FS: fully ball-jointed E9x M3 control arms

[Pete.J]

As per the title, I am selling a set of E9x M3 control arms, these aren't standard M3 control arms, these have additional ball-joints pressed in them. Read below for further details.

Location: Melbourne (near Essendon 3040)
Contact no.: 0435 378 857

Price: Mentioned below in the respective section for each arms set.

M3 rear control arms are ball-jointed on one side only, the outboard joint, (except for M3 toe-arms are ball-jointed on both sides). Non-M control arms have rubber bushings on both ends (except for the upper camber arm, which has a ball-joint on one end only). M3 arms are forged aluminium (extremely light) vs folded sheet metal for non-M (heavier, but cheap for mass production).

We manually pressed in ball-joints instead of the rubber in the M3 arms, to make fully ball-joined M3 arms.

The idea is, when you corner very hard, the whole car leans on the control arms, and the rubber bushings at the end of the control arms deform, causing alignment and geometry changes at the limit.

Overall the car feels nervous, and unsettled. If you look at rubber bushings, they're just made of a rubber mold with an outer metal shell usually, and an inner metal tube where the control arms bolt get threaded through.



Some have air pockets or pockets filled with hydraulic fluid like the cross section below. The caster bushings on non-M E8x/9x 1er and 3er are fluid filled.



If you look at ball-joints cross section, it's a completely solid joint, with zero play!!! It doesn't matter how hard you lean on them mid-corner, you will not be getting any alignment or suspension geometry changes. They transform the car and make it feel very predictable at the limit



Rubber doesn't have a linear spring rate, so it'll compress easily up to a certain point and then gets quite hard to compress it anymore, they're inconsistent-feeling. Ball-joints are nothing like that, they're solid, they don't budge from their place, they don't compress, they feel super consistent / confidence-inspiring at the limit, but they're also a fully articulating joint to allow the control arm to move freely within the geometrical axis it was designed to move in.

Based on all what I wrote above, heavy cars that have wide tyres will be the most disadvantaged with rubber bushings. Cause wide tyres will provide a ton of grip and the heavy weight of the body means that the control arms bushings will get squished in between the heavy weight of the car and high grip provided by the tyres. I've just described the E8x/9x platform basically

All the fastest E92 M3's around the Nürburgring have fully ball-jointed arms (Google Team Schirmer M3, sub 7min BTG time , and it's still a road registered car). Even Porsche advertises that they've fitted their 991 911 GT3 RS models with additional ball-joints compared to the standard 911 cars, ball-joints are definitely the way to go for any true sports car .

*Screenshots taken directly out of Porsche brochure off their website, this is for the 991 911 GT3 RS, notice how it says that both front and rear axles are fully ball-jointed





Pictures and price of the fully ball-jointed front M3 arms I am selling:

*arms were bought brand new, and ball-joints were bought separately brand new, and then I got the ball-joints pressed in. They have about 25,000km on them.

New arms were $550, ball-joints were $480, I paid $50 to get them pressed in, total is $1080. Today with the weak AUD, you're looking at $1,300 to build a set of arms like this.I am asking $800 for the front arms with the ball-joints







Pictures and price of the fully ball-jointed rear M3 arms I am selling:

*Rear arms have less than 4,000km on them they were installed in October 2019 on the car, the ball-joints pressed-in are genuine Lemforder ball-joints, made in Germany. No cheap Taiwanese/Chinese components.

Rear M3 arms are $650, ball-joints pressed-in plus specially machined tapered washers were $300, total for rear arms is $950. I am asking $750 for the rear arms set

[Redd]

I have the same GAS monoballs on the front tension arms. They are fantastic! Improves steering feel, turn-in and less diving under braking.

[Pete.J]

Sold! Thanks for looking

[Redd]

Can I ask where did u get the tapered washers?

[Pete.J]

Originally Posted by Redd

Can I ask where did u get the tapered washers?

The rear ball-joints was a custom solution. We used Lemforder ball-joints, which are the factory ball-joints used on the other end of the control arms. As mentioned above, E8x/9x ///M cars already have a ball-joint on one end, what we're achieving is ball-jointing both ends.

So you can buy standalone Lemforder ball-joints that are the right size for the control arms bore.

Then you'll need custom made tapered washers, so that the ball-joints sit flush against the knuckles. So if you look at the knuckles, the control arm mounting points are tapered.



The Lemforder ball-joints have flat ends, so we use the tapered washers to fill the taper on the control arm, and have the control arm sitting perfectly flush and secure against the control arm (larger contact surface area with the knuckle mating surface).

The washers look like this, this wasn't a project that I undertook alone. It was a group project with a few E82/92 135i/335i mates from Melbourne.



We got the washers very accurately measured, and machined through a friends' company that had contact with a machine shop and ordered enough for everyone that was part of the group buy.

[Redd]

Ah shucks. I don't suppose they would have another set of tapered washers available for sale?

[crille_hallden]

Hello Peter.

Do you have any performance experience from this mod by now?

Curious here in Sweden. 😇