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clunking in rear after upgrading spring rates and changing ride height

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clunking in rear after upgrading spring rates and changing ride height

 
Old 04-05-2018, 05:04 AM
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Default clunking in rear after upgrading DFV spring rates and changing ride height

Hi,

I just upgraded my Ohlins DFV suspension by:
  1. swapping front 10kg springs to rear
  2. upgrading front springs to swift 12kg
  3. changed tophats to SakeBombGarage's tophats with bearing
  4. installed SBG's lowering cups in the rear (despite the next item)
  5. Actually raised the ride height in the rear vs how I was running (because next item)
  6. went from 245 to 255 tires in rear, want to avoid rubbing (and because I'd bottom out going over speed bumps)
  7. I also installed spoon subframe rigid collars in the front and rear subframe/chassis
So all said, the first drive today was particularly noisy with clunking coming from the rear when I went over bumps.
I torqued everything to spec and I know all the DFV collars are tight (ride height and preload adjustment and lock collars).

It seems likes there is somehow slop in the rear suspension.. but again it is all torqued to spec and collars tight. I was initially using 14 clicks from full stiff on the DFVs, I adjusted to 18 clicks from full stiff, but still heard some clunking.
Could it be my CV cups?? Since I was lower for quite a while, would raising rear up 1/2" cause potential for clunking in CV cups?

Or do I really just need an alignment!? NOTE: car drives straight as an arrow but given all the suspension and subframe changes I have to believe an alignment is in order.
(I intended to hold off on alignment in case I wanted to adjust the ride height in the back still)

Last edited by snitm; 04-05-2018 at 07:39 AM.
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Old 04-05-2018, 05:09 AM
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Originally Posted by snitm View Post
Hi,

I just upgraded my Ohlins DFV suspension by:
  1. swapping front 10kg springs to rear
  2. upgrading front springs to swift 12kg
  3. changed tophats to SakeBombGarage's tophats with bearing
  4. installed SBG's lowering cups in the rear (despite the next item)
  5. Actually raised the ride height in the rear vs how I was running (because next item)
  6. went from 245 to 255 tires in rear, want to avoid rubbing (and because I'd bottom out going over speed bumps)
  7. I also installed spoon subframe rigid collars in the front and rear subframe/chassis
So all said, the first drive today was particularly noisy with clunking coming from the rear when I went over bumps.
I torqued everything to spec and I know all the DVF collars are tight (ride height and preload adjustment and lock collars).

It seems likes there is somehow slop in the rear suspension.. but again it is all torqued to spec and collars tight. I was initially using 14 clicks from full stiff on the DFVs, I adjusted to 18 clicks from full stiff, but still heard some clunking.
Could it be my CV cups?? Since I was lower for quite a while, would raising rear up 1/2" cause potential for clunking in CV cups?

Or do I really just need an alignment!? NOTE: car drives straight as an arrow but given all the suspension and subframe changes I have to believe an alignment is in order.
(I intended to hold off on alignment in case I wanted to adjust the ride height in the back still)
Go get a good alignment done since the geometry has changed then monitor it and report back.
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Old 04-05-2018, 05:45 AM
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You changed ride height, so you need an alignment. But...

You should make sure you are finalized on this ride height (unless you have a lifetime alignment plan someplace)

Perhaps more importantly, an alignment isn't going to correct a clunking noise

Did you clock the bushings? Did you forget to retorque one of the control arm bolts?

If you didn't clock the bushings, maybe you tore a bushing and that is what is making the noise.
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Old 04-05-2018, 05:58 AM
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Originally Posted by Car Analogy View Post
You changed ride height, so you need an alignment. But...

You should make sure you are finalized on this ride height (unless you have a lifetime alignment plan someplace)

Perhaps more importantly, an alignment isn't going to correct a clunking noise

Did you clock the bushings? Did you forget to retorque one of the control arm bolts?

If you didn't clock the bushings, maybe you tore a bushing and that is what is making the noise.
Since I don't know what it means to "clock the bushings" I definitely didn't do that.

I'll call the alignment shop and see if they can evaluate that aspect...
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Old 04-05-2018, 06:05 AM
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I only disconnected the front A arms to get reinstall the front shocks. Rear A arms weren't touched at all.

But I'll "clock the front A arm's bushings" ASAP. Hopefully no damage will have been done from driving 10 miles today..
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Old 04-05-2018, 06:44 AM
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It sounds like you searched what clocking is. Excellent! You probably saw why its so important to do anytime you change ride height. Knowledge is power.

Unless you changed ride height dramatically, you should be fine with only 10 miles.

Don't expect the alignment shop to understand what clocking is, since its not something that is ever done with stock suspension, which is all most shops ever see. Don't expect them to actually do it even of they do understand what it is. Though if they actually make any alignment adjustments beyond setting toe, they will end up reclocking some, but not all, of the bushings without even realizing it.

You'd really wan to go to a shop that specializes in modified cars. Or better yet, diy. Only way to know if its done right.
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Old 04-05-2018, 07:08 AM
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Originally Posted by Car Analogy View Post
It sounds like you searched what clocking is. Excellent! You probably saw why its so important to do anytime you change ride height. Knowledge is power.

Unless you changed ride height dramatically, you should be fine with only 10 miles.

Don't expect the alignment shop to understand what clocking is, since its not something that is ever done with stock suspension, which is all most shops ever see. Don't expect them to actually do it even of they do understand what it is. Though if they actually make any alignment adjustments beyond setting toe, they will end up reclocking some, but not all, of the bushings without even realizing it.

You'd really wan to go to a shop that specializes in modified cars. Or better yet, diy. Only way to know if its done right.
Yeah, if only I had an alignment rack at home
I explained clocking to the shop, but then asked the shop to loosen the A arm bolts to the chassis and re-tighten them -- to allow the bushing to untwist as needed.
Hopefully they "get it"... if not I'll deal with it by using a floor jack to raise my wheels up to normal ride height while I have my car up on my QuickJack.
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Old 04-05-2018, 07:26 AM
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Originally Posted by snitm View Post
I only disconnected the front A arms to get reinstall the front shocks. Rear A arms weren't touched at all.

But I'll "clock the front A arm's bushings" ASAP. Hopefully no damage will have been done from driving 10 miles today..

Just note that you still need to reset the bushing in the rear even if you didn't touch them, unless your rear height is identical (unlikely) to what they were originally clocked for.
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Old 04-05-2018, 09:05 AM
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Are your tophat nuts tight? Sway bar links?

All other bolts?

Something is likely loose.

the clunking is almost surely not due to un-clocked bushings...but you should remedy that anyway.
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Old 04-05-2018, 09:59 AM
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hard to say without being able to hear the type of clunk.

Check top hat was installed/assembled correctly (were you able to torque the top nut on properly, did the shaft spin?)
Check spring has enough preload and is not flopping around
Check no tools left in trunk, all interior panels are secured
Check trunk springs aren't binding
Finally if it still makes noise, remove full coilover assembly and make sure everything is tight and secure, jiggle it, shake it, make sure it's not making noise by itself to eliminate that as a source.

How many miles on your shocks, any oil leaking?
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