Sway bar install tips for C4?
02-10-2009, 07:20 PM
#1
Race Director
Thread Starter
Sway bar install tips for C4?
I've got some new aftermarket large sway bars to install and want to set them up correctly. I've done some searching and found some old posts about this. I thought I'd consolidate them here for easy reference. Does anyone know if these tricks work on all C4 years?
Vetracr - Add shims under sway bar mounts to adjust how fast bars respond.
Put a 1" spacer block between your frame and the bushings on the front of your car? If not, you may want to look into putting one on since you are working on making your sway bars more effective. I can't explain the benefit to the block, but Guldstrand sells them with their poly bushing kits and there is an apparent benefit to changing this geometry. If they say it works I don't doubt it.
Jackdaroofer - Here's another, maybe more important consideration if you are moving up to a bigger bar, particularly the 30mm in the front.
The end link bushings on the bigger bar will be further back than on your existing bar.
The vertical links will have to be forced rearward to link up with the bar. This puts them out of the vertical plane and can cause a bind on the lower control arm.
After much searching, I decided to cut the top two "tabs" (ears where the bolt goes through) off the vertical link and move them rearward on the square tube of the vertical link and reweld them. If you move them back so that the rear edge of the tabs lines up with the rear edge of the square tube (approx 1/4") you will have proper alignment.
NavyVet - the sway bar should move relatively freely up & down. A "trick" is to use alignment shim(s) to space the outer sway bar bushing shell away from the frame when you bolt it down. The bushing for the bigger (i.e., 30mm) bar tends to "crush" a bit in the factory shell making the bar very resistent to movement. Space as necessary so it moves up & down freely (not sloppy loose, but moves with only very moderate force). I learned this from a SCCA Nat'l Champion Vette AX'er who learned it from a multi-time champ in Vettes. Since their cars handle like they do, and they've studied this science more than I have, I tend to follow their lead and take advantage of their experience.
As Vetracer said, the factory end links are fixed, so they are only going to be at one height relationship with the lower a-arm, therefore it shouldn't matter where it's sitting when you tighten them - just so they move. Being so tight that they resist movement is partially defeating the function of the shocks and limiting the reactiveness of the suspension as it tries to keep the wheels on the ground. The one inch blocks tend to make the moving end more horizontally in line with the a-arm versus the factory position where the end is a bit more raised. Horizontal is one goal. No preload on either side is the other (unless doing serious corner weighting exercises that go beyond most people's capabilities and/or needs). The only way to achieve zero pre-load at normal weighted ride height is with adjustable end links.
Vetracr - If you look at the bend in a smaller, say 28mm front bar like the one that came on my '86 that I relpaced wit a 32mm there is a noticeable lack of bend in the larger bar. That means the sway bar is tilted down toward the end link, and is much more resistant to "bending" as it should which limits the travel of the lower "A" arm and of course everything attached to it like the wheel and tire. Sorta like the folding legs on a table, it hinges and jams.
The blocks prevent this from happening by lowering the front of the sway bar.
The Bus - Shim the front sway bar 3/16" from the frame mounting using washers. This improves turn in.
Solofast - Get the Koni Sport shocks for your 89. I am assuming that you have the Z51 suspension and the Koni's were developed specifically for the 89/90 Z51 springs and sway bars, I know, I did the development driving and selected the valving with Dean Dodge (who was then with KONI) and we tested them on my 89. Set the rears to full soft, or close to it, and expect the fronts to be about in the middle of the adjustment range. That way you can tune the car between runs quickly since you are just spinning the **** a quarter of a turn either way to fine tune the car....If you don't have the Z51 bars, springs and control arms you will likely need to get them to be competitive in A/S on a national level.
One last tip that was often an "Unfair Advantage".....The sway bar on the front of the C4 is huge, and a lot of the compliance in the swaybar system is in the bar mount bushings. You can make a HUGE HUGE difference in how stiff or soft the bar is by preloading of softening the preload on those bushings.....If the car is loose, you can stiffen the front bar by putting a large (1.5-2 inch) diameter washer on top of the rubber and clamping it in tightly. The extra preload will make a huge difference in front roll stiffness. If the car is pushing you can put an alignment shim or (in extreme conditions 2 shims) in between the two halves of the front bar bracket to soften the front bar. If you put a cable tie on the washer and on the shims, you can pull them out or put them in in less than two minutes....that is easily done between runs if you need to. It can turn a local event into a test and tune....If you doubt it, try it and you will be truly amazed....
Vetracr - Add shims under sway bar mounts to adjust how fast bars respond.
Put a 1" spacer block between your frame and the bushings on the front of your car? If not, you may want to look into putting one on since you are working on making your sway bars more effective. I can't explain the benefit to the block, but Guldstrand sells them with their poly bushing kits and there is an apparent benefit to changing this geometry. If they say it works I don't doubt it.
Jackdaroofer - Here's another, maybe more important consideration if you are moving up to a bigger bar, particularly the 30mm in the front.
The end link bushings on the bigger bar will be further back than on your existing bar.
The vertical links will have to be forced rearward to link up with the bar. This puts them out of the vertical plane and can cause a bind on the lower control arm.
After much searching, I decided to cut the top two "tabs" (ears where the bolt goes through) off the vertical link and move them rearward on the square tube of the vertical link and reweld them. If you move them back so that the rear edge of the tabs lines up with the rear edge of the square tube (approx 1/4") you will have proper alignment.
NavyVet - the sway bar should move relatively freely up & down. A "trick" is to use alignment shim(s) to space the outer sway bar bushing shell away from the frame when you bolt it down. The bushing for the bigger (i.e., 30mm) bar tends to "crush" a bit in the factory shell making the bar very resistent to movement. Space as necessary so it moves up & down freely (not sloppy loose, but moves with only very moderate force). I learned this from a SCCA Nat'l Champion Vette AX'er who learned it from a multi-time champ in Vettes. Since their cars handle like they do, and they've studied this science more than I have, I tend to follow their lead and take advantage of their experience.
As Vetracer said, the factory end links are fixed, so they are only going to be at one height relationship with the lower a-arm, therefore it shouldn't matter where it's sitting when you tighten them - just so they move. Being so tight that they resist movement is partially defeating the function of the shocks and limiting the reactiveness of the suspension as it tries to keep the wheels on the ground. The one inch blocks tend to make the moving end more horizontally in line with the a-arm versus the factory position where the end is a bit more raised. Horizontal is one goal. No preload on either side is the other (unless doing serious corner weighting exercises that go beyond most people's capabilities and/or needs). The only way to achieve zero pre-load at normal weighted ride height is with adjustable end links.
Vetracr - If you look at the bend in a smaller, say 28mm front bar like the one that came on my '86 that I relpaced wit a 32mm there is a noticeable lack of bend in the larger bar. That means the sway bar is tilted down toward the end link, and is much more resistant to "bending" as it should which limits the travel of the lower "A" arm and of course everything attached to it like the wheel and tire. Sorta like the folding legs on a table, it hinges and jams.
The blocks prevent this from happening by lowering the front of the sway bar.
The Bus - Shim the front sway bar 3/16" from the frame mounting using washers. This improves turn in.
Solofast - Get the Koni Sport shocks for your 89. I am assuming that you have the Z51 suspension and the Koni's were developed specifically for the 89/90 Z51 springs and sway bars, I know, I did the development driving and selected the valving with Dean Dodge (who was then with KONI) and we tested them on my 89. Set the rears to full soft, or close to it, and expect the fronts to be about in the middle of the adjustment range. That way you can tune the car between runs quickly since you are just spinning the **** a quarter of a turn either way to fine tune the car....If you don't have the Z51 bars, springs and control arms you will likely need to get them to be competitive in A/S on a national level.
One last tip that was often an "Unfair Advantage".....The sway bar on the front of the C4 is huge, and a lot of the compliance in the swaybar system is in the bar mount bushings. You can make a HUGE HUGE difference in how stiff or soft the bar is by preloading of softening the preload on those bushings.....If the car is loose, you can stiffen the front bar by putting a large (1.5-2 inch) diameter washer on top of the rubber and clamping it in tightly. The extra preload will make a huge difference in front roll stiffness. If the car is pushing you can put an alignment shim or (in extreme conditions 2 shims) in between the two halves of the front bar bracket to soften the front bar. If you put a cable tie on the washer and on the shims, you can pull them out or put them in in less than two minutes....that is easily done between runs if you need to. It can turn a local event into a test and tune....If you doubt it, try it and you will be truly amazed....
02-10-2009, 10:33 PM
#2
Melting Slicks
....the sway bar should move relatively freely up & down. A "trick" is to use alignment shim(s) to space the outer sway bar bushing shell away from the frame when you bolt it down. The bushing for the bigger (i.e., 30mm) bar tends to "crush" a bit in the factory shell making the bar very resistent to movement. Space as necessary so it moves up & down freely (not sloppy loose, but moves with only very moderate force). I learned this from a SCCA Nat'l Champion Vette AX'er who learned it from a multi-time champ in Vettes. Since their cars handle like they do, and they've studied this science more than I have, I tend to follow their lead and take advantage of their experience.
One last tip that was often an "Unfair Advantage".....The sway bar on the front of the C4 is huge, and a lot of the compliance in the swaybar system is in the bar mount bushings. You can make a HUGE HUGE difference in how stiff or soft the bar is by preloading of softening the preload on those bushings.....If the car is loose, you can stiffen the front bar by putting a large (1.5-2 inch) diameter washer on top of the rubber and clamping it in tightly. The extra preload will make a huge difference in front roll stiffness. If the car is pushing you can put an alignment shim or (in extreme conditions 2 shims) in between the two halves of the front bar bracket to soften the front bar. If you put a cable tie on the washer and on the shims, you can pull them out or put them in in less than two minutes....that is easily done between runs if you need to. It can turn a local event into a test and tune....If you doubt it, try it and you will be truly amazed....
One last tip that was often an "Unfair Advantage".....The sway bar on the front of the C4 is huge, and a lot of the compliance in the swaybar system is in the bar mount bushings. You can make a HUGE HUGE difference in how stiff or soft the bar is by preloading of softening the preload on those bushings.....If the car is loose, you can stiffen the front bar by putting a large (1.5-2 inch) diameter washer on top of the rubber and clamping it in tightly. The extra preload will make a huge difference in front roll stiffness. If the car is pushing you can put an alignment shim or (in extreme conditions 2 shims) in between the two halves of the front bar bracket to soften the front bar. If you put a cable tie on the washer and on the shims, you can pull them out or put them in in less than two minutes....that is easily done between runs if you need to. It can turn a local event into a test and tune....If you doubt it, try it and you will be truly amazed....
If you had the bar so loose that it rotated easily I am thinking that the response would be non-linear in that the front roll stiffness would be really soft until you took up the bushing slop and then the bar would come into play. That would make the car have more corner entry oversteer and then more push at the limit. The C5 bushings are designed to let the bar rotate, but the C4 bar should be clamped...
02-10-2009, 10:44 PM
#3
Team Owner
Member Since: Mar 2001
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If allowed in your class you want to put heim links on the end.
I really suggest buying a set, as they're hard to setup, and I've seen to many people break them.
I really suggest buying a set, as they're hard to setup, and I've seen to many people break them.
02-11-2009, 09:13 AM
#4
Race Director
Thread Starter
So just install the bars, test the car for oversteer/understeer and use the washer or shim in the front to correct? Any tips for the rear bar?
Brian, I have heim links on the rear but haven't bought front ones yet. I was going to then the bars came with all new poly. I'll budget for them later.
Brian, I have heim links on the rear but haven't bought front ones yet. I was going to then the bars came with all new poly. I'll budget for them later.
02-11-2009, 10:38 PM
#6
Race Director
Thread Starter
02-12-2009, 09:03 AM
#7
Melting Slicks
Just remember that the C4 is sensitive to too much roll stiffness in the rear. If you have too much it will jack up and cause some weird handling.
How much is too much?.. Well, it depends... Basically on what you have for springs, the ride height, and what you are doing with front bars..
With 84 Z51 springs and bars at stock ride height the early C4's will jack. Also I found that the 88 and later cars would jack with Z51/Z07 springs and the 26mm solid bar in the back. This is why the 1991 cars with the 26mm bar would jack in the back (with the stock front bar) and why they went back to the 24mm bar in the back for 1992....
As Clint Eastwood said... "Man's gotta know his limitations"..
How much is too much?.. Well, it depends... Basically on what you have for springs, the ride height, and what you are doing with front bars..
With 84 Z51 springs and bars at stock ride height the early C4's will jack. Also I found that the 88 and later cars would jack with Z51/Z07 springs and the 26mm solid bar in the back. This is why the 1991 cars with the 26mm bar would jack in the back (with the stock front bar) and why they went back to the 24mm bar in the back for 1992....
As Clint Eastwood said... "Man's gotta know his limitations"..
08-09-2010, 04:08 PM
#8
Race Director
Thread Starter
An update to this..
I was working on the front spring and wanted to jack up the suspension to ride height, so I could tighten the control arm and spring perch fasteners without trying to get under the low car. I found that the car wouldn't get anywhere near ride height before coming off the jack stands. I was lifting under each arm so as not to twist the sway bar. Something was so bound up the suspension couldn't move.
I unhooked the sway bar and used all my strength, it wouldn't rotate at all. I've been noticing a change in suspension harshness as the grease would go away. And I had taken the bar down to add new grease. This time it had no grease left at all, it had been to long. I added zerks this time to put new grease in. I also stopped using that thick suspension grease. I found it would turn to clay with dirt and couldn't be cleaned well. The Redline synthetic grease is working nice.
I added one washer between the bushing clamps to reduce load on the bushing. It moves with moderate force now and once everything was reinstalled, the suspension would nicely jack up to ride height. I could tell by jacking to the dirt line on the shock. After driving the car I could tell the suspension was working well again, before it also felt like a solid suspension!
I decided to remove the rear sway bar and add zerks there too. The rear sway bar was fine, it could rotate, and the grease was still there. I cut a shallow groove around the center of the bushing for grease to move through. It's an easy project.
I was working on the front spring and wanted to jack up the suspension to ride height, so I could tighten the control arm and spring perch fasteners without trying to get under the low car. I found that the car wouldn't get anywhere near ride height before coming off the jack stands. I was lifting under each arm so as not to twist the sway bar. Something was so bound up the suspension couldn't move.
I unhooked the sway bar and used all my strength, it wouldn't rotate at all. I've been noticing a change in suspension harshness as the grease would go away. And I had taken the bar down to add new grease. This time it had no grease left at all, it had been to long. I added zerks this time to put new grease in. I also stopped using that thick suspension grease. I found it would turn to clay with dirt and couldn't be cleaned well. The Redline synthetic grease is working nice.
I added one washer between the bushing clamps to reduce load on the bushing. It moves with moderate force now and once everything was reinstalled, the suspension would nicely jack up to ride height. I could tell by jacking to the dirt line on the shock. After driving the car I could tell the suspension was working well again, before it also felt like a solid suspension!
I decided to remove the rear sway bar and add zerks there too. The rear sway bar was fine, it could rotate, and the grease was still there. I cut a shallow groove around the center of the bushing for grease to move through. It's an easy project.
08-16-2010, 04:10 PM
#10
Aardwolf, your car's a track car, why not up the spring rates and reduce the sways? Sways reduce grip, use you springs to hold up the car in turns......just a thought.
Last edited by mustclime; 08-16-2010 at 08:01 PM.
08-16-2010, 04:53 PM
#11
Race Director
Thread Starter
I'm on a small budget!
I still can't understand why you would want the front bar bushings to be part of the spring rate. The harder it is to move the bar the worse control the shocks will have.
I still can't understand why you would want the front bar bushings to be part of the spring rate. The harder it is to move the bar the worse control the shocks will have.
08-16-2010, 08:16 PM
#12
One of the reason I hate sway bars is they make the car less consistent. Energy suspension makes sway bar bushings and mounts with grease fittings...you might try that. ran into this guy Steve Hoeschler a couple years ago and he had some interesting ways to pick spring rates for barless/ front bar only setups....you get board some time, read his threads over on the mr2oc forum....
http://www.mr2oc.com/showthread.php?t=298272
http://www.mr2oc.com/showthread.php?t=313691
Its an open forum so you can read with out being a member....Steve(xhead) was working on a rollex team last time I looked....now if I could just get the time to work out my motion ratios on my 93......
http://www.mr2oc.com/showthread.php?t=298272
http://www.mr2oc.com/showthread.php?t=313691
Its an open forum so you can read with out being a member....Steve(xhead) was working on a rollex team last time I looked....now if I could just get the time to work out my motion ratios on my 93......
08-19-2010, 02:30 PM
#13
Race Director
Thread Starter
Mine is handling much better without the binding. They will need to be rechecked/reshimmed as the paint wears off the bar I think.
Saw this recently:
Saw this recently:
