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      04-03-2008, 08:35 AM   #1
UR2SLOW1
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Just Sway Bars ?

So has anyone just replaced the sway bars on their 135i and if so what was the difference in handling and ride ?? Now that I fianlly have my car I'm thinking of this mod but don't want to get into springs as well. Anyone ???
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      04-03-2008, 09:37 AM   #2
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I have a different approach. Get some good two way adjustable shocks. Dial in a bunch of compression and see what it does to ride. I have 15 clicks of rebound and compression available. Starting with the shocks valved for the spring, if I can dial in +5 clicks, I need more spring. Once I get the springs dialed in then I can deal with the bar and will generally use the lightest bar possible.
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      04-03-2008, 06:02 PM   #3
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Quote:
Originally Posted by white911 View Post
I have a different approach. Get some good two way adjustable shocks. Dial in a bunch of compression and see what it does to ride. I have 15 clicks of rebound and compression available. Starting with the shocks valved for the spring, if I can dial in +5 clicks, I need more spring. Once I get the springs dialed in then I can deal with the bar and will generally use the lightest bar possible.
Wonderful, straightforward explanation of basic suspension tuning. :w00t:
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      04-04-2008, 03:51 PM   #4
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Quote:
Originally Posted by white911 View Post
I have a different approach. Get some good two way adjustable shocks. Dial in a bunch of compression and see what it does to ride. I have 15 clicks of rebound and compression available. Starting with the shocks valved for the spring, if I can dial in +5 clicks, I need more spring. Once I get the springs dialed in then I can deal with the bar and will generally use the lightest bar possible.
What the heck are you talking about?

Isn't the whole point of tuning your shocks to get to the point of having the shocks valved for the spring? How is it you are starting from that point?

And if your shocks are "valved for the spring", why should you care if you how many clicks you are from either extreme. It sounds like you are just looking for the stiffest spring your shocks can handle. How is this optimizing for anything (not that you mention what you are optimizing for)?

And how exactly do you "get the springs dialed in"? Last time I checked, they don't come with dials.

So Mikeo, I am having trouble seeing this as a "wonderful, straightforward explanation of basic suspension tuning".

I think UR2SLOW1 just wants to alter the balance of his car a bit. He is not going to buy double adjustable shocks, and "dial" full of springs before he looks at his bars. "Basic suspension tuning" means one "basic" change at a time. Changing just the rear bar seems like a good place to start.

But, um, thanks for the advice ...
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      04-04-2008, 04:40 PM   #5
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Sorry you didn't agree with white911's suspension advice. But that's racin' isn't it? :smile:
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      04-04-2008, 04:51 PM   #6
fe1rx
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Yes it is!

And hey, three days to go, so I am wound a little tight!
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      04-04-2008, 04:59 PM   #7
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No problem. You're gonna love it!
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      04-04-2008, 05:00 PM   #8
UR2SLOW1
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fe1rx is right on the money, I'm not looking for an all out suspension swap, I just want to eliminate some of the lean. My previous CL's and NSX's all had substantial lean till I replaced the bars and I'm hoping the same will be true of the 135.
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      04-05-2008, 10:34 AM   #9
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Swaybars alone do not make for a proper suspension set-up. Swaybars are a tuning tool. The right way to reduce lean is through increased spring rate. All BMWs come with very soft springs, due to their luxury car upbringings. Yes, the Ultimate Driving Machine is first and foremost made for the guys and gals who think they are driving enthusiasts but in reality they are looking for a well behaved, high quality German luxury car. Most of the folks reading forums such as this do not fall into that category. :biggrin:

These cars don't come from the factory with suspensions as "finely tuned" as a Z06 Corvette or Lotus Exige, not hardly. Not even the M3 - the stock spring rates are completely wussified, to suit the needs of 90% of the buyers that will never turn a corner on a race track or autocross in anger. Again, even if some of them slip into the forums, they are all in the "wash and wax" sections. :biggrin:

Spring rate (and adding a lot more adjustable negative camber range up front) is how enthusiasts begin to unleash the incredible handling of Bimmers. And once you've altered spring rate you need to compensate with shock valving, of course.

Shocks alone also do not make for the ideal handling set-up... although under very specific rules limitations you can make some custom shocks that up the effective spring rate (with high nitrogen pressure monotube adjustables). We've built some double adjustables to work in SCCA Stock classes that have higher than normal pressures and custom valving to compensate for the super soft OEM springs. The adjustable compression valving adds adjustable bump travel force to the equation, as a previous poster wrote.

Still, this is a backwards way of fixing a considerably soft spring rate, and only recommended if you are racing in a class that doesn't allow spring rate changes. Proper springs+shocks will transform these cars.

Cheers,
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      04-06-2008, 08:53 AM   #10
white911
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Quote:
Originally Posted by Fair View Post
Swaybars alone do not make for a proper suspension set-up. Swaybars are a tuning tool. The right way to reduce lean is through increased spring rate. All BMWs come with very soft springs, due to their luxury car upbringings. Yes, the Ultimate Driving Machine is first and foremost made for the guys and gals who think they are driving enthusiasts but in reality they are looking for a well behaved, high quality German luxury car. Most of the folks reading forums such as this do not fall into that category. :biggrin:

These cars don't come from the factory with suspensions as "finely tuned" as a Z06 Corvette or Lotus Exige, not hardly. Not even the M3 - the stock spring rates are completely wussified, to suit the needs of 90% of the buyers that will never turn a corner on a race track or autocross in anger. Again, even if some of them slip into the forums, they are all in the "wash and wax" sections. :biggrin:

Spring rate (and adding a lot more adjustable negative camber range up front) is how enthusiasts begin to unleash the incredible handling of Bimmers. And once you've altered spring rate you need to compensate with shock valving, of course.

Shocks alone also do not make for the ideal handling set-up... although under very specific rules limitations you can make some custom shocks that up the effective spring rate (with high nitrogen pressure monotube adjustables). We've built some double adjustables to work in SCCA Stock classes that have higher than normal pressures and custom valving to compensate for the super soft OEM springs. The adjustable compression valving adds adjustable bump travel force to the equation, as a previous poster wrote.

Still, this is a backwards way of fixing a considerably soft spring rate, and only recommended if you are racing in a class that doesn't allow spring rate changes. Proper springs+shocks will transform these cars.

Cheers,
Well said. Curiously changing the rear sway bar may be far more difficult and involved then changing the rear springs and shocks. Dialing in simply means you are matching rates to your driving environment. I did not dream up car set-up. There is much good reading available -- The Win series, Design to Win, Tune to Win,... How to Make Your Car Handle, etc. I believe in making one change rather then wholesale changes, otherwise you can not be sure of the net effect of each change.

The second part of this, as a former club racer, chief instructor for Porsche Club, and current DE Chair; I have had the opportunity to work with various race shops organizing classes for car set-up. I am by no means an expert at this; but, I rely on others who are quite successful.
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      04-20-2008, 07:08 AM   #11
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a rear swaybar could be helpfull in counter acting the factory understeer. I would make sure to track the car before the change to judge the highspeed cornering charicteristics first so as to not overdue it.

I think its best to track the car stock and see what the weak points are so you can get a good Idea about what needs to be improved.
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