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      05-23-2022, 03:22 PM   #1
JustinHEMI
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M Coupe suspension refresh.

Now that rod bearings, vanos, and brakes are done. I want to go after a suspension refresh next. All indications point to having the original shocks/struts/bushings on my 126K mile car.

While having the rod bearings/vanos done, I did have them replace the diff cover, subframe bushings because I felt those were beyond my ability on my back under jack stands.

I read this in another post here, is it a good list of what I should be doing?

"All the bushings. ALL. FCAB (front control arm bushing), ball joints (may require replacing the front control arm), RTAB (rear trailing arm bushings), Diff mount bushings, subframe bushings, and rear shock mounts to start. Engine mounts, transmission mounts, and various other rubber based suspension parts. For RTAB, get new updated M bushings and put on rear railing arm limiters. Shock mounts go with aftermarket. Optional to up grade other bushings, but I'd keep it stock if all you do is spirited drives."
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      05-24-2022, 07:09 PM   #2
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Yeah, that list is pretty comprehensive. It's often easier to replace the control arms rather than just the ball joints. Can get OE Lemforder ZHP control arms and they are exactly the same as the ones with the BMW stamp but cost way less. Will still have to get FCABs separately though, which can be either pressed into the old "lollipop" housing or bought already in the housing. You could include tie-rods in there too if you really want to do everything. Getting the limiters for the rear trailing bushings is apparently very important so don't skip that. Other things to check include the sway bar end links and sway bar mounts. Don't need to change these if they look fine.

I would also say to do the guibo while you're at it, and if necessary the driveshaft center support bearing. Definitely replace transmission mounts and can do the motor mounts too if needed. Make sure the transmission mounts don't get over-torqued because that will increase NVH a lot.

It's probably worth it to upgrade the rear shock mounts since the OEM ones fail so easily. Get something that's rubber rather than polyurethane though because poly will probably squeak. Get new rear shock mount gaskets. Might also want to put some E46 M3 strut tower reinforcement plates in the front; just take out the camber pin and throw it away to make the plates fit. Get some rear shock mount reinforcement plates too.

As for struts/shocks, you can't get OEM bmw anymore but supposedly the Bilstein B6 are very close, if not slightly better. The front struts have bump stops built in but you'll need new rear bump stops; bmw calls these "additional damper rear". Lots of different options if you want to change the springs or do coilovers, but those are the closest to stock.

My car only has 80k miles but I'm looking to refresh a lot of my bushings too. For everything you can get Lemforder or Meyle HD which are basically identical to OEM bmw parts. I searched around a lot to see if it's worth upgrading any of these parts and unless it's a track car it seems that factory-spec rubber is the way to go pretty much for all of these. Only things maybe worth going aftermarket on are the rear shock mounts and transmission mounts, but should still stick with rubber rather than poly. I briefly considered upgrading the FCABs but some BMWCCA people I met who did that talked me out of it.

On a side note you should change the transmission fluid and power steering fluid if they haven't been done already. If you think either of those fluids might be original you should probably do a second change a couple thousand miles after the first to make sure it's really clean.

Last edited by Coi; 05-24-2022 at 07:28 PM..
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      05-24-2022, 07:20 PM   #3
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Quote:
Originally Posted by Coi View Post
Yeah, that list is pretty comprehensive. It's often easier to replace the control arms rather than just the ball joints. Can get OE Lemforder ZHP control arms and they are exactly the same as the ones with the BMW stamp but cost way less. Will still have to get FCABs separately though, which can be either pressed into the old "lollipop" housing or bought already in the housing. You could include tie-rods in there too if you really want to do everything. Getting the limiters for the rear trailing bushings is apparently very important so don't skip that. Other things to check include the sway bar end links and sway bar mounts. Don't need to change these if they look fine.

I would also say to do the guibo while you're at it, and if necessary the driveshaft center support bearing. Definitely replace transmission mounts and can do the motor mounts too if needed. Make sure the transmission mounts don't get over-torqued because that will increase NVH a lot.

It's probably worth it to upgrade the rear shock mounts since the OEM ones fail so easily. Get something that's rubber rather than polyurethane though because poly will probably squeak. Get new rear shock mount gaskets. Might also want to put some E46 M3 strut tower reinforcement plates in the front; just take out the camber pin and throw it away to make the plates fit. Get some rear shock mount reinforcement plates too.

As for struts/shocks, you can't get OEM bmw anymore but supposedly the Bilstein B6 is very close, if not slightly better. the front struts have bump stops built in but you'll need new rear bump stops; bmw calls these "additional damper rear". Lots of different options if you want to change the springs or do coilovers, but those are the closest to stock.

My car only has 80k miles but I'm looking to refresh a lot of my bushings too. For everything you can get Lemforder or Meyle HD which are basically identical to OEM bmw parts. I searched around a lot to see if it's worth upgrading any of these parts and unless it's a track car it seems that factory-spec rubber is the way to go pretty much for all of these. Only things maybe worth going aftermarket on are the rear shock mounts and transmission mounts, but should still stick with rubber rather than poly. I briefly considered upgrading the FCABs but some BMWCCA people I met who did that talked me out of it.

On a side note you change the transmission fluid and power steering fluid if they haven't been done already. If you think either of those fluids might be original you should probably do a second change a couple thousand miles after the first to make sure it's really clean.

Thank you very much!

Yeah all fluids I changed immediate fore to aft. Also engine mounts got done during engine work.

I intend on sticking to OEM as much as possible and B6's are what I'm going with.

Again, thank you very much for the comprehensive response, I appreciate it.
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      05-25-2022, 03:04 AM   #4
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Quote:
Originally Posted by Coi View Post
Make sure the transmission mounts don't get over-torqued because that will increase NVH a lot.
I don't see the connection?

Quote:
It's probably worth it to upgrade the rear shock mounts since the OEM ones fail so easily. Get something that's rubber rather than polyurethane though because poly will probably squeak.
Do you have hands on experience with this by fitting poly ones yourself at that specific spot?
The reason I ask is that I read this a lot, but in my experience this is mainly result of hearsay.
I've polybushed my complete car myself and have not had any such problems. And such things can also be very product specific. There are products out there that are very badly designed (for instance polybushings without greasetrap) and products that are very well designed.

And this is a long time ago, about 10 years ago, but they still don't squeak after a decade. Some polybushings I even had to make myself, or at least remake them as way less was available and some e36 bushings could be made fit with some work on the lathe.

And of course the one that does the fitting is a very important factor. Lots of idiots out there....

Quote:
Originally Posted by JustinHEMI View Post
"All the bushings. ALL.
If you're planning to do all the bushings it would have been better to had them done when the subframe bushings were done.
the inner bushings of the control arms are difficult to get to. Dropping the complete rear axle would have been easier.
When I did my rear axle, dropping it took about 2 hours, but removing all 19 bushings took me just 3 hours, so under 10min per bushing, without having special BMW tools. Just a generic bushing extractor kit and some sockets rings etc (make due). Replacing giubo and propshaft bearing etc then is also much easier.
There are even bushings above the gearbox that are then easier (shift linkeage)
For dropping the rear axle you realistically need a carlift and transmission jack.
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Last edited by GuidoK; 05-25-2022 at 03:15 AM..
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      05-25-2022, 07:45 AM   #5
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Quote:
Originally Posted by GuidoK View Post
I don't see the connection?


Do you have hands on experience with this by fitting poly ones yourself at that specific spot?
The reason I ask is that I read this a lot, but in my experience this is mainly result of hearsay.
I've polybushed my complete car myself and have not had any such problems. And such things can also be very product specific. There are products out there that are very badly designed (for instance polybushings without greasetrap) and products that are very well designed.

And this is a long time ago, about 10 years ago, but they still don't squeak after a decade. Some polybushings I even had to make myself, or at least remake them as way less was available and some e36 bushings could be made fit with some work on the lathe.

And of course the one that does the fitting is a very important factor. Lots of idiots out there....


If you're planning to do all the bushings it would have been better to had them done when the subframe bushings were done.
the inner bushings of the control arms are difficult to get to. Dropping the complete rear axle would have been easier.
When I did my rear axle, dropping it took about 2 hours, but removing all 19 bushings took me just 3 hours, so under 10min per bushing, without having special BMW tools. Just a generic bushing extractor kit and some sockets rings etc (make due). Replacing giubo and propshaft bearing etc then is also much easier.
There are even bushings above the gearbox that are then easier (shift linkeage)
For dropping the rear axle you realistically need a carlift and transmission jack.
Thank you for the insights. I've been reading over the tech manual and I agree with you, would have been better to do it when it was in for the other items. I can handle shocks/struts pretty easily on jack stands it seems, but I think I may just take it back to the shop for the bushings. Yeah I'll be paying labor, but I just don't think I want to take all of that apart on jack stands.
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      05-26-2022, 02:11 AM   #6
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Quote:
Originally Posted by GuidoK View Post
I don't see the connection?
I was just trying to say that it's pretty easy to over-tighten the bolts on top of the transmission mounts. This squashes them down and removes their ability to absorb vibration, introducing excessive harshness and noise into the cabin. It effectively turns it into a much, much stiffer mount. It's especially easy to over do with aftermarket bushings. That's why with certain aftermarket bushings some people report a huge increase in noise and vibration while other people with the same one say the noise level is the same as stock. The OEM transmission mounts are kinda weak with their hyperboloid shape, so getting a more cylindrical bushing can help especially considering how finicky the 1-2 shift is on the Z4M's transmission.


Quote:
Originally Posted by GuidoK View Post
Do you have hands on experience with this by fitting poly ones yourself at that specific spot?
The reason I ask is that I read this a lot, but in my experience this is mainly result of hearsay.
I've polybushed my complete car myself and have not had any such problems. And such things can also be very product specific. There are products out there that are very badly designed (for instance polybushings without greasetrap) and products that are very well designed.

And this is a long time ago, about 10 years ago, but they still don't squeak after a decade. Some polybushings I even had to make myself, or at least remake them as way less was available and some e36 bushings could be made fit with some work on the lathe.

And of course the one that does the fitting is a very important factor. Lots of idiots out there....
I helped install offset poly control arm bushings on a friend's track car (not a bmw) and with a targeted application of grease during install those still don't squeak after a few years and many track days. Haven't been re-greased at all. So I totally agree that they can be ok in certain examples.

I've also ridden in other peoples' modified/track cars that squeak really noticeably and heard lots of first person accounts (talking to people at car meets, autocross, or the track) of poly bushings making noise and even if they were greased liberally they needed frequent re-greasing. One of the people who said this is a tech at a very well known shop in my area that sets up Porsches and BMWs as track cars, and they specifically recommended to me not to put poly FCABs on my BMW. Not all poly bushings are designed properly and some are hard to install correctly the first time. It's all a matter of if it's worth it for those potential downsides.

Either way, for a street car there isn't really an advantage to poly bushings it seems, especially for something like rear shock mounts. There's certainly reasons to use poly for certain bushings on track to decrease deflection (as long as temps aren't too high) and it won't necessarily make noise but on the street it may not be worth the risk in case it does.
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