[dleccord]

when installing the front sway bar for the E90's, does the front suspension need to be preloaded? if so, can i preload at the rotors and then tighten down the bolts?

[mweisdorfer]

You dont want to pre-load the swaybar past its natural state. It should have zero load at ride height. 18 3/4" is ride height for a 335i with no lowering springs etc. 17 3/4" is probably close to ride height for a lowered car. You measure from the bottom of the fender to top of the Hub.

If you have a lowered car, you probably want to consider adjustable swaybar links. Hotchkiss is at very good and high quality product.

[feuer]

It wouldn't matter if suspension is loaded or not as sway bar will rotate.

[bbnks2]

Originally Posted by feuer

It wouldn't matter if suspension is loaded or not as sway bar will rotate.

The sway bar is a lever. The lever is most effective when it is operating in the correct position and leverage is applied by the suspension properly. The sway bar should be adjusted at natural ride height so that the tab "points" toward the rear of the car (parallel to the ground). Suspension load does make a difference.

When you lower the car you generally need to shorten the end links. Not only will this keep the sway bar in the proper orientation but it will also keep the sway-bar form hitting control arms and chassis under compression.

[feuer]

Originally Posted by bbnks2

The sway bar is a lever. The lever is most effective when it is operating in the correct position and leverage is applied by the suspension properly. The sway bar should be adjusted at natural ride height so that the tab "points" toward the rear of the car (parallel to the ground). Suspension load does make a difference.

When you lower the car you generally need to shorten the end links. Not only will this keep the sway bar in the proper orientation but it will also keep the sway-bar form hitting control arms and chassis under compression.

That is not what OP is asking. At least not how I understand his question. OP wants to know if suspension need to be loaded to tighten the bolts on the sway bar as when suspension need to be loaded when you tighten the bolts on the control arm. So the answer is no. It would not matter as the sway has ball joint that will rotate 360 and the sway itself will rotate around in its bushing. There was nothing said about adjusting. Or car being lowered. So again, it would not matter.
Also, depending on suspension design and geometry some links need to me shorten and some lengthen when is lowered.

[dleccord]

Originally Posted by feuer

That is not what OP is asking. At least not how I understand his question. OP wants to know if suspension need to be loaded to tighten the bolts on the sway bar as when suspension need to be loaded when you tighten the bolts on the control arm. So the answer is no. It would not matter as the sway has ball joint that will rotate 360 and the sway itself will rotate around in its bushing. There was nothing said about adjusting. Or car being lowered. So again, it would not matter.
Also, depending on suspension design and geometry some links need to me shorten and some lengthen when is lowered.

This guy gets it.

But do you guys understand my reasoning on lowering my car on jackstands? That is my car's front weight will be on its rotors. I don't think at that point we need to do any measurement because it's "carrying weight".

[Jeff@TopGearSolutions]

I will say it's easiest to install the sway bar (in the front) with the car on ramps. With the load on the car, everything lines up. You'll have to fight it if you jack up one side only.

[bbnks2]

Originally Posted by dleccord

This guy gets it.

But do you guys understand my reasoning on lowering my car on jackstands? That is my car's front weight will be on its rotors. I don't think at that point we need to do any measurement because it's "carrying weight".

I see what you mean. No preload required when torquing the nuts on the end-links.

The other question you asked:

If you are going to jack the car up by the hubs then you do need to measure... The suspension needs to be at ride height to adjust the end-links properly and that will be hard to eyeball by just jacking up both hubs. You could end up jacking up both sides too much, which would put the suspension into "bump" travel. This would be equally as erroneous as adjusting the end-links with the car on jack stands while the suspension is in a state of "droop."

[dleccord]

Forgot most important key. Both hub and rotors will be on a jack stand. Theoretically it is leveled.


Also do I do and links first or front sub frame bushings first.

[bbnks2]

Originally Posted by dleccord

Forgot most important key. Both hub and rotors will be on a jack stand. Theoretically it is leveled.


Also do I do and links first or front sub frame bushings first.

Why are you making it so hard on yourself? Lowering the hubs onto jackstands sounds dangerous. Just put your wheels on and put the car on some ramps... it's not that hard. Have the bottom end link connected already. The top one is easier to reach.

No clue what you mean with the subframe... definitely bolt the bar to the chassis first!

[feuer]

Originally Posted by bbnks2

No clue what you mean with the subframe... definitely bolt the bar to the chassis first!

Sway bar bushings are bolted with two bolts onto the front subframe. Easy to strip btw.

[bbnks2]

Originally Posted by feuer

Sway bar bushings are bolted with two bolts onto the front subframe. Easy to strip btw.

Yeah I realized what he meant afterwards... I thought bolting it up to the subframe was a given. You'd never be able to tell how long to make the end-links if you didn't lol

I was confused about end-links too the first time I installed coilovers. It's so simple though it's kind of surprising how difficult it is to find the right info on how to set it up correctly.

[juld0zer]

BMW's instructions tell you to tighten the endlinks with the suspension at ride height.

My only further suggestion is to retighten/recheck them after 100km, and to replace the locknuts each time they are disconnected.