Corner Balancing Trouble Shooting

[Steven Seiler]

In March I was able to get my car to corner balance and align (see pic1)

Pic 1

After tracking in early April, I have been unable to get my car to properly corner balance. I did go two off during a track event. If the car is level, the corner balance is significantly off (see pic2) with a cross balance of 65% / 35%. The only way that I have found to get the corner balance marginally close is two raise the right side of the car about 3" higher than the left side of the car.

Pic 2

For trouble shooting I have switched my springs and dampeners on the rear from left to right without any change. I have removed the springs.
At full droop with spring tension off, the right ball joint is 111 mm below the frame. The left side hangs 64 mm below the frame. The frame is sitting level in the garage (see pic3).

Pic3

At full bump, The right ball joint is 136 mm above the frame, while the left ball joint is 155mm above the frame (see pic4).

Pic 4

Manually lifting the control arms reveals approximately the same effort to bring through range of motion.
Total excursion of the right ball joint is 247 mm, while total excursion of the left ball joint is 219 mm.
There is definitely a difference between both sides. I have cleaned the helm joints with brake cleaner and compressed air to ensure the were no rocks binding anything. This did not change the droop and bump distances. The bottom of the rear chassis is level with a laser level.

I have put straight edges on all the control arms to check to ensure nothing is bent. The only thing that I found is the right lower control arm has a slight bend in the middle (see pics 5 and 6).

PIC 5. PIC 6

I am still assuming something is bent or bound on the suspension to create the inability to corner balance the car that I can not find. Does anybody have experience with this? I am considering the following next steps determine a solution of this problem. First take off both axles and place control arms back together. Measure the droop and bump again to see if anything changes. This would eliminate the axles / CVs as a source of the binding ( I'm not even sure if this step makes sense).
If there is no change in the droop and bump, then take off all of the control arms to see if there is one that is bent that I can not visualize. I have templates and new control arms except for rear upper. At the same time check all the heim joints to see if one is excessively bound.

Does anybody have any other wisdom or ideas? Should I be looking at something else? Is there a more effienient way to figure this out?

 

[Nine Four Motorsports]

Hey Steven, Brian from Nine Four Motorsports.

It's really challenging to diagnose an issue through pictures, when the easy "in person" checks don't reveal the issue first. I'm not sure where you are located, but we'd be happy to work your car into our schedule to diagnose and repair it. In the meantime, I'll give some generic information from what we have seen on our NP01s.

- Bent or broken suspension piece/s (ex. push rod, control arm, heim end, etc.)
- Loose adjuster. (ex. loose jam nuts on the push rods can allow the rods to rotate and lengthen/shorten on track)
- Your issue does not really sound like a binding issue.
- Typically, any bend in a control arm is less than desirable. What looks like a small bend with a straight edge, can be a large measurement difference at the ends of the control arm. Even if the lower control arm does not turn out to be the source of your issue, it should be replaced.
- We have seen what appears to be a "light" off damage suspension components. We have seen bent control arms, bent aluminum push rods, and bent heim ends. We have not seen rockers bend, but we have seen them crack.
- This sounds elementary, but always check the basics first. Basics of everything, even your setup equipment. I have seen first-hand where two scale pad wires were switched, and it led to hours of headache trying to set up the car before someone finally found the switched wires.

If you have any other questions, or would like to talk in more detail, please let me know.

Thank you,

Brian

 

[C.Plavan]

Also may be obvious, but I have done it before. Make sure FARB and RARB are disconnected.

 

[LGMan717]

Doesn't sounds like a binding issue to me. Sounds more like something is bent.
I doubt its an axle....
Replace that bent control arm
Remove and inspect the pushrods and the rockers. (I had a 2 off and turned a pushrod into a boomerang a few weeks ago, also cracked a rocker)
Can you tell what is acting as the stop on each side in bump and droop? Compare those parts side to side for damage.
I would pull the entire rear suspension apart to look for bent things.
Are the bolts holding the camber plates on the end of the upper a-arms tight against the upright?
Check the welds on the lower A-arm pushrod clevis - I had one of these crack after an off track excursion.
Check each clevis where the a-arms attach to the transmission.

Check the front of the car too.

 

[Steven Seiler]

I live in Colorado; a little far from Alabama. Thanks for all the suggestions. I will start taking the car apart and see if I can find out what is the problem.

 

[Steven Seiler]

I have not started to pull things apart yet. Just for documentation purposes, I measured the droop and bump in the front with the frame level, and the springs off. The left front droop is 11 mm compared to 17mm on the right. The bump is 139 mm on the left and 137 mm on the right. Total excursion between the two is 150 mm on the left and 154 mm on the right. Much closer to each other. I would think this points to the problem being in the rear. That slightly bent lower control arm is the front right. I still plan on changing that also.