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AS someone interested in a suspension upgrade I was looking at the Pfadt chart and noticed that the ZR1 sway bars are measurably more stiff than the Z06 but still relatively more streetable than the T1's. I haven't found many articles on upgrading to the ZR1. I'm figuring there is a reason but am considering all options before I throw my money down. My vette is a 2000 with the FE1 option. 70,000 miles.
Going with the ZR1 bars would increase oversteer considerably since the rear bar is stiffer in relation to the front bar. That car has wider tires on the rear and this means it needs more rear bar to balance it. If you were to go that way you'll either oversteer or you'll need to increase the rear tires size to keep it balanced.
Since you have no adjustment capability with that bar there is no way to fine tune the bar stiffness unless you get some bushings with different stiffness that you can put in and adjust the stiffness that way. Expect that you would need poly bushings on the front bar and rubber in the back bar to help get it balanced, or you'd need to weld some type of adjustment scheme on the rear bar.
One of the good things about the Johnny O bars is that they have some adjustment and you can dial in the rear bar relative to the front. This way they can accommodate a number of different spring setups and get closer to a good balance by adjusting the rear bar.
Stiffer is not necessarily better. You want the softest suspension you can get away with. The softer the suspension the more traction you will have unless you are bottoming out or have excessive roll. That is why a stiffer suspension in the rear causes overseer. You would think it would be the opposite. When NASCAR drivers stiffen the suspension they call it "loose" because of the handling. The stiffest suspension you can have is none at all and on a perfectly flat surface that would be fine. It the real world that would be miserable. The road has irregularity's and the wheel needs to stay in contact.
Thicker (stiffer) sways make an independent suspension less independent. There is a lot that goes into suspension tuning. A true track car wouldn't be very comfortable on the street but the FE1 suspension is a soft ride, a little soft for the track. I found it a bit floaty. It didn't make me feel like I was driving a true sports car. With the Z06 suspension you really feel the bumps. You have to control the wheel when going over them. They may be undesirable to some.
Stiffer is not necessarily better. You want the softest suspension you can get away with. The softer the suspension the more traction you will have unless you are bottoming out or have excessive roll. That is why a stiffer suspension in the rear causes overseer. You would think it would be the opposite. When NASCAR drivers stiffen the suspension they call it "loose" because of the handling. The stiffest suspension you can have is none at all and on a perfectly flat surface that would be fine. It the real world that would be miserable. The road has irregularity's and the wheel needs to stay in contact.
Thicker (stiffer) sways make an independent suspension less independent. There is a lot that goes into suspension tuning. A true track car wouldn't be very comfortable on the street but the FE1 suspension is a soft ride, a little soft for the track. I found it a bit floaty. It didn't make me feel like I was driving a true sports car. With the Z06 suspension you really feel the bumps. You have to control the wheel when going over them. They may be undesirable to some.
Hope this helps.
Excellent explanation. Thanks.
Long story short. Got motivated yesterday and crawled under my vette. Previous owner replaced oem shocks with Bilsteins. Not sure which model.
Measured the rear sway bar and got 19mm (which corresponds with FE1 specs). Measured the front and got 31mm! I think that is C6Z06 territory. Looked a little more and the links were metal. Bushings are rubber. Appears that most of my work has been done for me.
Great that suspension has been upgraded but why would you run FE1 rear and significantly upgrade the front but leave rear oem. Will this be unstable at higher speeds? On the phat chart the relative rate for the C6Z06 rear is greater than the front. Should I replace the rear sway bar to more closely match the C6Z06.
Solofast's point about Johnny O might be the way to go.
The FE1 sway looks like spaghetti compared to the Z06. Your current combination will not necessarily be unstable on the street but will under-steer. It might feel like you are pushing the front end into corners. The opposite would be over-steer where the back end wants so slide (more dangerous but some people like it).
I did the C6 Z51 sways with metal end links and the ZO6 shocks. Best upgrade for the money, less than $500. My car corners totally flat and has the firm new car feel without being harsh. Mines a 97 M6 with 100K on the clock. I did the upgrade about 2K miles ago.
I just put used 2003 C5Z51 sway bars on My 2001 Vert along with new urethane bushings on the control arms. I also had to replace all the delaminated end links and the front ride height adjustment bolts were squished to the side. This is on a 47,000 mi car. I could never tell if the ride control **** was working or not before. I thought the car had been lowered too far but it turns out the front adjusters were set at normal ride height. The problem was squished front adjusters and floppy end-links. I have only driven the car 3.5 miles since the suspension rebuild but I'm certain the original 15-year old F45 shocks work now. I bought some heavy duty front ride height adjusters that have an extra 1/4" of padding so I screwed them all the way up and the front end still rides 13/16" higher than it used to. From what little time I got behind the wheel it seems to ride competition stiff when the **** is set on the first two settings but seems to soften up a bit when turned all the way over to the softest ride setting.
I also went with the shock and sway bar package from Gene at Cultrag Performance. This on a 1998 stock street car. I am well satisfied with the results. It was a huge improvement over stock. I also bought the metal end links.
Springs, bars and shocks and wheel and tire size all work together, if you want to change bars you should look for a package that has been engineered to work with your particular setup.
If you can't find that, you would be best to change to a complete package that works for your wheel and tire sizes.
In the old days you could just slap on stiffer bars and that would make a huge difference in handling, but car nowadays are much better balanced and are, in general stiffer than they used to be.
An upgraded set of matched bars (like the Johnny O bars) are a good starting place, but in any case it is always a good thing to have some adjustability to dial the car in and fine tune the handling.
If you're going to start mixing and trying to match different bars you will need to plan on doing a good bit of testing to get it to all work together.
As noted above, slapping a set of bars intended for a C6z, with its much wider rear tires in the back and more weight up front isn't going to give you a balanced setup on a C5 with soft springs.
Suspension setup is like a Rubix cube. If you know what to do and how to tune it, it's pretty easy to get it sorted out. If you don't you can end up twisting and turning and never get it right. In addition, testing is mandatory if you're trying to make the car handle properly as the only way to know what its doing is to take it to the limit in a controlled situation.
so much this. when you just change one piece often you find it brings about something you like along with something you don't
every car i have ever setup has required testing and minor changes along the way to sort out what the car was doing.
OP, have you considered just finding a wrecked z06 and taking the springs and sways? it's inexpensive and a great matched street combo
With that said the C6 Z51 bars are a very popular mod for a reason.
It has worked for a lot of people on this forum and others.
The stiffer springs will feel harsh if your roads are not well maintained.
The suspension also needs to be adapted to your terrain.
also a good point. if you have rough roads the stock coupe suspension may actually be better. traction is the #1 thing to concern yourself with and going too stiff can make a car skip and break over rough terrain / wavy / bumpy roads.
sways can help a bit with the body roll, BUT, the drawback to this is the car will have sharper limits. a little body roll is actually easier for most drivers to control if they are pushing a car. stiff cars have much less warning when you get near the end of your circle of traction
How can an amateur test their suspension outside of emulating what the pros have done? Buying track time has got to cost a pretty penny.
The best way to do that is to go to an autocross test session. Most folks that set up a test session will have a variety of handling areas, fast and slow corners, offsets and slaloms and you should be able to get a good handle on how the car works, and for a few bucks it's easily affordable. There are generally test sessions early in the spring, or in southern climes most any time of the year. Contact your local SCCA region or NCCC chapter and find out when and where any test sessions are planned. Here in the Midwest there are generally three or four that I can go to each year, and more if I wanted to drive a couple of hundred miles.
The biggest thing you need is to bring some "adjustability" with you. That is, have a set of bars you can adjust or bring different bushings (stiff to soft) so that you can tune the bars a bit. While adjustable bars are great, remember that bushing stiffness is a big contributor and you can do a lot of tuning with sway bar bushings too.
The other thing is that at typical test sessions there are generally folks who are knowledgeable and are more than willing to drive your car and tell you what it needs.
Finally, the most important thing to do prior to any test session is to get the tires that you are planning to use on the car. Trying to do a proper setup on a set of old hard tires is just wasting your time. Moreover, if you change tire sizes after you've done your tuning, it's often back to square one to get it dialed back in on new, fresh, different size tires.
The reason the person may have put a bigger bar on one end of the car is that the SCCA only allows you to change the sway bar on one end of the car and stay legal in stock class. The Strano bar is a popular mod and while you may have some more understeer that can be addressed by using bigger tires on the front when you go to the autocross and put on your race day tires.. As noted above, there are lots of things that can be changed to arrive at a good setup, you just have to get it to all work together.
The OP mentioned living in the mountains. The roads in many of those regions will tell you what your suspension is doing. The roads probably wind around and have hair pin turns (not what most of us are used to when we think of highway driving).
The best way to do that is to go to an autocross test session. Most folks that set up a test session will have a variety of handling areas, fast and slow corners, offsets and slaloms and you should be able to get a good handle on how the car works, and for a few bucks it's easily affordable. There are generally test sessions early in the spring, or in southern climes most any time of the year. Contact your local SCCA region or NCCC chapter and find out when and where any test sessions are planned. Here in the Midwest there are generally three or four that I can go to each year, and more if I wanted to drive a couple of hundred miles.
The biggest thing you need is to bring some "adjustability" with you. That is, have a set of bars you can adjust or bring different bushings (stiff to soft) so that you can tune the bars a bit. While adjustable bars are great, remember that bushing stiffness is a big contributor and you can do a lot of tuning with sway bar bushings too.
The other thing is that at typical test sessions there are generally folks who are knowledgeable and are more than willing to drive your car and tell you what it needs.
Finally, the most important thing to do prior to any test session is to get the tires that you are planning to use on the car. Trying to do a proper setup on a set of old hard tires is just wasting your time. Moreover, if you change tire sizes after you've done your tuning, it's often back to square one to get it dialed back in on new, fresh, different size tires.
The reason the person may have put a bigger bar on one end of the car is that the SCCA only allows you to change the sway bar on one end of the car and stay legal in stock class. The Strano bar is a popular mod and while you may have some more understeer that can be addressed by using bigger tires on the front when you go to the autocross and put on your race day tires.. As noted above, there are lots of things that can be changed to arrive at a good setup, you just have to get it to all work together.
More great advice. Thanks.
Have to look into the rules to see if adjustable end links count against any SCCA/NCCC. Not familiar with either
That explains the fat 265 40 R17's on the front. Just about all the wheel well can handle.
I did some reading and apparently bushings can get pretty soft and cause all sorts of anomalies. Imagine every angle of the suspension moving a few degrees while you are driving. So I also just ordered some bushings. I guess that's my weekend.
I'm sure the tires are contributing, but not at this level.
Have to look into the rules to see if adjustable end links count against any SCCA/NCCC. Not familiar with either
That explains the fat 265 40 R17's on the front. Just about all the wheel well can handle.
In SCCA the bar at one end of the car is free. You can have adjustable end links on the bar that you change from stock, the other end needs to remain stock. NCCC is more restrictive, not changes from stock for bars or end links...
My guess is that the previous owner set the car up for autocross per SCCA rules, and that's why you have what you have on the car. That would make a lot of sense.
Poly bushings are a PITA. They can be loud and squeak and require greasing and some are never quiet. You can't buy rubber bushings without buying new control arms, but that is an option, and it's a lot easier to replace the control arms than it is to do bushings.
Lastly, there are a couple of threads in the road racing and autocross page having to do with bushings, replacement and control arm distortion. Might be worth a look before you go to all the work of replacing bushings..
If I were doing it again, I'd get a set of new control arms and when new I'd flip the rear bushing (really easy to do) on the upper control arms and that is all you ever need to do to keep the control arms from deforming and the bushings walking out of the control arms.
I also went with the shock and sway bar package from Gene at Cultrag Performance. I also sent my PCM to Chuck Cow. The handling is like night and day. The tune is what makes it even more fun. The throttle response he changes makes it instantly go. Quick note, When I told chuck what I was doing, and all the other upgrades, headers, etc, and that I was DAV
He told me that -being a veteran he was giving us a discount-Thanks Chuck.. Genes total package,Cow Tune, and HINSON C5 Corvette Ceramic Coated Stainless Headers and X pipe were worth time and money on a tight budget..
Enjoy the suspension up grade mike v
I also went with the shock and sway bar package from Gene at Cultrag Performance. This on a 1998 stock street car. I am well satisfied with the results. It was a huge improvement over stock. I also bought the metal end links.
Originally Posted by mike venth
I also went with the shock and sway bar package from Gene at Cultrag Performance. I also sent my PCM to Chuck Cow. The handling is like night and day. The tune is what makes it even more fun. The throttle response he changes makes it instantly go. Quick note, When I told chuck what I was doing, and all the other upgrades, headers, etc, and that I was DAV
He told me that -being a veteran he was giving us a discount-Thanks Chuck.. Genes total package,Cow Tune, and HINSON C5 Corvette Ceramic Coated Stainless Headers and X pipe were worth time and money on a tight budget..
Enjoy the suspension up grade mike v
Thank you for your business and the positive feedback.
__________________ Phone: 484-334-8833 Owner of CULTRAG Performance
10-14-2016, 09:21 AM
Not sure which model. 
