ACS Suspension Install

Repository of 'how to do' articles relating to the Z3 and M roadster/coupe
Post Reply
siwilson
Joined: Fri 19 Jun, 2009 09:54
Posts: 790

  M roadster S54
Location: Horley

ACS Suspension Install

Post by siwilson »

I have been thinking about a suspension upgrade for quite a while now and having done the due diligence came to the conclusion that while I wanted an upgraded setup, I didn’t really need a coilover setup. The general consensus across the various BMW bulletin boards is that for a ‘standard’ setup, Bilstein sports shocks combined with either H&R or Eibach sports springs is the setup to go for. The AC Schnitzer sports suspension package is a combination of Bilstein sport shocks combined with some specially tuned Eibach springs. Tuned I might add, at the Nurburgring. A typical comment seems to be that while the AC Schnitzer kit is good, it is not worth the extra money over an ‘unbranded’ Bilstein/H&R setup.

After trawling the web I discovered that I could actually get the AC Schnitzer sports suspension kit for the same price as the ‘unbranded’ Bilstein/H&R setup. I have to confess to being a bit of a brand junky, so the opportunity to have a branded AC Schnitzer setup for no incremental cost had to be seized.

An added bonus with the AC Schnitzer setup is that it is approved by BMW, so your insurance company should look a little more favourably on it than a Halfords special. Yes, it could have come from new with this kit installed at the dealership. It may also help if you need to make any warranty claims.

Disclaimer: The following information is provided as information only and is a diary of my experiences installing the AC Schnitzer sports suspension kit. I am in no way advocating that anyone should use this as an instruction manual. If you plan to do this install yourselves then read the proper manuals and seek expert advice.

Before we start, here is how my car sits before the install

Image

Image

Image

Image

The AC Schnitzer sports suspension form my 2001 ///M Roadster came from Rossiters. Chris Rossiter is a really nice guy to deal with and true to his word he shipped via courier over night.

Image

Tools you will need:

1x600mm breaker bar because some bolts were VERY tight
1x17mm socket for the wheel bolts
2x18mm sockets or 1x18mm socket and an 18mm ring spanner for the front strut lower bolts and rear shock lower bolts
1x16mm socket and 1x16mm open ended spanner for the front ARB drop links
1x21mm deep socket for the front strut top nut
1x6mm hex key for the front strut
1x13mm socket for the front and rear strut/shock upper mounting nuts

I decided to start with the front as this is the most complicated bit. First job is the crack the wheel nuts with the wheels on the ground. The get the car on axle stands. There isn’t a decent place to jack up the front in one go without removing the engine under tray, so you have to do it one side at a time. I placed the jack slightly forward of the jacking point so I could use the jacking points as the location for the axle stands. Once the car is on the axle stands, off come the front wheels.

The front suspension of the Z3 comes from the E36 3 series and uses a McPherson strut arrangement. This means that when the strut is removed the front hub will need supporting so it doesn’t stress the brake hoses or the ball joints.

Here you can see the hub suspended from a cord. The cord is tied off to an engine lift point at the top and a wheel bolt at the bottom. Make sure you put some protection between the cord and anywhere it touches the bodywork.
Image

The first job is to disconnect the front anti-role bar drop link. I used a socket on the front and an open ended spanner on the flats of the drop link behind the strut. This is also a good time to unclip the brake hose, ABS and brake pad sensors from the strut. Note that the plastic clip can become brittle and break like mine did.
Image

Next job is to remove the three bolts that connect the bottom of the strut to the hub. The top one is a through bolt with a washer and nut and the other two are bolts that screw directly into the hub.
Image

Image

When these three bolts are removed the front hub will drop and be suspended on the cord. I placed the jack under the hub while I removed the bolts and then let the hub down gently.

Now remove the top mounting nuts. It’s a sensible idea to loosen all three and then remove only two. Put your hand underneath and grab the strut while you remove the last nut or the strut will drop on the floor. Ask me how I know. :rolleyes To get the strut out you need to lower it down through the ABS cable and then angle the top of the strut backwards to clear the wheel arch. Then you can guide the lower end back through the ABS cable and voila!
Image

Repeat the same process for the other side. Note that both sides have the ABS sensor, but only one of the front hubs has a brake pad wear indicator. Don’t worry that one side is missing.

Now retire to your garage for the ‘interesting’ bit. Unless you plan to use all new parts and build a complete new, leg you will need to disassemble the old leg. To do this you need to undo the top nut that holds it all together.

CAUTION: Even with the strut removed from the car, the suspension spring is under a lot of compression. DO NOT attempt to undo the top nut unless you have relieved the pressure with a decent spring compressor. I used a cheap two piece spring compressor from Halfords and while I was successful, it did not feel safe. Next time I would hire a decent one piece spring compressor. The problem is that the front springs on the Z3 are coiled at quite and angle. Due to this, the spring compressor I used did not grip the spring very well. Relieve the pressure on the top nut with a spring compressor.

TOP TIP: you need a bench with a vice and a decent spring compressor.

On the standard strut, there is a 21mm nylock nut. There is also a 6mm hex socket in the top of the piston so you can prevent the piston turning while you undo the nut. The challenge is that when you put a socket over the nut, you cover up the piston. There is a special tool available that holds the piston still while you undo the nut, but I couldn’t find somewhere to hire one. What I did was to use a seep 21mm socket and grip the outside with some mole grips. I then fed a 6mm hex key down though the socket into the piston. You have to insert the long end of the hex key to reach the piston, so you will need something to help you grip the short end. Small box spanner or deep socket with an extension should work OK. The 21mm nut is stiff, but not that tight. Once you have a couple of turns on it you can dispense with the hex key. Initially I had trouble gripping the socket with the mole grips, so I ground a couple of flats on the outside of the socket with a grinder. A bit ghetto, but it worked. Once you have the top nut off you can disassemble the strut. Make a note of the order everything comes off.

TOP TIP: As you undo the strut top nut, the top strut mount should start to get loose. If it doesn’t and everything is following the nut up the thread then you still have some spring tension there. STOP now and figure out why there is still spring pressure there before continuing.

Here you can see my new strut in the vice ready to be built. I used an old leather rigger glove to prevent scratches.
Image

I decided to invest in almost all new parts. I replaced all the nuts and bold, springs pads, washers and covers. Total cost around £60. In fact, the only thing I didn’t replace was the upper mount itself as these are about £60 each on the ///M and not readily available. If I was doing this again I would replace these parts as the upper mount, referred to by BMW as a ‘guide support’ contains a bearing.

Image

On mine, the bearings on both sides were full of grit and muck. I cleaned them out with solvent and re-greased them. Far less lumpy, but not perfect.

Image

Parts to mount top of strut

31 33 1 092 887 Self Locking Collar Nut - £0.24
STRUT TOWER
31 33 1 094 288 Washer Gasket - £1.62
31 31 2 489 795 Front Spring Strut tower reinforcement – Not replaced

Parts list in order of installation on strut

31 31 1 139 453 Covering Cap - £0.64
31 12 1 095 420 Self-locking hex nut (M14x1.5) - Supplied with strut
31 33 2 227 897 Guide Support Left – £42.96
31 33 2 227 897 Guide Support Right – £42.96+
31 33 1 110 196 Dust Protection Collar - £0.94
31 33 2 227 342 Support - £5.05
31 33 2 227 903 Upper Spring Plate - £4.90
31 33 2 227 902 Spring Pad Upper - £3.54
SPRING
31 33 1 124 322 Spring Pad Lower - £2.09
STRUT

Parts to mount bottom of strut

31 31 1 136 465 Hex Bolt w/ Washer - £0.51
07 11 9 905 753 Self-Locking Hex Nut - £0.68
07 11 9 931 021 Washer - £0.25
07 11 9 905 853 Fit Bolt - £1.11

New ABS/Pad wear sensor cable holder

33 18 1 181 310 Cable Holder - £0.51

The first thing you notice as you start to assemble is the different in the height of the springs.

Image

When you install the spring pads you will notice that there is a step in the pad. It is important that the step buts up tightly with the step on the bottom cup in the strut and also that the end of the spring fits snugly against here as well.

Image

Image

Image

Now its time to compress the spring. Sorry I don’t have a photo of this, but my mind was otherwise occupied. You need to compress the spring enough so that the upper spring plate with the upper spring pad attached seats on the piston before it rests on the spring. Then install the rest of the parts and do up the nut.

Installation of the front struts is a reverse of the removal. Put the strut in place, install the top nuts and then the lower bolts. Reconnect the front anti-role bar drop link and clip the hoses and cables back in. For the top nuts I did them up tight enough so that there was no movement and then left the final torque setting until the car was back on its wheels. For the lower bolts, I did torque them up and did a second check when the car was on its wheels.

When Installed, the front struts should look like this.

Image

Total time taken was around 4 hours, which included some bad language the time it took to modify that 21mm deep socket.

REAR

The rear install is MUCH easier and only took me 2 hours start to finish. The first thing is to put some chocks under the front wheels, crack the rear wheel nuts and get the rear end on the axle stands. Jacking up the rear of the car is a much simpler process. The trolley jack goes directly under the rear diff. Make sure the jack does not touch the alloy diff cover, but sits under the cast main diff housing. You see on mine that someone has kindly marked an X marks the spot at some point in the past. The axle stands go under the jacking points as before.

Image

With the car on the axle stands, remove the wheels and let off the handbrake. First job is to disconnect the rear ARB form the trailing arms. This required a 13mm socket and does not require much force. You should also unclip the handbrake cable.

Image

Next you remove the lower bolt for the rear shock. This requires an 18mm socket and was quite tight. I used my 600mm breaker bar to shift this.

Image

It’s a good idea to support the rear hub with the trolley jack as this makes the removal of the bolt easier and also prevents the hub dropping suddenly. With the rear bolt removed you can lower the hub. With the rear ARB already disconnect the hub lowers enough to get the spring out.

Image

I used a crow bar to help lever the spring out. Just watch out not to squeeze the ABS cables on the trailing arm. As the spring came out it also removed the rubber spring pads. This was a good opportunity to clean the area.

Image


As you can see, there is a marked difference in the length of the springs.

Image

The next job is to install the new spring pads and rear springs. If you find you have uneven ride height between front and rear you can adjust this slightly by using a different thickness lower spring pad. BMW make a 5mm, 7.5mm and a 10mm spring pad. The standard one that I used is the 7.5mm one.

Top Tip: I found it easier to put the top spring pad on the car, but insert the lower pad into the spring. Then insert the spring and mount the lower spring pad on its mount. The top of the spring does not look like it will line up with the top spring pad, but it will come back as the trailing arm is raised. You just have to guide it into place as you lift the arm.

Next job is to remove the old rear shock. With the bottom already done all you need to do is undo the top two 13mm nuts. If you have a roadster then this is easy as you can gain access just by pulling back the hood well lining. I didn’t need to remove any trim fasteners. If you have a Coupe then you have a bigger job to remove the interior trim.

Image

One thing I did find is that the rubber cover you see in the picture actually holds the shock in place after the bolts are removed. When you remove this rubber cover, the shock will drop to the floor. It’s not a bad idea to have someone or something to catch this as it falls as it could hit the ABS cable.

Parts required for rear (each side)

31 33 1 092 887 Self Locking Collar Nut - £0.24
REAR SHOCK MOUNT
33 52 1 137 360 Self locking hex nut (M10 1x8) - £.037
33 52 2 225 906 Plate - On back order
33 52 2 225 911 Protection tube - £1.62
SHOCK
07 11 9 900 402 Hex Bolt - £0.60

33 53 1 093 935 Spring Pad Upper - £3.83
SPRING
33 53 1 136 386 Spring pad 7.5mm - £3.11

Optional, Rogue Engineering RSMs

Annoyingly My Schnitzer rear shocks did not come with new nuts for the piston, so I had to use the old ones. You can see in the picture, the infamous Z3 rear shock mounts. Mine were replaced recently under warranty, but I had no plans to keep them. I upgraded to the Rogue Engineering RSMs. Installation instructions here - http://www.rogueengineering.com/pdf/re_rsm.pdf

Image

Here are the old and new shocks side by side. See the difference in the length. This really illustrates why you really should replace your shocks if you plan to lower the car. With a standard shock and a shorter spring, the shock will spend more time in a more compressed state and wear more quickly. One thing to note is that the BMW rear bump stop is no good on the Schnitzer shocks as they have a smaller diameter rod. I have contacted Rossiters about this to see if Schnitzer make a bumop stop and for some reason it was not included in my kit.

Image

Here you see the Rogue Engineering RSM in place. They really are a quality piece of kit. Unfortunately I don’t have a decent picture of it, but apart form the improved quality, the RE top mounts have one other nice feature. They bolt up form below instead of above. With the RE top mount kit you get a rear shock tower re-enforcement plat that has integral bolts. It installs from inside the car so that the captive bolts point down into the rear wheel well. The shock can now be installed or removed without disturbing the interior. Nice for Roadster owners, a godsend for Coupe owners!

Image

To install the new rear shock, feed the shock up into the wheel well, guide over the bolts and install the 13mm nuts from below. There is also a gasket that goes between the top of the RSM and the inside of wheel well. The rear top nuts were where I had the only real PIA with the rear install. The nuts are very close to the protection tube that protects the piston on the shock. In my case this meant I could not get a socket on all the nuts. I had to use an open ended 13mm spanner. This just made the install a little slower. If you have a thinner walled socket you may be OK here.

When the top mount is done up, you can install the bottom shock bolt. You might think that the shock is pointing in the wrong direction to line up with the lower mount. This is because the RSM is a low stiffer than stock and also because the lower arm is not in the right place yet. Raise the trailing arm with the jack, line up the shock with the mounting hole and install the bolt. Note the washer that goes between the bolt head and the shock. This was supplied in the Schnitzer kit and is there to prevent the shock becoming detached should the lower rubber mount fail. I think that happened to someone here recently.

Image

Last job is to reconnect the rear ARB and clip the handbrake cable back into place.

I did up all the rear bolts hand tight and did the final torque setting with the car on its wheels.

Job Done!

After 2 days, I measured the ride height. My driveway is a little lumpy to say the least, so I plan to take another measurement on flatter ground some time in the future

Before After
Front Left 26” 25.5”
Rear Left 26.75” 25.75”
Rear Right 26.5” 25.5”
Front Right 26” 25.25”

After 2 weeks, it has settled a litle further. Ride heights are now as follows.

Front Left 25.5”
Rear Left 25.5”
Rear Right 25.7”
Front Right 25”

My drive is a little on the lumpy side, which probably explains the little differences. Here are the after pictures.

Image

Image

Image

Image

Update: It was well worth it. The ride is a little firmer and you can feel the road under you more than before, but you get used to it. 2 weeks on and any additional harshness as a rsult of the suspension or Rogue RSMs has now faded into the background. It really does ride the bumps better.

I hope you find this write-up useful, but please do not take my experiences as gospel. YMMV.

Simon
Last edited by Anonymous on Mon 09 Mar, 2009 10:06, edited 5 times in total.
2001 M roadster S54 Laguna Seca Blue
paulg
Joined: Sat 12 Nov, 2005 18:18
Posts: 269

  Porsche

Post by paulg »

Fantastic write up. Not sure I fancy taking that on.
DavidM
Z Register member
Joined: Fri 10 Oct, 2003 08:29
Posts: 1504

  Z4 M roadster
Contact:

Post by DavidM »

Simon, you're a far braver man than me - I got Rossiters to do my install
User avatar
Gazza
Joined: Tue 04 Oct, 2005 20:58
Posts: 9521

  M roadster S54
Location: Romford Essex

Post by Gazza »

Well done Simon, excellent write up.

Where are Rossiters based?

Gazza.
Gazza

"Understeer is when you hit the wall with the front of the car, oversteer is when you hit the wall with the rear of the car. Horsepower is how fast you hit the wall and torque is how far you take the wall with you"

Z3 S54 M roadster Image, BMW Z1, BMW M3 CSL, Z4M Coupe
ImageImage
siwilson
Joined: Fri 19 Jun, 2009 09:54
Posts: 790

  M roadster S54
Location: Horley

Rear install added

Post by siwilson »

Update, rear install now added.
2001 M roadster S54 Laguna Seca Blue
spence88mph
Joined: Wed 10 May, 2006 06:56
Posts: 38

  M roadster S50

Post by spence88mph »

again, excellent write up!!! thanks!!!
DavidM
Z Register member
Joined: Fri 10 Oct, 2003 08:29
Posts: 1504

  Z4 M roadster
Contact:

Post by DavidM »

garythefish wrote:Well done Simon, excellent write up.

Where are Rossiters based?

Gazza.
Norfolk ...

Rossiters Limited,
Manor Road,
Dersingham,
Norfolk,
PE31 6LD

Tel: + 44 (0) 1485 540000
Fax: + 44 (0) 1485 544800

e-mail: info@rossiters.net
User avatar
///m murf
Z Register member
Joined: Fri 29 Oct, 2004 18:26
Posts: 147

  Z4 M roadster
Location: Downham in the Isle

Anti roll bar links

Post by ///m murf »

Hi Simon

Great install pics

I was lucky when I installed mine as I have a air compressor and air ratchet for removing and installing the top strut nuts and the link bar nut which can be a pain because of corrosion, but while I'm on this subject did you make sure the flats on roll bar link on the ball joint go back in line with the strut as the TIS manual I have goes to great lengths to tell you this twice on the same set of instructions.
I wonder if it is this that is prematurely wearing out the ball joint on the H&R anti roll bar fitted cars :?:

Enjoy Mark
Mark
The Original ///M Roadster + maybe just a couple of mods! Gone but never forgotten, now in a Z4
siwilson
Joined: Fri 19 Jun, 2009 09:54
Posts: 790

  M roadster S54
Location: Horley

Re: Anti roll bar links

Post by siwilson »

///m murf wrote:Hi Simon

Great install pics

I was lucky when I installed mine as I have a air compressor and air ratchet for removing and installing the top strut nuts and the link bar nut which can be a pain because of corrosion, but while I'm on this subject did you make sure the flats on roll bar link on the ball joint go back in line with the strut as the TIS manual I have goes to great lengths to tell you this twice on the same set of instructions.
I wonder if it is this that is prematurely wearing out the ball joint on the H&R anti roll bar fitted cars :?:

Enjoy Mark
Air tool are on my Christmas list. Your right, the link bar nut was a real PIA to undo. Due to corrosion its stiff all the way up the thread and because it has a long thread and starts to waggle about.

I didn't pay any particular attention to the way the flats were aligned. There is no recess for them to sit in and the ball joint seems to move in equal amounts in all directions. What I read from that section of the TIS is that the ball pin must sit flat against the back of the damper. I'll go back and take another look at it at the weekend and probably align the flats. It can't do any harm.

Simon
2001 M roadster S54 Laguna Seca Blue
Rags
Joined: Mon 26 Jun, 2006 20:02
Posts: 92

  M coupe S50

Post by Rags »

ah, good right up.

Noticed you are in Horley.

I work in Crawley so I guess you do mine as well :lol:
siwilson
Joined: Fri 19 Jun, 2009 09:54
Posts: 790

  M roadster S54
Location: Horley

UPDATE: After one week

Post by siwilson »

OK, after one week living with the new under-carriage I can confirm a few things.

The initial "you can feel the road under you", which I would now call harshness, is gone. You get used to the feel pretty quick, and what felt a little stiff to being with now feels no more harsh than stock. This is good.

The improved handling is obviously still there, but what I now know is that I really need to dump these Conti tyres I have on there sooner rather than later.

The drop has settled a touch lower, but not much. I did have my first encounter with a speed hump and you do have to be a little more careful, but not much.

I also update the initial post with some part numbers and prices.

Simon
2001 M roadster S54 Laguna Seca Blue
User avatar
c_w
Joined: Thu 19 Aug, 2004 16:50
Posts: 4032

  M roadster S50

Post by c_w »

Simon, whats the ride hieght like front to back? as most lowering kits I've experienced seem to sit the back too low IMO even when unladen without passengers.
siwilson
Joined: Fri 19 Jun, 2009 09:54
Posts: 790

  M roadster S54
Location: Horley

Update: after pictures added!

Post by siwilson »

c_w wrote:Simon, whats the ride hieght like front to back? as most lowering kits I've experienced seem to sit the back too low IMO even when unladen without passengers.
Chris,

As you can see from the after pictures, the rear is pretty good. The ACS kit lowers the rear more than the front, but IMO it now looks more even.

A big improvement in my book.

Simon
2001 M roadster S54 Laguna Seca Blue
Post Reply