M3 swaybar mount. good or bad?

[mspiegle]

I was talking with TC Kline today and Pete recommended AGAINST using the M3 swaybar mounts. He said that as you turn the wheel, you're turning that mount and changing how the swaybar functions. He prefers leaving the swaybar mounted to the control arm because you'll get the same force from the swaybar regardless of how much you turn the wheel.

What are your opinions on this?

[NC325iC]

do you have m3 struts?

[rs4pro3]

hum I don't buy that, the way the m3 sway bar is mounted makes the bar more effective, From the factory the m30 only got a 19mm front bar where as the 325is got a 20mm bar. The m3 style longer links make the bar effectively larger. on my 85 325e, I'm ussing m3 mount and a 21mm cabbry front bar, and have had no desires to go aftermarket.

[mspiegle]

hum I don't buy that, the way the m3 sway bar is mounted makes the bar more effective, From the factory the m30 only got a 19mm front bar where as the 325is got a 20mm bar. The m3 style longer links make the bar effectively larger. on my 85 325e, I'm ussing m3 mount and a 21mm cabbry front bar, and have had no desires to go aftermarket.

True, the new location may give the bar a better advantage, but do you see the point he was trying to make? I think it sounds logical, but i'm curious if it holds any weight. He thinks the best solution is to get a big ass swaybar up in front and just bolt it to the stock location.

Now obviously i'm getting 2 totally conflicting pieces of data. GC reccomends the M3 mount, TCK does not. They both sell race-winning suspension kits.

And no, I don't have M3 front strut housings.

[rs4pro3]

I sort of see his point, as the strut housing turns, so does the sway link, and the angle that it is to the bar, which in turns changes the direction the forces acting on the sway bar and the suspension. That could have some effect on the handleing but I doubt it's much to even notice. In my opinion GC just copied what BMW did on the motorsport cars, if you notice the e30 and E36 m3's all had the sway links mount to the strut housing, where as the non M version had them mount to the control arm. And now all the E46's use strut mounted links, and even now the E90 does also, but it has a built in twist to it more then likely to conteract those changes.

[Beej '86 325es]

Honestly, I don't see how the M3 mounting points would make that much of a difference. It seems like it would improve the handling by moving the mounting point further outboard, but at the same time hurt handling by mounting it further away.

I just think the 325 mounting is simpler .

[rs4pro3]

Well it depends on what you refer to as simple, the stock e30 mount has more parts to it, as you have the U-shaped bracket that bolts to the control arm and then to the sway bar link. The reason the longer link is more effective as it creates a greater moment effect of the sway bar on the suspension. In the stock setup the sway bar pulls up on the control arm and tries to compress the other strut assembly, where as with the m3 setup the sway bar pushes directly up on the other strut housing.
I also like the m3 links as you can use adjustable links easier to correct for the geometry changes that occur when you lower the car or from sag that occurs as the chassis ages. This geometry change is a lot of reason people have problems breaking the tabs on the subframes when adding larger bars. As Now the bar is being pulled on in 2 directions versus just one as was designed. Here is a picture of my lowered e30 with m3 stock links.

The arrows are the 2 directions the bar is being pulled in when the suspension compresses, you can see by the cracks in the bushing it put a lot of wear and tear on the bushing, this also inturns pulls on the rear of the mount and could eventualy cuase it to break.
Now here is a picture of the same car and same suspension but now with adjustable links

The length has been changed on the links to make the angle between the bar and the link as close to 90 degrees as possible, this way the bar is only being acted on in one direction and is more effective.
Same idea as to drilling extra holes in the end of the bar, if you move the link to a different hole it changes the angles and makes the bar stiffer or softer as it's now being pulled on in multiple directions versus just one.
I hope this clears it up some, everybody has there own ideas of what the best suspension setups are, and frankly those change for both drivers and for the car being driven.

[BimmerToad]

Drilling more mounting holes can change the effective size of the sway bar because you're adjusting the mechanical advantage of the system. Move the mounting links farther towards the rotational center of the bar, you loose leverage, and the bar becomes 'stiffer,' and vise versa.

While the angle of the bar 'arm' to the link is important, I think the adjustable leverage is a larger reason why adjustable bars work like they do.

As for the end links, both the oem and aftermarket have articulated bearing joint ends, which would move to eliminate most of this twist which might change the geometry of the swaybar. Overall, a sway bar is going to change geometry during the full range of motion, and there isn't much you can do about it.

That said, the M3 links allow you to run a smaller sized bar more effectively, so I'd say go for it. I'm running m3 links with the stock iS bar (20mm)

[rs4pro3]

ya that's what I meant, just in different terms, as changing the angles changes the mech. advantage or moment arm.

[rwh11385]

Some of the race guys, like B. Watts and the RRT clan go with no rear bar and the 325 swaybar setup. Say it's the best way to fly.

If you don't care about very detailed physics and engineering involved, and whatever final reason some see the 325 setup as "better", and just want a cheap upgrade, there's the M3-link fashion.

I've personally haven't decided to actually install my m3-style tabs and endlinks, nor re-install the rear bar yet. I think I like the setup now, and don't fix what isn't broken... (although rear camber does need to increase some...)

[mspiegle]

I sort of see his point, as the strut housing turns, so does the sway link, and the angle that it is to the bar, which in turns changes the direction the forces acting on the sway bar and the suspension. That could have some effect on the handleing but I doubt it's much to even notice. In my opinion GC just copied what BMW did on the motorsport cars, if you notice the e30 and E36 m3's all had the sway links mount to the strut housing, where as the non M version had them mount to the control arm. And now all the E46's use strut mounted links, and even now the E90 does also, but it has a built in twist to it more then likely to conteract those changes.

That's a good point. I didn't realize all the newer cars were using this system.


Good info @ heeter too.

Some of the race guys, like B. Watts and the RRT clan go with no rear bar and the 325 swaybar setup. Say it's the best way to fly.

If you don't care about very detailed physics and engineering involved, and whatever final reason some see the 325 setup as "better", and just want a cheap upgrade, there's the M3-link fashion.

I've personally haven't decided to actually install my m3-style tabs and endlinks, nor re-install the rear bar yet. I think I like the setup now, and don't fix what isn't broken... (although rear camber does need to increase some...)

[BimmerToad]

Generally you want to eliminate a lot of the roll in the front suspension to decrease weight transfer in the rear for putting down the power, (read: understeer) and because McPherson strut suspensions suck when it comes to the important camber curve. Once the control arms are parallel w/ the ground, any more suspension compression takes away from your negative camber.

By putting a fat bar up front, you eliminate a lot of this positive camber gain and can gain a little bit of overall front end grip. Add some static neg. camber and you're good to go :up:

Besides ... M3 end links are cheap, and with OEM options of a M3 front bar (19mm), iS bar (20mm) or cab bar (21mm), it's a good cheap upgrade.

[1991 318is]

Angles and radii.

At racing speed on a half mile circle track, the steering angle of the wheels is about 5 degrees. Most of the radical steering inputs are at low speed or parking. Two heim joints handle this amount of deflection very well. With M3 links the bar is twisted a greater amount for the same droop and bump. With the inner balljoint in the crossmember as the pivot and with 1" bump, the stock mount moves a lesser distance than the outer ball joint. I'm goint to be doing some work on the front of my E30 and plan on going to M3 type mounts. I'll measure and try to calculate the relationship.