I am interested in "ultimate" street suspension set-up. Is the T1 "factory" package as good as it gets? Are HAL adjustables a suitable shock upgrade with this suspension, considering $$$, or are Penskes the "only" way to go? Opinions, based on "real world" experience, would be greatly appreciated.
Thanx
In considering suspension changes for the C5/Z06 there are some basic goals that you should be aiming for and should have a basic understanding of the stock suspension and its limitations.
From the factory the car is dialed in for good handling and safety for the common driver. It is by far marginal for track use but has great potential if tuned correctly.
It is too high.
There is too much body roll
There is too much understeer.
Initial turn in is poor, grip could be much better.
It will snap spin if overcorrected too much
There is too much dive under hard braking
Power cannot be laid down as quickly and effectively as it could
Early shocks and shock dampening were poor.
The basic "Zero" scrub suspension is great and has a lot of potential
1. Lowering the car is the first thing that needs to be done, which is even recommended by the tape you get from Chevy. Lowering past the factory recommendations is necessary for track use. For this the front spring perch bushings need to be have 2/3 removed and you will need longer rear spring bolts. Hardbar makes a nice Titanium set. Lowering drops the Center of Gravity and the Roll Center. Lowering for competition (past the factory recs.) will cause the car to be a pain to drive on some roads that are bumpy.
2. Alignment needs to be more aggressive. How aggressive you get towards a full competition alignment depends on what you are using the car for and what tires you are using. You should at least dial in more negative camber in the front and rear and a touch more Toe IN in the rear. Always get as much positive caster without sacrificing camber.
Corner weight the car to check the cross corner weight % and balance of the car. Make the car as light as possible and shift weight as far right and rearward as possible. Reduce rotational mass where ever possible.
3. The factory T1 kit is a good step forward. The T1 bars are great but stiff and may be harsh on the street. The T1 springs are stiffer but result in a higher ride height. The T1 shocks are stiffer but are tuned to work with ALL of the other T1 parts. They do not work well with themselves.
4. The '04 shocks are an improvement.
5. The problem with almost all OEM and aftermarket shocks are that the shafts are too long for a lowered car. I would NOT consider the HAL shocks. Koni's are a great shock but with only marginally shorter shafts. Penske's, Moton's and JRZ's are the only shocks that come with appropriate short shafts.
Although they all are expensive I prefere the Penske Double Adjustables as they are rebuildable, revalvable, can be upgraded to coil overs, can be upgraded to the triple adjustables, are upside down...ie the shock body is mounted up to reduce unsprung weight, have reservoirs, are US made, are proven, can be customized to any spec, and bump and rebound can be easily tuned on the car. For a street suspension I would recommend the DA's. The best thing I like is that you can use them on the street, then make 2 quick adjustments and they are set up for the track....this is wonderful on a dual use car. I would not go coil over unless I was very serious about competition.
(NOTE: If you are competing in SCCA T1 then all you can use is either OEM or the T1 kit)
6. I like the VB&P Extreme front spring instead of the T1 spring and possibly the rear Extreme spring as well.
7. VB&P also makes a nice poly graphite suspension bushing kit as does Doug Rippie & LG Motorsports. Note: the T1 A-Arms have better bushings but are the same as OEM A-Arms. You can replace the bushings in the OEM A-Arm.
8. VB&P also have better ball joints
9. There are hemijointed kits for the tie rod ends to reduce bump steer induced by lowering.
10.Increasing the tire width in front relative to the rear will increase turn in and front grip and reduce understeer.
I haven't had to replace any of the hemi joints as yet. Mine are all teflon lined.
Penske shocks are the 8100 series and are monotube racing shocks.
Vette Brakes & Products
I have not modified the A-Arm mounting points. (I am not allowed to in the classes I race and there is really no need to) The VB&P Extreme front spring, lowering and upgrading the OEM Brakes reduces the dive under braking and lowers the stopping distance.
F/R should be near 51%/49% or tighter
FL heaviest, RR lightest, my overall weight is 3041#
Cross weight %'s should be within 1.0%-0.5%, they are the most critical
Do not forget, besides a correct alignment, wheels and tires are one of the most important suspension componants.
If the car is dual use then you will have to mark the street alignment and the track alignment and switch at the track.
Here are my (starting) settings
Front: Street/Track/AutoX
Camber: -1.0 to -1.5/-1.8/-2.4 (degrees)
Caster: as much positive as you can get
Toe OUT: 0.0"/ 0.0 to 1/16" each/ 1/8" each, max total 1/4"
Rear:
Camber: -1.0/ -1.3/ -1.5 (degrees)
Toe IN: 1/16"/ 1/8"/ 1/4" each, max total 1/2"
Note that low speed AutoX has the most extreme maxed out negative camber and toe settings. The track and autoX settings will prematurely wear street tires very quickly.
I run Hoosier tires for track and AutoX, 305/30x18 in the front and 315/35x17 in the rear this equalizes the tire contact patch area, puts more grip in the front and aids turn in. Also with a stiffer side wall (30 aspect ratio) the tire response is much more crisp. They also resist the braking dive much better. The 35 aspect ratio in the rear allows the car to squat under hard acceleration which aids traction. The car is neutral in handling.
Wheels are polished CCW's (Complete Custom Wheel), 18x11 and 17x12. These come with the maximum allowable positve offset for SCCA competition (+0.25"/wheel)
Heim joints can make some minor noise when the bars are not being torqued but definetely worth it. I am not lowered and do not get ANY body roll with the T-1's. I have had them on my car for 3 years now and not had to change the heim ends.
__________________
RICK 99 FRC, LPE C5-R 427 TT from 21st CMC, LPE Minitubs, Boost Controller. A ZO-6 Prototype. Born: 12/3/98 725 RWHP 800 TQ
I still have my true line laser and caster/camber gauge from the racing days so setting alignment will be a piece of cake.
Everything that you are doing makes sense, I do have a couple follow ups...
How much ballast did you have to add to get there? Any suggestions on attachment?
I had been looking at brembo's but I see that both Alcon and Wilwood make kits as well, any thoughts? I don't want to go the dilled or slotted route, I had a real bad experience with drilled rotors, just a nice serving plate sized floating disc-
How do these kits work with the ABS?
Any tire compound suggestions? Or are these sizes limited to one compound?
I assume that the CCW's have the best strength/weight/cost ratio?
5. The problem with almost all OEM and aftermarket shocks are that the shafts are too long for a lowered car. I would NOT consider the HAL shocks. Koni's are a great shock but with only marginally shorter shafts. Penske's, Moton's and JRZ's are the only shocks that come with appropriate short shafts.
Although they all are expensive I prefere the Penske Double Adjustables as they are rebuildable, revalvable, can be upgraded to coil overs, can be upgraded to the triple adjustables, are upside down...ie the shock body is mounted up to reduce unsprung weight, have reservoirs, are US made, are proven, can be customized to any spec, and bump and rebound can be easily tuned on the car. For a street suspension I would recommend the DA's. The best thing I like is that you can use them on the street, then make 2 quick adjustments and they are set up for the track....this is wonderful on a dual use car. I would not go coil over unless I was very serious about competition.
Why would you not consider the HAL shocks? I have a set on my car and I've also had Koni's on another car. The HAL shocks are 12 point adjustable, which is much better than a Koni. Those Penske's and Moton's are nice, but they cost way too much $$ for the common man. What gives?
You mentioned that the Z stock has way too much understeer. If anything, I feel like it may have to much oversteer. I have longer bolts in the rear and have cut 3/4 of bushing to the front. I am constantly seeing more and more that the back end gets real loose going around tight turns. It happened to me last night. I have been playing with tire pressure and right now I have about 35psi front and rear. What are you guys running.
This may be due to the F1's not being hot due to the cold temps outside but it was damn scary when the back end whipped around.
How do you recommend reducing overstear in my car. I am considering Hotchkis or T1 sway bars. Maybe this will increase understeer a little. I definitely need better tires.
__________________
You'll never soar like an eagle, if your surrounded by turkeys.
DaveGP if you have adjustable shocks just incress your compression on the front or turn down the rebound on the rear. You could raise the rear 1/4 in or dial in a little more toe in the rear. A stiffer front sway bar or softer rear bar or like GM just did try changing the bushing on the bars harder front softer rear.
__________________
2001 Torch Red, SCCA Solo ll Specs.
02 Audi Allroads 2.7TT RS4spec. 03 Range Rover
86 K100RS Carmra Moto. 05 R1200GS been to Alaska
What exactly would raising the rear a 1/4 in do? My rear is low but not too low. The car sits pretty evenly front to rear. Does dropping the rear end make the sway bar stiffer by applying weight????? This may cause the rear to be stiffer than the front enducing oversteer.
I do not have adjustables. Was going to go with Bilstein and T1 swaybars.
Penskes DA's are far superior with a larger monotube design & shaft which is inverted to save unsprung weight. Penskes have 6 Bump settings and up to 28 rebound settings; in addition they can be adjusted with Nitrogen pressure. They also have reservoirs with almost double the amount of fluid availavble than a Hal shock has, which is critical to performance. In addition they can be upgraded to triple adjustble and coil over very easily. If you really want to get crazy a "third spring" which is completely adjustable and can tie 2 or 4 shocks together into a completely Active System can be added as well. "Weight Jackers" can also be added to the Penske system.
My impression are that Hal's are an upgrade street shock where as Penske's are truley a racing shock.
David GP: The oversteer you are experiencing is probably a function of the tires and poor rear traction or bite.
The static understeer I was referring to is on Turn IN and Mid Corner. Mid Corner only and not Turn IN understeer can be corrected with the throttle but the cornering speeds and corner exit speed is lower.
It is quite possible to rotate the Z06 with throttle and torque and counter act understeer and if its done too aggressively oversteer can be induced. If then this oversteer is overcorrected the car will snap spin very easily in the opposite direction.
It is much better and faster to correct the problem by tuning the suspension than by having to correct it in mid corner and turn exit every time.
Originally posted by DJWorm Hal shocks are probably OK for the street.
Penskes DA's are far superior with a larger monotube design & shaft which is inverted to save unsprung weight. Penskes have 6 Bump settings and up to 28 rebound settings; in addition they can be adjusted with Nitrogen pressure. They also have reservoirs with almost double the amount of fluid availavble than a Hal shock has, which is critical to performance. In addition they can be upgraded to triple adjustble and coil over very easily. If you really want to get crazy a "third spring" which is completely adjustable and can tie 2 or 4 shocks together into a completely Active System can be added as well. "Weight Jackers" can also be added to the Penske system.
My impression are that Hal's are an upgrade street shock where as Penske's are truley a racing shock.
David GP: The oversteer you are experiencing is probably a function of the tires and poor rear traction or bite.
The static understeer I was referring to is on Turn IN and Mid Corner. Mid Corner only and not Turn IN understeer can be corrected with the throttle but the cornering speeds and corner exit speed is lower.
It is quite possible to rotate the Z06 with throttle and torque and counter act understeer and if its done too aggressively oversteer can be induced. If then this oversteer is overcorrected the car will snap spin very easily in the opposite direction.
It is much better and faster to correct the problem by tuning the suspension than by having to correct it in mid corner and turn exit every time.
I know you have more knowledge regarding shocks and Z06's, but I can tell you the HAL's are a solid upgrade and fine for mild track use. I don't compare these shocks to 3k coil overs because they're not in the same league. I compare these shocks to Koni's, which I feel they compare well against. My Koni's were more expensive and not better than my HAL's. As you pointed out, there is a street setup and a total racing setup. I bought these shocks because I like having the ability to adjust my shocks without taking the wheels off.
Does dropping the rear end make the sway bar stiffer by applying weight????? This may cause the rear to be stiffer than the front enducing oversteer.
When you lower the rear you preload each end of the swaybar equally. It's for this reason that adjustable endlinks are used. You can adjust the length of the endlink/s and thereby remove any preload.
With the driver or an equal amount of weight in the drivers seat you can remove or add preload on a swaybar by shortening or lengthening an endlink as necessary. This is done in conjunction with a good alignment while using scales. Note: you are not physically moving components such as the battery (or adding weights in the form of ballast) but just equalizing the weight distribution as much as possible.
Quote:
What exactly would raising the rear a 1/4 in do? My rear is low but not too low.
You need about 1/2" of rake on the car. That is you want the rear about 1/2" higher than the front. This is necessary to prevent lifting at speed. You don't want to go too low on either end because you run the risk of having the shocks bottom out. Not only does this increase ride harshness but when a shock bottoms out it effectively increases the spring rate on that end. This can induce sudden under/oversteer on the affected end. It's as if you suddenly had an ultra stiff spring. If on the rear you get oversteer, on the front, understeer. It's also hard on the shocks.
Regarding HAL shocks there was a thread on another forum where someone had a bad experience with them. Apparenly the lower front shock mounting holes (the holes through the "dogbones") were enlarging to such a degree the shocks became loose at the mounts.
No Doubt, I see where you are headed with the bar preload
DJWorm, how did you get those cross % without adding RS ballast, unless you are much skinnier than I am... hmmmm, after looking down at my waistline my bet is that you probably are...
Did your wheel/tire recommendation require rear tubs?
Has anybody measured and run the #'s to get front and rear roll centers on the stock suspension?
LG Motorsports has this coil over package. I did the testing and shock valving myself. It eats the bumps and is very well balanced. I ran a 2:24.xx with them at Road America in Elkhart lake just recently.
They are a direct fit bolt in, with no modification necessary. they eliminate all the rubber in the shocks and use a sphearical bearing at each end of the shock and bolt up the the stock points.
We also use Hypercoil springs which are the best there are.
The shocks are an aluminum threaded body Bilstein Gas filled shock with custom valving. They allow for total corner weight % adjustment.
The price for the full set up is $2195.
We will also have a complete monoball bushing replacement kit for the lower A arms within 3 to 4 weeks.
Thanks.
Lou Gigliotti LGM
972-272-7753
__________________
Last edited by L G Motorsports : 11-22-2003 at 07:43 AM.
AutoForums.com is the premier network of enthusiast-owned
enthusiast-operated automotive communities.
We operate more than 100 automotive forums where our users consult peers for shopping information and advice, and share
experiences and opinions as a community.
Linear Mode
