You've probably often hear me say or read a comment about how I feel regarding BMW M suspension:  "It's EDC or bust"

My bottom line.

M cars are street cars by design, the suspension needs to adapt to varying road conditions while giving you superior performance potential. 

This is an M5, it needs to do it all. 

This is the BMW brochure lip service: 

Link to YouTube Video from BMW M. 

"Electronic Damper Control (EDC) automatically or manually adjusts each damper to suit the driving conditions meaning you enjoy outstanding comfort along with the best in BMW on-road safety. EDC reduces variations in wheel load, ensures tyres have excellent traction and counteracts bodyshell movement regardless of the weight your automobile may be carrying or the state of the road's surface. 

Sensors constantly monitor all factors influencing the vehicle's behaviour and occupants' comfort, in order to precisely adjust the damper control. In a fraction of a second, the signals are analysed by the EDC microprocessor and orders are sent to the actuators on the shock absorbers, which, with the help of magnetic valves, are variably adjusted to provide optimal suspension.  

The influence of potholes and unevenness on the road surface is reduced to minimum.In addition to increased driving comfort and improved roll characteristics on the tyres, EDC also contributes to vehicle stability and safety.

By reducing the nose's tendency to dip when braking and improving the tyre traction, EDC shortens the braking distance when braking heavily. The damper adjustment means that even when braking with ABS the vehicle chassis remains upright on the road and all four wheels have the largest possible contact to the surface."

The Track Car Use Case. 

There's a reason the latest Pikes Peak winners all use a form a EDC, and that it was banned from F1: if your suspension can adapt to the changing road conditions, it can keep you on the edge of the traction circle. 

We unfortunately don't have any motorsport level options for the E6x M5/M6 and E9x M3 chassis. 

Track use is one of the few situation under which EDC should be eliminated from an M car. 

The dampening curves of the OEM EDC shocks and even the B16 Damptronics from Bilstein simply cannot sustain the forces exerted on the chassis as you use wider, stickier tires and more aggressive alignment settings.  

 

The OEM E60 M5 Suspension Design

The E60 M5 was very well engineered in many aspects: this is a point I will keep driving home whenever I work on this car.

The suspension was a key area to the E60's handling prowesses. It remains one of the best full size chassis BMW ever produced, and certainly holds the crowd for the best M5 steering feel of all time. 

Double-joint spring-strut McPherson front axle.

That was the predecessor to the subsequent Double wishbone front suspension on the F10.

Double wishbone rear suspension.

 

The Suspension Removal Process.

It's a complete pain in the ass to work on a complete aluminum suspension over time as every other component seizes and opportunities to stripe and shear bolts are plenty. 

It seems BMW knew something about working with aluminum suspension components. They designed ways to service the suspension in a smart, efficient way. 

Tricky and counter-intuitive car to work on, but it's worth it in the end.

Front Struts. 

This one was simple, but we didn't read the TIS before getting in there - rookie mistakes. 

The steps. 

1. Remove the end links & headlight level sensor (passenger side only). 
2. Remove the wishbone component connecting the knuckle and end links. 
3. Remove the caliper and let it hang. 
4. Support the knuckle with a jack and remove the 3x top mount bolts (and all unclip EDC wires)  
5. Get the top of the strut to clear the fenders.
6. Loosen the strut collar and get a wedge in there to create separation. 
7. Start smacking with a soft hammer on the lower spring perch aiming upwards. 
1. Knowing we would throw these out, we smacked with impunity. 

Bonus: you may need to remove the cabin filters and its underlying plastic panels to access one of the top mount bolts. It depends if you like bending plastic or not. 

Rear Struts. 

The E60's rear suspension is glorious, and easy to work on (somewhat). This one was pretty straight forward. You'll need a helping hand. 

The steps. 

1. Remove wheel liner. 
2. Remove the trunk liners and foam covers off the top mounts. 
3. Unbolt the end links on the lower suspension arm and headlight level sensor (passenger side only). 
4. Unbolt the lower end of the strut from the knuckle. 
5. Unbolt the top mounts and EDC plug. 
6. Pry bar the suspension to lower it. 
7. Work the strut out of the wheel well completely. 

The B16 Damptronic Installation Sequence.

They do however have some shortcomings. Bilstein didn't deem it fit to provide a set of new end links and top mounts. 

Build your struts.

You need to transfer over a few pieces from the OEM struts to the B16s. Follow their instructions to a tee. 

Please stay safe when removing the OEM top mounts from the OEM struts. Mine didn't launch to the skies - but we never know. Safety first.  

Notes on the front. 

The front requires transferring the entire OEM top mount assembly to be transferred.  You do not reuse the OEM strut bolt as Bilstein uses a different diameter nor the bump stops as they are integrated. 

Notes on the rear. 

As with the fronts, the whole top mount assembly is transferred. You also need to transfer the bumper stops as they are not integrated by Bilstein at the rear. 

Bolting down the rear top mounts can be a PITA as the EDC wiring comes out of the top rod. 

Bilstein has designed the rod with 2x flat edges to hold in a vice grip. Bolt them down with a ratcheted wrench. You'll finish the torque sequence when on the car. 

Install your struts.

This process is rather simple, it's like reinstalling the OEM struts. 

You may face issues sliding the front struts into the knuckle. 

Don't despair.

If that happens, you can slide the top mounts into position of the chassis pretty easily and use a jack and the vehicle's weight to get them to sit correctly. 

It's what we had to do. 

Wire & Plug your EDC.

Bilstein provides the proper connectors and front connector adapters to fit with your OEM EDC connectors.

The front requires the wheel liners to be loosened as the wiring needs to be wired by the ABS line.

Bilstein recommends you do the driver side by sending the wire down, and the passenger side by sending the wires up from the wheel well. 

Next up: fitting the complementary Dinan suspension parts

...and the failed fitment experiments.