Suspension Improvements Options

[TrakCar]

Over the weekend I took the Camaro out to the Midwest Musclecar Challenge (www.midwestmusclecarchallenge.com/).

I had a blast, however I now am much more humble about my driving ability.

I have the power, I have the brakes, now I am ready to begin improving the suspension on the Z.

This, is where you guys come in.

Usage
Street - 1-2 times a month to work or cruises
Track - 3 or 4 track day events per year
Autocross - occasionally

Details about the car:
1991 Z28 hardtop

LS1/T56 Stock rear with 3.42 posi
C5 corvette front brakes, factory 91 z rear disks (HP+ pads and ATE superblue fluid)
weld in subframe connectors
Spohn tubular K-member

Suspension
boxed rear control arms
solid panhard bar
Factory 91 Z28 front and rear swaybars (not sure of size)
Eibach sportline springs (fronts cut 1 coil to level ride height after LS1 transplant)
no name shocks and struts from prior to 2003 when I bought the car.

Wheels/ tires
18X8 (245/40/18) front 18X9.5 (285/35/18) rear street tires. 200 treadwear

Be aware, I am not a rich man. changes only come slowly when I can scrape together extra cash. I need a priority list to tackle for best bang for the buck.

Questions:
1) I know I should replace the shocks/struts. should I jump straight to double adjustable or is there a less expensive option that will help?
2) Have I totally screwed myself up by cutting the coils on the Sportlines? What rates should I target?
3) Should I skip coils and struts and convert to coil overs?
4) Can I have a good setup for both track day and autocross without changes?

[RacingZ-44]

Over the weekend I took the Camaro out to the Midwest Musclecar Challenge (www.midwestmusclecarchallenge.com/).

I had a blast, however I now am much more humble about my driving ability.

I have the power, I have the brakes, now I am ready to begin improving the suspension on the Z.

This, is where you guys come in.

Usage
Street - 1-2 times a month to work or cruises
Track - 3 or 4 track day events per year
Autocross - occasionally

Details about the car:
1991 Z28 hardtop

LS1/T56 Stock rear with 3.42 posi
C5 corvette front brakes, factory 91 z rear disks (HP+ pads and ATE superblue fluid)
weld in subframe connectors
Spohn tubular K-member

Suspension
boxed rear control arms
solid panhard bar
Factory 91 Z28 front and rear swaybars (not sure of size)
Eibach sportline springs (fronts cut 1 coil to level ride height after LS1 transplant)
no name shocks and struts from prior to 2003 when I bought the car.

Wheels/ tires
18X8 (245/40/18) front 18X9.5 (285/35/18) rear street tires. 200 treadwear

Be aware, I am not a rich man. changes only come slowly when I can scrape together extra cash. I need a priority list to tackle for best bang for the buck.

Questions:
1) I know I should replace the shocks/struts. should I jump straight to double adjustable or is there a less expensive option that will help?
2) Have I totally screwed myself up by cutting the coils on the Sportlines? What rates should I target?
3) Should I skip coils and struts and convert to coil overs?
4) Can I have a good setup for both track day and autocross without changes?

Hi,
It seems like you have plenty of power and more than enough brakes, but the cut sportlines and the no-name shocks are holding you back. As far as the shocks, unless you have reason to believe you need to dial in the shocks to within an inch of their life, there is no real need for the double adjustable shocks, again unless you are doing some serious road racing but at 3 to 4 events per year, you aren't. The best option would be Koni Single adjustables, but even needing singles is debatable depending on who you talk with. Sometimes having that adjustability only hurts you because you actually have TOO many options for damping. Plus, they are more expensive than most and if you are on a budget, there are good options. For third gens, as you know, they take a strut in front versus shocks/springs all the way around. All that being said, the full set of Konis singles are about 650 from Strano but there might be better prices out there too. A good set of Bilsteins will serve you well for what you are describing. You can buy a set of standard bilsteins, no adjustment, for 679. The thing is the Koni's have to be adjusted off the car.
I drive a fourth gen with the Strano springs in F/R, they are 550# in front and 150# in the rear. I would shoot for at LEAST that spring rate. A lot of the guys who run at top events will tell you you need 900-1000 in front and maybe 250 on the rear. I still street drive mine so that spring rqte is way too high. With the 550/150 option and Koni singles, my car drives fantastic, is very competitive at the track, and I can still drive it home.
Skip the coil over set up as it's not necessary or worth the investment for the amount of racing you do.

The other thing is if you lowered the car with the cut springs, you technically need an adjustable panhard bar (not solid) to recenter the rear diff after lowering the car. With the car sitting level, measure the fender to tire distance on the rear end. They should be identical. If not, you need the adjustable pan hard bar to recenter the rear. Especially if you lowered it more than an inch or so.

And if you don't already have a "wonder bar" for your front subframe to stiffen up the steering box issues, you need to buy one first. That by itself will make the car drive and feel different immediately.

Anyway, just my .02 cents...

[trackbird]

Hey James! Good to see you around. That car is absolutely GORGEOUS!!! You should probably just call me one night and we can get you pointed in the right direction. I like setting up 3rd gens...

I'd avoid the coil over conversions. You can do the job with Ground Control stuff and not have to get too creative. Single adjustable Koni's work great on these cars. Get the 3rd gen front and rears (the monotube rears are quite good, and I like them better than the twin tube 4th gen shocks). 36mm hollow front bar (or a 35mm solid). 21mm solid/22mm hollow rear bar and I'd run a 1,000 in lb front with a 225 in lb rear spring (give or take). I found it ok on the street with that setup and my old 3rd gen was super balanced and easy to drive. Toss in a set of camber plates from Hotpart and you're done (and a good PHB, preferably with rod ends).

[TrakCar]

Hi,
It seems like you have plenty of power and more than enough brakes, but the cut sportlines and the no-name shocks are holding you back. As far as the shocks, unless you have reason to believe you need to dial in the shocks to within an inch of their life, there is no real need for the double adjustable shocks, again unless you are doing some serious road racing but at 3 to 4 events per year, you aren't. The best option would be Koni Single adjustables, but even needing singles is debatable depending on who you talk with. Sometimes having that adjustability only hurts you because you actually have TOO many options for damping. Plus, they are more expensive than most and if you are on a budget, there are good options. For third gens, as you know, they take a strut in front versus shocks/springs all the way around. All that being said, the full set of Konis singles are about 650 from Strano but there might be better prices out there too. A good set of Bilsteins will serve you well for what you are describing. You can buy a set of standard bilsteins, no adjustment, for 679. The thing is the Koni's have to be adjusted off the car.
I drive a fourth gen with the Strano springs in F/R, they are 550# in front and 150# in the rear. I would shoot for at LEAST that spring rate. A lot of the guys who run at top events will tell you you need 900-1000 in front and maybe 250 on the rear. I still street drive mine so that spring rqte is way too high. With the 550/150 option and Koni singles, my car drives fantastic, is very competitive at the track, and I can still drive it home.
Skip the coil over set up as it's not necessary or worth the investment for the amount of racing you do.

The other thing is if you lowered the car with the cut springs, you technically need an adjustable panhard bar (not solid) to recenter the rear diff after lowering the car. With the car sitting level, measure the fender to tire distance on the rear end. They should be identical. If not, you need the adjustable pan hard bar to recenter the rear. Especially if you lowered it more than an inch or so.

And if you don't already have a "wonder bar" for your front subframe to stiffen up the steering box issues, you need to buy one first. That by itself will make the car drive and feel different immediately.

Anyway, just my .02 cents...

Thanks for the reply.

1) I do have the Wonderbar, it had one from the factory.
2) I did check when lowering the car, the rear is still centered.
3) I believe the Eibach sportlines are 714# front with progressive rears. cutting the coil I believe gets me around 800#. I may be ok there for now. I thought I may need to lower the spring rate in the front.
4) the only reason I mentioned coil overs is I hate spending money twice. if I upgrade the struts now then plan to move to coil overs later I would rather just take the plunge. It sounds like they aren't worth it for me.
5) it sounds like just better struts and shocks will help, that will be my first move.

Thanks again for the reply.

[TrakCar]

Hey James! Good to see you around. That car is absolutely GORGEOUS!!! You should probably just call me one night and we can get you pointed in the right direction. I like setting up 3rd gens...

I'd avoid the coil over conversions. You can do the job with Ground Control stuff and not have to get too creative. Single adjustable Koni's work great on these cars. Get the 3rd gen front and rears (the monotube rears are quite good, and I like them better than the twin tube 4th gen shocks). 36mm hollow front bar (or a 35mm solid). 21mm solid/22mm hollow rear bar and I'd run a 1,000 in lb front with a 225 in lb rear spring (give or take). I found it ok on the street with that setup and my old 3rd gen was super balanced and easy to drive. Toss in a set of camber plates from Hotpart and you're done (and a good PHB, preferably with rod ends).

I'll give you a call sometime soon. I knew asking this board would be a good idea.

[CrashTestDummy]

Keep a close eye on that K-member. Few ever survive the stress road racing puts on them. I'd inspect closely at least once a year, and anytime the car 'feels funny'.

[TrakCar]

Keep a close eye on that K-member. Few ever survive the stress road racing puts on them. I'd inspect closely at least once a year, and anytime the car 'feels funny'.

Thanks. I have heard that before. I do a nut and bolt on the car each spring before I beat on it. So far so good after 5 years. However to be fair I really don't drive it that much other than track days.

[BumpaD_Z28]

Pics of the car ???

Just for reference I'm running 850# front 225# rear ground control "weight jacker" springs, rod ended rLCA's and PHR, with 36/24 sway bars and Koni single adjustable ... My rears or on car adjustable so I thnk that makes them the 4th gen version (I forget)

~Dave

[nape]

If you want to get serious about the street tire events, you'll want to upgrade to 18x11 all around so you can stuff 315s under there. That'd be your quickest upgrade.

Here's my suggestion for suspension setup for 200TW tires:
-800-900lb/in front springs, 150-225lb/in rear springs, 34-36mm front bar, 19-21mm rear bar.
-Koni Yellow struts/shocks.
-Unbalanced Engineering PHB relocation brackets (to lower the roll center, this will necessitate higher spring rates, probably 250-350 for STs.)

Coilovers don't work very well on the front without longer A-arms, you end up very camber limited.

[TrakCar]

I thought I would update the group.

I have the Memphis track Event this weekend. (autocross, HPDE, and drag race)

Changes for this event:
1) Swap the fleabay "racing" seat for a Sparco Evo
2) Added a power steering cooler since I was puking fluid out the cap after every session. (I know the best solution is a turn one pump, but they are on back order)
3) Re-route the clutch line off the header & flush/ fill the clutch system.

I am thinking about attending a SCCA autocross Test-N-Tune event Saturday May 31st. If I do then I believe the next step is to purchase and install KYB AGX shocks and struts. that will blow my budget for a while. It will be nice to have plenty of runs to change shock settings and see how it affects the car.

I do believe this will be a LONG term suspension tuning project.

I guess I need to start finding different size swaybars and possibly springs.

Mostly I need to get more seat time! I think autocross may be the cheapest/ only option I have to improve.

[TrakCar]

Pics of the car ???

~Dave

Pics, I got some pics.

https://flic.kr/p/nBeUjN

Of course the best pictures in that album aren't my car.

[Smitty2919]

That's my buddies brown C2 that you have a picture of!

He said it was a blast going that weekend.

[TrakCar]

I took the car to the F-body event last weekend. notes from the event:

car weight with 90% full tank and 185lbs driver

3420 with 57/43 front rear bias. I didn't get side to side.

1) 18" 285/ 245 rear/ front street tires suck on my setup. Loose as hell, no ability to pedal the throttle to control through a long corner. (sorry, best way I can describe it. I enter the corner as fast as possible, then use the throttle for weight transfer to get the car to "slide out" to the outside apex)
2) switched to 555r2 in 275/40/17 all around. no tread left so basically 100 treadwear slicks. The difference was amazing. balance was there, could use the throttle to control the car much better. I believe I went from 1m 24s to 1m 19.1s with no other changes.
3) second day it rained, so I switched back to the street tires. I switched front to rear though to see what the difference was. Much better balance on auto-x. not as much grip as slicks (go figure) best time w/slicks 57.56, best time on damp with street tires 58.51. I think both times could have been better.
4) I need better brake proportion. C5 z06 front. stock 91 discs rear are good, but too much front bias.

Plan for improvement:

1) Koni yellow shocks struts.
2) adjustable prop valve
3) 18x10 all around (285/35 front, 295/40 rear) I hate the way the 285/35 doesn't fill the rear wheel opening.

4) swaybars/ springs

[trackbird]

I'd run the same size tires on both ends. As you already found out, they balance much better on a "square" setup (all corners the same).

[Pablo]

2) Added a power steering cooler since I was puking fluid out the cap after every session. (I know the best solution is a turn one pump, but they are on back order)

Actually there's a much easier and cheaper solution to this isssue: http://www.rockauto.com/catalog/moreinfo.p...&cc=1095667

This is a p.s. pump cap from a mid 90s dodge truck. It has a rubber baffle on the stem (you can see it in the pic) that completely eliminated leaks on my car. I don't have a cooler either. I think the main issue is not that the fluid overheats but rather it just sloshes out of the cap under hard cornering. YMMV but it works for me.

[slowTA]

That's the same power steering cap I used on my TPI motor for a few years, it wasn't perfect but helped quite a bit.

[dailydriver]

2) Added a power steering cooler since I was puking fluid out the cap after every session. (I know the best solution is a turn one pump, but they are on back order)

Actually there's a much easier and cheaper solution to this isssue: http://www.rockauto.com/catalog/moreinfo.p...&cc=1095667

This is a p.s. pump cap from a mid 90s dodge truck. It has a rubber baffle on the stem (you can see it in the pic) that completely eliminated leaks on my car. I don't have a cooler either. I think the main issue is not that the fluid overheats but rather it just sloshes out of the cap under hard cornering. YMMV but it works for me.

Does this only fit older, 3rd gen, L98 type pumps, or will it work on the newer, LS1 style Delphi (??) pumps?

[Pablo]

2) Added a power steering cooler since I was puking fluid out the cap after every session. (I know the best solution is a turn one pump, but they are on back order)

Actually there's a much easier and cheaper solution to this isssue: http://www.rockauto.com/catalog/moreinfo.p...&cc=1095667

This is a p.s. pump cap from a mid 90s dodge truck. It has a rubber baffle on the stem (you can see it in the pic) that completely eliminated leaks on my car. I don't have a cooler either. I think the main issue is not that the fluid overheats but rather it just sloshes out of the cap under hard cornering. YMMV but it works for me.

Does this only fit older, 3rd gen, L98 type pumps, or will it work on the newer, LS1 style Delphi (??) pumps?

I don't know. The cap is the same as the stock cap except for that baffle, so if an older stock cap fits you are good. If anything, it's only a couple of bucks so it might be worth the gamble to you to find out.

This post has been edited by Pablo: Jun 2 2014, 07:34 AM

[slowTA]

The cap will fit but the dipstick part is too long.

When I bought the cap I noticed the dipstick was a bit different, so I just swapped the rubber washer on to the original cap. But 4th gen dipsticks are a slightly larger diameter.

[gscherer78ta]

And if you don't already have a "wonder bar" for your front subframe to stiffen up the steering box issues, you need to buy one first. That by itself will make the car drive and feel different immediately.

Anyway, just my .02 cents...

Curious- What is a "wonder bar"? Sorry if this is a stupid question but I've not heard that term before.