high speed handling (and low speed cornering) suspension parts

Hey - i have a 96 z28 M6 (bone stock suspension for now) - and i'm just going to do a suspension upgrade before anything else. I was thinking of the SLP Stage One upgrade with reinforced panhard rod and LCA's ($750 isn't a bad price :) and some Home Depot subframes (just find out where to weld them first) with RK Sport 3-point strut tower brace, but I want to know what you all think? Also, I plan on going with SLP Headers next for my 96 (straight bolt-in - no replacement Y-pipe .. i already have SLP Loudmouth), so i dunno if i'll have clearance issues with the 1" drop from the Stage One package. If any of you have input, I'd like to hear it!

thanks!

oh yeah, I'd like to keep the suspension cost under a grand if at all possible :)

Oh yeah, speeds I'm talking about (handling-wise) are in excess of 90+ .... :)

thanks again!

i don't think the SLP package will cut it. i have their 1LE RLCAs which are cheap, but just stamped steel parts. You'd be better off getting some stronger cylindrical type RLCAs, same for their 1LE panhard rod bar, just stamped steel. i recently replaced it with a BMR adj panhard rod and their bolt-in RLCA brackets and the rear handling improvement was noticeable with just the addition of those two.

i'm also running Eibach Pro kit and Koni SA (no complaints there), so the car is lowered 1.25" and the brackets ARE NEEDED. For real.

also, for road racing, i've heard the stock rear sway bar will not cut it and the 1LE front sway bar will be barely adequate.

oh yeah, the most important mod is... subframe connectors. double diamond even better. should be done first.

What about the shocks and springs they use for the package though? The Eibach springs and SLP Bilsteins ... aren't those good? i mean - if i go ahead and buy the slp bilsteins and eibach springs, i'm already looking at $600-650 ish ... so why not just pay another $100-150 and get the reinforced LCA's and panhard bar - then just sell them later after i get something better?

Actually I am very happy with the Level 1 on my T/A. It is faster and easier to autox than my '98 1LE Z28 was, and while the 1LE was more stable at extreme speeds; I attribute that to the Koni shocks over the SLP Bilstens. I plan to replace the front shocks with Koni's next year.

For all but the most hardcore road course use, the Level 1 is a great street/autox suspension.

Check the GP forum at ls1.com for a great deal on this suspension. I would avoid the reinforced LCA's and panhard as they have poly bushings which will bind if not cleaned and lubricated often!

For serious road course use, I would suggest Koni SA's, LG springs, LG poly/rod end LCA's and panhard, LG torque arm and a 32mm 1LE front bar. Stick with the 19mm rear bar.

If you are looking for high speed handling then unfortuately the most important improvement is the most expensive; shocks. Without them you will never have the stability you need. I too use Koni SA shocks with Eibach prokits , not the ideal setup due to the Eibach's progressive rate ( mine are the older 360-600 lb/in kind) but I have heard some people are happy with Bilsteins but they will need to be re valved if you are going to use a better spring. I have no problems with the 1LE LCAs but do recommend a better panhard rod. BTW 1LE parts are all rubber and not poly. I am not a fan of any poly in a LCA unless the other end is a heim joint.

Subframes , which I highly recommend , are more important to keep your car together than to improve handling. They may improve handling but I got mine on my car within a few months of buying it and before I ever really got to test the handling capabilities so I'm not sure they help the actual handling.

Yes, the 1LE LCA's and PHB use a higher durometer rubber bushing, the SLP reinforced arms use poly bushings.

Does RK Sport sell a 3-point STB? I thought they only sold the Hotchkis ones and those are two point. The Edelbrock and KB's are three points.The cowl attachment point is a lot more important because there is more front to back flex than side to side, at least in 4th gen cars that don't have struts. The LG's 4 point can work too, though IMO they don't attach to the optimal point on the cowl.

to MrBigXL
I got a notice from the com staff that you replied to this post but it never showed. ???

you said: "slp bilsteins and eibach springs, i'm already looking at $600-650 ish ... so why not just pay another $100-150 and get the reinforced LCA's and panhard bar - then just sell them later after i get something better?"

okay, but good RLCAs and panhard rod from BMR will cost just a little more. don't forget the brackets if you lower the car. but you also said you wanted to road race at 90+ mph.

Do you mean attending some 'track days' or lapping sessions?

Several things to remember: real road racing is EXPENSIVE and will require massive brakes, roll cage, rod-end suspension pieces, etc. a daily driver will never cut it. also recently read of the danger of driving around town with a roll cage and no helmet.

For all around driving and decent autox, the SLP Stage 1 is OK. I guess that sort of answers your question. My first post of it not cutting it was based on your 90+ mph road racing comment.

I really don't think stock brakes will last too long if you push em like that.

As the others have said, get the Koni's. I would strongly recommend doubles over singles, especially for road racing. On the spring front note, the SLP level 1 springs (which I've used) are not as good as the Eibach Pro Kit (also used). The ideal spring though will be strait rate (using now). The rates will vary based on use and which swaybars you use.

On the suspension member front, I would hold off until you can purchase LCAs and PHR with rod ends. Poly bushings in either the LCAs or PHR will cause binding which is the last thing you want in any racing situation. Also make sure that the company you purchase from uses good quality 3 piece rod ends (Aurora, FK, QA1) or they will wear out VERY quickly.

As Mr Big noted, you need to decide what you are looking for. If it is a track car for lapping and street driving, I'd recomend the following package based on my experience:

Springs 800 front, 125 rear
bars 32mm Addco front, 24mm GM rear (21mm adjustable would work better for a little more $$)
Shocks Koni Doubles
Rod ended PHR and LCAs
LCA brackets
Torsen T2R differential
shorter than stock torque arm
SFC
Roll bar (not a full cage but a good idea for rollovers at the track)

That would be a good start anyway. In my opinion, decide what you want in the end and save your $$ for those parts. Don't waste your time and money on intermediate steps or you'll have a garage full of "extras" that you'll never use like I do ;-)

Jason S.

Springs 800 front, 125 rear
bars 32mm Addco front, 24mm GM rear (21mm adjustable would work better for a little more $$)
Shocks Koni Doubles
Rod ended PHR and LCAs
LCA brackets
Torsen T2R differential
shorter than stock torque arm
SFC
Roll bar (not a full cage but a good idea for rollovers at the track)


OOoooo! I want this stuff too!! esp the T2R (still planning that one) :bow:

If you would like help, let us know. We have setup many road race and autox 3rd and 4th gens. My '96 SS SCCA SM autox car currently has the following:

650/300 springs
Koni Doubles (custom valving in the rear pair)
Unbalanced Engineering LCAs
Unbalanced Engineering PHR
Unbalanced Engineering PHR lowering brakets
32mm Addco front swaybar
Unbalanced Engineering adjustable 21mm rear swaybar
GW Track link (soon to be replaced with a UE unit)
GW subframe connectors
Unbalanced Engineering LCA brackets
T2R
Autopower roll bar
315 Kumo's on all 4 corners
98+ front brakes (soon to be replaced by the light weight UE setup)
GTP Stage II heads
Ultradyne 230/238 .565/.565 cam

Jason S.

Originally posted by MrBigXL
Springs 800 front, 125 rear
bars 32mm Addco front, 24mm GM rear (21mm adjustable would work better for a little more $$)
Shocks Koni Doubles
Rod ended PHR and LCAs
LCA brackets
Torsen T2R differential
shorter than stock torque arm
SFC
Roll bar (not a full cage but a good idea for rollovers at the track)


OOoooo! I want this stuff too!! esp the T2R (still planning that one) :bow:

Whew, that's a lot of front spring and a lot of rear sway bar IMHO. FWIW, Koni themselves start to get leary about running much more than 600's with their shocks in off the shelf form. I've held totally blown Koni's in my own two hand that were run with 800's, it was ugly, and the scariest part was the spring was so stiff it was not apparent clearly the shocks were toast. I, quite frankly think the 500 spring/35 bar setup works quite nicely on the track.... But some guys want to control the brake dive more, and so we may run up to 600 (some have 650's) with a Addco 32mm bar. But I don't personally think that 800's are needed. More than doubling GM's speced springs for the 1LE (meant to Showroom Stock racing, though the 4th gen never did). Also, DA's have no warranty which may be of some interest to someone.

A 24 rear bar is ton. I'd sooner run more rear spring than that much bar. Granted the T2R is a sweet piece and gets power down anyway, but less rear bar would tighten the car up off of corners (especially tight ones) because: You wouldn't have the inside rear so light, therefore it doesn't get torched as easily, and the Torsen doens't have to bias torque to the loaded (with cornering force) rear tire to keep traction. Result, less power oversteer. Also, you can't shorten a 21mm if adjustable bar enough to equal a 24. If you think an adjustable 21 would be better than a straight 24, a 22 (Addco) may be more suitable. I should note that you can get bars in every diameter from 17-25mm *except* 20mm for the rear of an f-body.

I also don't believe in shorter than stock torque arms. In ever experience I've had with them, they singnificantly change the instant center (by design), which helps for launching, but does effect the turning. I've never had any luck with them, and with the advent of the T2R haven't needed to mess with them anymore. When a torque arm is needed, we use Random Tech arms......

Just my ever so humble opinion....

Hey Sam,

I just wanted to say congrats on the nationals win in ESP this year (hadden't had a chance to do that yet). After many conversations with Jeff at Pro Parts, I'm aware of Koni's thoughts on more that 650lb springs in conjunction with their stock valving. In the grand scheme of things compromises must be made or we'd be on Penke/OLN Triples. I really do wish there was a more robust double adjustable shock out there for those on a budget (myself included) but I don't think the robustness of other shocks makes up for their lack of adjustability when seting up a car. As far as the warentee goes, most race parts don't have them so it isn't something that enters my mind often. You have to pay to play right? ;-)

As for the rear bar, I have yet to have issues with unloading the inside rear wheel, especially with the lowered rear roll center. Even without, I have not seen issues with wheel spinup on non-T2R equiped cars (my road race car included).

A shortened and adjustable 21mm rear bar can be as stiff as an unshortend 24mm rear bar. Try out the deflection calcs yourself if you don't believe me. They work out everytime I run them, not to mention the testing proves the calcs out.

On the torque arm front, the real beauty of the whole torque arm rear suspension is that the length of the torque arm does not factor into the roll center position. Anti-squat and roll center can therefore be delt with indipendantly. In my experience, and again the theory bears this out, there is no difference mid corner, but there is a big difference on corner exit and entry. Granted on corner entry a shorter arm is undesireable, so this implies that an uncoupled torque arm is the best design.

Wow, I did a lot of disagreing with you there Sam. I don't want to offend, I just have a different opinion I guess.

Jason S.

Originally posted by UnbalancedEng
Hey Sam,

I just wanted to say congrats on the nationals win in ESP this year (hadden't had a chance to do that yet). After many conversations with Jeff at Pro Parts, I'm aware of Koni's thoughts on more that 650lb springs in conjunction with their stock valving. In the grand scheme of things compromises must be made or we'd be on Penke/OLN Triples. I really do wish there was a more robust double adjustable shock out there for those on a budget (myself included) but I don't think the robustness of other shocks makes up for their lack of adjustability when seting up a car. As far as the warentee goes, most race parts don't have them so it isn't something that enters my mind often. You have to pay to play right? ;-)

As for the rear bar, I have yet to have issues with unloading the inside rear wheel, especially with the lowered rear roll center. Even without, I have not seen issues with wheel spinup on non-T2R equiped cars (my road race car included).

A shortened and adjustable 21mm rear bar can be as stiff as an unshortend 24mm rear bar. Try out the deflection calcs yourself if you don't believe me. They work out everytime I run them, not to mention the testing proves the calcs out.

On the torque arm front, the real beauty of the whole torque arm rear suspension is that the length of the torque arm does not factor into the roll center position. Anti-squat and roll center can therefore be delt with indipendantly. In my experience, and again the theory bears this out, there is no difference mid corner, but there is a big difference on corner exit and entry. Granted on corner entry a shorter arm is undesireable, so this implies that an uncoupled torque arm is the best design.

Wow, I did a lot of disagreing with you there Sam. I don't want to offend, I just have a different opinion I guess.



No offense taken.... Obviously we have very different thoughts on the subject. :) And thank you for the congrats on the ESP win... Between that and my ProSolo title in my FS car, it was a gooood year for me in F-bodies! :D

Now back to your regularly scheduled debate!

The trouble with running the Koni's with higher spring rates than the shock is speced for is simply, it eventually blows them up.... Not really any different than running a stock shock or a cheapy off the shelf part with heavy lowering springs. The recoil of the spring eventually breaks the shock..... Now a Koni is pretty robust, and likely would last quite a while if it was valved to handle a heavy spring like an 800. I'm not saying you can't use a Koni and/or a heavy spring, it's just that *if* I ran such stiff springs, I'd certainly have revalved the Koni's accordingly. 'Course, I wouldn't run that stiff a spring...... A warranty may not be a big deal to you with a tracked car, but I'd be willing to be it might matter to others. :)

I'm very suprised you haven't had a problem with wheelspin.... Although it does lessen with road speed and higher gears. However, you also have a shorter torque arm and a lower rear roll center, both of which I assume were done to help the wheelspin, at least partially???? The T2R works so well that it makes having to go with short torque arms and such a lot more of a choice instead of a Must-do.

If a sway bars stiffness is it's diameter to the 4th, that means that roughly a 24mm bar is about 40% stiffer than a 21 with the same length arms (unless my math is really bad...). In order to make a 21mm bar 40% stiffer, you have to shorten the arm length a like amount. Now a rear bar on an F-body has an arm length or about 10", shorten it 40% and you'd have to be at about a 6" long lever arm to get a similar roll stiffness.

To finish, I just wanted to address you last paragraph.... I agree that shorter arms generally help corner exit traction. However, they do it at the expense of front grip. Basically we can make a car get power down really well, but the pwoer on balance usually sucks. To compensate, one has to stiffen the rear end (ironically taking mechanical grip away again). I personally prefer to make the car work (balanced) as best I can without giving away mechanical grip. The use of a really good differential largely negates the need for trick torque arms, etc...

Sam,

While we're on the subject of differentials are there any problems with running a T2R on a daily-driven, street car on street tires?

I would also like to congradulate you on your sucess at Nationals! :bow:

Also FWIW I do appreciate you posting here and on LS1.com. Its really nice to run across someone with so much experience who is willing to share :cool:

Originally posted by 01 FS Z28
. . .
If a sway bars stiffness is it's diameter to the 4th, that means that roughly a 24mm bar is about 40% stiffer than a 21 with the same length arms (unless my math is really bad...). In order to make a 21mm bar 40% stiffer, you have to shorten the arm length a like amount. Now a rear bar on an F-body has an arm length or about 10", shorten it 40% and you'd have to be at about a 6" long lever arm to get a similar roll stiffness.
Congrats, Sam.

Back to the tech . . .
Sway bar stiffness is also partly a 2nd power function of arm length (for the end of arm displacement effect of the torsional part of the bar) and partly a 3rd power function (for the bending of the arms themselves). That puts the arm length for the 21mm equivalent of a 10" arm 24mm bar somewhere between about 8.5" and 9".

Norm

Originally posted by Soma07
Sam,

While we're on the subject of differentials are there any problems with running a T2R on a daily-driven, street car on street tires?

I would also like to congradulate you on your sucess at Nationals! :bow:

Also FWIW I do appreciate you posting here and on LS1.com. Its really nice to run across someone with so much experience who is willing to share :cool:

:o Thank you.

I drive my '91 car all over the place with a T2R in it. No problems what-so-ever. One word of warning though..... Because it is a high bias differential and our cars have as much punch as they do, you do have to pay attention in the wet. Nothing violent, but it will step out under power pretty damn easily in low-grip conditions because it torque-biases so much...... We've got units running around with well over 20k miles an not a lick of trouble.

And I enjoy (usually) posting to these boards. It's nice to communicate with others who have similar interests, and for some reason you guys don't carry a "internet mechanic" chip on the shoulder like a lot of other list's members do. :cool: Some poeple you can't discuss anything with.....

I would like to chime in and thank you guys for having discussions like this. I have nothing to add, but I learn a lot from those that do!

:bow: