Paging Evil Dave (or other Z suspension experts)

[AZhitman]

Just replaced the entire front suspension setup in the RB-powered '72 Z with adjustable LCA's and tension rods.

Lowered on Eibachs and Koni adjustables, with 16x8 wheels, 245/45/16 tires.

Looking for some good alignment specs for street use (so I can give them to my alignment shop).

TIA!

[evildky]

Camber: A good starting point is about 1.5 degrees of camber all around, this aids with turn in and steady state turning without sacrificing tire wear on a street driven car. You could run less For a track car much more makes the car twitchy at speeds and for an autocross car more like 3 degrees up front and the back will depend on your ability to put the power down. I like less camber on the rear in a high horsepower car, for a car closer to stock hp levels you can run more camber without the loss of corner exit traction.

Caster:I'd shoot for a minimun of 3 degrees for a street car. For a track or autocross car 4 ro 5 degrees is a minimum and more if possible, you might find that your wheel tire combo limits the amount of caster you can dial in before somethign starts to rub on lock.

Front Toe: Street driven or track zero degrees you might opt for a total of 1/8 toe out if you like to hit the switchbacks, for an autocross car 1/8 to 1/4 total toe out, really makes the car eager to turn, can and twitchy at speeds.

Rear Toe: Street and track, again zero degrees, for an autocross car 1/8 to 1/4 toe in tightens up the turns.

[AZhitman]

You're a Godsend buddy. Thanks Dave.

[gmac708]

Just replaced the entire front suspension setup in the RB-powered '72 Z with adjustable LCA's and tension rods.

Which ones did you end up getting? Did you make your own? Any review?

[AZhitman]

Update (and needing some input from Dave / Gord / others):

Ok, so now the Z is on the Megan /McKinney coilovers, with the adjustable LCA's and adjustable tension rods. Not slammed, still 1.5" between tire and fender lip.

A couple issues:

1) coilover "clunk" - All I can say is, GRRR. I realize they're going to be noisier than stock suspension, but the clunk when turning the wheel at low speeds is annoying. Any ideas?

2) Adjustable tension rods - The bracket for the heim joint interface with the tension rod mount on the chassis is a PITA. I know the bracket is supposed to remain "flat", as in, keeping the rod through the heim joint perpendicular to the ground, but mine wants to turn (when I tighten the control arm bolts behind the frame mount. Ideas?

3) Harshness - OK, this one's my fault, for going with ALL poly bushings for the entire suspension. My question is, if you wanted to change ONE set of bushings that would make the most difference in reducing ride harshness, which would it be? She's amazing on smooth surfaces, and the damping for large oscillations is great - but it's the small road imperfections that are the most jarring. Something that crossed my mind, but I wanted to ask the pros, CAN I use a small rubber bushing where it goes through the chassis mount? Thoughts?

4) Alignment settings - Dave gave me some good settings before, but I was talking with some of the local Z guys who said that keeping the rears as "straight" as possible (zero camber) while dialing in 2 degrees in the front, would give it a nicer feel for street use (considering the power the RB is making). Thoughts?

5) "Vibration" on hard acceleration - R200LSD, original axles (U-joint style), new driveshaft, poly mustache bar bushings and diff bushings. Feels almost like the axles might be "binding" a little or have some roughness when I give it heavy throttle and the rear squats. I have a CV axle conversion here (not yet installed) - Think that might resolve this issue, or is there something else I should look at?

Thanks in advance, guys - Trying to get her ready for MSA Nats next weekend, would like to address as much of this as I can before then.

Pics of the LCA's and TC rods:

[evildky]

1. Are you running camber plates? If so the clunk could be the pillow ball, some camber plates I've seen have journals too large allowing the pillow bearing to slide up and down a bit, if this is the case you can shim them. Preload? the clunk could be spring seat hop if you are running less than zero preload, the fix, add some preload or some zero rate filler springs. Gland nut? if the incorrect gland nut is used or a spacer isnt unsed ro somehting is loose the strut cartrige can move a bit making a clunk, the solution is to do whatever is needed to make the insert fit snugly.

2. I'm nto familiar wiht that particular lca/t/c rod setu but, you might need to spread out that tc mount and add some shims to allow for flat mounting and full articulation of the rod end.

3. The aformentioned LCA TC rod setup will only make it more harsh. I think inboard lca bushings and tc rod bushings remaining stock would smoothe things out a lot! Also spring rate and shock valving come into play, as does wheel diameter and tire sidewall. Larger wheels with shorter sidewall tires might handle better but smaller diameter wheels with more tire sidewall absorb more of the imperfections in the road.

4. We're both right. like I said 1.5 is a good starting point.Tire selction comes into play as well, zero camber rear will give you better corner exit, more camber gives you better steady state corner speed. more camber up front hels againw ith steady state cornering but the more camber you run on the street the more tire wear you'll see, it's a trade off.

5. Poly mustache mounts on a stock mustache bar? I doubt would be an issue. Poly on a billit mustache bar might well be a recipe for vibration. YOu didn't mention the pinion mount? a RT mount wiht a poly mount will transmit more vibration than a stock mount with the snubber. Bad U jounts on stock half shafts can certainly cause a vibration. You didn't mention the engien/trans mounts. Poly will make the car vibrate but more of an issue at idle, makes the car buzz. I don't know how well the swap kit you used is engineered but the trans output shaft and the diff pinion flange should be paralell but not perfectly lined up, if they are lined up the U joints develope flat spots and vibrate.

[AZhitman]

1. Are you running camber plates? If so the clunk could be the pillow ball, some camber plates I've seen have journals too large allowing the pillow bearing to slide up and down a bit, if this is the case you can shim them. Preload? the clunk could be spring seat hop if you are running less than zero preload, the fix, add some preload or some zero rate filler springs. Gland nut? if the incorrect gland nut is used or a spacer isnt unsed ro somehting is loose the strut cartrige can move a bit making a clunk, the solution is to do whatever is needed to make the insert fit snugly.

2. I'm nto familiar wiht that particular lca/t/c rod setu but, you might need to spread out that tc mount and add some shims to allow for flat mounting and full articulation of the rod end.

3. The aformentioned LCA TC rod setup will only make it more harsh. I think inboard lca bushings and tc rod bushings remaining stock would smoothe things out a lot! Also spring rate and shock valving come into play, as does wheel diameter and tire sidewall. Larger wheels with shorter sidewall tires might handle better but smaller diameter wheels with more tire sidewall absorb more of the imperfections in the road.

4. We're both right. like I said 1.5 is a good starting point.Tire selction comes into play as well, zero camber rear will give you better corner exit, more camber gives you better steady state corner speed. more camber up front hels againw ith steady state cornering but the more camber you run on the street the more tire wear you'll see, it's a trade off.

5. Poly mustache mounts on a stock mustache bar? I doubt would be an issue. Poly on a billit mustache bar might well be a recipe for vibration. YOu didn't mention the pinion mount? a RT mount wiht a poly mount will transmit more vibration than a stock mount with the snubber. Bad U jounts on stock half shafts can certainly cause a vibration. You didn't mention the engien/trans mounts. Poly will make the car vibrate but more of an issue at idle, makes the car buzz. I don't know how well the swap kit you used is engineered but the trans output shaft and the diff pinion flange should be paralell but not perfectly lined up, if they are lined up the U joints develope flat spots and vibrate.

I'll answer what I know... Looks like I'm in for a Master's-level edumacation on the topic.

1) Got camber plates. Not certain if the pillowball journal is the issue - how can I test for this, Dave?
As far as preload, no - they were set to snug the coil, but no preload.
I'll check the gland nut, but I'd think (since the setup was all designed to function together), that'd be the last possibility.

2) The rod end (at the chassis) would only go up/down, so maybe I'm lost on the "shim / flatten" idea.

3) That's what I was afraid of. What do you think of the idea of running a small bushing to isolate the T/C rod from the chassis? Plenty of sidewall (245/45/16 all the way around).

4) Ok, cool. Not too worried about tire wear, but not too worried about optimum cornering for street use either. I'd rather do away with some of the "skittishness" when cornering on an uneven / rough surface.

5) Can't recall the pinion mount, but I know I've got the stock limiting strap in place (new).
No "swap kit" on this car - All fabricated. Trans mount is stock rubber isolator on a home-brewed beefy trans mount bracket (thick steel). Engine mounts are Delrin on alloy blocks (but engine vibration actually is pretty minimal - super-smooth at idle).
I'm thinking the most likely culprit under hard acceleration is my halfshaft U-joints. I'll look at the relationship of the output shaft and pinion flange and see what the angle of the shaft is.

Thanks for walking me through this stuff Dave!

[evildky]

1. You should be able to see the pillow ball (or spherical bearing) that the strut bolts to in the camber plate, and it should be resting against a seat in the camber plate, jack up the car and unload the suspension, see if there is now a gap between the bearing and the shoulder in the camber plate, if there is no gap then the pillowballs are snug in their journals and not the issue.

2. you said the tc mount would not sit flat against the tc mount in the chassis, I assumed this was because the bracket was binding on the rod end, if thats not eh problem then my response was off base. If it won't sit flat because it does not fit the tc mount properly then I guess you need to machine it or fab a new adapter.

3. It's worth a shot, all these handling improvements come at a price, you have to pick your own happy compromise.

4. "skittishness when cornering on an uneven / rough surface" If we're talking aobut an off camber turn bigger sway bars will improve the feel. Less rear camber makes the back end looser in the corner but gives better rtraction for corner exit, more camber improves in corner traction but makes corner exit loose. If we are talking about an off camber turn. more front camber again helps with stability in corner but less will make the front end push. any of that help?

5.Delrin engine mounts and rubber trans mount? So if the drive train is gonna move it's gonna be on that rubber trans mount.

[AZhitman]

Ok, gave it a much better once-over today.

Pillowball is all good. No motion. Looks like the left side steering arm has some slop in it, inside the gator. Oh, joy.

I meant to say that the TC mount (the U-shaped bracket) wants to rotate in the "cup" (where the rubber bushing would have been). Obviously, it should remain straight, so that the axis of motion of the TC rod remains up/down.

Got fat sway bars already F & R. Today, I did dial the rear wheels in to as close to 0* as I can get them. I'll have to get it on an alignment rack to check F camber / caster. I did a "tape-measure toe" check on the front, but that's about as accurate as eyeballing it... so I'll leave the fine-tuning to the suspension shop as well.

I'll probably lean towards a little bit of "push" for this car, considering it's a street car and I don't need either of us "looping out" in traffic when she gets into boost.

Ran outta time before I could look at driveline angles. Thinking I might put it on my lift for that, so I can see it with the weight ON the suspension.

[evildky]

Gator? Inboard tie rod?

Oh so the mount spind inisde the moutn pocket, so it's not tigntening enough? maybe add a lock washer between the rod moount and the giant washer?

Swap to a lighter rear bar or remove ti all together, it'll give you better tradtion on uneven surfaces. while degreasing oversteer.

[AZhitman]

Gator? Inboard tie rod?

Oh so the mount spind inisde the moutn pocket, so it's not tigntening enough? maybe add a lock washer between the rod moount and the giant washer?

Swap to a lighter rear bar or remove ti all together, it'll give you better tradtion on uneven surfaces. while degreasing oversteer.

Gator = the bellows-shaped rubber "boot". Yep, inboard tie rod. Fun fun.

Yep, think I'll do a fat lock washer. Still looking at using a small bushing between the TC rod mount and the frame. It'd be a dense rubber. I'll post results.

I can definitely lose the rear bar. I'll drop the links and see how it handles. That shouldn't affect straight-line launch, should it? (considering the rear squats evenly)

[evildky]

It actually should help the straight line launch