Poor-sha

I wonder how much of this is a result of those upper control arm bushings binding. It appears to act like a big rubber spring.

Bill Dearborn

I spent about 4 hours today working on the rear camber/caster. I couldn't see any reason why the left rear camber had gotten so far negative. Every thing was on my red nail polish marks I made last year and the control arm bushings all looked good.

I set the driver's side first. I got the caster adapter installed and then zero'd the gauge to the adapter with the idea that I could just work off from Delta changes. Didn't happen. With the gauge zeroed with the car sitting on the ground 0.0 caster changed to +1.6 caster with the car in full droop. That is when I thought all I have to do is change it to +2.0 and when the car is lowered it will drop to +0.8. Wrong!! I got +1.5 or something like that after I lowered the lift. So then I changed to zeroing the gauge to the slope of the garage floor and just put it on the adapter and just used the gauge to see which way the changes were moving and guessing about how far since the numbers didn't seem to correlate to what I would see on the ground. After a while I got the left rear camber to -1.8 and the left side caster to +0.8. One thing I did to speed things up was remove the wheel and attach my Longacre Caster/Camber gauge to the hub. That made it easy for me to see both gauges by just moving my head a little so I could twist on both control arm cams and adjust them until I got the readings I wanted to see.

The right side of the car was pretty similar although it didn't go any faster than the left side. Say about 2 to 2.5 hours each side. Right side camber came out at -1.9 and caster was at +0.8 deg. As they say that's close enough for government work. It would be a lot easier to do this on a set of wheel stands.

I did find that my adapter fits in the holes in the knuckle loosely and will move. When I was taking caster readings I would reach up and make sure the adapter was fully seated before recording a measurement. There were a couple of tenth's play in the adapter movement. If a shop is doing this on an alignment machine and using the GM gauge that fits into the adapter there could be an issue with the adapter sitting correctly on the knuckle especially since the GM gauge is probably heavier than the one I have. If the person working on the car doesn't notice the adapter has tilted out of the holes there could be a significant error in reading the caster.

Bill

Poor-sha

Bill, did you do anything to settle the suspension in between raising and lowering the car?

Bill Dearborn

Yes, once the lift was down I went around to each corner and placed my arm on the car and then jumped up and down with all my weight being applied to the car with my forearm. Once I finished that I would open one of the doors and stand on the door sill and jump up and down and then go to the other door and do the same thing. I had the tires on masonite panels with large construction type garbage bags between the panels. When I was using the door sill to jump up and down I could get the car moving quite a bit and I could hear the panels move. I just kept bouncing until all the sticking noises stopped.

I also moved the car back and forth about 5 ft 10 or so times to see if that made the suspension settle any more. Since I knew what the readings were on the car before I just checked the camber readings at the other three wheels to see if it came back to them. Once I started the bouncing in the door opening I didn't have to move the car anymore.

Bill

Mad Dog 24

Wow now that was a process.... but successful in the end. I was hoping you would get an answer to the unequal camber numbers. Unfortunately to realize a bent suspension component one has to purchase a new part to compare. I will be for my uca soon.

Bill Dearborn

Ran into the next problem today. Went to set rear toe. Initial measurement had 3/32 toe in and thrust angle with the rear wheels turned to the right. I was able to move the left rear toward more toe out but the right rear wheel is at its max toe in with the adjustment cam. I either have to install the Granatelli tie rods or try and redo the right side camber and caster so I have a couple tenths less camber thus gaining some toe adjustment room.

GM says to leave one shim in place at the rear upper control arm dog bones and I am not sure why they say that. Would it be a good idea to replace the GM shim with thinner shims so I could gain some negative camber and then adjust the lca cams to reduce the camber and to set the caster. I could also put thinner shims behind the rear dog bone which would add to the positive caster.

Trying to decide what to do now. March 30th is coming fast and I still have to change the oil, change brake pads and adjust the brakes along with weigh my rear rotors. I have decided not to screw around with the front axle alignment other than to make sure the steering wheel is straight after I get done with the rear.

Bill

Mad Dog 24

Bill, we tried a long time ago removing all the rear UCA shims. While we got big camber numbers there was no way to get toe in any good spec. Even with the GM recommendation of not removing them its still hard to get good camber and toe together. I've been running .05 out in the rear. We did trim some of the inner plastic shield to access them easier.

Your are welcome to my Granatelli toe rods if you need them quick as I don't for another 6 weeks, still in the box. They are nice and will allow any amount of toe in or out with little flex. LMK.

Bill Dearborn

Thanks for the offer on the toe rods. I ordered a set the day before. Waiting for them to get here.

Bill

Bill Dearborn

As some of you know from my previous posts I have been attempting to set my rear wheel alignment using a two post lift and making adjustments to camber and caster by first getting a reading with the car on the ground and figuring out how much I have to add or subtract to each setting to get where I want to be. Then I raise the car and use the full droop caster/camber readings to add or subtract the deltas I figured out before.

This works decently on Camber, not so well for Caster and can cause a problem that will damage your caster gauge adapter. What I found is the adapter can't be installed in the knuckle unless the the suspension is depressed almost completely. Once installed the left side lower control arm and the shock end clear the adapter. Not so on the right side. I installed the GM adapter with the adjustable pin at the highest point and raised the car. Once I got under the car to read the gauge I attached to the adapter I noticed the top end of the adapter was almost pulled out of the upper hole in the knuckle. This was because the lower control arm was pressing against the bottom of the adapter and pivoting it around the fixed pin in the lower hole. The problem is that pin fits tightly in the hole and the uneven pressure from the control am bent the pin as it levered the bottom of the adapter toward the knuckle and pulled the top of the adapter inward toward the middle of the car.

Installing the adapter with the adjustable pin in the lower hole (which is mandatory if you are using the GM gauge) in the knuckle seems to avoid this problem.

Bill

dvandentop

i just picked up the gm guage off ebay luckily for $200 shipped on ebay surpringly it was new in box!!
atleast have all the pieces to the puzzle to get this done once i get my new shock controller

Bill Dearborn

Spent most of today helping setup another member's car and then went back to mine. Can get -1.7 camber on both rear wheels, can get +0.7 caster on both rear wheels but can't bring the right rear wheel into a zero toe or toe in condition. Minimum we could get was 3/16 toe out with .5 degree thrust angle. Tomorrow the goal is to reduce camber to -1.4 on each side and see if we can get the rear toe down to the -0.5 mm spec'd by DSC. I figure it is better to have even cross caster, toe in set properly and next to 0 thrust angle than to have a little more negative camber. No idea when the Granatelli Tie Rods for the rear will show up. Sent email to vendor yesterday and haven't received reply yet.

We think the car isn't assembled exactly square with the rear cross member offset from the center line of the car by a small amount. I know my C6Z rear cradle was offset by about 0.1 in to the right.

Bill

spearfish25

I just got my car aligned and with +0.8 rear caster and -2.0 camber, rear toe was a problem on the right as well. Very slightly out (can't recall the value now). The left rear he got to 0 toe.

Somehow my left front was significantly toed in which explained my left steering input to go straight. No idea how that happened but noticed it one day after jacking up the car and swapping tires around.

0DSC Sport

Bill go back and look again at the rear toe make sure that only one washer was pulled off the upper arm first .Then check my spec again it's toe out your looking for in each rear -.5mm its close on the toe rod your at the end of adj. But it's there push the frt of the rear wheel out you will find out there is lots of adj you will have to move adjuster in to bring toe back in . There is plenty of sloppy play in the adjustment to get what you want. I like -1.7 camber in rear .

Bill Dearborn

Well we got it set this morning. Thought I would mark the cams where they are now and the give up on caster and gain a little camber, set my toe and wait for the Granatelli links to come in. That way all I would have to do would be to move back to the marks install the Granatelli links, set toe and thrust and be done. Marked the cams and started doing the adjustments and things didn't change as expected. So moved the cams back to the marks and checked to see where we were on toe and thrust and it fell right into a 1/32 of toe in and damn near 0 thrust angle. I decided to let it stay there and torqued everything down. On the way home from the shop we were using the car drove straight as an arrow. After we got my car off the lift we put the other car we worked on yesterday back on the lift because we knew the camber gauge had gotten our ot calibration when we switched to my car the night before. All 4 wheels were set 1 degree less than what we thought we had set them at. By now we were getting pretty good at making adjustments and were able to make the camber adjustments front and rear without affecting caster. Then we set rear toe on this car and all of the problems we had on my car were present except the corrections had to be made on the left side Vs the right side. So we made one big change and moved back to where we were and it fell into line with 1/32 toe out and near perfect thrust angle. So we had two cars with -1.7 rear camber and +0.7 rear caster. The only difference was mine was + 1/32 of toe in and Eric's car at -1/32 of toe out. DSC's -0.5 mm toe out recommendation is right about 3/64 of an inch toe out. Eric wanted the toe out and I don't mind the slight toe in so I will run that way at VIR on Mar 31st, Apr 1,2. If the Granatelli toe links come in I will install them and set to a slight toe out. If I feel like it I should be able to actually play with different rear toe angles at the track to do some experimenting.

Bill

Mu$cle

I learned a lot from Bill over the past two days. I'll have a chance to see how the DSC setting perform on 3/20 & 3/21 at VIR.

cvp33

I'll be there as well for Track Daze. I have the DSC mod and their alignment. I'm losing count but I think we have at least 4 Z06's.

0DSC Sport

I would like to be there but I will be coming back from Sebring. VIR loves a soft car make sure to have the touring profile in the sport mode or even the track mode its the shock calibration you want to take from the touring and run in the track. Last year at IMSA we went from running 1.53 to running a 1.511 just by going softer and softer in setup almost a rain setup its crazy what can be gained there.
Have Fun

Poor-sha

I'll be there as well assuming I can get the new shocks on and alignment set.

c5racr1

started prepping for the dsc alignment on a 2017 Grand Sport, only 1 shim per bolt in the upper control arm. think GM figured something out. Ill let y'all know what the factory spec was before and after.

Bill Dearborn

Z51s come from the factory with 2 and the Z06s come with 1. I assume they are treating the GS like the Z06. GM's Track Alignment TSB from a year ago references the differences between the Z51 and Z06.

Bill