post.

5.M0NSTER

Hey LX, what is it that you're aiming for exactly. Is it slight lowering with good comfort and less roll/dive/pitch?

You and I probably have some different goals for our cars, but I think you're discounting CC plates too soon. My suspension setup has completely transformed my car, while increasing harshness by an acceptable amount (to me anyway). It is tolerable, but the dividends returned way outweigh the stiffness price.

The 2 biggest factors are dampers (I set my Konis to full soft on the street and 3/4 stiff front 1/2 stiff rear on the track) for controlling fast transitions and maximizing grip, and then camber.

The second factor in tremendous cornering ability my car now possesses is the Steeda HD plates. I'm sure they add a bit harshness since they are mostly metal with some high durometer rubber vs the stock softer rubber mounts. So perhaps the Konis contibute some stiffness and the HD plates contribute the rest. But the pay off in terms of eliminating understeer and adding "hook up" and "on rails" feeling is amazing.

I had mine adjusted by a reputable local shop, and a full year later tires are wearing even, and no increase in NVH. I'm running -2.0 and -2.1 degrees camber up front too.

I didn't have to do UCAs or even the CC plates. I chose to do the CC plates since my car sees track duty every summer. And I love taking clover ramps at 60mph with no issues or even tire squeal. Plus I think adjustability is the key to great performance and a decent ride on the streets.

P.S. Thanks for summarizing spring rates and heights. That's good stuff!

5.M0NSTER

Hey Rocky, if you were to change, what would you go with now? I know you mentioned Bilsteins. Is your main complaint the stiffness or harshness over bumps?

PonyMuscletang13

Very Very informative post. This helps a ton! Thank you!

My current setup is the BC Racing Coilovers with Whiteline adjustable Upper/Lower comtrol arms, Whiteline Relocation Brackets, Whiteline Panhard Rear Bar, Whiteline Chassis Brace, Whiteline adjustable Front Sway Bar.

So yes, most parts are Whitelines. Not because I like them any better than other brands but just so happens that the shop carried this brand exclusivity at the time.

I hear you having adjustable components can be a headache sometimes when not done correctly. I ended up installing all of these nonsenses mostly due to my lack of knowledge (still). The suspension setup is the hardest of all mods IMHO.

It looks like back to square one haha. The car sits perfect now (maybe it's a little low...) except a little too stiff for a daily not enough travel distance. Trying to go back(?) to conventional shocks & springs, get that 'just right' sporty ride experience. I think I need help lol.

PonyMuscletang13

This is how my car sits right now

m05fastbackGT

Marty, the stiffness I can deal with by setting the Koni yellows to full soft.. It's the harshness when going over bumps that get on my nerves more than anything else lol.

lsxjunkie

I didn't want to do the camber/caster plates because I don't have anyone local I trust to do the alignment. My spring rates are higher than most aftermarket offerings, but at nearly stock height, which is fine for me, as I drive this car almost 20,000 miles a year through all sorts of conditions. The only thing I'd like to do now is settle the rear axle down over rough roads, but I'm not spending the money for a Watts, so I'll just live with it.

Rog13GTCS

Looks good, love the stance.

5.M0NSTER

Beautiful! I think it's difficult to pull off black wheels on the SGM, and you did it. Sweet looking ride!

I see. That is hard to address while maintaining a stiff chassis and good handling. You could try lower spring rate I suppose, but that comes at a handling price too.

I have 2 thoughts:
1) PHB might help. You clearly don't need it to re-center, but most come with higher durometer rubber, so it moves around less. I have not experienced wheel hop since my new suspension was installed. I used to get it with the stock TP a lot. I credit the steeda adjustable PH bar for that.
2) I'm surprised you have your konis so much towards stiff. I have mine on full soft on the street, and I sometimes wish I could get softer, LOL.
But I'm guessing that part of the reason for rear end bounce or float so to speak is because Konis are made for lower springs than what you're running. So they may not have enough pre-compression at ride height since you're on level with a stock GT. Not to mention your GT doesn't weigh as much a GT500 further amplifying the issue sine those are some stiff springs! So if you were to drop it 1" it may get better? Perhaps. That's my theory.

m05fastbackGT

And I don't want to sacrifice good handling Marty.. So it appears I have 2 options to select from, either deal with the harshness from the Koni Yellows or as Patrick suggested, upgrade to Bilsteins and see if that would make a difference

PonyMuscletang13

Thanks guys. I too love the current stance but not so practical as a daily. It's not too bad though, I've seen much lower. I'm thinking about a half an inch higher than now, just not sure which springs will accomplish that.

lsxjunkie mentioned the Whiteline springs have somewhat bouncy spring rates @ 194lbs front and 174lbs rear (I'll need to confirm with Whiteline), I've been looking at the H&R Sports (1"/1.6"). It's listed as one of the recommended from Maximum Motorsports to pair with the Bilsteins.

The google image search is not doing much good, I came to realize the advertised heights differ depending on trim lines (base, trackpack...) there's also tires/wheels size factors. Simply put, cannot tell accurate how the stance will look like until install. One of the reasons I went height-adjustable Coilovers but now going back... getting headaches.

What's a 'good' spring rates then. Higher the stiffer? In the rear or the front? So confusing.

laserred38

what are you guys taking about? I run 55psi in the front and 60psi in the rear

Kytann

Always good to see some real data.
Last year I compiled a bunch of spring rate data before getting my current setup. Just for data purposes I'll combine it here with the data you posted.

My old data
Front 154 lb/in Rear 122 lb/in Base GT (2013)
Front 200 lb/in Rear 175 lb/in Drop 1.00 Front, 1.25 Rear Steeda Sport
Front 225 lb/in Rear 185 lb/in Drop +.20 Front, 0.8 Rear Steeda Comp
Front 239 lb/in Rear 203 lb/in Drop 1.00 Front, 1.50 Rear Eibach Pro-Kit
Front 195 lb/in Rear 175 lb/in Drop 1.25 Front, 1.50 Rear Steeda UltraLite

My stock data and your stock data look reversed
Then again, Witelines site data looks way too high for the rear spring at 274 lbs/in, which is 100 more than you listed.

Whiteline Data (From Their Site)
Front 194 lb/in Rear 274 lb/in Drop 1.38 Front, 1.77 Rear Whiteline

Your Data in the same format
Front 123 lb/in Rear 156 lb/in Base GT
Front 131 lb/in Rear 167 lb/in GT Track Pack
Front 148 lb/in Rear 181 lb/in Boss 302
Front 139 lb/in Rear 191 lb/in Boss Laguna Seca
Front 234 lb/in Rear 197 lb/in '11-'12 GT500 SCT Perf Pack
Front 257 lb/in Rear 200 lb/in '13-'14 GT500 SCT Perf Pack

FYI, I'm currently running Steeda Sports combined with Bilsteins Shocks all around. Mostly happy with it.
Biggest handling difference came form Anti-roll bars though

Mr. V

I have the Steeda sports springs and Koni sport shocks/struts. I've been considering switching to bilstein. How is the ride/comfort of your set up?

Kytann

Kinda weird, I'm not entirely happy, but then I am picky as hell. If I had the money to do it I would sell them and buy some Coilovers. Maybe next year.

It's also hard to give a comparison without having tried both variations, but I can compare them to stock and to my old BMW Z3.

Compared to my stock setup, it's alot stiffer. Kinda busy, but NOT harsh. Sharp edged bumps disappear, but large movements feel like the suspension doesn't move at all. It's almost bouncy, but not.
Before I bought them I spent alot of time reading reviews, and one of the opinions that stuck out for me was that "the Bilsteins are both too soft and too hard at the same time". At the time it didn't make sense, now it does. That was on a BMW M5 board, and to be fair, BMWs come with nice shocks factory.

I remember really liking the Koni Yellows I had around 2002 on my Eclipse GT. Of course 15 years ago I wasn't nearly as picky. My advice would be to just keep your current setup until you have the chance to ride in someones car with Bilsteins. If you lived near Minneapolis I'd volunteer.

PonyMuscletang13

I'm doing the exact opposite. Coilovers to conventional shocks & struts, Bilsteins being my first pick.

The Coilovers were a logical choice. At the time, most people running Koni's or would recommend Koni's over anything and that's what I'd get but somehow I wasn't getting a good vibe. Plus I had trouble selecting which lowering springs to get and the shop suggested Coilover setup having the height adjustability.

They gave me Race-like ride experience over the years but I came to conclude it is not the practical set up for a daily driven car. Also, mine being an entry-level product (BC-Racing) and not the popular ones like KW's might have come in play to contribute the ride quality.

What did you mean by 'too soft and too hard at the same time'? Are you referring to the ride quality being inconsistent?

Kytann

Not really inconsistent.
It's hard to describe in words. I think it's really the difference between high speed impacts and low speed impacts. On paper, it sounds great to have high speed impacts (sharp edged bumps) blow through to the soft settings, but to have low speed impacts (dips in the road) react very stiffly. In practice, it feels alien.
It may just be that it's not what I'm used to at all, so it working differently feels weird. I can't pick out any one thing the car does wrong, in fact it seems to handle very well for it's size and weight. So I am probably just being picky.

Also, keep in mind our Minnesota roads are ****, as frost-heaves do a number on them. So out here we need more compliance than in certain sunnier parts of the country.

PonyMuscletang13

Still confused heh.

The roads here in Southern California is not any better if not worse than other states. More compliance, more travel is exactly what I'm seeking and was hoping to achieve just that by going back to conventional setup.

Firm, yet good ride quality, as is expected of a performance car - is what I want. We're talking about the Bilstein HD Series B6 Performance, yes? Which lowering springs are you running Kytann, if you don't mind asking? Year of your car?