BMW 1-Series Forum (F20) 135i - 1Addicts.com > Second Generation 1 Series Forum > 2012 BMW 1-Series Sporthatch (F20) Discussion > anti-roll bars for F20
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      11-21-2015, 05:58 PM   #1
BMWboy1973
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anti-roll bars for F20

Hello,

I tuned my car, installed Schnitzer springs on my BMW F20 with M-pack. front lip, rear wing, and the car handles so much bether, especially while doing hi-speed drive.
My question is, if anyone have installed anti-roll bars, if you did, can you feel the difference ?

keep well everyone
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      11-22-2015, 02:21 AM   #2
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The car has such bars from the factory, but it is possible to install thicker ones. By only changing the rear bar, you can tune the balance of the car. Stiffer bar to get more oversteer and less traction, thinner bar for more understeer and more traction. Notice that when you go for stiffer springs or anti-roll bars, you also need stiffer dampers. Also notice that the anti-roll bars are more noticeable when you have soft springs.
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      11-22-2015, 09:20 AM   #3
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I have Birds Anti roll bars with Birds b1 springs.

Car corners flat and as said above Bids combination is thicker rear anti roll bar and soft rear springs.

Works well
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      12-11-2015, 02:27 AM   #4
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How does it impact the balance of the car? My logic says flatter and more grip? What's the compromise?
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      12-11-2015, 04:11 AM   #5
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ST Suspensions do a set of thicker sway bars for the F20/F21, at a very reasonable price too. A lot cheaper than Eibach.
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      12-11-2015, 06:24 AM   #6
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Quote:
Originally Posted by harkes View Post
How does it impact the balance of the car? My logic says flatter and more grip? What's the compromise?
Thicker swaybars will make the suspension less independent. If you run over a bump with the outer wheel in a corner, the inside wheel will be unloaded.
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      12-11-2015, 11:08 PM   #7
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So on uneven surfaces especially while cornering you might loose traction. As always there is a trade off.
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      12-12-2015, 06:57 AM   #8
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Also, if you find the right stiffness with very stiff swaybars, that means softer springs. The car will corner flat, but will pitch more (squat and dive). The opposite strategy is stiff springs and soft swaybar. Very little pitch, but more roll.

Notice that swaybars are very nice for fine tuning the balance of the car, if you only change the stiffness in one end of the car. If you run rather stiff coilovers, you might even disconnect one swaybar completely. Remove the front one for better turn in, and the rear one for better traction.
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      12-14-2015, 01:02 AM   #9
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Stiffer rear ARB used with softer rear springs and LSD is how Birds set up my car. This combination works very well on the road with OE adaptive damping.

Will do some track time with this set up in the spring next year.
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      12-14-2015, 01:22 AM   #10
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Quote:
Originally Posted by Bee Pee View Post
Stiffer rear ARB used with softer rear springs and LSD is how Birds set up my car. This combination works very well on the road with OE adaptive damping.

Will do some track time with this set up in the spring next year.
Most cars are set up with slightly stiffer wheel rates (springs) in the rear than the front. The reason is that the rear end should catch up with the front when going over bumps to avoid excessive pitching and stay more level.

I guess Birds did this to adjust the balance towards oversteer without making it under damped and without sacrificing traction.
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      12-14-2015, 02:53 AM   #11
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Quote:
Originally Posted by ovekvam View Post
Most cars are set up with slightly stiffer wheel rates (springs) in the rear than the front. The reason is that the rear end should catch up with the front when going over bumps to avoid excessive pitching and stay more level.

I guess Birds did this to adjust the balance towards oversteer without making it under damped and without sacrificing traction.
My cars Birds spring rate/ARB setup compared to stock is

Front firmer Birds B1 springs and thicker B1 ARBs
Rear softer Birds B1 springs and thicker B1 ARBs.

Birds recommend only upgrading firmer rear ARB in conjunction with LSD so as traction is not compromised due to firmer rear ARB, which will reduce rear wheel travel.

The cars ride is near stock in comfort but well controlled and sport/sport+ is firmer but still very useable on UK roads as car doesn't bounce as can sometimes be the case with firmer suspension on uneven surfaces.

My car started out with Birds ARBs and H&R springs which again was fine as H&R spring rates aren't as hard as say eibachs.
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      12-14-2015, 03:05 AM   #12
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Quote:
Originally Posted by Bee Pee View Post
My car started out with Birds ARBs and H&R springs which again was fine as H&R spring rates aren't as hard as say eibachs.
Interesting. For earlier BMW models, it has mostly been the other way around, H&R being stiffer than Eibach.
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      12-14-2015, 06:12 AM   #13
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Quote:
Originally Posted by ovekvam View Post
Interesting. For earlier BMW models, it has mostly been the other way around, H&R being stiffer than Eibach.
Not these days, TUV certs, for both eibach and H&R springs, show some interesting info wrt wire diameter and number of coils.
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      12-14-2015, 06:40 AM   #14
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Quote:
Originally Posted by Bee Pee View Post
Not these days, TUV certs, for both eibach and H&R springs, show some interesting info wrt wire diameter and number of coils.
But I don't have there documents, so I can't verify.
Is it Eibach that has gone stiff, or H&R that have gone soft?
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      12-14-2015, 07:01 AM   #15
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Page 4 of the forum link below has some extrapolated data comparing stock M135i and M235i springs rates with aftermarket springs.
http://www.babybmw.net/forum/viewtop...79484&start=45
H&R offer bespoke sport springs for each of these 2 cars whereas Eibach proline is the same for both Mx35i.
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      12-14-2015, 07:44 AM   #16
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Quote:
Originally Posted by Bee Pee View Post
Page 4 of the forum link below has some extrapolated data comparing stock M135i and M235i springs rates with aftermarket springs.
http://www.babybmw.net/forum/viewtop...79484&start=45
H&R offer bespoke sport springs for each of these 2 cars whereas Eibach proline is the same for both Mx35i.
Thanks! Seems like H&R are more front stiff, and Eibach stiffer in the rear. If the spring rates are correct, I think the H&R set would feel stiffer and corner flatter, but cause more understeer than Eibach.
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      12-15-2015, 03:01 AM   #17
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Quote:
Originally Posted by ovekvam View Post
If the spring rates are correct, I think the H&R set would feel stiffer and corner flatter, but cause more understeer than Eibach.
Yes, maybe, with springs by themselves but as I'm running upgraded ARBs I can't comment.

However, the combination of ARBs and springs [+ M4 LCA's] with stock MPSS tyres, the handling balance thru corners [tight&slow or fast&open] is neutral.
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      12-18-2015, 01:27 AM   #18
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For what it's worth as an example only, I fitted bigger springs onto my truck which were also a fair amount stiffer than the stock springs as they were designed to carry more weight which I did not have. I left off the rear ARB (Anti Roll Bar) entirely and did not get any noticeable body roll.

The Front ARB was a different story though. Removing the front in addition to the rear was like being in a boat when changing lanes on the motorway. Passengers were scared. It was hilariously funny.
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