Bumps in a corner=white knuckles. Options

[FASTFATBOY]

I recently bought a car to start trackdays and Autox. Its a 99 Z28 with Strano Springs, 1LE front bar stock rear bar. Koni Da on front Sa on rear. Spohn LCA in rear with the matching PHB(Poly bushings). Poly bushings in all swaybar mounts. Totally rebuilt suspension in front.

The fronts are set 4 clicks from full soft on compression, havent checked rebound. Havent checked the rears they are all supposed to be out of the box installed.


I have been feeling the car out, I recently pushed it on an off ramp near home, car has good grip but if you hit a bump with it loaded it WILL get your attention. Car is all over the place you immediately start fighting the car. Its done it 3 times now.

No bumpsteer kit on the car for reference.

How do you adjust the SA rears? How do you adjust rebound on the front DA?

[rocky]

FYI Koni has it on there site on how to adjust them. I printed them off and put them in my tool box for quick reference for when I want to try adjusting mine. It is not hard if I remeber right the rears have a dial on the body. And the fronts I believe you have to take them off or find a way to get them fully extended to turn the rod while you push the button to adjust. I am sure someone will tell you how for sure but I would still print a copy to keep just in case.

[firehawkclone]

We are going to need a little more info. Like what it actually does? Like does the rear get loose ect. What are your alignment specs? Double check everything on suspension.

[JimMueller]

How do you adjust the SA rears? How do you adjust rebound on the front DA?

The front DA rebound is adjusted with a rotary dial near the top of the shock. You use something like a small allen wrench to turn the dial left or right to adjust rebound. Some people have installed the components in a method which makes it inconvenient to adjust, like a spring coil blocking access to the window, etc.

I know you asked about SA rears, but the DA rears have the rebound adjustment on the top of the shock, under the carpet, and the same bump dial on the bottom like the fronts. I don't recall which adjustment the SA's have, but I'd bet they are in the same location.

[00 SS]

Agreed, more info is needed. However, IIRC, the front compression should be set at full soft and the rebound set at about 50%. Set the rear shocks at about 30% up from full soft. This should be a reasonable starting point with Strano springs and the bars you describe. If your alignment is funky, this may not work well. A good starting point for the alignment is -1.5* camber, 4.5* caster and 0 toe. With strano springs, this alignment should be achievable.

Also, if you have an adjustable PHB and LCA's, make sure the rear is set up square to the car.

[prockbp]

Your current issues don't have anything to do with dampening. Don't even touch the settings on your Konis yet.

Your rear control arms and panhard bar are complete junk. Poly bushings do not allow the rear suspension to work properly, and that is going to cause severe oversteer. Your car will feel very stable to a point, and then in a split second you'll be losing the rear. If you must upgrade the rear control arms and panhard bar, then you need to use components that have spherical bearings(rod ends). Your stock control arms would work better for cornering than your spohn control arms with poly bushings.

One of the best upgrades you can do to the rear end is change the stock panahard bar to a panhard bar that has spherical bearings.

The ONLY thing you should do with that rear end set up is drag race, and even then the poly bushings will interfere with the motion of your rear end.

This post has been edited by prockbp: Nov 16 2010, 06:23 PM

[trackbird]

Good catch Josh, I missed the poly in the LCA's and PHB. That's the first thing I'd change. I'd also verify that there are bump stops on the car and I'd add some rebound to the car. Probably 1/4 of the total travel down from "full" rebound on both ends (and fine tune from there). I typically ran about 4 clicks of compression on the front of my 4th gen with 600 in lb front springs and DA shocks. So I won't say you're wrong to try that setting, I had good luck with it (but opinions always vary).

Beyond that, I'd start looking for a dead shock that's leaking or broken (you may not always see that from the outside). But I'd start at the top of this list first.

[Blainefab]

Agreed on getting rid of the poly bushings in the rear, first.

Make sure the upper panhard brace is tight, and all control arm bolts are tight.

Make sure the swaybar endlinks are not overtight - just snug is OK, bulging poly is too tight.

What tires and what pressure are you using?

What exactly does "Totally rebuilt suspension in front" mean? OEM replacements or more poly? The only places poly is recommended on these cars are swaybar D bushings/endlinks, TA and trans mount, and maybe the chassis end of the rear LCA's.

This post has been edited by Blainefab: Nov 16 2010, 09:47 PM

[FASTFATBOY]

Thanks for the help guys.

To be more specific, the steering wheel goes back and forth like a bumpsteer issue, almost like the suspension is in a bottom out situation. When it hits the bump when loaded you immediately start fighting the wheel. Car doesnt seem to be sliding around just bouncing hard and the wheel is back and forth.

The front was rebuilt with stock replacement MOOG stuff. Here is a link to what the car has.

http://www.ls1tech.com/forums/vehicle-clas...trano-more.html


I knew the rear end stuff was a Problem after the reading "Chassis Engineering" By Herb Adams, good book. In this book nylon bushings are recommeneded, anyone use them and where are they sold?


Alignment is to factory specs

[robz71lm7]

Failed caster bushings caused my car to become almost uncontrollable when hitting a bump in corner entry to mid turn. I wasted a lot of time chasing gremlins to find that was the issue.

[FASTFATBOY]

Failed caster bushings caused my car to become almost uncontrollable when hitting a bump in corner entry to mid turn. I wasted a lot of time chasing gremlins to find that was the issue.

Caster bushing?

[FASTFATBOY]

SO which LCA/PHB combo? I looked on Strano's site Buy some UMI with poly on one end and rod end on the other?

WHats the skinny on the Roto-joint deal?

[firehawkclone]

SO which LCA/PHB combo? I looked on Strano's site Buy some UMI with poly on one end and rod end on the other?

WHats the skinny on the Roto-joint deal?

I can't tell you about the roto-joint, but I've had my PHB on for 5yrs plus and trailing arms both with double hiem's. Still tight with no noise. It is a Ca track only car though.

I would do the double rod ends myself.

[Blainefab]

For a mostly street car, I'd use poly one end/rod end the other rear LCA's. For a mostly track car I'd use rodends both ends. For either use, the panhard is best with rod ends both ends.

A new Moog caster bushing was in the link you posted, if all that new stuff is on the car, properly installed and with tightened fasteners you're in pretty good shape - what I don't see are tie rod ends, they go about 90K mi with street use, much less with track use and sticky tires. Also the hubs are suspect at that mileage.

To do a quickee tie rod check, roll the drivers window down, put the key in and turn enough to unlock the column but don't start the motor. Stand outside the car with one hand on the wheel and one hand on the RF tire, gently turn the wheel back and forth, feeling for directly related motion of the tire - if there's a spot where the wheel turns with no motion of the tire, tie rod ends are the prime suspect, then the steering intermediate shaft, then the rack.

Jack up each corner, grab the wheel top and bottom and try to rock it in/out - any play here (assuming your lugnuts are tight) indicates a worn hub.

A whacked alignment and/or badly worn tires can make the car darty on bad pavement - there should be a sticky here with recommended alignment settings. The trick is finding a shop that has good equipment and will align to your spec and not just light up the green lights on the machine.

This post has been edited by Blainefab: Nov 17 2010, 08:57 AM

[FASTFATBOY]

Don't want rod ends on both ends, I street drive the car too much.

I may do the Spohn Del a Lum deal on both ends or the UMI Roto joint on both ends. Thoughts. anyone use these?


WHat are some other suspenion companies who sell stuff for these cars I can look up?


BTW Sam, thanks for the time on the phone today.

This post has been edited by FASTFATBOY: Nov 18 2010, 01:03 AM

[sgarnett]

The Spohn Del-Sphere joints are very similar to the UMI Roto-Joints. My rear LCAs have Roto-Joints at the rear and the Howe rubber bushings (much stiffer than stock) at the front. I already had the Howe's or I might have tried Rotos at both ends. So far, I like them just fine, but it's too early to say.

For the PHR, good-quality teflon-lined rod ends are quiet and last a long time (it's much more rod-end-friendly than the LCAs), so there's no reason to look any further.

The 3rd gen rear Koni (which many use on 4th gens), you will need to disconnect the lower end, extend the shock, reach up and press the button on top of the shock, and turn it to one of the 4 detents. The 4th gen rear Koni adjusts from the top. The carpet is already perforated over the shocks, so you can use a sharp knife to cut along the perforation, lift the flap, remove a foam insert, and there's the shock. Put the foam back in, trim off any frayed fluff from the felt padding, and tuck the flap back down. It's nearly invisible. Or, you can lift the carpet.

[FASTFATBOY]

Well I found most of the problem, I got to piddlin around today with the car. The owner that installed the shocks said"Installed as they came out of the box".

I checked the rears, right rear almost full loose, left rear almost full tight(SA'S). Right front 6 clicks from full soft, left front 4 clicks from full soft on compression(DA'S). Didnt look at rebound it got dark.


I set the rears on full soft, fronts 4 clicks from full soft on compression. WOW what a difference!

[v7guy]

probably a bit "late to the game" but here's another vote for rod/rod PHR. it really helps out the rear of the car. I also have rod/rod LCAs and while they did add some NVH it's not anywhere close to an issue for me. The rear still steps out under bumps/washboard but it grabs quickly and repeatedly. It was a bit unsettling at first but after I knew what the car would do I feel pretty comfortable with it.

[Sam Strano]

Well I found most of the problem, I got to piddlin around today with the car. The owner that installed the shocks said"Installed as they came out of the box".

I checked the rears, right rear almost full loose, left rear almost full tight(SA'S). Right front 6 clicks from full soft, left front 4 clicks from full soft on compression(DA'S). Didnt look at rebound it got dark.


I set the rears on full soft, fronts 4 clicks from full soft on compression. WOW what a difference!

I'm glad you found out just how critical shock damping is to how the car works, even if was sort of by mistake. (IMG:http://www.frrax.com/rrforum/style_emoticons/default/smile.gif) So much for those that think adjusting shock damping really doesn't matter--clearly you can drastically change a car's behavior that way. (IMG:http://www.frrax.com/rrforum/style_emoticons/default/smile.gif)