Hey guys,

I have a 1995 Z28 Vert. Recently I went to my tire shop & had them install the Eibach pro kit 3831.140 along with a set of C6 Replica's (not sure what brand)wrapped in Nexen N3000 Tires (245/40r18 front, 275/35r18 back) My setup before was the factory 16" 245/50r16 & it rode like a caddy smooth up to obscene speeds. Ever since the drop & new wheels I've have horrible vibrations & took the car back 3 times to have them try to figure it out. They've road force balanced it by the center hub & last time using their new finger setup (which uses the lug nuts) & it doesn't seem to get rid of the vibrations. I have the old Bilsteins up front (B46-1913 & newer BE5-2407's in back) Right now the vibrations aren't too bad at about 80 but at 70 & 90 plus it's a chuck wagon going down the interstate. Also going over bumps feels like the shocks can't keep up with the higher spring rate. I realize by going up to a 18" wheel that it will be harsher & I've read about the issues with both sets of shocks.

So far my thoughts are:

- Maybe the pinion angle is off from lowering?
- Need better shocks, but probably not the vibration issue
- I have him searching for the factory wheels so I can isolate the new wheels / tire combo & put the old ones back on.
- If anyone near Nashville, TN has a set of (known good wheels & tires) I could borrow I'd be glad to pay some $$ to try them out

Any other ideas would be appreciated

Thanks,

Sean

 

I would go after the pinion angle first

 

Thanks for the reply. I'll look into that.

Anyone else with the same lowering kit end up having to move to an adjustable torque arm?

 

Like wrd1972 said its the pinion angle off ,and thats putting strain on the u joints and thats where you getting the vibration.Search and you will find LOLTS of posts on what else needs to be done after you lower your car. For example; it needs a front end alinement, but you should use different numbers than stock.

 

95zsean thanks for the reply, an alignment was performed when the lowering kit was installed, but I didn't get a copy of the numbers. Since you seem to have a similiar setup which adj-torque arm did you go with & what's the recommended alignment specs for our lowered z's. I'd like to get the one that moves the front mounting point away from the trans, but since it's lowered I wasn't sure as to which mfr had the best clearance.

 

All my suspension stuff is UMI, and my Adj. torque arm goes to the trans, and is set -2degrees. Unless your going to make "Alot" of power I'd use the trans mount one as the ones that mount to the tunel tend to vibrate inside the car.

I used "Injuneer's" line up numbers: +4.0 Caster, -1.0 Camber, 0.1 Toe, and have had NO wear problems.

This year I did the LS front break upgrade and he could no get those numbers!!!! but it was close.

I also added KYB AGX's front and back and it made a "BIG" differance, no more bouncing..

I did alot more than that to it this winter....I guess i should update my sig......