Help adjusting coilovers

[tonysaur]

Hi friends, I installed ST XA coilovers 2 weeks ago. I’ve been trying to make all 4 corners even with a 1.5” drop or at least make the fronts even and backs even, but the task seems impossible. Whenever I raise or lower one wheel, the other 3 wheels will raise or lower an unpredictable amount and I never know if it will be raised or lowered. How did you go about leveling all 4 corners when adjusting one corner drastically changes other corners? Here are the best numbers I was able to get so far just randomly raising and lowering at arbitrary amounts:
Perch height/Fender to top of rim height in mm
Driver Front 126/130.8
Passenger Front: 115.1/135.1
Passenger Rear 44.4/133.4
Driver Rear: 44/140.5

The fronts tend to raise and lower together, for example raising the driver front 3mm will also raise the passenger front 2mm. Seems like I keep chasing evenness, but can never achieve. Then the rears also change, which also affects the front. Please help, what are your strategies? This seems to be more of a Tesla specific issue with the incredibly rigid frame, I hadn’t had this problem on my 94 Honda Prelude with coilovers.

 

[John in LB]

When leveling, focus on the bottom of the battery pack, near the lift points, instead of the fenders. The goal is to minimize torsional stresses on the car's frame. I got my 4 corners within 3 mm from each other.

If you look at the owner's manual for China MY, you can see height specs and location... in the alignment section.

 

[QtownTaxiGreg]

I have never done anything like that but the above advice seems sensible. I really know very little about car suspensions but I have curious mathematical mind.

Intuiatively I would attack it as what is known as an iterative process. You need to make one small adjustment, see what happens and note the effects on the other three corners. Then make a reverse adjustment to the diagonally opposite corner to see those effects.

Between those 8 data points you should have enough information to calculate an adjustment to each corner that gives a net level. Intuitively, not a promise.

It is a bunch of simultaneous equations. You can Google that and it will give you a maths lesson you can really use.

There are three embodied assumptions:

1. It's just a bunch of springs.

2. Anything you do to the left will have the exact same effect when done to the right, but mirrored.

3. And an up move anywhere has the mirror opposite effect of a down move, at the other corners.

Also that you are starting from somewhere roughly balanced and not overly torquing the battery / body at the get go.

To the extent that it is properly shagged at the moment, that will result in more iterations being performed under the 3 assumptions, until you are all done.

 

[tonysaur]

The numbers don’t make sense. For example, here is my latest adjustment for the passenger front height:
Passenger front movement: -2.7mm
This single 2.7mm drop caused odd affects to the other 3 corners:
driver front: -3.2mm
Passenger rear: -4.1mm
Driver rear: +.9mm

As you can see, the drop in the passenger front caused an amplified drop in the driver front and passenger rear, which makes absolutely no sense. The only thing that does make sense is the increased height at the opposite corner in the driver rear.

 

[QtownTaxiGreg]

Hmm. The numbers are very weird indeed! On the face of it I have no idea what is happening. On the other side of that is the happy fact that I don't need to for the maths to work!

If you now drop the driver rear 9mm it will make the maths easier.

Before you do that, are any of the corners close to where they need to be at this point? Actually, better not to know as it may mess with the systematic approach! Delay that.

 

[QtownTaxiGreg]

It seems like the body is well flexible when you have put a 13.1mm skew into the rear by shifting the front around a relatively small amount. I am tempted to call it measurement error but I don't know enough about it to go there.

A better plan at this stage may be to attempt to reverse the last change by bumping the passenger front back up the same 2.7mm and see where that lands.

 

[tonysaur]

The rears are easy, but time consuming to adjust as I have to remove the strut and spring to adjust the collar with absolutely zero resistance. The Fronts are difficult but quick to adjust because I just have to remove a wheel to adjust the collar in-place, however that collar is frikkin hard to turn because of the spring pressure, I’ve already broken 3 adjustment notches, any more and I won’t be able to adjust them in-place anymore. Cheap plastic garbage collars.

Another annoying thing is after adjusting a collar, it takes 2-3 days of driving 2 hours a day for the height change to settle in. For example I just dropped the driver rear by 5mm, I drove around for 20 minutes on bumpy roads and only measured a 0.6mm drop! Like come on man, I gotta wait 2-3 days for it to drop the other 4.6mm. This is so frustrating.

 

[tonysaur]

When leveling, focus on the bottom of the battery pack, near the lift points, instead of the fenders. The goal is to minimize torsional stresses on the car's frame. I got my 4 corners within 3 mm from each other.

If you look at the owner's manual for China MY, you can see height specs and location... in the alignment section.

What tool do you use to measure distance between floor and battery pack? I can’t use a caliper down there, or a solid ruler. I suppose I could use a tape measure, but would have to bend it when it hits the battery pack and I wouldn’t get a very accurate reading.

 

[QtownTaxiGreg]

I feel your pain. There has to be a better way if it is taking so much driving for anything to be measurable.

 

[John in LB]

What tool do you use to measure distance between floor and battery pack? I can’t use a caliper down there, or a solid ruler. I suppose I could use a tape measure, but would have to bend it when it hits the battery pack and I wouldn’t get a very accurate reading.

Measuring tape, in combination with level that is up against battery. The spec says +/- 5mm... (3/16") so, you should be able to measure within that accuracy.

 

[John in LB]

1st, drive suspension for ~1000 miles, making adjustments as needed.

Then confirm it is level.

Fnally, take it in for alignment (with 300 lbs of weight in driver/passenger seats as per spec).

At the end of process, it felt pretty solid, less squirmy...

 

[ngng]

What tool do you use to measure distance between floor and battery pack? I can’t use a caliper down there, or a solid ruler. I suppose I could use a tape measure, but would have to bend it when it hits the battery pack and I wouldn’t get a very accurate reading.

Use a measuring tape from the battery pack points to the floor. It’s accurate enough.

It’s a lot harder to adjust on the car, especially with those crappy adjusters. Honestly, if I need to make an adjustment I’ll pull the fronts and conpress the springs so there’s no tension. Rears are a few nuts to drop the arm as well.

At this point I’d probably pull all and set the corners off the car instead of making small adjustments like you’re doing.

Once you are satisfied with your ride height you should corner balance the car. It’s probably way off

 

[Sweed269]

Chasing the ride height is a fools errand.
Let's assume your springs aren't terrible and are similar enough to not matter side to side.
First set the total length to the required setting. Then measure the thread gap to the adjuster and set them the same side to side. If the front or rear needs adjusted do it as a pair.
If you mostly ride alone then the driver side will ride lower and you can level this by adding 2mm extra preload to the driver's side springs. When you get it aligned add 100-150 under the driver's seat.

Corner balancing is the gold standard if you can find a place to do it. Make sure it's fully settled and close to desired height.

 

[QtownTaxiGreg]

And lo, there is a better way!

 

[tonysaur]

Ok friends, I been adjusting these coilovers like crazy. The perch heights are all over the charts. The front 131.5mm and 115.1mm, the rear 40mm and 44.4mm. Compressing the spring is super annoying to adjust the fronts, I kept breaking the plastic tabs trying to adjust in place, I found that unbolting the three top hat mounts and pulling the shock down allowed for much easier adjustment because I spin the whole piston, spring, and top hat together. I don’t have to overcome the friction between the adjustment and spring collars being smashed together.

That being said @Sweed269 is right, chasing exact ride height is a fools errand. My tools are to precise, and I will never achieve 2-3mm tolerance. I’m at a 5mm tolerance right now. I removed a 20lb baby seat and it threw off all the measurements by 2-5mm. I’m just gonna leave it as-is, good enough.

 

[Sweed269]

I went down this rabbit hole and there are just too many variable that change for ride height to be a good balancing tool. Bushing flex, chassis flex and suspension bind all make it a moving target. Alignment is changing with adjustments too and effects the height.
I would personally even out the fronts and rears, then call it a day. Maybe add a couple mm to the heavy side.

 

[ngng]

I went down this rabbit hole and there are just too many variable that change for ride height to be a good balancing tool. Bushing flex, chassis flex and suspension bind all make it a moving target. Alignment is changing with adjustments too and effects the height.
I would personally even out the fronts and rears, then call it a day. Maybe add a couple mm to the heavy side.

what do you mean balancing tool? i preset all four corners prior to install, measured the ride height, wrote down the approx height change with 10 turns, then dialed the car in with the appropriate ride height and rake. rears are quick, fronts were more of a pain since there was tension, but since i was raising the car, it wasn't too bad. corner balance and alignment afterwards

 

[Sweed269]

Adjusting 1 corner affects the other 3. Then you need to put the car down and move it around to settle the suspension. Even if you don't adjust it, just lifting moving and remeasuring will change you measurements. It's simply not repeatable unless you have it on posts instead of wheels and on a perfectly level surface with no dips or undulations.

 

[ngng]

Adjusting 1 corner affects the other 3. Then you need to put the car down and move it around to settle the suspension. Even if you don't adjust it, just lifting moving and remeasuring will change you measurements. It's simply not repeatable unless you have it on posts instead of wheels and on a perfectly level surface with no dips or undulations.

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I don't completely agree with that. If the fronts and rears are set equally prior to install you can very close. Make equal adjustments, roll car to unbind suspension, measure ride height. That being said, ride height is important but it's not the end all be all for a street car. Get it close, corner balance, then align.

I have the same setup you do (except I use Intercomp scales) and have had similar results with, and without hubstands on my race car.

 

[Sweed269]

Most garage floors are not really flat. At least mines not. I feel that using the fixed points of the damper are better for a home setup than the ground clearance as it has a lot of stacking tolerances. Ground should be checked to make sure it's in the range you want. I personally had all kinds of trouble adjusting without scales using ground or fender clearance.