Front Suspension Questions

[IdahoZ]

I have the front end off the car and was trying to decide what to do with the front suspension. I went ahead and relocated the lower control arm pivet holes up 3/4" to help with the bumpsteer per the JTR manual. The previous owner of the car installed eccentric bushings on all forner corners. I will not be racing this car but would like a nice agressive street machine. A little info on my car before I ask my questions.

 

1972 240z

400 sbc / 400 hp / 400 lb ft torque

T-56 transmission

2600 lbs

Hypercoil coil overs 175 f / 225 r from MM

Lowered 1"

Tokico Illum struts

7" x 16" zero offset wheels with 225/50/16 tires

Will be installing sub frame connectors and strut tower bracing

 

Questions

 

1. Can I run the eccentric bushings after relocating the pivet holes in the crossmember? Looks like I will plenty of clearance as long as the eccentric hole is on the bottom and does not pivet up past say 90 dgrees, otherwise the CA will hit the crossmember.

2. The eccentric bushings look like they have been shaved a bit, as they are different sizes. Previous owner must have shaved them to fit the crossmember. How are these suppose to pivet? Does the aluminum eccentric core rotate inside the plastic bushings, or are the bushings suppose to rotate inside the control arm?

3. My eccentic cores are longer than the bushings when installed in the CA, which would mean the aluminum core would rotate inside the bushings which are press fit in the CA. Would this not change the camber as the CA moves up and down since the pivet point in the eccentric bushing is not centered but offset.

4. I have also heard about TC rods breaking when urethane bushings are used. The PO installed one of those ball and cup units that use the stock rubber bushing in the back. Has anyone experienced TC failures with this type of set up?

 

 

Thanks.

[blueovalz]

I am not familar with the front eccentrics, but from what you've provided, I'll add:

 

Would this not change the camber as the CA moves up and down

Yes, the camber will change with adjustments made using these bushings (which is one reason for their design)

 

The PO installed one of those ball and cup units that use the stock rubber bushing in the back. Has anyone experienced TC failures with this type of set up?

I don't recall any issues with the T/C rods using these types of bushings (Most likely because they allow the rod to pivot easily). I've read that these types of bushings do increase ride harshness over the rubber though.

[IdahoZ]

The eccentric bushings were on the front of my car when I purchased it. I understand that these bushings will affect camber when adjusted and the bolt tighted, but my question is how are they designed to rotate. The bushings on my car have been modified somewhat and I do not have any installation instructions so i do not know if they are installed correctly. I was wondering if these bushing were designed such that the aluminum eccentric core rotates inside of the poly bushings or if the poly bushings were suppose to rotate inside the control arm? In my mind when I visualize the aluminum eccentric core rotating inside the bushing, I can see the control arm moving in and out as the suspension moves up and down during normal driving. It would make more sense to me to have the bushigs rotate inside the control arm where the pivet point would be centered like a stock or urethane bushing setup. Does anyone using these bushings still have their instructions? If so, can you scan them and send them to me?

 

As for the TC rod setup, I think I wll try it for now and see if I like it. I was just concerned about stressing my raod to the point of failure. Again this setup was on the car when I purchased it, and I have since rmoved everything from the front end to detail it. Does anyone have instructions on how to set up the TC rod ball and socket kit? It looks like the kit came with a gauge of some kind and installation instructions.

 

Thanks.

[Pop N Wood]

I have been running the eccentric bushings and ball and socket TC mounts you mention for the past 18 years. The "urethane" bushings that were causing all of the TC rod failures did not use the ball and socket. This meant the TC rod had to flex to allow the suspension to articulate. My guess is eventually the rods work hardened and snapped. Kind of like breaking a coat hanger by bending it repeatedly.

 

I don't know why you couldn't use the eccentric bushings with the relocated bumpsteer mod. But I don't see the point. Put the hole were it belongs and go back to stock or urethane bushings. If you have to rotate the eccentric bushings down, then that is the same as drilling the hole lower.

 

Supposedly the eccentric bushings can slip. They are not unsafe, but like I said if you are relocating the cross member pivot hole, just get rid of the eccentrics.

[blueovalz]

I can see the control arm moving in and out as the suspension moves up and down during normal driving.

 

I'm a bit confused (but that's not unusual any more) about this. The control arm will not move in and out as the suspension moves up and down. My understanding (again, based upon my use of REAR eccentric bushings) is that once the bushing is adjusted, it is then tightened into this "set" position, and then remains fixed as the suspension moves up and down. To the best of my recollection on my rear pieces, the aluminum eccentric rotates, which then positions the Delrin bushing up, down, left, or right. I am also guessing that once this adjustment is made, then tightening the large bolt that goes through the bushing will clamp it between the two sides of the cross-member and thus fix or "set" the position. I eventually replaced mine due to wear issues that allowed some slop to develop.

 

I am guessing that the part on the eccentrics that is supposed to rotate, is the part that allows some means of turning it (e.g. hex pattern for a wrench).

[spotfitz]

but my question is how are they designed to rotate.

Thanks.

The core is rotated, after loosening the bolt, and then a special wrench is used to turn the eccentric center.

http://www.thezstore.com/page/TZS/CTGY/PSDC07A

From that link:

"Note: Your mechanic may not have the camber wrench to adjust this kit! See below for the proper wrench."

[JMortensen]

I have been running the eccentric bushings and ball and socket TC mounts you mention for the past 18 years. The "urethane" bushings that were causing all of the TC rod failures did not use the ball and socket. This meant the TC rod had to flex to allow the suspension to articulate. My guess is eventually the rods work hardened and snapped. Kind of like breaking a coat hanger by bending it repeatedly.

 

I don't know why you couldn't use the eccentric bushings with the relocated bumpsteer mod. But I don't see the point. Put the hole were it belongs and go back to stock or urethane bushings. If you have to rotate the eccentric bushings down' date=' then that is the same as drilling the hole lower.

 

Supposedly the eccentric bushings can slip. They are not unsafe, but like I said if you are relocating the cross member pivot hole, just get rid of the eccentrics.[/quote']

I think Pop makes a good point here. When you rotate the front camber bushing, you are changing the bumpsteer.

 

Also, when the control arm moves it doesn't go straight up and down. It swings in an arc because it is attached to the TC rod. The eccentric bushings don't really allow for this swing because the bushing material is so hard and so thin. I haven't seen it but I would expect this to result in cracking of the front crossmember around the bushings. I think you might even see this tendency with poly bushings, but again I haven't seen it myself.

 

What works best in the front control arm bushings is something that doesn't have a lot of resistance to the swinging motion of the control arm. A heims joint really does the best job here IMO. If it's not a race car a person could probably get away with poly for a long time, but rubber wouldn't stress the crossmember as much.

[cygnusx1]

With a stock spring you may get quite a bit of travel and the induced "arc" from the T/C rods will stress the inner bushings/crossmember/inner LCA, but if you are running "race" springs and heavy swaybars, your normal suspension travel range will be pretty short. I think it would take a VERY long time to fatigue any metal in the front suspension structure. Besides, engineers select pretty malleable metal for front suspension parts for this reason exactly.

 

The aluminum portion of the eccentric bushings, front and rear, should become a SOLID part of the car after is set and locked. The aluminum should NOT rotate. The nylon bushing should slip (rotate) over the aluminum or inside the LCA as the arm swings up and down. The bushings will STILL adjust camber even if you relocated the mount hole.

 

SIDE NOTE: If you run poly T/C bushings, use a stock soft bushing on the back of each T/C rod instead of the poly.

 

Enjoy Z.

[fastzcars]

quote by jmortenson:

Also, when the control arm moves it doesn't go straight up and down. It swings in an arc because it is attached to the TC rod. The eccentric bushings don't really allow for this swing because the bushing material is so hard and so thin. I haven't seen it but I would expect this to result in cracking of the front crossmember around the bushings. I think you might even see this tendency with poly bushings, but again I haven't seen it myself.

You took the words right out of my mouth Jon !

[Pop N Wood]

Well, just had the cross member out to cut the L6 motor mounts off and no cracks in 18 years of using eccentric bushings. I will probably get rid of them when I do the bumpsteer mod in a year or two. I'll let you guys know should anything turn up.

 

Now broken TC rods, there have been several posts on those.

[IdahoZ]

Thanks for all of your input and information on this. I agree that if I have to adjust the eccentric bushing such that the hole is at the bottom of its arc, I have just waisted my time relocating the pivet hole in the cross member and have introduced the bumpsteer I was trying to eliminate. I have decided to take pop n wood's and jmortensen's advise and use urethane or OEM rubber bushings in the front and ditch the eccentrics. I think this may be the best for the street and for what I will be using the car for. I haven't decided on the TC setup yet, but will probably go OEM here also. The only problem is finding the steel rod that goes between the bushings as I have not found anyone who sells these and my is gone, i.e. not used with the ball and socket kit. I really appriciate all of your input, this site has really been a big help in building my Hybrid. I wouldn't even try it without you guys.

 

Side note - I just ordered a set of 16" x 7" Centerline Ventura's. On sell for $150 each. I want to machine a custom center cap for them, as the Centerline caps are pretty ugly, IMO. Will let you know how it turns out. Going to order my bushing now.

[cygnusx1]

if I have to adjust the eccentric bushing such that the hole is at the bottom of its arc,

 

I dont think anyone said you had to do that. The eccentric bushings work as well relocated as they do in the stock location. No difference at all.