Need help diagnosing a suspension noise

RedDotRacer · 01-27-2014, 10:14 PM

Recently installed a set of AST 4100 coilovers and now hear a loud popping sound from the rear when going over big bumps at speed. It seems like it's worse on the driver side rear. It's not all bumps, but just occasional and it's loud. The set was bought used with only 5k miles and they seem to all be working with no leaks. I feel like it's something simple, but can't figure it out.
I had a friend whose a tech at a bmw Indy shop do the install.

Its the z4 m specific kit with spherical RSMs and hyperco 5.5" 650 rear springs. Anyone have experience with this? All suggestions for solutions would be much appreciated!

Also called Vorshlag and they are not sure either without seeing the car.

ZStig · 01-27-2014, 11:13 PM

do the springs feel loose in their sitting position?

RedDotRacer · 01-27-2014, 11:27 PM

Quote:

Originally Posted by ZStig

do the springs feel loose in their sitting position?

Yes, the tech at first suggested a helper spring because he thinks it's moving. Vorshlag said this application should not use one.

The HACK · 01-28-2014, 12:34 AM

Spherical RSMs make all sorts of noises.

RedDotRacer · 01-28-2014, 12:57 AM

Quote:

Originally Posted by The HACK

Spherical RSMs make all sorts of noises.

I understand that, but this noise can't be normal. It's a very sharp loud pop almost as though someone used a slingshot to shoot a rock under your car.

The HACK · 01-28-2014, 10:14 AM

I know exactly what it is. The rear springs are caught on the collar and won't rotate, and there's torsional energy stored up when they compress. When you hit a bump, the stored up torsional energy all of a sudden releases, creating that "PING!" sound that reverberates throughout the chassis. And once they settle back down, the spring occasionally get caught on the collar and wash, rinse, repeat.

I used to get the same noise on my GC kit, but only after I lifted up the car and put it back down (springs fully unseated and reseated on perch) and only after I hit a big bump after lifting up the car. Then I put a couple of thrust sheets (they're thin little plastic rings sandwiched between thin aluminum rings that allow the springs to rotate freely) and haven't had the same noise since.

ZStig · 01-28-2014, 10:36 AM

maybe you can also spray some lube on the spring perches?

mtrhed · 01-28-2014, 05:42 PM

As referenced above most likely either the spherical RSM's or lack of thrust sheets. I have the 4150's with thrust sheets and RE RSM's and they are silent. Could be something else, but those are your most likely culprits.

The HACK · 01-28-2014, 07:04 PM

Quote:

Originally Posted by ZStig

maybe you can also spray some lube on the spring perches?

Not sure if I'd use lube there, it's bound to attract dirt and gravel and cause the binding problem to get worse.

I would try thrust sheets and see if that helps. If not, change out the adjustable perch with an adjustable, articulating weight jack.

RedDotRacer · 01-28-2014, 11:14 PM

Never heard of thrust sheets. Where's a good place to get these? The set was bought used with under 5k miles. The previous owner never had these issues and didn't need any extra components.

mtrhed · 01-29-2014, 12:07 AM

Hi there!

http://www.swiftsprings.net/products...rsal/misc.html

$50 or so for both sides. They go above and below the spring. Rear shock mounts are also suspect. I was steered away from the spherical mounts because of the noise issues. The RE mounts are tits!

If the previous owner didn't have any noise issues are you sure everything is installed/torqued correctly? Swaybar endlinks reconnected? I have been really happy with the fact that my AST coilovers/Vorschlag camber plates are so quite.

RedDotRacer · 01-29-2014, 09:44 PM

Thanks for all the suggestions. I'm going to take it to a shop that is a licensed vendor of ast suspensions and see what they say. The thrust sheets seem cheap enough to try as well.

3002 tii · 01-31-2014, 06:36 AM

Quote:

Originally Posted by RedDotRacer

Thanks for all the suggestions. I'm going to take it to a shop that is a licensed vendor of ast suspensions and see what they say. The thrust sheets seem cheap enough to try as well.

Hpa should also sell the thrust sheets

RedDotRacer · 03-07-2014, 09:53 PM

Update: had the shop install some new non spherical RSMs from RE. No more noise!

The HACK · 03-07-2014, 10:26 PM

Quote:

Originally Posted by 3002 tii

Hpa should also sell the thrust sheets

That's where I got mine.

RedDotRacer · 03-09-2014, 09:57 PM

Shop is saying the ast 4100 can't go too low because the adjuster is hitting something and needs to be modified. I could have my wording mixed up here, but anyone else have an issue with lowering restrictions?

3002 tii · 03-10-2014, 10:21 AM

Quote:

Originally Posted by RedDotRacer

Shop is saying the ast 4100 can't go too low because the adjuster is hitting something and needs to be modified. I could have my wording mixed up here, but anyone else have an issue with lowering restrictions?

It's quite the opposite, AST41's were meant to run low and if anything can't go too high else they will "top out"

01-27-2014, 10:14 PM	#1
RedDotRacer Private First Class 16 Rep 175 Posts Drives: 07 Z4mc Join Date: Dec 2011 Location: San Diego iTrader: (1)	Need help diagnosing a suspension noise Recently installed a set of AST 4100 coilovers and now hear a loud popping sound from the rear when going over big bumps at speed. It seems like it's worse on the driver side rear. It's not all bumps, but just occasional and it's loud. The set was bought used with only 5k miles and they seem to all be working with no leaks. I feel like it's something simple, but can't figure it out. I had a friend whose a tech at a bmw Indy shop do the install. Its the z4 m specific kit with spherical RSMs and hyperco 5.5" 650 rear springs. Anyone have experience with this? All suggestions for solutions would be much appreciated! Also called Vorshlag and they are not sure either without seeing the car.
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01-27-2014, 11:13 PM	#2
ZStig instagram 997turbotom 279 Rep 7,376 Posts Drives: Interlagos Z4MR Join Date: Jun 2008 Location: Delray Beach, FL iTrader: (4)	do the springs feel loose in their sitting position? __________________
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01-28-2014, 12:34 AM	#4
The HACK Midlife Crises Racing Silent but Deadly Class 1820 Rep 5,337 Posts Drives: 2006 MZ4C, 2021 Tesla Model 3 Join Date: Oct 2007 Location: Welcome to Jamaica have a nice day iTrader: (1)	Spherical RSMs make all sorts of noises. __________________ Sitting on a beat-up office chair in front of a 5 year old computer in a basement floor, sipping on stale coffee watching a bunch of meaningless numbers scrolling aimlessly on a dimly lit 19” monitor.
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01-28-2014, 10:14 AM	#6
The HACK Midlife Crises Racing Silent but Deadly Class 1820 Rep 5,337 Posts Drives: 2006 MZ4C, 2021 Tesla Model 3 Join Date: Oct 2007 Location: Welcome to Jamaica have a nice day iTrader: (1)	I know exactly what it is. The rear springs are caught on the collar and won't rotate, and there's torsional energy stored up when they compress. When you hit a bump, the stored up torsional energy all of a sudden releases, creating that "PING!" sound that reverberates throughout the chassis. And once they settle back down, the spring occasionally get caught on the collar and wash, rinse, repeat. I used to get the same noise on my GC kit, but only after I lifted up the car and put it back down (springs fully unseated and reseated on perch) and only after I hit a big bump after lifting up the car. Then I put a couple of thrust sheets (they're thin little plastic rings sandwiched between thin aluminum rings that allow the springs to rotate freely) and haven't had the same noise since. __________________ Sitting on a beat-up office chair in front of a 5 year old computer in a basement floor, sipping on stale coffee watching a bunch of meaningless numbers scrolling aimlessly on a dimly lit 19” monitor.
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01-28-2014, 10:36 AM	#7
ZStig instagram 997turbotom 279 Rep 7,376 Posts Drives: Interlagos Z4MR Join Date: Jun 2008 Location: Delray Beach, FL iTrader: (4)	maybe you can also spray some lube on the spring perches? __________________
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01-28-2014, 05:42 PM	#8
mtrhed Second Lieutenant 13 Rep 279 Posts Drives: 06 AW Z4MR/w211 e63 AMG/325XiT Join Date: Oct 2012 Location: SoCal iTrader: (0)	As referenced above most likely either the spherical RSM's or lack of thrust sheets. I have the 4150's with thrust sheets and RE RSM's and they are silent. Could be something else, but those are your most likely culprits. __________________ 06 Alpinweiss Z4M R Anthracite Apex EC-7 9F/9.5R, 245/275 Super Sport's, 17" Kosei K1 255/40r17 Direzza II, SS Lines, Pagid RS29, Ate SuperBlue, VT Comp. MM's, RE trans. mounts, AST 4150, Swift springs, Vorschlag camber plates, RE RSM, H&R swaybars, spherical rtabs, SuperFlex poly fcabs, StrongStrut Braces, Euro Headers, Stromung exhaust, ESS Tune, Eventuri intake
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01-28-2014, 11:14 PM	#10
RedDotRacer Private First Class 16 Rep 175 Posts Drives: 07 Z4mc Join Date: Dec 2011 Location: San Diego iTrader: (1)	Never heard of thrust sheets. Where's a good place to get these? The set was bought used with under 5k miles. The previous owner never had these issues and didn't need any extra components.
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01-29-2014, 12:07 AM	#11
mtrhed Second Lieutenant 13 Rep 279 Posts Drives: 06 AW Z4MR/w211 e63 AMG/325XiT Join Date: Oct 2012 Location: SoCal iTrader: (0)	Hi there! http://www.swiftsprings.net/products...rsal/misc.html $50 or so for both sides. They go above and below the spring. Rear shock mounts are also suspect. I was steered away from the spherical mounts because of the noise issues. The RE mounts are tits! If the previous owner didn't have any noise issues are you sure everything is installed/torqued correctly? Swaybar endlinks reconnected? I have been really happy with the fact that my AST coilovers/Vorschlag camber plates are so quite. __________________ 06 Alpinweiss Z4M R Anthracite Apex EC-7 9F/9.5R, 245/275 Super Sport's, 17" Kosei K1 255/40r17 Direzza II, SS Lines, Pagid RS29, Ate SuperBlue, VT Comp. MM's, RE trans. mounts, AST 4150, Swift springs, Vorschlag camber plates, RE RSM, H&R swaybars, spherical rtabs, SuperFlex poly fcabs, StrongStrut Braces, Euro Headers, Stromung exhaust, ESS Tune, Eventuri intake
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01-29-2014, 09:44 PM	#12
RedDotRacer Private First Class 16 Rep 175 Posts Drives: 07 Z4mc Join Date: Dec 2011 Location: San Diego iTrader: (1)	Thanks for all the suggestions. I'm going to take it to a shop that is a licensed vendor of ast suspensions and see what they say. The thrust sheets seem cheap enough to try as well.
	Appreciate 0 Quote

03-07-2014, 09:53 PM	#14
RedDotRacer Private First Class 16 Rep 175 Posts Drives: 07 Z4mc Join Date: Dec 2011 Location: San Diego iTrader: (1)	Update: had the shop install some new non spherical RSMs from RE. No more noise!
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03-09-2014, 09:57 PM	#16
RedDotRacer Private First Class 16 Rep 175 Posts Drives: 07 Z4mc Join Date: Dec 2011 Location: San Diego iTrader: (1)	Shop is saying the ast 4100 can't go too low because the adjuster is hitting something and needs to be modified. I could have my wording mixed up here, but anyone else have an issue with lowering restrictions?
	Appreciate 0 Quote

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