M6 sway bar upgrade question

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Da_Hose
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M6 sway bar upgrade question

Post by Da_Hose »

Hey folks. I am thinking of upgrading my front sway bar to the E28, M5 version. Looking at the M5 parts diagram, the stock mount looks like the same type of tabbed mount we use on the M6. So if I order an M5 sway bar with stock sized poly bushings, will that fit in my stock M6 clamps? Or could I use the M5 clamps?

Thanks for any feedback, peoples.

Jose
1987 M6 - My dream car
BlackBetty
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Post by BlackBetty »

On a side note, UUC is coming out very shortly (weeks) with a sway bar kit for our cars. Call them for further details.
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Post by winfred »

i have m5 bars on both ends of mine with euro m635 springs and itz niiiiiice, my chassis started off as a 635 and the front mounts are not even close (i don't know if the m6 used a different mount, i just built a solution instead of buying one, drivers side worked with a modified e34 mount, other side is different) i was able to modify them though. boxed in the mounts on the struts so they wouldn't be ripped off
3/81 633 m30b35 & getrag 260/6, motronic 1.3 -sold

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Brucey
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Post by Brucey »

there are several different M6, M635, M5 bars that fit. You can buy the right mounts for each bar from BMW and weld them in. The bars are identified by dia on the ETK and the mounts/rubbers that match are listed there too.

The thickest M5 mounts are much more substantial than the stock mounts; they need to be.

A word of caution; Bilstein strut inserts contain long bump stops which come into the travel early on and significantly contribute to roll stiffness.

The thickest E28 chassis ARBs were supplied with the E28 M5 for one year, and AFAICT that spec of bar was to be used with Boge struts, not Bilsteins. the Boge struts didn't have the same bumpstop characteristics.

So those M5 bars and Bilsteins together is I think a stiffer setup in roll than any factory spec.

cheers
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Da_Hose
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Post by Da_Hose »

I haven't tracked my car and once I get my 2002 up and going, I doubt I ever really will. I do drive it aggressively in the canyons, but never break neck speeds. It's a GT car, not a sports car after all.

All that said, I do want to reduce roll but being an M6, I don't want to cut off the factory mounts to put on a non-stock piece. I like the idea of being able to return to stock. I did weld on the sub-frame adjusters, but that was a very unique and MUST do kind of thing. I can always turn them back to stock settings if I raise the car and same with a bolt on sway bar mount.

I know the stock mounts are a weak spot, but I have ideas to work around it. :wink:

Interesting info. about the stops, Brucey. I might expect the bump stops to be long on the HD's, but not on the sport cartridges.

Main thing at the start, is whether or not factory M5 bushings fit the stock M6 clamps. Does someone have measurements, or side-by-side pics? I will order some stuff if I HAVE to and compare myself, but it sure would be nice if someone has one of each laying around and could help me out.

Jose
1987 M6 - My dream car
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Post by GripGreg »

Jose`
Make double sure you beef up the sway bar mount area!
My friend, 'JohninSimi' installed a larger diameter sway bar on his,
I think, 633; went on a run & broke the mount area.
I might install a strut tower brace, but, I'm not foolin' with the sway bar.
Good luck,,,,Greg
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Da_Hose
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Post by Da_Hose »

I hear ya, Greg and Brucey. I have an idea of how I could beef up the sway bar mount without cutting off or really altering the stock mount points.

Jose
1987 M6 - My dream car
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Post by GazM3 »

One thing to consider that with most cars stuffing up the front roll bar will give more front understeer. I run a softer 19mm bar in the front with the stiffer M bar at the rear. If I was to get a stiffer rear anti-roll bar for the rear if out the factory one back on the front.
BMW’s
84 E24 M635csi
90 E34 M5 3.6
94 E34 540i/6 SC E85
97 E36 M3 euro SC U/C
97 Z3 2.8 widebody

OTHERS
11 Audi S5 3.0 SC
19 VW Amarok V6
rmorin1249

Post by rmorin1249 »

I found out when shopping for new bushings (31352226001) for my front sway bar that it is a 25 mm bar, different from the US models as they use a 21 mm front bar. My rear bar is 16 mm (33551129700).

Update: After getting the 25mm bushings I found out that my front sway bar is, in fact, 19mm. This was a surprise as realoem lists a 25mm bar as OE on the Euro M635. Very strange.
Last edited by rmorin1249 on Sun Feb 09, 2014 7:35 pm, edited 1 time in total.
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Post by ericono »

I just looked at UUCs website. You have to search for M5 because I couldn't find them under M6...when I did find them and looked at the specs, whoa, the front is 27mm and the rear is 22mm. They are both adjustable. I don't know enough yet to know if any of that is good or bad, but it is big, with a name to match, "SwayBarbarian".

Any opinions out there on this set up or how to best utilize it?

Eric
'85 M635, '00 528iT, '98 Z3
rmorin1249

Post by rmorin1249 »

Sounds a bit much for a street car.
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Brucey
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Post by Brucey »

I agree with Gaz; a stiffer front bar only will make the car a bit understeery, especially on the way in to a corner. However it might be just what you want when you are on the throttle coming out; it all depends how much power and grip you have, and how you want to drive the car.

Fundamentally stiffening the roll bars does two main things;

1) it stiffens the whole car in roll. This keeps the tyres flatter onto the road surface. Arguably gripper rubber (than the chassis was originally designed for) is wasted without geometry changes and/or changes in overall roll stiffness. Unlike camber changes, increased roll stiffness helps in the corners but without causing uneven tyre wear on the highway.

2) It changes the front-rear balance of the car. Whichever end of the car you make stiffer loses net grip. It'll never be perfect in all conditions, and once the whole suspension is stiffer then the transitions from understeer to oversteer will be a good deal more abrupt.

If you are tearing around a racetrack then you have to aim for the balance that will net you most lap time; probably setting the car up so that you can steer it on the throttle in faster corners will do this. Whatever you do, in slow corners you will probably be fighting understeer on the way in and oversteer on the way out.

It is worth bearing in mind that with the suspension we have, once the outside struts have compressed a couple of inches the bump stops (which BMW more accurately calls 'supplementary springs') are firmly in play (external at the rear, internal to the strut insert with front Bilsteins). Even with stiffer ARBs fitted you are still looking at about 1/3 each of the force (on the outside struts) from the ARB, the main spring, and the bump stop. This means the way the car responds to changes in the ARB setting is different to other cars where it might be 50-50 with the main springs because there is no bumpstop involvement in normal cornering.

If you don't have an adjustable ARB on your 6er you can (if your bumpstops are in good shape and you are running sport Bilsteins) still experiment and alter the balance quickly by adjusting the rear ride height; this brings the rear bump stops in and out of play and this alters the roll stiffness at the back end; lower is stiffer.

One general comment is that with any (slightly front heavy) RWD car like ours you are not (IMHO) that likely to turn the car into a death trap by making small changes to the ARBs. This is in contrast to most FWD cars where you generally stiffen the rear ARB to allow more mid-corner throttle. In the dry the effect can be dramatic and results in rather joyously swift and precise cornering. That a small change like that could turn endemic mushy understeer into a beautiful balance is almost unbelieveable unless you experience it first hand. [BTW You know you have run out of leeway when spectators tell you that you are on three wheels mid-corner.... :shock: ] However, in the wet, the same car can be real handful; just backing off the throttle slightly mid corner can have the back end stepping out and you have no place to go then...

cheer
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Post by GazM3 »

The 6er being an old car does roll around abit so it definetly could benfiit form upgraded anti roll bars but id definitly upgrade both or the Rear only, not the front only (but thats me). If you run staggered (that being larger) rims and tyres at the rear it will inhernatly understeer also so stiffening up the front bar will make it worse, but as Brucy said safer in wet weather.

Ive recently added some offset roll centre adjusing blocks to the front which have certanly helped dial out some unwanted understeer (see page 9 or 10 in my project thread for pics and details)
BMW’s
84 E24 M635csi
90 E34 M5 3.6
94 E34 540i/6 SC E85
97 E36 M3 euro SC U/C
97 Z3 2.8 widebody

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Post by Da_Hose »

Hmmmmm ..... sounds like what I am hearing is to try increasing the rear swaybar to 21mm and see how that drives. Then consider the 25mm if it feels out of balance.

I thought I remembered someone saying their M6 was running a 25mm front and stock rear with good results. Am I just not remembering that correctly?

Jose
1987 M6 - My dream car
rmorin1249

Post by rmorin1249 »

Da_Hose wrote:Hmmmmm ..... sounds like what I am hearing is to try increasing the rear swaybar to 21mm and see how that drives. Then consider the 25mm if it feels out of balance.

I thought I remembered someone saying their M6 was running a 25mm front and stock rear with good results. Am I just not remembering that correctly?

Jose
Turns out my Euro M635 has a 19mm front bar. I found this out when trying to install the 25mm bushings that I ordered based on information in realoem. Can't explain why I have a 19mm front bar since I have no evidence that anything has been replaced on my car other than normal wear and tear items.
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Dinan

Post by ian m635uk »

My m635 also had 19mm front and 16mm rear. It rolled way too much for me. You need the 25mm mounts when upgrading. The 19mm mounts are tiny compared withe 25mm ones.

I upgraded the whole suspension as i wanted to track the car.
I ended up with the following
Dinan sport springs
Bmw 25 mm front arb with correct mounts
Rear adjustable 21mm dinan arb
K-mac front adjustable top mounts
Ireland engineering rear toe and camber plates.

Car is set up on a 4 wheel hunter system with increased front camber.

Car drives very flat in corners, is well balanced and will 4 wheel drift when limit is reached. Turn in is good, rear end will step out quickly compared to standard and you have to be sharp to catch it. Overall a massive improvement compared to the standard set up.
rmorin1249

Re: Dinan

Post by rmorin1249 »

ian m635uk wrote:My m635 also had 19mm front and 16mm rear. It rolled way too much for me. You need the 25mm mounts when upgrading. The 19mm mounts are tiny compared withe 25mm ones.

I upgraded the whole suspension as i wanted to track the car.
I ended up with the following
Dinan sport springs
Bmw 25 mm front arb with correct mounts
Rear adjustable 21mm dinan arb
K-mac front adjustable top mounts
Ireland engineering rear toe and camber plates.

Car is set up on a 4 wheel hunter system with increased front camber.

Car drives very flat in corners, is well balanced and will 4 wheel drift when limit is reached. Turn in is good, rear end will step out quickly compared to standard and you have to be sharp to catch it. Overall a massive improvement compared to the standard set up.
Yep, same as mine but since I don't track my car I find it fine for normal driving.
Chris Wright

Post by Chris Wright »

Da_Hose wrote:I thought I remembered someone saying their M6 was running a 25mm front and stock rear with good results. Am I just not remembering that correctly?
I think that is backwards? :-k
Hmmmmm ..... sounds like what I am hearing is to try increasing the rear swaybar to 21mm and see how that drives. Then consider the 25mm if it feels out of balance.
You should talk to GWL (PM him and ask him to post here), he has gone through this with his M6. He bought a set of M5 bars (25mm/18mm) and put the rear one on because it would bolt right up and found he liked the stock M6 22mm front (or is it 21mm?) with the M5 18mm rear, but when he welded on the front M5 25mm bar it threw it out of balance and he had to upgrade the rear to a larger 19mm bar to get it back in balance, but I'm not sure he likes it as much?.

Check out his comments on his set-up:
viewtopic.php?t=6538&

Some more comments on sway bars:
viewtopic.php?t=6371&
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Da_Hose
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Post by Da_Hose »

That post from GWL is the one I remembered, Chris. Thanks for linking it.

Hmmm....... He has the same size wheels all around, but I run a staggered setup. That will automatically lead to an understeer heavy condition. Sounds like what I should do is start by getting an ST rear swaybar and that might be all I need.

Jose
1987 M6 - My dream car
GazM3
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Post by GazM3 »

I'm now thinking of going to a thicker rear bar as now I have staggered tyres 225 front 245 rear has made it understeer on the road a little.
BMW’s
84 E24 M635csi
90 E34 M5 3.6
94 E34 540i/6 SC E85
97 E36 M3 euro SC U/C
97 Z3 2.8 widebody

OTHERS
11 Audi S5 3.0 SC
19 VW Amarok V6
luminus

Post by luminus »

As I side project, I build and have sold e28/e24 front and rear sway bar reinforcement kits, you're interested. The front is actually a replacement for the stock mounts so you can use standard Energy Suspension bushings:

Image

I should have another batch made up soon. The rear parts just keep the existing mounts from being ripped off:

Image

pm me for more details, and of course I'll post a new thread when the next set are ready.[/img]
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Post by Feld1128 »

rmorin1249 wrote:
Da_Hose wrote:Hmmmmm ..... sounds like what I am hearing is to try increasing the rear swaybar to 21mm and see how that drives. Then consider the 25mm if it feels out of balance.

I thought I remembered someone saying their M6 was running a 25mm front and stock rear with good results. Am I just not remembering that correctly?

Jose
Turns out my Euro M635 has a 19mm front bar. I found this out when trying to install the 25mm bushings that I ordered based on information in realoem. Can't explain why I have a 19mm front bar since I have no evidence that anything has been replaced on my car other than normal wear and tear items.
I just found out the same thing with mine, it is supposed to have 25mm front and 18mm back which was confirmed when we ran the vin#. Turns out I have the same setup as you contrary to the build sheet 19 front 16 back, so I upgraded to 22mm front and 18mm back with ST suspension kits and urethane bushings. Have not had a chance to drive it since it is getting painted but will next week. Sounds to me like BMW ran out of the M bars and installed regular 6 bars in our cars.
rmorin1249

Post by rmorin1249 »

Feld1128 wrote:
rmorin1249 wrote:
Da_Hose wrote:Hmmmmm ..... sounds like what I am hearing is to try increasing the rear swaybar to 21mm and see how that drives. Then consider the 25mm if it feels out of balance.

I thought I remembered someone saying their M6 was running a 25mm front and stock rear with good results. Am I just not remembering that correctly?

Jose
Turns out my Euro M635 has a 19mm front bar. I found this out when trying to install the 25mm bushings that I ordered based on information in realoem. Can't explain why I have a 19mm front bar since I have no evidence that anything has been replaced on my car other than normal wear and tear items.
I just found out the same thing with mine, it is supposed to have 25mm front and 18mm back which was confirmed when we ran the vin#. Turns out I have the same setup as you contrary to the build sheet 19 front 16 back, so I upgraded to 22mm front and 18mm back with ST suspension kits and urethane bushings. Have not had a chance to drive it since it is getting painted but will next week. Sounds to me like BMW ran out of the M bars and installed regular 6 bars in our cars.
Very interesting. Since I am not tracking my car I plan to keep my present bars as I just replaced both end links and bushings.
Feld1128
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Post by Feld1128 »

I am thinking about replacing end links but not sure how to determine if they need replacing.
rmorin1249

Post by rmorin1249 »

Feld1128 wrote:I am thinking about replacing end links but not sure how to determine if they need replacing.
One of my front ones was broken so I went ahead and replaced both. They are relatively cheap. Bought them from Autohaus AZ.

I inspected the back ones and the rubber looks a bit brittle so I'm going to replace them when I replace my pittman arms. I'm going to try BavAuto parts and see how they compare to OEM. They are about half the price.
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