Rear Sway Bar Performance Upgrade

[Fierofool]

I have been working on reinstalling a front sway bar on the rear of my 86SE.  I encountered lots of puzzles while attempting to mount it in the same place as Aerodonamic (Don Hulse) had installed it.  The original installation worked very well as the car had often been put through it's paces.  Not having his original installation parts at hand, I had to work through the problems to duplicate the install. 

First, he had drilled into the rear of the cradle.  In order to have the bushings located on the straight part of the bar, the bushing mounts had to be located very close to the side wall of the cradle.  Though there's access to the inside, there isn't enough room to put a nut on the bolt. Long bolts can also get into the control arm bushings inside the cradle


Second, not being able to determine what size bolt and thread he used, I did trials until I found bolts I thought were correct. 

Third, because the length of the curved portion of the bar is so long, a 7/16 hole, shown in this pic, had to be drilled in the center rib of each control arm, in order to move the mounting brackets forward enough to bolt to the very rear end of the cradle.  This end link location also puts the head of the bolt and bushing directly underneath the CV boot.  Though there's enough clearance for operation, it makes it very difficult to insert the bolt.


Fourth, once the end links were installed and the ends of the sway bar were bolted to them, the sway bar was brought up to mate the bushings to the cradle.  I found that flanges on the sides of the cradle wouldn't allow the bushing mounts to be pulled fully against the cradle surface.  The sway bar also hit the crossmember.



So, now I start the problem solving.  Found some bolts that felt right to mount the bushings to the cradle.  Went to Tractor Supply and for a couple of dollars, got automotive grade bolts for the end links and bushing mounts.

Drew up a design for a spacer plate to go between the bushing mounts and the cradle to allow clearance at the interference points indicated above and took the drawing to the machine shop.

Got them back the next day and set forth installing the bar.  The spacers were just the ticket.  Slotted to match the ProThane bushings from The Fiero Store, because the holes on the two sides of the cradle were differently spaced.  NOTE:  These aren't the spacer mounting pads I eventually used. 


I installed the spacers and bolted up the end links.  Plenty of clearance at the cradle and the crossmember.



The rear sway bar did change the handling characteristics.  Because it felt so much different on curves, I was very cautious and worked my way up when taking curves with any speed.  It made the car feel like it had power steering.  As I gradually increased speeds through the same set of curves over the next few days, I became more and more uncomfortable with the feel, especially on a left turn.  Not wanting to push it and risk a spinout on a public road, I went to a couple of vacant shopping centers.

I soon found out that the rear bar didn't improve handling, but made it worse.  On a hard right turn, the car stuck to the turn.  Understeer was greatly reduced.  On a hard left turn, understeer was reduced even more.  To the point of creating uncontrollable oversteer.  Thinking that the bar might not be placed equally at the bushing mounts, I went back underneath to make a front to rear adjustment if needed and found that one bolt on each side was stripping out of the cradle. 

Even with the work Don had already done in advance, this was a difficult install, trying to find the correct bushing and end link bolts.  The end link bolts are very critical because the paddle ends should be parallel to the control arms once the bar is installed and everything is bolted down. 

For that reason, I've been working on a new design that will allow us to use one of the holes already drilled in the control arm.  It's the proper space and doesn't have any of the clearance problems with the CV boot. 

The mounting plate will have threaded studs spaced for the factory bushing mounts.  The reason for this is that some have found that poly bushings are a little harsh for their taste, or their total setup causes more oversteer than they want.  Factory rubber bushings reduces this situation.  It will still accept the ProThane bushing mounts without any modifications. 

This will be a complete No-Drill mounting system.  It does require about 10 minutes of welding, though.  It will be designed to mount the bar at the front of the cradle and give clearance for the exhaust, one of the reasons some mount the bar at the back.  In this picture, I've inserted bolts into the two factory holes to show location.  With the bar mounted to the rear of the cradle, you can see why the need for the extra hole. 


This is the passenger side.  The bolt to the left is the factory hole that would be used for a stock bar mounted at the front of the cradle.  The bolt at the right was used by Addco when they designed their front mounted sway bar.  My new design is intended to let you use the mount for front or rear cradle mount, but you would need to drill the extra hole in the control arms for a rear mount.

Before I go and have just 1 set made up for my car, is anyone else interested in a pair?  At the moment I don't know what they will cost.  The original plates cost me $50 for the pair.  He said that subsequent half-dozen orders would greatly reduce the price. 

I'm taking my drawings down to the machine shop this afternoon.  LET ME KNOW ASAP IF YOU WANT TO ORDER A SET.  I'LL TRY TO HAVE SOME PRICE RANGE THIS AFTERNOON.

THESE ARE FOR THE 84-87 CRADLES WHEN INSTALLING A STOCK 84-87 FRONT SWAY BAR ON THE REAR.

[Fierofool]

The shop owner said he could produce 3 sets for $40 @ set.  The unit price goes on down as the quantity goes up.  He will start production on Monday for the pair he's making for me for $60, so you can see how price comes down. 

I need to know by no later than 10AM Monday.

[scottb]

I know its a bit late, but........ i have access to a milling machine. just saying

[Fierofool]

Yeah, he's modifying the CNC program for the original design this weekend.  Is the mill a CNC unit or hand crank, autodrive?  Can you efficiently operate it?  I haven't laid hands on one since early 1999.  Access to it might come in handy for other things members might need done, though. 

[scottb]

Its an antique milling machine......

I do i have a question: why did you slot the spacer? With the bishing holder slotted there isnt a reason to slot the spacer.

[Fierofool]

Because the holes Don drilled on the two sides of the cradle were spaced differently.  I made it easy enough for the machine shop, rather than having to make one with different spacing for each side. 

[Fierofool]

MOUNTING A STOCK 84 THRU 87 SWAY BAR ON THE REAR OF AN 84 THRU 87 FIERO

FOR CORRECT POSITIONING, THE CAR SHOULD BE BACKED ONTO RAMPS OR ON A WHEEL LIFT RACK.  THE SUSPENSION SHOULD BE LOADED AS IF BEING DRIVEN ON A LEVEL SURFACE. 

The mounts are designed to be used for a front or rear cradle mount, utilizing the stock front 84-87 sway bar.  When mounted to the front of the cradle you can use the rearmost factory holes in the rear control arms.  If you mount the bar on the rear of the cradle, you must drill holes in each control arm.  The pads give added clearance to the exhaust system and bring the bar ends more parallel to the control arms, give a stronger attachment than bolting into the cradle and eliminates bolt interference with control arm bushings.
 

Before beginning, look at your sway bar.  You will see that one end is rounded while the other end is either pointed or has a flat edge.  This is the driver’s side as was originally mounted on the front of the car.  Using my combination of bolts and washers for spacers, the pointed or flat end should be to the passenger side if you are mounting to the front of the cradle as in my illustrations. 

To start the process, I used the factory sway bar bushings and their housing.  The reason I did this is because they aren’t slotted.  It will position the mounting pads so that either aftermarket poly or stock bushings may be used.  Some say they have found the poly to be a little too stiff, creating oversteer, or too noisy and went back to the stock rubber bushings and housing.  Because poly housings are slotted, it’s possible to weld the pad to the cradle in a position that doesn’t allow proper alignment should one want to return to rubber mounts.  I only tightened the nuts on the mounting pad studs enough to still allow rotation and some side to side slip on the sway bar.  This allowed fine tuning of the pad to the cradle.
 

To be sure that I had the bushings as much on the straight portion of the bar as possible, I positioned the studs inboard, leaving the larger portion of the mounting pad to the outboard side.  You might want to do a trial fit with the studs to the outboard side if you decide to do a rear of the cradle mount.  There’s ample room to do it at the rear because the rear of the cradle is spaced closer together than the front and the bushings would probably still be on the straight portion of the bar.

Using GM recommendations for installing front end links, I tightened the nut, compressing the bushings, until the nut fully bottomed out on the last thread of the bolt.  That pretty much took out all front to rear and side to side movement of the bar. 

I then raised the bar with the floor jack, just to the point that the pads came into contact with the cradle and began to level out against the cradle.  I could still slide the bushings and pad side to side to align it with the cradle. 
 
 
Be aware that you need to put the outer edge of the pad flush with the outboard edge of the cradle.  This is especially true on the passenger side, giving clearance for access to the nut for the front motor mount.  It also leaves room for full access to the control arm bushings on either side. 
 
 
Once everything was satisfactory, determined that the end paddles were horizontal to the control arms, the end links were as vertical as possible, the pads were welded into place.  Now, I will remove the stock swaybar bushings, install the poly bushings and evaluate the handling.  If I find them unsatisfactory, I can go back to a softer factory bushing. 

[Fierofool]

Got the plates welded into place.  I managed to get all 4 sides to give it a solid bond and to prevent water from getting between the plate and cradle.  Hope the bead holds.  It's been 16 years since I've welded.  I used a little flux core wire feed welder for the job.



In my initial test drive on some local rural roads, just swishing it back and forth, left to right, the reaction in both directions seems to be equal, so the left turn oversteer I was experiencing is gone.  It's still very stable at 45-50 mph during regular driving.  In the next two weeks, I'll gradually work up to more and more aggressive maneuvers only to the point that I begin to feel safely uncomfortable with it.   

[Fierofool]

The car drives like it has power steering.  It's very easy turning into curves with just 1  hand but I feel more comfortable with 2 hands because of what I feel is oversteer.  This sensation wasn't there before installing the sway bar at the rear nor the front of the cradle, so one conclusion is that a rear bar does reduce the inherant Fiero understeer tendancies.

In both front and rear cradle installs, I tightened the end link nuts until they bottomed on the shoulder of the bolt.  About 2 inches worth of thread.  I believe this made the rear too tight because the poly bushings were partially crushed.

This morning I backed off 3 turns on each rear end link nut.  I just did a test drive and the adjustment is noticeable.  Though there's still some feeling of oversteer, it's much less than before the adjustment. 

Once decompression of  the bushings occurs, I will probably start playing with rubber bushings to develop a feel I'm satisfied with.

[Fierofool]

After today's club meeting, MikeMac opened his shop to me so I could take a look at the suspension on the 86SE to try to determine what was causing the serious oversteer.  Several other members went along and with input and assistance from everyone, we think we found the problem, or at least a remedy. 

There is about a 1/4 inch space between the front bushings and the flanges on the chassis that the front cradle bolts go through.  A little prying with a bar shows that the front of the cradle can move side to side.  We looked at Ron768's 85 that has poly bushings installed, and it's a slip fit.  No space between the bushings and the chassis flanges.

On the other hand, Scottb's 86SE is stock and his is pretty much like my 86SE, except that the front of his cradle doesn't move when a pry bar is used.  Raydar and Scottb finally determined that one of the front cradle bolts was not the correct bolt.  It's not the correct diameter, which probably allows the bushing to slide. 

Next step is to replace the front cradle bolts and probably go with poly in those two mounts.  Stay tuned. 

[Raydar]

Maybe more work than you want to mess with, but I am still of the opinion that you could solid mount the cradle without experiencing any significant increase in vibration. Remember, all of the 88s are solid mounted. I also have poly bushings everywhere in the suspension (blue car) and everywhere but the trailing links (white car) and don't find either of them to be too harsh. You're welcome to drive either of them, if you'd like to.

[Fierofool]

How long, far, and fast can I drive the blue one?

[TopNotch]

Rodney Dickman sells aluminum cradle bushings, which allow you to easily solid-mount a pre-88 cradle.

[Raydar]

Charlie, you can drive it home for the appropriate sum.

[Raydar]

Rodney's bushings...
http://rodneydickman.com/catalog/product_info.php?cPath=26_44&products_id=270