09-24-2013, 07:15 AM | #1 |
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Strut tower brace and sway bars for F20/21
Hello
I want to reduce bodyroll without using stiffer springs or dampers. I'm trying to find a strut tower brace (STB) and/or bigger sway bars for my F20 118i. The only company I can find is SPR racing. Are there others options ? |
09-24-2013, 09:54 AM | #2 |
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Modern cars have a very stiff body, so I highly doubt that any sort of brace will make any difference to how the car drives. Stiffer swaybars is the way to go if you refuse to change springs/dampers.
Which suspension do you have from the factory? There might be stiffer factory swaybars available from BMW, meant for some other option, or the M135i. |
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09-25-2013, 01:19 PM | #3 | |
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An option is to install the M-sport swaybars, but a friend with racing car set-up experience says going from 12mm to 13mm swaybars will have almost no effect. So I was looking for 16mm or more swaybars with hard Polyurethane bushings, but without succes. KW or Bilstein coil shocks are too hard for me (and my kids), so that option is a no go. |
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09-25-2013, 01:50 PM | #4 |
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The stiffness of a swaybar is proportional to diameter to the fourth power, so going from 12 to 13 mm is a 38 percent increase in stiffness.
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09-26-2013, 02:40 AM | #5 | |
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Following that rule a 16mm would be extremely stiff and probably cause side effects that I don't want. Because once you start changing suspension related parts, you know it 's very easy to make the handling worse instead of better. The BMW 13mm swaybar is not that expensive, so I'm going to install one and try to find polyurethane bushings. Thanks for the advice ovekvam. |
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09-26-2013, 04:07 AM | #6 |
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But remember that the springs and dampers are contributing quite a lot when it comes to reducing body roll, so a 38 percent increase in swaybar stiffness will not be very significant. If you only upgrade one end of the car, you will however notice a change of balance (making front end stiffer will make the car understeer more). Beware that polyurethan bushings can be noisy, making squeaking sounds. They need to be lubricated, as the bar is rotating inside them. The stock rubber bushings are twisting with the bar.
Also notice that adding stiffer swaybars with stock dampers will make the car feel slightly underdamped when driving in bumpy corners. Last edited by ovekvam; 09-27-2013 at 12:55 AM.. |
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09-27-2013, 12:30 AM | #7 |
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Yes, my understanding is that if you are intending to reduce body roll to any significant degree, you first invest in firmer springs with matched dampers. Sway bars do help a little, but are more for tuning the balance - thicker front increases understeer, thicker rear increases oversteer. You may also find you get a more progressive, consistent and safer response from improving springing and damping rather that just putting big sway bars on.
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