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      11-18-2018, 08:14 PM   #13
ashiohsiao
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Drives: 2012 F20 118i
Join Date: Oct 2018
Location: Taiwan

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Quote:
Originally Posted by ovekvam View Post
My car has very good traction, so I would be willing so sacrifice a little bit of that for less understeer. That is why stiffer rear swaybar and narrower rear tyres seems like the way to go.
Just got back from a trip

Yeah, upgrading sway bars to tune handling is definitely a good way, and I am happy to read that you are also using a 15mm for the rear~

At first I made a bad call upgrading the rear from 13mm to 19mm without consulting Shaikh (I also upgraded the front from 24mm to 28mm at the same time), and though the body roll was significantly reduced when cornering, the ride was actually quite a lot harsher!

Contrary to sales pitch saying stiffer sway bars reduce body roll without compromising comfort, I did feel the ride was compromised a LOT! Especially the rear... it was very jumpy and way too loose when I took it for some touge driving testing...

Later I learned about Shaikh's broad direction on sway bar tuning is:

For RWD:
- Upgrade the front sway bar is usually okay (on mine 24mm to 28mm)
- Upgrade the rear sway bar only by a very small amount, maybe the next thicker one (on mine 13m to 15mm)

For FWD/AWD/4WD:
- Using the OE front sway bar is usually more ideal
- Upgrade the rear sway bar is totally fine, and you can increase the thickness more

Then I tried to find what sway bars were available here in Taiwan for my F20, and for the front, there were KC Design, H&R, Eibach, and HardRace, and all of them were 28mm. For the rear, there were M135i/M140i OE 15mm, Eibach 16mm, HardRace 19mm, H&R 20mm, and KC 21mm. I also found a table someone made to compare the increase in stiffness in % (the last column), but I think not sure how accurate this table is.
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So I had my consultation with Shaikh, changed to the 15mm, and now the ride feels a lot more composed and stable, still maintaining like 70-80% of stock comfort, but less floaty, and the reduced in roll is not at all worse than the 19mm.

Before I trimmed the bump stops, I wanted to get a comparison reference, so I also did give this setup a touge driving test, and found that the handling was still more towards understeer-y when pushed hard. It was only after I trimmed one section off the front bump stops that the understeer was completely gone