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nachos23 02-08-2010 12:49 PM

Swaybar pre-loading; questions
I have a '04 330Xi that I've lowered using Bilstein Sport Struts and shocks and H&R springs. The Question; been reading alot in regards to front swaybar pre-loading and from what I've read, lowering the car adds pre-loading to the front swaybar + that I should remove the pre-loading to get the best handling on the car..... Found some Adjustable Swaybar links @ TMS (not on website yet, but confirmed they have have them this morning)..... IS this a worthwhile investment? Will I notice the difference and finally, how do I go about setting up the adjustable links to remove the pre-loading while maintaining equal corner weighting to the front tires. HOw can I check corner weights without a costly Corner Balancing......

Anyone know of a shop that does corner balancing (not sure if necessary) and cost(s)?

theblue 02-08-2010 03:19 PM

you have a street car so it probably doesn't matter enough. I would first so a visual check to see if you have preloading. If you do then you can get adjustable end links to remove it if you want.

It's not a matter of good or bad, it's just different. If you have some preloading, you might like the extra "horizontal spring rate" that you're getting.

propr'one 02-08-2010 03:26 PM

My iX is a different generation, but i disconnected my front swaybar altogether, helped with understeer a little

nachos23 02-08-2010 03:52 PM


Originally Posted by theblue (Post 1388765)
you have a street car so it probably doesn't matter enough. I would first so a visual check to see if you have preloading. If you do then you can get adjustable end links to remove it if you want.

It's not a matter of good or bad, it's just different. If you have some preloading, you might like the extra "horizontal spring rate" that you're getting.

Thanks for the info.. It's the visual check I'd like to know more about. Is it just a matter of lowering the car and then "dialing out" the adjustable link until there is no pressure on the sway bar @ rest? How do I see a "load" on the sway bar to tell if it's pre-loaded? Considering the work I've done to this and other cars, seems like I should know this answer..... but never looked @ sway bar loading before.....Should the sway bars be "loose" when it's normally @ rest (on the wheels; not jacked)? DOn't mind spending the $$$, but I'm not one to spend $$$ just to say I dit it.....

theblue 02-08-2010 06:52 PM

you don't want it loose because that would yield unpredictable handling (it would feel like no sway bar, then BOOM! SWAY BAR IS WORKING as you turn). You want it firm as in no wiggle with all wheels on the ground, but no tighter unless you want preload.

Understand how a sway bar works... it's a sideways spring that connects the left arm to the right arm. As you go into a turn and load on one side of your suspension, it will transfer resistance to the other side. The bigger and stiffer your sway bar gets, the more load is transferred. The downside is that as you increase the size of a sway bar, you remove the independent nature of the control arms and turn into a beam suspension which will make the car more likely to snap and slide instead of lean and grip and also act skittish on uneven/bumpy roads.

If you're still with me then your logical question is why do you even want swaybars?? (why not just stiffer springs). The answer is because really stiff spring rates make the ride horrible on a street car, and are not easily adjustable like swaybar is on a track car.

nachos23 02-09-2010 02:04 AM

thanks. DId understand and understood the principle before.... what I was curious and you've answered is what it should feel like to be setup properly. What I had assumed, but we all know about assuming....... So I can check to see if it's pre-loaded now by checking the "play" or looseness of the links..... If there's pre-loading, then I'll grab the adjustable links and install...

rmanaudio 02-09-2010 01:14 PM

What you wanna do is measure how large of a endlink you need and get +/- .5 inches. You want the car in natural state when you install them. So put it up on a ramp and install them to tight and even feel...this will give you normal state!

nachos23 02-10-2010 12:19 AM

Since mine are fixed now, I guess the way to check if i'm getting pre-loading would be to put my car on the ground after dis-connecting the existing links from the strut mount and seeing how they line-up with the mounting holes when the car is @ rest?

RMPMOTORS 02-10-2010 09:59 PM

We do corner balancing!

nachos23 02-11-2010 02:58 AM


Originally Posted by RMPMOTORS (Post 1389619)
We do corner balancing!

Thanks Rocca,

Keep that in mind.... biggest question is to check the swaybar and see of theres' pre-load on it.... If you've read the thread, what else could I do to the suspension to improve traction.... should I look to larger sway bars, or am i "splitting hairs" @ this point? Alex @ Daytona (good friend of mine) suggested upgrading swaybar bushings to Urethane to remove play if I wanted to get a better feel, but suggested I leave the stock swaybar in place.... Your thoughts?

How much for corner balancing and is it really worthwhile for a street driven car?



rmanaudio 02-11-2010 03:46 PM

A corner balance would be nice...if its not too expensive...let us know how much it costs Rocco.

RMPMOTORS 02-12-2010 09:37 PM

EDIT: I see your not running coilovers!

Lowering both side of the car the same will not change the preload of the sway bar BUT when you get in the car and change the height on the drivers side it will.

Preload on sway bars is easy to check BUT will be very hard to keep set, do to the changes in weight on a daily driven car.

Changing the amount of people in the car, baggage, fuel, etc. all will change the preload and the corner balance.

When we setup race cars it is with the driver inside, and approx amount of fuel that will be in the car. Then we setup preload on the bars to 0. Unless we want more pressure on a certain wheel. (tracks with more right or left turns)

If you don't have coilovers I can check your corner weights if you like. Most BMW's that have not been in a accident are usually pretty good.

We have alot of road race experience and most of our gained time is from suspension setup (some cars in the sub 1min26 time at Mosport).

Poly bushings will tighten up the car in the turns and are a good idea.


nachos23 02-12-2010 09:55 PM

Hey Rocco;

I would consider tracking the car, but it's a daily driver...... can;t affrod to put into wall @ it's an Auto...... Driven Mosport when I was much younger and used to run two 1/4milers (Chevy and Ford), 1 off-road Mazda and a track car original BMW 2002.... Spent alot of time around the tack myself since as well, my brother owns a Ferrari FIA GT race team. (CR Scuderia). We've been racing since kids..... but I feel I can get more out of the car in the overall stability and responsiveness......

The car has been lowered using H&R Sport springs and Bilstein Sport Shocks/struts. I've added an ACS Strut brace. Been considering KMAC Camber plates to reduce camber to spec (@ -2.5 now) but that will further reduce handling, so I may leave camber @ -2.5. The reason for the question in regards to corner balancing was to address some stuff I'd read about pre-loading of Sway Bars on lowered cars and could I have pre-loading occurring that would reduce the effectiveness of the sway bar..... Found adjustable XI end links @ TMS (not yet posted on their website, but Doug confirmed to me). Was considering the purchase of these but how to correctly adjust and if required.......was really the question. Also been considering an after market sway bar, but Alex @ Daytona is pushing me away from that option. Understand you guys know each other. Bought my car from Alex + Johnny.... also used to maintain their computers.....

If you're open on Sat I could drop by and you could have a look @ the condition of the bushngs and whether to replace.... See a fair bit of clearance inbetween my sway bar bushings and the sway bar...... Finally, try finding aftermarket suspension parts for an XI......

nachos23 02-12-2010 09:59 PM

My front sway bar uses a 23.5mm diameter bar. I've seen poly @ 23mm and 24 mm, guess I'd go with 24...... shouldn't there be a 23.5mm bushing or is the 0.5mm spacing normal? You carry the correct ones I need?

RMPMOTORS 02-12-2010 10:04 PM

Take 1 nut off 1 side of your sway bar, lower the car and see if you can put the sway bar back on (level ground). If you can, then there is no need for adjustable links.

Larger sway bar in the front will only make the front push more then it does.

On our CTCC/KONI E90's we still use stock bars, just higher spring rates.

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