another reminder - CHANGE YOUR RSMs!!!

[M3_boogie]

Over the long weekend, I finally got around to installing my GC RSMs (Rear Shock Mounts). I know there have been numerous posts about why to do this and some writeups, but let this be a reminder to everyone that hasn't do it to DO IT NOW!!!

I have a 99 M3 with 63k miles on it, and the previous owner is a very good friend of mine (I was his best man at his wedding). I KNOW how he drove this car... he babied it to say the least, for the 3 years he had it. I bought it from him knowing it would be in good shape and figured some of the problems that are typical with E36's would not have arisen yet here.

Having said that, I pulled out the stock RSMs and luckily the shock towers were in good shape, no cracks or anything around the bolt holes.... BUT the RSMs were in very bad shape. The both had tears 360 degrees around on the bottom side, not visible until they were removed from the shock assembly!!! There were little bits of rubber inside the trunk when I pulled back the carpet as well.

Moral of the story: If this car has bad RSMs, YOUR CAR CERTAINLY DOES!!! Change them ASAP before you have cracked shock towers and need expensive welding to fix. Even if you are planning a suspension upgrade, do the RSMs NOW - it will save you time in the long run because once you put the GC RSMs in, you don't have to tear your trunk apart later to put the new stuff in.

<B>Procedure</B>
I followed the Bentley for removal of the trunk liner and rear shocks from the car. Then followed Matthew C Smith's writeup (http://www.rose-hulman.edu/~smithm3/mods/GC_RSM/index.htm) for assembling the GC setup (I have stock shocks currently), but here are a couple tips:

Assemble the GC RSMs onto the shocks EXACTLY as they come zip-tied together per GC's instructions, BUT you have to remove and discard the "shroud" (# 6 below) from the stock shocks along with the stock RSMs (# 8, 9, 13, 14). So the shock before reinstalling should look like this: on top of the stock washer (# 7) add the big washer GC supplies, then the bottom bushing, lower 1/2 of the mount, new gasket (replaces #13), upper bushing, re-use # 10 and nut #11 (or to be really good, replace with new locking nut). This slides up into the upper 1/2 of the mount - aka the reinforcement plate (with the bolts facing down from inside the trunk).

As far as the orientation of the lower 1/2 of the mounts goes, I put the wider edge towards the middle of the car and the narrower edge towards the outsides of the car.

[Modena NYC]

sheeeeiit! Thanks for the heads up...i guess i'll plan this for the spring...

Is it a simple enough DIY?

[M3_boogie]

yup very simple DIY. Bentley plus the above link pretty much summed it up. If you have questions though, feel free to ask.

[cpunk2]

Yes it is a very simple DIY me and my friend without clear instructions finished the job (both sides) in about an hour. I replaced them with the e46 and z3 reinforcement plates and i couldnt be happier. alot more solid and much smoother! any who hasnt done this its easy and you need to do it anyway!!!

[MGregski]

Thanks for the info Brian.

[andylv]

Thanks for the write up. I'll be installing Koni SAs and GC RSM this week. Your write up is very helpful.

[Modena NYC]

So you don't have to worry about a spring compressor or anything? Sorry, i must still be thinking about the suspension in my Acura and that I would not want to tackle without air tools...

[M3_boogie]

no, you don't have to take the rear springs out to change the RSMs. (the front suspension has the shock inside the spring, not the rear).

[Stinky]

I had a little squeaking in the back on my 98 w/ ~70K. Here's how mine looked:

[bigmansM]

Dude my rsms were so much worse.

Would installing a rear sturt bar be considered a substitute for replacing the rsm's? also wouldnt the bar help keep them running strong?

[STL Avus M3]

I wouldn't think so. The bar would just prevent the towers from flexing. I can't see how it would prevent wear on the suspension from up and down movement.

[Balthazarr]

The strut bar has to affix to the top of towers just like an RSM flange.
It will help, but don't rely on it to do the job the new RSM will do.
Not all will fit with GC without some grinding.
Then you compromise the integrity of the bar.

You could probably invert the entire GC assembly with the lower stepped plate pointing downward from inside and the upper flange on the bottom so the studs are in the same orientation as the stock RSM's, but i wouldn't.

[John H]

I'm currently on my 3rd set, @ 90k miles.

Each time I replaced them (40k and 70k) they were totally hosed.

They should be considered a maintenence item, and not a "only if you drive your car hard" repair item.

- John

[Hellrot Sachin]

Originally posted by M3_boogie
Assemble the GC RSMs onto the shocks EXACTLY as they come zip-tied together per GC's instructions, BUT you have to remove and discard the "shroud" (# 6 below) from the stock shocks along with the stock RSMs (# 8, 9, 13, 14). So the shock before reinstalling should look like this: on top of the stock washer (# 7) add the big washer GC supplies, then the bottom bushing, lower 1/2 of the mount, new gasket (replaces #13), upper bushing, re-use # 10 and nut #11 (or to be really good, replace with new locking nut). This slides up into the upper 1/2 of the mount - aka the reinforcement plate (with the bolts facing down from inside the trunk).

Maybe I have this all wrong.. but I'm looking at the instructions from GC and it appears as though the stock washer ends up on the inside of the car, atop the upper bushing...


As far as the orientation of the lower 1/2 of the mounts goes, I put the wider edge towards the middle of the car and the narrower edge towards the outsides of the car.

The instructions refer to a step.. race cars step inward, street cars step outward.. is this flat area the step?

Thanks guys,

Sachin

[jeebus]

I need to change mine one of these days. They don't make noise and my car only has 32k on it. The previous owner was very careful but I bet they still look bad.

[Balthazarr]

The large dish-shaped washer goes under the 17mm nut on top of the GC bushing.
Just as it did with the stock RSM. Concave side up.

[Balthazarr]

Originally posted by Hellrot Sachin


The instructions refer to a step.. race cars step inward, street cars step outward.. is this flat area the step?

Thanks guys,

Sachin

Sachin, the bottom plate looks like a hat.
For street, the hat fits into the tower.
For track, you invert it.

I could have this backwards, so check with GC.
Mine are set up with hat (step) inside the tower.

[M3_boogie]

Originally posted by Hellrot Sachin
Maybe I have this all wrong.. but I'm looking at the instructions from GC and it appears as though the stock washer ends up on the inside of the car, atop the upper bushing...

The instructions refer to a step.. race cars step inward, street cars step outward.. is this flat area the step?

Thanks guys,
Sachin

If, by "stock washer" you mean #7 from the picture in my 1st post, that stays on top of the shock assembly between #5 and the bump stop (#4). The thing that ends up "inside the car, atop the upper bushing" is (as Balthazarr said) the dish-shaped washer #10 along with the nut #11. With the GC setup, the 2 bushings are not actually attached to anything, they just sit inside the mount - one on the outside (ie in your wheel well) and one on the inside (ie in your trunk). The bottom one is held in by the big washer GC supplies and the top one is held in by this cup (#10) and the nut (#11).

The outdated GC instructions (http://www.mpactmotorsports.com/gallery/gcinst/GCINST001) referring to the "step" are referring to the lower bushing. Per my phone conversation with GC, I left the bushings in the orientation they came zip-tied - with both steps (upper and lower bushing steps) facing inward (ie exactly opposite to the above GC instructions).


Originally posted by Balthazarr
The large dish-shaped washer goes under the 17mm nut on top of the GC bushing.
Just as it did with the stock RSM. Concave side up.

Correct. The "large dish-shaped washer" is #10.


Originally posted by Balthazarr
Sachin, the bottom plate looks like a hat.
For street, the hat fits into the tower.
For track, you invert it.
I could have this backwards, so check with GC.
Mine are set up with hat (step) inside the tower.

There seems to be some confusion here. I think you are referring to the actual lower 1/2 of the mount (ie the metal part that the bolts from the upper 1/2 of the mount feed through). I don't think you should futz with the orientation this part, as it seems to me that this + the upper 1/2 of the mount are what spreads the force out, so you don't put as much stress on small sections of your shock tower.

The GC instructions referring to street vs. track setups seem to be referring to the lower bushing, not the lower 1/2 of the mount.
The only thing I read about (on these forums somewhere) flipping the actual mount (lower 1/2) is for use with a shortened suspension setup. Do a seach for that info.

The only question in my mind about the lower 1/2 of the mount was which way it should sit rotationally (ie - the mount pointing up into the trunk, but unlike the stock mounts, they are not oval-shaped - one edge is longer than the other). I forgot to ask GC about this and put it in with the longer edge towards the center of the car and the shorter edge facing the wheel. I'll confirm this with GC when I do my RTABs (since you have to take the rear shocks back out again then) and post it here.

[Balthazarr]

M3 boogie, Since GC makes the modified setup with tracking in mind, their kit results in shorter shocks. Then inverting the lower plate so hump compensates for the shorter bumpstop with the bushings contiguous is pretty much the same as a track setup isn't it?

When you say "rotationally", and then say "pointing up into the trunk" I don't follow with reference to which side faces the car centerline.

[Balthazarr]

Also, the steps on the bushings should touch each other for track.
So the way you have it is correct if you want the race configuration.

I'll have to look at mine since it's been months and I don't remember how I have them positioned.
I do remember that it was quite a job enlarging the bushings and washers without a vise to hold them for drilling to accommodate the stems of the ext adj konis.
The bumpstops had to be done as well.

[M3_boogie]

Originally posted by Balthazarr

When you say "rotationally", and then say "pointing up into the trunk" I don't follow with reference to which side faces the car centerline.

Sorry, that is confusing :confused:

I meant, I have the lower 1/2 of the mount pointing up into the trunk from the wheel well but the only quesiton in my mind is which way "rotationally" it should be oriented: since it is not oval, should the longer edge be towards the center of the car or towards the outside of the car.

Someone posted pictures of both these "rotational orientations" somewhere on this forum, I just can't seem to find them. I'll contact GC when I do my RTABs to verify which way is correct.

edit - translated into readable english

[Hellrot Sachin]

I just spoke with ground control and you're right about the step.. The step refers to the "nipple" on each of the new bushings, top and bottom.. For race (or in my case, with H&R Coilovers), the recommendation is to leave it so the bushing "nipples" are facing each other, just like they come zip tied.. "Street" would be the exact opposite..

With regard to the orientation of the lower 1/2 of the mount, the longer border/edge should face the middle/center of the car.. I hope this clears things up..

I have about 20k miles on my e46 mounts with Z3 plates and hope to rip into this weekend... I'm not too skilled on the car but hopefully I won't break anything :) .. I'll keep you all posted,

Sachin

[Balthazarr]

Thanks Sachin.
Looks like I'll be doing some inspection to see how those bushings are oriented.
As if I don't have enough to do on this car.:rolleyes:

M3 boogie, I remember seeing tose pics in a thread about a month ago.
I can't find them either as I looked for them before reading this thread.
Must have spent close to an hour.

[M3_boogie]

Originally posted by Hellrot Sachin
With regard to the orientation of the lower 1/2 of the mount, the longer border/edge should face the middle/center of the car.. I hope this clears things up..


Thanks for making the call to GC Sachin. Looks like I guess-timated mine correctly then.


Originally posted by Balthazarr
M3 boogie, I remember seeing tose pics in a thread about a month ago. I can't find them either as I looked for them before reading this thread. Must have spent close to an hour.

Glad I wasn't the only one who wasted too much time trying to find those again. ;)

[Virg///M3]

Damn!!! I did not know. Thanks...

[bobbyp]

OK, where do you get the GC RSM's? Appreciate the heads up and explanation on replacement. Also, do you need to jack the car up to do this? I have the Bentley and am now learning to be a DIY'er.

[Balthazarr]

It's easiest to do when you take the wheels off. You want to unload the suspension.
You have to remove the old RSM(s) and can't do that without unbolting the shock from the lower mount and removing it from below.

[Hellrot Sachin]

Well, I just got back from my mechanic (didn't have the tools or the patience to make it a DIY, especially since I paid $30).. I had the e46 rsms with Z4 Reinforcement plates and guess what, they looked PRISTINE!

About 15k miles on them, no track events and always gentle over the bumps.. H&R Coilover suspension, anyway, mine looked fine but I went ahead and replaced them since I have the parts..

Anyone want to buy the e46 mounts with plates from me, I'd hate to toss them in the trash..

Sachin

[Jordanst2]

just being a little paranoid.... but I've read about nuts, washers, ect in the shock mount, i went an bought a pair of e46 rsms with the z3 reinforcement plates, I assumed that I bought the whole rsm unit, is this the case or do the dealer items also come in peices?

[M3 Pete]

It's easiest to do when you take the wheels off. You want to unload the suspension.
You have to remove the old RSM(s) and can't do that without unbolting the shock from the lower mount and removing it from below.I never unbolted my shocks from the lower mounts. You can simply compress the shock to get the top low enough to remove the RSM. Of course, if you have nice new shocks, this could be harder than with my old worn out stock ones. Speaking of which, I better give GC a call and order those Konis ...

[Colicious]

i just replaced mine today :cool:

[Casebrius]

If people don't know already, if you are going to use stock RSM's, get the E46 Convertable ones, they are supposed to be a little stouter. Also, It's imperative that you put the washers back on right, your shiny new RSM's will last for approximately 1.5 potholes if you don't have the washers on right.

[1024m3]

Just curious....
Do yours squeek over bumps? I put white grease on mine and they still squeek a little. I have Koni's

[M3_boogie]

I think Windex works on those, as it does on the UUC tranny mounts in the TMEs.