Ride height/shock adjustment asymmetry

[John H]

*The TLDR/outcome here was that the shock was completely toast. "that'll do it".


To get the car level in the front took a large difference in shock adjustment. This is with the same spring preload on either side. The only thing I know that would cause this is a lot more weight on that corner (not the case) or a spring rate difference (unlikely). Nitrogen pressure? (how much can that impact ride height?)

The left spring (right side of picture) compressed length is a little over 1/4 shorter than the other side and that's roughly equal to the difference in adjustment that was needed.

 

[DrPyro2k]

@John H - Not sure if I can help you, as I have never tried to corner balance the car myself (I'm in the process of getting all of the parts and learning). But my understanding is this... Rush pressurizes the nitrogen to a set pressure, and adjusts the shock height by screwing in/out the primary piston (silver part) with respect to the gold part. They have a little jig to set the distance between the eyelets. Then they install the spring till it engages, then add some preload. Once installed on the car, then you corner balance to get the weights correct. If you want to change the ride height (assuming the nitrogen pressure is OK), you need to adjust the screw between the piston (silver part) and the eyelet holder (gold part).

The original corner balance/ride height had 8 threads showing below the gold ring on the left side, and 11 threads showing on the right side for the front. The rear was more symmetric.

I would be curious how many hours of operation do you have on them, and what tracks (basically how bumpy). My guess is that Sebring you might be luckily to get a weekend out of a set (when really pushing it). I got about 14 hours at MSR Houston (bumpy track, but not THAT bumpy)

 

[David Hosie]

David is correct, ride height is adjusted with shock length not the spring platform. Please lift the car to droop and check your shock pressures.

 

[John H]

Appreciate it guys, but I do know how to adjust a shock, I just don't know for sure why the left spring is more compressed.

As I said there is the same 1 turn preload on the springs on both shocks, the height was not adjusted with the spring perch, it was adjusted by threading out the lower body from the piston rod. Because this is not a two piece lower body, the spring position on the lower body changes when you do this. On a two piece it would stay in the same place.

Please lift the car to droop and check your shock pressures.

I ordered what I need yesterday but it wont be here till Thursday and I was supposed to go shake down Saturday. I'm relatively confident now though this is the issue.

 

[David Hosie]

Confused what was the purpose of the OP, were you looking for input? Something is way out if you have a 1/4-1/2" differance in front shock lengths. Please remember that ride height changes will also effect toe alignment. Our procedure is to set both shocks to same length then adjust corner weight with the spring perch. Its unusual for it to be more than 3 turns difference.

 

[John H]

Confused what was the purpose of the OP, were you looking for input? Something is way out if you have a 1/4-1/2" differance in front shock lengths.

The purpose was/is to confirm something was wrong, which you've confirmed. And to identify the cause/solution. I don't see the confusion. I'm trying to get it sorted ASAP so I don't end up eating registration fees.

Please remember that ride height changes will also effect toe alignment. Our procedure is to set both shocks to same length then adjust corner weight with the spring perch. Its unusual for it to be more than 3 turns difference.

Yea since everything was out of whack up front I assumed the car didn't come setup and I started setting it up and ran into this which I thought shouldn't be happening which you've confirmed.

 

[David Hosie]

The purpose was/is to confirm something was wrong, which you've confirmed. And to identify the cause/solution. I don't see the confusion. I'm trying to get it sorted ASAP so I don't end up eating registration fees.



Yea since everything was out of whack up front I assumed the car didn't come setup and I started setting it up and ran into this which I thought shouldn't be happening which you've confirmed.

Every car goes through a full set up on the scales before leaving the factory. Yours did also. What were you leveling and where were those measurements being taken? Every chassis has minor variances the pick-up points do not so this can have an impact on what you are trying to do when "leveling". We take calls 24/7 and are happy to work through questions with anyone experienced or otherwise.

 

[John H]

Every car goes through a full set up on the scales before leaving the factory. Yours did also. What were you leveling and where were those measurements being taken? Every chassis has minor variances the pick-up points do not so this can have an impact on what you are trying to do when "leveling". We take calls 24/7 and are happy to work through questions with anyone experienced or otherwise.

Sorry this is becoming frustrating because we're not on the same page or you're not believing what I'm conveying. I suggest calling me this afternoon or tomorrow to discuss but I'm going to give you the full play by play at this point since constraining things to the most pertinent details has apparently led to misunderstanding.

The first thing I noticed was the camber was way out of spec and uneven. There was a degree difference between sides. So I started checking the full setup and noticed the ride height was off and very un-level. Now expecting I needed to do a full setup (at the time assuming it wasn'tt, because of these observations) I ordered some camber shims. While ordering them Blair did confirm they were aligned before shipping, but the alignment was obviously out so I started working on correcting the ride height first (measured at the dictated front most cross member). Once I had it leveled camber matched again, but as I leveled it I very quickly found what I've been describing here. One side was taking a lot more adjustment than the other and the spring was compressed more at rest (again, despite equal preload).

Oh no I said to myself this isn't right, lets check with others, maybe there's something I'm missing. Leading to this post.

Now with those full details that hopefully clear up any misunderstanding, and moving on to getting me to the track this weekend so I don't throw money down the drain.

Given that you align them before leaving (which I figured you did), what could explains this? At this point my best presumption is the shock pressure. At first I didn't think that would be the case to this degree but since I first posted i've come to understand that yes, an issue would cause the suspension to significantly sag on that corner, which would throw everything out of spec. I don't have the tools to measure the shock pressure right now and am waiting on them, they are now delayed till Friday.

But, if there's a better suggestion given all these details that I can direct attention to in the meantime I'd love to hear it. (I can't direct my attention to not adjusting the height with the spring perch, because I was never doing that)

 

[DrPyro2k]

@John H - Definitely give them a call, they are always helpful to diagnose issues. Things might come across a little curt on the forum, but they are very willing to help!

Now on to your issue... My best guess is that one of the shocks has leaked out its Nitrogen. When mine were below the specified pressure ride height was lower. I never measured it directly, but I would bottom out the car over the worst bumps at our track. After rebuild, things look better for ground clearance. (I'm still working on getting an alignment space/tools setup for the couple of us that share a garage, then I'll be able to quantify and track setup)