BC Racing Coil Rear Clunk

MR6

MR6

:
2009 Mazda 5 Touring & 2012 MS3
Since the day one the rear BC Racing coils have been an issue. Over smooth undulations, driveways, or dimpled roads it doesn't make a sound. But over "quick", high frequency bumps like expansion joints and sunken man holes, it clunks...LOUD. It's as if there's a gnome hiding in my wheel wells just wailing on my shock mounts with a sledgehammer.

Thanks to sac and silent for suggestions. I didn't ignore you guys just been busy with all kinds of stuff, the van included. So far, to troubleshoot this infuriating clunk, i've double checked ALL bolts in the rear to make sure they were torqued to spec, they are. I went ahead and even replaced a few bolts with new i had bought but didn't bother to put in. I've removed the shocks repeatedly, checking the collars and re-tightening the top mounts. At this point i'm driving around without the MS3 sway. I've also removed the SPC camber arm from the passenger side and have re-installed the OEM. Still clunks...

I'm at my wits end. I shot an email out to BC yesterday asking for a warranty replacement of both shock and mounts. I wish i had Googled "BC Racing rear clunk" BEFORE i ordered my set. The hits were SOOOO much that I may have gone in a different direction. Don't get me wrong, when it's not clunking, i love, love, love the setup. But it never fails. I'm driving along happily and CLUNK! DAMMIT@#$@#! I'm putting both the RSB and SPC back on this weekend and awaiting the response from BC. In the meantime, no highway trips for the wife and kids. I let her use it locally for errands but i give her the speed for road trips. This issue has been taxing, to say the least.

On another note, the front end rattle-click i thought was the coil was not. I pulled the coil and the mount was solid as a rock. I hit it with the impact (it moved a smidge) and slapped it back in. I'm going to start with the inner and outer tie rods and work my way up to the control arm. If that doesn't work i'm going to set the van on fire and dance around it naked...
 
I wouldn't have suggested this earlier in the troubleshooting process, but now that you're at this level of frustration and time invested:

Why not take the BC setup off the car (reinstall stock parts obviously) and see if the sound disappears. At this point it may very well be worth the sanity check to confirm that the noise you are chasing is indeed in the BC setup and not something else that just started making noise at coincidentally the right time.

If the stock suspension makes the noise disappear, reinstall one BC part at a time and see when the noise appears. As you probably know by now (I'm guessing you've had the rear suspension apart several times now) you can change one entire side on the rear in like 30 minutes.
 
Last edited:
My guess is a bad shock. Do you still get clucking when going over, say the man hole mentioned above, slowly??

You can try a USB cam fix to a clamp hooked up to a laptop. Sit in the rear while the wife drives and hit record and observe. Makes some marks on the shock valve/piston on the max compression and see how far it is going (you have to take dust boots off). Also, observe if the springs are crashing on itself.

See below and go straight to ‘On “Crap”’ - at the bottom.
http://farnorthracing.com/autocross_secrets6.html
 
sac02 said:
I wouldn't have suggested this earlier in the troubleshooting process, but now that you're at this level of frustration and time invested:

Why not take the BC setup off the car (reinstall stock parts obviously) and see if the sound disappears. At this point it may very well be worth the sanity check to confirm that the noise you are chasing is indeed in the BC setup and not something else that just started making noise at coincidentally the right time.

If the stock suspension makes the noise disappear, reinstall one BC part at a time and see when the noise appears. As you probably know by now (I'm guessing you've had the rear suspension apart several times now) you can change one entire side on the rear in like 30 minutes.
Click to expand...

Thought about this but chucked the oem stuff way back. I barely had space in my garage to do the work so keeping parts around really wasn't an option. Do or die approach unfortunately. I would swap the shocks with my MS3 but i don't have anywhere to get a 2nd car up in the air. If BC ignores my plea, i'm gonna buy a single KYB with mount just to prove the point......think happy thoughts, think happy thoughts (wiggle)

Silentnoise713 said:
My guess is a bad shock. Do you still get clucking when going over, say the man hole mentioned above, slowly??

You can try a USB cam fix to a clamp hooked up to a laptop. Sit in the rear while the wife drives and hit record and observe. Makes some marks on the shock valve/piston on the max compression and see how far it is going (you have to take dust boots off). Also, observe if the springs are crashing on itself.

See below and go straight to On Crap - at the bottom.
http://farnorthracing.com/autocross_secrets6.html
Click to expand...

A lil over my head but great link...

My guess is bad shock as well. I haven't tried the low speed test yet but i will. this test would only clunk though if it's reaaally bad, no?

I like the idea of marking the piston. But i'll do it like we do on motorcycles and just wrap a zip tie around it and see how far up the stroke it ends up. I don't have any evidence of bottoming out on the wheel wells or tires though but it's worth trying while i have her up in the air again tonight.

I'll get a video too before i start working on her. As expected, the noise quiets down a lot after she's been up in the air. While that's telling, it doesn't pin point the issue. Not to me anyways :(

phunky.buddha said:
Sway bar links bad?
Click to expand...

Naah. Been driving without the rear sway for a week and the sound is unchanged.

I know i'm grasping at straws, but here's a thought....Could it be that the eyelet at the bottom of the shock is slightly over bore? That would be leaving a bit of play for the bolt to bang around. But how to test for that? I've whacked the shock with a rubber mallet and heard nothing. I find it hard to believe that BOTH of my brand new shocks are actually blown.
 
Are your adjusters loose? Had to lock mine in with Loctite. What about the mounts? Maybe they're not bolted in all the way and the whole shock is bouncing up and down on the mount bolts?
 
you probably have a blown strut.

I got one from the factory too. it happens to the best of us. dont hate on BC, if you send them a "blown strut test" video. they will send you a new strut for free.
 
phunky.buddha said:
Are your adjusters loose? Had to lock mine in with Loctite. What about the mounts? Maybe they're not bolted in all the way and the whole shock is bouncing up and down on the mount bolts?
Click to expand...

Checked all of the above already

Bonks said:
you probably have a blown strut.

I got one from the factory too. it happens to the best of us. dont hate on BC, if you send them a "blown strut test" video. they will send you a new strut for free.
Click to expand...

I think so too. I'm making the video tonight. It's all over the forums for all kinds of different cars. In turns out you and I are faaaar from the first to receive blown shocks from BC out of of the box. but i'm def not hating on them. I love the setup save for this issue. I'm giving them a chance to respond to my email by today then i'm calling them Monday. I prefer email cuz it avoids all the he say, she say BS
 
I did it via email.. they just take there sweet time too respond, so try to cover it all in one message lol
 
So i open up my browser to come over here and post an update. My gmail is set to open automatically and there is a pleasant surprise :)

Thank you for your in depth response.

Please excuse the late response, I was not here until yesterday due to a family emergency.

I will get 2 new rear shock replacements out to you ASAP.

Regards,

Sam


Tech Department
BC RACING NORTH AMERICA
1-321-206-6381 TEL
1-800-741-1972 FAX
Click to expand...
(alright) (yippy) (cryhard)(dance)(idhitit)(humpleg)(nana) (breakn)
If this doesn't fix it....there WILL be fire and gratutious nudity!
 
Replacements arrived! i asked for mounts. but they only sent the shocks. And to that, they only sent the threaded body/shaft. Meaning i have to dissemble the current shock and reuse the bottom and top mount. A real b**** since i split the rod on of them torquing the hell out of it. Now i have to make a clean grind through the top of the shaft to get the top mount off. fun stuff :) hoping to tackle it Thursday...
 
Hey MR6. Before installing the new inserts (or you can do this on the old ones but try to do it), could you PLEASE take some simple measurements!? I am looking for the following to compare to YS.

Just the insert:
1) Total length of the strut from top to bottom
2) Total length of the strut body
3) Total length of the exposed rod
4) Turn to “softest” setting and compress the piston rod down completely, total length of the exposed rod (when compressed).
 
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