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      06-20-2013, 03:02 PM   #1
DeepOvertone
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Yet ANOTHER suspension upgrade question.

Before any one gets too upset at me please know that I have searched and read and I don't feel that the answers I'm looking for are out there in the way I'm asking for them.

What I have: 2013 135is..
What I want to maintain: as much of the "good ride" as possible IE vibration isolation, low impact harshness so on and so forth.
What I want to improve: I'd like to improve the turn in, decrease the understeer and improve ability to oversteer if desired.

With the availability of the M3 components such as anti sway bars, bushings, and linkages... or even the BMW performance shocks and springs.. everyone says these things are an upgrade as far as handling. I believe this is true but rarely does anyone say which handling dynamic each upgrade improves and what its drawbacks are.

As an example, I'd love to have a sticky post with a chart that details each component and its impacts both positive and negative. I know that each individual part is part of a tuned system and replacing one part of that system with a "better part" can actually make the entire system worse. Are there any upgrades that positively affect the handling system without any negative side effects?

Thanks for the info...
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      06-21-2013, 03:16 AM   #2
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Quote:
Originally Posted by DeepOvertone View Post
What I have: 2013 135is..
What I want to maintain: as much of the "good ride" as possible IE vibration isolation, low impact harshness so on and so forth.
What I want to improve: I'd like to improve the turn in, decrease the understeer and improve ability to oversteer if desired.
Your criteria is spot-on for buying the Birds B1 suspension kit. Only issue is that it's not cheap, especially so, given you'll be having shipping costs and import costs from the UK.

However, it's a great suspension improvement over stock, much more compliant so massive improvement in ride quality (as long as you bin the RFT's as well) and much better steering response combined with a little extra oversteer.

Birds website......

http://www.birdsauto.com/
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      06-21-2013, 03:22 AM   #3
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Upgrade rear sway bar it will increase oversteer. Upgrade front with M3 wishbones and it will decrease understeer. If you want nice ride look in to Bilstein B12 kit.
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      06-21-2013, 07:14 AM   #4
John_01
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Quote:
Originally Posted by DeepOvertone View Post
What I want to maintain: as much of the "good ride" as possible IE vibration isolation, low impact harshness so on and so forth.
What I want to improve: I'd like to improve the turn in, decrease the understeer and improve ability to oversteer if desired.
I think its going to be quite hard to satisfy your criteria. If you really want a car that has sharp turn in and the potential for controlled oversteer I think you need to sharpen up every aspect of the suspension. It means springs, dampers, sway bars, front M3 arms, rear Sub-frame Bushes, and finally an LSD as well! Its not realistic to expect the same comfort as the stock car. It will become more like the comfort level of an M3, or actually bumpier because of the shorter wheelbase. Is your objective to make the car ride and handle as close as possible to a M3?

Quote:
Originally Posted by DeepOvertone View Post
With the availability of the M3 components such as anti sway bars, bushings, and linkages... or even the BMW performance shocks and springs.. everyone says these things are an upgrade as far as handling. I believe this is true but rarely does anyone say which handling dynamic each upgrade improves and what its drawbacks are.
The performance suspension is a good upgrade. Its not very harsh by itself (assuming you upgrade to non-RFT tires), so I think its a good compromise if you are keen to maintain a reasonable degree of ride comfort in a car you will use as a daily driver.

The M3 front arms are also recommended for sharpening the steering response. They help a lot due to the added negative camber and they also give much, much improved steering feel. I added the front arms at the same time as the performance suspension. It does transfer a bit more harshness and vibration through the body of the car. I think it comes from the M3 front arms rather than the performance suspension, but I can't be 100% sure. Overall its not bad, but not quite the same comfort as the stock car. On decent roads it is still a comfortable car, but you will become more aware of things like potholes and disjointed concrete slabs.

Recently I had the rear sub-frame bushes upgraded to M3 items. IMO, this is really needed to go with the from M3 arms. If you want to drive the car fast and hard, it is an essential mod. It makes the car a lot more predictable, safer and easier to drive. Without the rear sub-frame bushes the car had great steering and was fun to drive, but the rear-end would feel disturbingly loose at certain times. The car was had an imprecision in pretty much any situation and I had just got used to continually making small corrections though the steering. After changing the sub-frame bushes the whole car feels tighter and I noticed even the steering response get sharper. There is some vibration transmitted though the M3 sub-frame bushes. It seems there is probably more harshness than what you feel though the M3 front arms. You may not like the harshness, but if you want the car to handle well and stay in control of it, I say its the job that needs to be done.

I think others can give more advice if they have tried different combination of mods. I just give my opinion based on what I have tried.
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      06-21-2013, 08:35 AM   #5
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Thanks for the info guys, I should have mentioned that I'm going to get rid of the run flats as soon at they wear out...

I think I'll start an excel document that would be modifiable for the suspension bits. I'll upload it here and if anyone sees fit to download it and add any info to it I'd appreciate it.
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      06-21-2013, 01:44 PM   #6
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Here is a Document I made with a table in it. If anyone would care to fill out any part of the table that they feel they have a SOLID understanding of the information requested then that would probably help a LOT of people.

Go ahead and re-upload in your reply. The next person will be able to view it and edit it and so on down the line till we have a good feeling that information contained within is acurate. You may also add lines to the table if there are pieces that I forgot to add. Lastly, if you edit the information in the table, please Bold your changes and change the revision number one digit higher. Thank you.
Attached Files
File Type: doc 1 Series Suspension Components Rev 0.doc (30.0 KB, 54 views)
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      06-21-2013, 08:42 PM   #7
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Hi DeepOvertone,

I looked at your document, but I think its a bit simplistic to think that each modification can be understood in isolation. It really depends on the context for the modification. It depends what suspension modifications have already been done, what the car is being used for, the quality of the roads, and what the user can accept in loss of ride quality.

For example if people are building a track day car, in most cases they wouldn't even care how much harshness comes though the suspension. Also the sequence of mods will make a difference. People may notice and increase in vibration and harshness of M3 front arms in isolation, but if they already using camber plates with spherical bearing mounts, then they probably wouldn't notice any change. The same thing with sway bars, because the sway bar will perform completely differently whether the car has stock suspension or a high rate coil-over setup.
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      06-21-2013, 11:38 PM   #8
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DeepOvertone - see my post http://www.1addicts.com/forums/showthread.php?t=786982.

The M3 front suspension adds some very nice steering feel and response - but the bushings are HARD. You really feel a jolt when going over any kind of sharp edge (uneven concrete slabs or metal strips). Not sure I'd do it again.

The M3 rear subframe bushings are virtually mandatory. They're expensive (generally 6 or 7 hours of labor) but make a huge difference.

Just picked my 2013 128. When the suspension gets too soft (as it will) at 30,000+ miles, I'll do the rear subframe bushings again and put in a set of Bilstein HD or Koni Yellow shocks.
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      06-22-2013, 08:01 AM   #9
DeepOvertone
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Quote:
Originally Posted by John_01 View Post
Hi DeepOvertone,

I looked at your document, but I think its a bit simplistic to think that each modification can be understood in isolation. It really depends on the context for the modification. It depends what suspension modifications have already been done, what the car is being used for, the quality of the roads, and what the user can accept in loss of ride quality.

For example if people are building a track day car, in most cases they wouldn't even care how much harshness comes though the suspension. Also the sequence of mods will make a difference. People may notice and increase in vibration and harshness of M3 front arms in isolation, but if they already using camber plates with spherical bearing mounts, then they probably wouldn't notice any change. The same thing with sway bars, because the sway bar will perform completely differently whether the car has stock suspension or a high rate coil-over setup.
I understand that most of what you are saying is probably true but I think you are also over complicating it. I understand that different combos will act differently but I'm really just interested in what each modification does on its own. For example, if someone had a completely stock car, what would upgrading the front sway bar change? Same goes for each and every modification I listed.... What would they do alone? This would give some nice information for people to then decide what mods to do in respect to what they are trying to accomplish. You said that someone who is building a track day car wouldn't care about NVH... True, but someone who isn't building a track day car WOULD and thats why I'm trying to compile this info.

We can figure out what these mods do when combined at a later date.. Just starting with the basics of info here. Thanks
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