Strut Top Mount Questions

[robinasu]

Questions for you all:

1. Anybody know why the rubber perch in the upper strut mount should be "coded" as in this picture?



The shock doesn't rotate with the wheel. The only thing I can think of is they want the beginning of the coil to start at the same symmetrical point in the upper strut mount- essentially outboard of the strut shaft on each side.

2. The upper strut mount attachment holes seem to allow for some adjustment but I don't see how it can since the A-arm and tension strut lock the camber and caster. Toe is adjustable with the steering tie rods. I looked in TIS but couldn't find anything about upper strut mount adjustability.

Any ideas or guides out there for our cars?

[argento]

FWIW I address this topic in my DIY, link below. The DIY is really long but see if it helps answers your question. The coding, IIRC, helps alilgn the spring orientation so both sides end up the same hieght Or at least that was my experience with it…

I reference other DIYs I used as well…so check those out….

https://www.bimmerpost.com/forums/sh...php?p=28001474

[robinasu]

Ah, ok, perhaps the coding of the spring to the upper mount is to aid in installation. Once installed and weight on the springs there should be no difference to ride height, I would think?

Thanks for the link.

[robinasu]

Awesome write up. You must be a technical writer.

I think the coding aids installation by putting the start of the coil to the outboard side of the strut piston on each side, which gives more room for installation while the strut flexes a bit without the vehicle's weight on the spring. Once loaded the upper and lower strut mounts are parallel and equal force is applied to the upper and lower spring perches. I would think one end of the coil ends 180 deg opposite the other to balance load on the piston. I will look tomorrow.

[rlaggan]

Some other things..

Coil clocking is critical for straight ahead wheel alignment, counteracting crowns in the road and also makes it critical to either be sitting in drivers seat during alignment, or bring exercise weights for tech to place on drivers floor.

Slow or erratic automatic return to center , especially during slow parking maneuvers, will occur if not clocked.

Both visual level of car and headlight height is amazingly heavily affected if end of spring is not in pocket. Equivalent to putting a 1" lift on a random corner of your car.

The bearing condition at top of mount is much more critical to straight line issues (aside from tire pressure of course) than the clocking, if in fact the bearing is totally worn or seized.

The upper and lower pockets, along with 2 upper insulators, and especially the bump stop , are hugely responsible for road noise, slamming, jarring etc, and in fact the bump stops on all bmws are a active component, not a fail safe device as in other cars...the bump stop is to be regularly 'used' to dampen during hard braking and the oem strut does NOT have any other means to protect against metallic bottoming out =instant destruction of strut. Overall length of bumper compared to a new part is a good way to check, and any cracks at all mean it's toast.