Ride height changed after CMP/Vincebar

[eacmen]

Mine too. The tires don’t sit flat on the ground until the car rolls. They stick in as the car gets put down since the outside of the tires grabs the ground first. Then they deform and the car looks like it has a bunch of positive camber and high ride height until you drive or roll it. Pushing down on it is not enough to release the grip that the tires have on the ground and spring them outward laterally.

ah yes. when setting ride height i have slip plates under each tire. pretty key thing i forgot to mention.

[AussieE46M3]

Hey guys,

I've replaied to Cubieman's email and offered what input I can.

Based on the little bits of extra information here, I want to ask have you rolled the car forward and backward yet?

Due to the way the suspension works, the track width changes in travel (this is why slammed cars have excessive toe in problems). If you have jacked the car and put it back down, the tyres can jack the rear of the car as they are resisting the lateral displacement of when the car settles into its set ride height.

I agree. Keep in mind, changes in height at the spring will result in about a 150% change at the wheel.

I find the best way to imagine it is the spring is a pivot point and the upper arm is a see-saw as the weight of the car hasn't changed significantly and thus the spring should not be more or less compressed after install.

With the roughly 2/3 motion ratio of the spring makes the inner end of the arm (from spring) 2/3 of the arm length and thus the outer end is 1/3 of arm length so you can put that as the inner end is twice as long as the outer end.

With that in mind if the subframe is raised 8mm, the outer end of the arm goes down only 4mm and thus that is the change in ride height. For the non-metric guys that's 0.1575". This doesn't account for reinforcement plates just before vs after and would be smaller again. The plates I sell are 2mm so that becomes 6mm up, 3mm down (3mm ride height raised).

This is an amount that is hard to notice and generally very easily compensated for with height adjustable coil overs. I had BC BR's on my M3 with these bushings for many years and could probably go 1" lower than a flush fit tyre on mine.

To Answer your other question, the reason the subframe is raised more than the plate thickness is to account for the effects of lowering the car. Just like in the description pasted above, this generally isn't the first suspension mod and is for the majority of the time fitted to cars that are lowered.

When you lower a car (dependent on how much of course) a lot of things change such as track width (stated above), axle misalignment and also where the car sits on it's dynamic camber/toe/roll centre plots. Because these changes in geometry are almost always parabolic, if your static position is further along the plot line the change in camber, toe & roll centre geometry you experience in bump is more dramatic for the same amount of vertical displacement than it would have been if the car was at a taller static ride height.

The change in track width is also known to cause excessive extension of the axle CV's which factored with excessive misalignment is known to cause CV failure (often seen in drifting but makes the reduced life obvious). One solution is axle spacers which are common in drifting otherwise, raising the subframe brings everything back closer to the geometry it was designed to function at on lowered cars.

You'll see on the Team Shirmer cars and many other quality tracks cars they they employ eccentric spherical bearings in aluminium housing pressed into the upright and subframe on newer beemers to achieve a similar effects geometry wise. The benefit of raising the subframe is you get to keep stock rubber or sealed ball joints and correct axle misalignment while their approach uses exposed sphericals which require additional maintenance which is an acceptable compromise on a race car and only corrects the geometry side not the driveline part. This is where they instead custom fab the subframe to raise the diff relative to the subframe & body to straighten out the axles to the upright.

I went for subframe raising bushings because it felt a lot simpler.

Feel free to share some pics of the installed springs and try rolling the car a few feet back and forth to see if it settles into the old ride height +3mm.

[Cubieman]

Can someone put my mind at ease and tell me that this upper control arm listed as "right" is for the passenger side (US car).

https://www.turnermotorsport.com/p-15692-33326781626-genuine-bmw-part/

I appreciate everyone's help and Cayn's very detailed information. Just trying to figure out what could have changed the ride height as the bushings should not have raised them this significantly.

Here are some before/after shots, also I rocked the car back/forth to no avail.

[eacmen]

Can someone put my mind at ease and tell me that this upper control arm listed as "right" is for the passenger side (US car).

https://www.turnermotorsport.com/p-15692-33326781626-genuine-bmw-part/

I appreciate everyone's help and Cayn's very detailed information. Just trying to figure out what could have changed the ride height as the bushings should not have raised them this significantly.

Here are some before/after shots, also I rocked the car back/forth to no avail.

Part looks correct.

Part ending 626 is right side
Part ending 625 is left side

Doesnt matter if its rhd or lhd.

The part of the bushing that sticks out points towards the rear of the car.

[Cubieman]

Also changed were these reinforcement plates for the spring perch, they are the same thickness and I already tried swapping them out with the same result.
I also installed Turner RTABS vs. some random poly stuff the PO had in there.

Still have yet to bolt the axles/driveshaft/Exhaust etc. so if there is something I'm missing I'm all ears as I'm banking on driving the car fixing the ride height. Only one way to find out I suppose.

[maupineda]

Man don’t loose sleep over this, adjust the height and be done with it. Who cares if it rose a bit, is weekend car, not an F1

[jet_dogg]

Man this would bug the shit out of me. Hopefully it resolves itself after a drive.

[Cubieman]

Man don’t loose sleep over this, adjust the height and be done with it. Who cares if it rose a bit, is weekend car, not an F1

I cannot make any height adjustments on the spring, it's bottomed out, the 4mm drop is more like a full 1"+, I just hope driving it settles it down.

[karter16]

You need to drive it for a while. When mine came down it was a good inch and a half higher and settled over the next week or so. (Everything was torqued correctly in the normal position)


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[heinzboehmer]

Yeah drive it. Just swapped street brake pads back in this evening but didn't get a chance to do much else. Car looks like a monster truck and will continue to until I drive it around.

[George Hill]

The car isn't fully assembled?

[Cubieman]

The car isn't fully assembled?

No, just got the brakes on and the axles bolted last night, still have to install the driveshaft/full exhaust/heatshelds/rear seat etc.

I did have the diff. and muffler bolted up at one point and still had the same ride height.

[George Hill]

Maybe there is an issue, maybe not, but if the car isn't assembled you aren't making and apples to apples comparison and as such may be jumping the gun.

[enjoy_m3]

^ He's right. Put all together and then drive the car around and re-inspect. (sidenote: I have figured out a way to mis-install the rtab brackets, but caught it, lol)

[Cubieman]

^ He's right. Put all together and then drive the car around and re-inspect. (sidenote: I have figured out a way to mis-install the rtab brackets, but caught it, lol)

Can the RTAB brackets really be reversed and still bolted up flush??

I didn't label mine as they were powder coated. Both are torqued and flush w/ body.

Here is a shot of the driver's side RTAB bracket installed fwiw. Hope to have car ready to drive by tomorrow.