Re: Do we have a suspension rebuild 'how to'?

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Tone
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Re: Do we have a suspension rebuild 'how to'?

Post by Tone » Wed Apr 16, 2008 4:25 pm

Having just fitted new springs and topmounts to mine, I definitely think a detailed writeup would be useful.

The haynes manual was as much use as a chocolate fireguard. Luckily I had a few mates around to point out what to unscrew/what to leave alone.

My useful hint - Don't overtighten the nut on the arb droplink, causing it to snap and leave your car stranded up on axle stands :oops:
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Meany
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Re: Do we have a suspension rebuild 'how to'?

Post by Meany » Mon Apr 21, 2008 10:02 pm

Building Up & Fitting Front Suspension Struts

Tools needed; 22mm socket (With sides filed down flat to fit a spanner) & 6mm Alun key for strut top-nut, 18mm Socket & spanner, 16mm socket & spanner, 13mm Socket; Various breaker bars & ratchet drivers as required; Jack, Axle Stands, wheel chocks, somewhere suitable to jack the car up.

Before getting stuck in, a few useful tips;

1. This guide is based on my experiences replacing the suspension on my M3 Evo, so although other models will undoubtedly be similar there may be some differences I am unaware of; Please treat this as a guide only and if in doubt consult a qualified mechanic. Neither I or anyone else take responsibility for injury to yourself or damage to property from following this guide!

2. I rebuilt my suspension using Bilstein Yellow Struts & Eibach Pro-S springs; When ordering the Bilstein struts, they come with new top-nuts and dust-covers so there's no need to order new ones separately.

3. Genuine BMW bump-stops are too big to fit the Bilstein struts, but can be modified to go on & give at least some protection from bottoming-out (Discussed further below)

4. With the above Bilstein/Eibach combination and a complete set of new fittings you wont actually need spring-clamps to do this job as moderate hand pressure is sufficient to compress the Eibachs far enough to fit the top-nut.

Building up;

1. First up is to make sure you have all the necessary bits. I decided the best way to go about the rebuild is to replace the top-mountings at the same time as these are prone to failure, and as the rest of the components arent too expensive I replaced everything, enabling me to build up the new struts before touching the car and minimising the amount of messing about and down-time for the car. This approach also means I wont have to strip it down again to replace anything else that might wear out when re-using old tired bits. If you take my approach then you'll need everything from this illustration [Linked with thanks from BMWinfo.com] between No5 & No 10 inclusive, and also Number 12 which is the lower spring-pad;

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2. Now you've got all those lovely shiny new bits it's time to build the new struts ready to fit to the car; First of all, fit the lower spring-pad onto the strut (A) and fit the spring, making sure you get it the correct way up for a snug fit on the pads top and bottom (B) Note that the pads should be positioned so the ends of the spring butt up to the 'steps' in the pads.

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3. Next stage is to fit the bumpstops. As you can see from the pic (C) standard bump stops are FAR too tall to fit as the Bilstein strut has a wider shoulder than standard, but with a little modification (D) they will go on with enough clearance (E), and although they wont give the same protection from bottoming out it's got to be better than the alternative, which is nothing.

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4. Having fitted your newly modified bump-stop & the strut top pad, next up is the new topmount & the two washers underneath it (F). The big, brass-coloured one should sit on the spring pad with the dome facing up, while the smaller ally one goes on top of this with the flat side down (G) then the topmount goes onto this; For the Evo the topmounts are handed, but have a big L and R stamped into the top to tell which side is which, and with a bit of pressure (I rested the strut on the floor & leaned on it a little) you should get enough clearance to put the top nut on finger-tight and hold the lot together, giving you something like (H)

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5. Last thing left to do before attacking the car is to tighten the top nut, which as you will have noticed by now is going to be a pain (I). Basically, you need to be able to fit a 6mm Alun Key in the top of the strut to hold it still while tightening the nut using a 22mm socket. I'm sure there's a BMW special tool for the job, but I Made my own by buying a spare 22mm 1/2" drive socket and filing the sides down flat, so I could get a grip on it with an adjustable spanner (J). Took me about 20 minutes, and once you've done this it's a simple matter to put the socket on the nut, slip the alun key through the middle and steady the strut while you tighten the nut right down (K)

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Once the top nut is fully tight (You'll feel it bottom out & it wont want to turn further) just push the plastic dustcap over the nut and you have a fully assembled front strut; Once you've built the other side to match you're ready to start attacking the car. This first stage took me a little over an hour, including messing about figuring out how best to trim the bumpstops.

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Meany
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Re: Do we have a suspension rebuild 'how to'?**GUIDE ON PG2**

Post by Meany » Mon Apr 21, 2008 10:09 pm

Fitting new struts to the car;

The first thing to do before getting stuck-in to fitting your new struts is to loosen your wheelbolts, then get the car up on axle stands & take the wheels off. As you need to be able to move the suspension to do this job, I found the best place to support the car underneath is where the cross-brace for the transmission tunnel bolts up. That way you can put your jack under the standard jacking-points to lift the car and wont be trying to work around them during the job. Lift the bonnet too to gain access to the nuts on the topmounts.

1. Once you've got the car safely on stands and taken your wheel off, you'll be presented with the view below. First thing is to unhook the pad wear sensor wire (Left-side only), ABS sensor wire & the brake hose from their clips on the back of the strut, and the wires from the clip on the front; Then remove the nut attatching the droplink to the strut (L). The nut itself is a 16mm, and you'll also need a 16mm spanner to grip the joint immediately behind the nut and stop it spinning freely. I found this a real pain to undo, and one side was totally seized on so despite two of us trying with some rather long breaker bars I was forced to fit new droplinks as well.

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2. Next, on the bottom of the strut are 2 18mm bolts holding it in place, one on either side at the very base, and one nut & bolt further up, opposite the hose/wire clips (M); I firstly removed the two lower bolts completely, but before removing the middle supported the lower arm suitably (I used my jack, as pictured) to save it dropping right down and straining the brake hose unduly. I also found it needed some support from the side to save the brake disc flopping over, so I used a handy block of wood but anything similar will do the trick.

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3. Once you've supported the lower arm & taken the bolts out, wiggle the suspension mount from the strut bracket and the only thing holding the strut on the car will then be the three nuts in the engine bay; Undo these while keeping a good hold on the strut from underneath to stop it from dropping and upsetting the wires or hoses in the arch; You can hold the strut in one hand & undo the nuts with the other but I found it easier to have a little help taking the nuts off while I held the strut. Once it's loose, it should lower down far enough to let the top end swing out from under the arch, then lift completely clear. Careful not to snag those wires on the way out! Comparison of manky old strut (Complete with seized-on droplink) and swanky new uprated kit;

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4. If you havent bought all new kit then this is the point where you'll need to start messing about with spring clamps to swap some of those maky old bits on to your new struts, using the first part of this guide; If you're going to do this then PLEASE make sure you use a bench vice and some good spring-clamps before undoing the strut top nut as these springs are under serious pressure and you WILL hurt yourself if you attempt to remove the nut without securing the spring first.

5. When refitting the new strut, fit the circular top reinforcement plate over the three bolts on the topmount and reverse the fitting procedure; However, when lining up the nuts with the top turret housing, be sure to have the arrow pointing FORWARDS on the car for correct alignment (P)

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Meany
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Joined: Sun Oct 02, 2005 8:33 pm
Location: North West

Re: Do we have a suspension rebuild 'how to'?**GUIDE ON PG2**

Post by Meany » Mon Apr 21, 2008 10:11 pm

Hope this helps all you guys plannig to take this on; Feel free to ask questions, or point out anything I might have omitted :lol:

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