Cause of squirrelly feel on hard acceleration?

[VetteMed]

Entire suspension has been redone with poly bushings, and Banski rod ends in the rear.

[scottfab]

Originally Posted by rhipsher

Mine felt like that until I rebushinged the entire car with poly. Brand new inner/outter tie rods. And rebushing the steering rack. All my problems were gone instantly. I do all of my own work because I do a better job than any shop. The only thing I use a shop for is to mount and balance my tires and do a road force alignment. Thats it.

Ya know I'd bet most of us do our own work but that's just a guess. Oh boy time for another "poll" to find out.

I've done everything from rebuild the ZF6 to fixing the electronics in the door chime. And I published "How to" pictorials on the ZR-1 Net Registry page for many of these. The only time mine has seen a shop was to verify the alignment I did using a square and a tape measure . Even with tire replacement I just take the wheels down. No sense in traumatizing the car by letting it see the inside of a shop.

I need to go check my steering rack in the next few days. Could it be ???? hmmmm

Another thing that leads to twitchy steering is out of spec toe in. If it's too close to zero...... not good.

[tomtom72]

Disclaimer: I've never done an alignment using the string method. I've never rebuilt any of the suspension myself.

With that said Andrew I'm thinking
1.) just on hard acceleration? Not just going very fast down the road, as in steady state velocity?
I think it's the Camber settings if they're at zero(?) you get very quick steering, but ya have to pay attention & stay on top of the steering. I think?

2.) Too much weight transfer under hard acceleration due to too much rear end squat? I don't really know what to do about that as it's supposed to be 'designed' in to our rear suspension. Maybe too much HP? I'm just throwing this out there as I pulled this out from you know where.

3.) check the rack for too much free play. My backyard method would be to center the wheels, and then move the steering wheel and see how long it takes the tire to react. I would think you would get a sense if it took too much steering wheel movement to get tire movement? What about the rack mount points?

4.) the thrust angle thing along with the rest of the alignment specs would be on my list also. I had a 'pulls right slightly' going on after my last alignment but it turned out to be the rear toe! I had no trouble with straight line stability, at constant velocity or under acceleration, just that slight pull to the right.

5.) You rebuilt the suspension so is it possible something failed ( due to a defect ) in the front end? Like maybe just at one side of the car? Like an end link or bushings?

6.) bad shocks? Like the rears compress too easily & unload the front too much? Hey, how important is our front spoiler to stability?

okay I think I'm out in left field now so I'll be still.


Tom

[VetteMed]

Originally Posted by tomtom72

Disclaimer: I've never done an alignment using the string method. I've never rebuilt any of the suspension myself.

With that said Andrew I'm thinking
1.) just on hard acceleration? Not just going very fast down the road, as in steady state velocity?
I think it's the Camber settings if they're at zero(?) you get very quick steering, but ya have to pay attention & stay on top of the steering. I think?

2.) Too much weight transfer under hard acceleration due to too much rear end squat? I don't really know what to do about that as it's supposed to be 'designed' in to our rear suspension. Maybe too much HP? I'm just throwing this out there as I pulled this out from you know where.

3.) check the rack for too much free play. My backyard method would be to center the wheels, and then move the steering wheel and see how long it takes the tire to react. I would think you would get a sense if it took too much steering wheel movement to get tire movement? What about the rack mount points?

4.) the thrust angle thing along with the rest of the alignment specs would be on my list also. I had a 'pulls right slightly' going on after my last alignment but it turned out to be the rear toe! I had no trouble with straight line stability, at constant velocity or under acceleration, just that slight pull to the right.

5.) You rebuilt the suspension so is it possible something failed ( due to a defect ) in the front end? Like maybe just at one side of the car? Like an end link or bushings?

6.) bad shocks? Like the rears compress too easily & unload the front too much? Hey, how important is our front spoiler to stability?

okay I think I'm out in left field now so I'll be still.


Tom

Tom, all good things to consider.

At constant speed, the steering feels stable, with that slight pull to the right. Not darty at constant high speed for the most part, just while accelerating.

Shocks were rebuilt by Bilstein a few years ago, perhaps 30k miles on them (PO sent them out). Not that this is a guarantee of anything! I don't feel the floaty bouncy feel that I felt in my other Z when the shocks needed to be redone.

Steering rack, and steering rack mount bushings, are all original, and I'm a bit suspicious about that being an issue.

A defective front end component is certainly possible. On my old GMC truck, I had a new tie rod fail 5k miles after rebuild of the whole front end.

Thanks,
Andrew

[scottfab]

If the car wants to walk to the left under WOT that is "torque steer".
Basically the twist of the body from high torque. It's a fairly well understood problem with the C4 frame. Lots of thread on it recently under the Killebrew fix, the factory cross brace, R-D racing cross brace and I am sure others.
That's different from "twitchy" steering.
It can make you look like you've been drinking if you have twitchy steering on a rutted road.

[PhillipsLT5]

I think it is toe, camber & caster all cut in 1/2
That is how I did mine with me sitting in the car
You can contact VBP to be sure

[VetteMed]

Originally Posted by PhillipsLT5

I think it is toe, camber & caster all cut in 1/2
That is how I did mine with me sitting in the car
You can contact VBP to be sure

I think just the toe gets cut in half - it's listed as "total toe", half on each side.

Camber and caster are unrelated from side to side, and so are set as written.

[PhillipsLT5]

I just got off the phone with them, it applys to toe, camber & caster, cut all in 1/2

[VetteMed]

Originally Posted by PhillipsLT5

I just got off the phone with them, it applys to toe, camber & caster, cut all in 1/2

I don't understand... That means they only want 2.5-3.5 degrees of caster? Why would that be halved?

[rhipsher]

Originally Posted by VetteMed

Entire suspension has been redone with poly bushings, and Banski rod ends in the rear.

Ball joints to? Batwing bushings also? Just trying to narrow it down. If every things been done then I would have to say alignment time.