Explain sway bar binding to me

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Jake Stumph
Posts: 64
Joined: Thu Nov 21, 2013 2:40 pm
Car#: 200
Location: Irvine, CA
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Explain sway bar binding to me

Postby Jake Stumph » Mon Mar 27, 2017 7:41 pm

Hey everyone, been chasing a handling issue down with my BMW. Sometimes it will be neutral, and other times it will default to interminable, serious understeer. For once, it's not the operator's fault. I drove a friend's car, that for all intents and purposes, is identical to mine: Same car, same dampers, springs and rates, alignment setup, diff, etc. Our cars are almost carbon copies in the suspension area, EXCEPT for the front anti roll bars. My bar is a bit larger. I drove his car and it is completely neutral-to-tail happy at all times. He can steer his car around corners with the throttle, while I have to wait forever until I'm basically through the corner to power out.

After some furious Googling, I can't imagine the difference in bar size (~2mm) is causing this handling discrepancy. Perhaps my front sway bar is "binding." Can someone clearly explain what anti-roll bar binding is, and how to test for it?

From what I gather, I need to unhook my endlinks and see if the bar can twist freely in it's bushings/mounts. Is this correct? Is there anything else I can test/check to see if the sway bar is my issue? I tried unhooking it completely, but that made the front end way too vague and prone to wandering.

Thanks,
- Jake
https://www.facebook.com/JakeStumphRacing #200 H-Street, Silver Civic Si Sedan.

Ira Cruz
Posts: 70
Joined: Thu May 15, 2008 11:25 am
Club: No$
Car#: 789

Re: Explain sway bar binding to me

Postby Ira Cruz » Mon Mar 27, 2017 11:55 pm

Hi Jake,
Have you replaced bushings, tie rods and other basic suspension bits? There could be a part that hasn't been refurbished that could be the culprit.
After I replaced them, car behaved consistently. Then I proceeded with setup/settings (the hardest process).
Have fun!!

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Adam Tarnoff
Posts: 287
Joined: Thu Feb 27, 2014 8:38 pm
Club: CASOC
Car#: 49

Re: Explain sway bar binding to me

Postby Adam Tarnoff » Tue Mar 28, 2017 10:14 am

Shim the swaybar bracket if it's too tight. What you're looking at is too much stiction, so that's a good way to reduce it. It could also be that the bar is too big.
#49 C Street Mazda RX-8

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Sean Fenstermacher
Posts: 355
Joined: Mon Nov 23, 2009 2:56 pm
Club: SCNAX
Car#: 81

Re: Explain sway bar binding to me

Postby Sean Fenstermacher » Tue Mar 28, 2017 12:33 pm

If the sway bar can move relatively smoothly, then check the endlink lengths to make sure preload is removed.
Hopefully, you have adjustable endlinks.

Jake Stumph
Posts: 64
Joined: Thu Nov 21, 2013 2:40 pm
Car#: 200
Location: Irvine, CA
Contact:

Re: Explain sway bar binding to me

Postby Jake Stumph » Tue Mar 28, 2017 2:10 pm

Update: turns out the bar was super bound up. With the endlinks unhooked, I had to use both hands and wrench the bar around before it would move at all. Ground down the bushing about 1/8" and it was much better, but still a bit stiff on the initial movement. Shimmed the brackets with two washers and now the bar moves super smoothly. The difference in the way the car drives, even just around town is astounding. Going to play with the amount of washers used and fine tune the amount of "pre-load" the bar experiences.
https://www.facebook.com/JakeStumphRacing #200 H-Street, Silver Civic Si Sedan.


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