BMW M3 Forum (E90 E92)

BMW Garage BMW Meets Register Search Today's Posts Mark Forums Read


Go Back   M3Post - BMW M3 Forum > E90/E92 M3 Technical Topics > Suspension | Brakes | Chassis
 
GT Haus
Post Reply
 
Thread Tools Search this Thread
      10-28-2008, 04:46 AM   #1
MDCTFTW
Lieutenant Colonel
44
Rep
1,972
Posts

Drives: E92 DCT
Join Date: Apr 2008
Location: Norcal

iTrader: (0)

When installing springs how tight do you tighten the top perch nut?

One thing I've always wondered when I install suspension is how tight should the top perch bolts be tightened? Since the strut tower is threaded, what if the two sides are uneven? Couldn't that make the ride height different on both sides?

I've attached a pic (thanks Speedtrap for the borrowed pic). Say for instance the top nut is tightened to 1 on one side and 2 on the other. Won't the ride height be different on both sides? Or is the general rule of thumb to make both sides about even?

Also ... if you tighten both sides to position 1 or both to position 2 won't that yield different ride heights? That's a good inch right there. I know those positions are extreme ends of the threads, but I'm just trying to make my point here.

Or am I just being overly anal? Haha.
Attached Images
 
__________________


MDCT ... so you can drive and eat a hamburger at the same time.
Appreciate 0
      10-28-2008, 09:51 AM   #2
Radiation Joe
Veni Vidi Vici
Radiation Joe's Avatar
United_States
39
Rep
2,749
Posts

Drives: '11 JB/BBe-6sp-e90
Join Date: Jul 2008
Location: Macungie PA

iTrader: (0)

Garage List
2011 e90 M3-Sold  [4.25]
2003 RS6 - Sold  [0.00]
2009 e90 M3 - Gone  [0.00]
2003 M3 SOLD  [0.00]
old 2002  [5.00]
The position of the nut has no affect on ride height. It just affects the maximum droop the suspension can acheive. Ride height is determined by the spring perch on the strut.
Appreciate 0
      10-28-2008, 12:31 PM   #3
MDCTFTW
Lieutenant Colonel
44
Rep
1,972
Posts

Drives: E92 DCT
Join Date: Apr 2008
Location: Norcal

iTrader: (0)

Quote:
Originally Posted by Radiation Joe View Post
The position of the nut has no affect on ride height. It just affects the maximum droop the suspension can acheive. Ride height is determined by the spring perch on the strut.
Is that true? Here's another picture that again shows the extreme cases. Would these two setups yield different ride heights? Or is it the spring rate that is determining the ride height?
Attached Images
 
__________________


MDCT ... so you can drive and eat a hamburger at the same time.
Appreciate 0
      10-28-2008, 12:45 PM   #4
consolidated
Lieutenant Colonel
consolidated's Avatar
69
Rep
1,833
Posts

Drives: F80 M3
Join Date: Jun 2007
Location: Texas

iTrader: (2)

Garage List
Lower nut looks like more preload to me, car won't have much sag which could be undesirable.
Appreciate 0
      10-28-2008, 12:47 PM   #5
Technic
Lieutenant General
Technic's Avatar
United_States
315
Rep
11,842
Posts

Drives: 2015 320i
Join Date: Apr 2005
Location: Ft Lauderdale, Florida

iTrader: (18)

Quote:
Originally Posted by MDCTFTW View Post
Is that true? Here's another picture that again shows the extreme cases. Would these two setups yield different ride heights? Or is it the spring rate that is determining the ride height?
If everything in both illustrations are exactly the same except the nut position, once you lower the car the spring will compress to the same steady state height regardless of either setup.

The ride height will be determined by the spring itself and the shock/strut base position (the "sleeve" where the bottom of the strut is inserted) as previously explained.
Appreciate 0
      10-28-2008, 01:00 PM   #6
MDCTFTW
Lieutenant Colonel
44
Rep
1,972
Posts

Drives: E92 DCT
Join Date: Apr 2008
Location: Norcal

iTrader: (0)

Quote:
Originally Posted by Technic View Post
If everything in both illustrations are exactly the same except the nut position, once you lower the car the spring will compress to the same steady state height regardless of either setup.

The ride height will be determined by the spring itself and the shock/strut base position (the "sleeve" where the bottom of the strut is inserted) as previously explained.
Ok cool I guess that makes sense, but how about in the extreme case if the uninstalled strut has a top mount that is compressing the spring even more than the normal weight of the car would when it's installed? This would the car to be even lower right?
__________________


MDCT ... so you can drive and eat a hamburger at the same time.
Appreciate 0
      10-28-2008, 01:47 PM   #7
Technic
Lieutenant General
Technic's Avatar
United_States
315
Rep
11,842
Posts

Drives: 2015 320i
Join Date: Apr 2005
Location: Ft Lauderdale, Florida

iTrader: (18)

Quote:
Originally Posted by MDCTFTW View Post
Ok cool I guess that makes sense, but how about in the extreme case if the uninstalled strut has a top mount that is compressing the spring even more than the normal weight of the car would when it's installed? This would the car to be even lower right?
... then we would not be talking about the same setup, as one strut will compress the spring more than the original strut, something like a coilover vs. standard strut.
Appreciate 0
      10-28-2008, 01:53 PM   #8
!Xoible
Banned
United_States
573
Rep
46,037
Posts

Drives: ....
Join Date: Nov 2006
Location: .

iTrader: (4)

Garage List
2008 M3  [3.50]
2007 335i  [4.50]
2008 528i  [4.00]
2006 Infiniti - G35 ...  [4.00]
pm longtran
Appreciate 0
      10-28-2008, 02:23 PM   #9
Speedtrap
Lieutenant Colonel
United Kingdom
26
Rep
1,799
Posts

Drives: A very fast car :)
Join Date: Sep 2008
Location: London

iTrader: (0)

Thanks Did not even know that myself.
Appreciate 0
      10-28-2008, 04:28 PM   #10
MDCTFTW
Lieutenant Colonel
44
Rep
1,972
Posts

Drives: E92 DCT
Join Date: Apr 2008
Location: Norcal

iTrader: (0)

Quote:
Originally Posted by ///Mantis View Post
pm longtran
I think I asked him in a thread before ... the one where he showed some pics after his drop and he didn't torque the bolts to any specific value.
__________________


MDCT ... so you can drive and eat a hamburger at the same time.
Appreciate 0
      10-28-2008, 08:49 PM   #11
rzm3
Moderator
rzm3's Avatar
245
Rep
4,605
Posts

Drives: E92 M3
Join Date: Aug 2007
Location: USA

iTrader: (14)

so what's the official say on this?
__________________
E92 M3 DCT
Appreciate 0
      10-28-2008, 09:27 PM   #12
MDCTFTW
Lieutenant Colonel
44
Rep
1,972
Posts

Drives: E92 DCT
Join Date: Apr 2008
Location: Norcal

iTrader: (0)

Quote:
Originally Posted by rldzhao View Post
so what's the official say on this?
I think as long as the uninstalled spring is not compressed more than it would be with the weight of the car then it should even out.
__________________


MDCT ... so you can drive and eat a hamburger at the same time.
Appreciate 0
      10-29-2008, 01:15 AM   #13
JAJ
Captain
18
Rep
951
Posts

Drives: 2014 Shelby GT500
Join Date: Apr 2008
Location: Vancouver, BC

iTrader: (4)

The top of the spring sits on a spring perch that's mounted to a bearing that's bolted (with three small bolts) upside-down inside the fender. The bottom of the spring sits on a perch that's clamped to the top of the damper body. The spring sits between these two perches.

The nut you are wondering about in the original post just keeps the damper rod in place - too loose and it will rattle, too tight and it will damage the threads and maybe the rubber bushing it sits in the middle of. Other than that, it has no effect on the ride height.
Appreciate 0
      10-29-2008, 01:49 AM   #14
MVEED3
Second Lieutenant
United_States
2
Rep
297
Posts

Drives: '08 e90 M3/'12 S1k
Join Date: Sep 2008
Location: San Diego

iTrader: (11)

You'll feel when the nut makes contact, sandwiching the washer assembly. IIRC, a 10mm socket fits over the top of the shock shaft. I used a ratchet on that and an open-end box wrench on the nut and squeezed to an approximated 18-20ft-lb. RealOEM doesn't have torque specs so I assumed this based on previous M3 specs. You can always torque the nut down after the assemblies are installed on the car. This may even be easier since the shaft shouldn't spin with the car on the ground under the spring's tension.


Allen
__________________
2012 Bluefire S1kRR
Ohlins~Akra~Brembo~Lightech~Gilles
2008 Sparkling Graphite e90 M3 6spd
KW~Akra~PFC~Advan~Yoko~UUC~BMW Performance~BMWCCA
Appreciate 0
      10-30-2008, 07:44 PM   #15
badfish
Major
badfish's Avatar
35
Rep
1,035
Posts

Drives: E92 AW M3
Join Date: Feb 2008
Location: SoCal

iTrader: (0)

Garage List
2008 M3  [0.00]
Does this help? Taken from here.
Attached Images
 
__________________
Appreciate 0
      10-30-2008, 08:01 PM   #16
rzm3
Moderator
rzm3's Avatar
245
Rep
4,605
Posts

Drives: E92 M3
Join Date: Aug 2007
Location: USA

iTrader: (14)

this definitely helps. thanks.
__________________
E92 M3 DCT
Appreciate 0
      11-21-2008, 08:38 PM   #17
rzm3
Moderator
rzm3's Avatar
245
Rep
4,605
Posts

Drives: E92 M3
Join Date: Aug 2007
Location: USA

iTrader: (14)

UPDATE:

Tighten to 64Nm! The tightness of the nut WILL slightly affect the position of the guide support and therefore the ride height. This is torque spec from BMW.
__________________
E92 M3 DCT
Appreciate 0
      11-21-2008, 08:58 PM   #18
gthirtyfizle
Colonel
gthirtyfizle's Avatar
89
Rep
2,807
Posts

Drives: E92 M3 AW
Join Date: Jul 2008
Location: NYC

iTrader: (4)

I tightened this up today being that I had that clunking sound. However, I did not tighten it with the torque measurer being that the dealer wanted me to leave the car there for the day for something that would take 5 minutes. So I took it to my mechaninc, he tightened it down with a wrench and the sound is gone. Didnt turn too much but there was deff some room.
Appreciate 0
      01-20-2015, 01:49 PM   #19
BLKLYZ
Brigadier General
BLKLYZ's Avatar
United_States
61
Rep
3,033
Posts

Drives: E90 M3 AW
Join Date: Aug 2010
Location: FT. Bragg, NC.

iTrader: (19)

Garage List
2007 335i  [4.50]
Great info
__________________
ModeCarbon V1 CF lip/Platte Forme AG CF Side Skirt ext./OSS/B&G Springs/CF Hood Vents/Performance Spoiler/LCI Tails
Appreciate 0
      01-23-2015, 06:22 PM   #20
admranger
Captain
admranger's Avatar
18
Rep
604
Posts

Drives: 2002 M3, 2005 X5, 2011 M3
Join Date: May 2011
Location: Las Vegas

iTrader: (0)

Quote:
Originally Posted by BLKLYZ View Post
Great info
Except the ride height argument is wrong...

The bearing rides on the shaft collar. The tightening of the nut serves to hold the strut in position in the collar. It does nothing to the ride height unless your car sits with the shocks fully extended, which it doesn't...

I'm not even sure the torque number is correct. I'll have to look at the manual to be sure.
__________________
'11 E90 M3, Mebourne/Black/Fox Red/Black, 6MT, PP2, heated seats, moonroof, split folding rear seats, iPod/USB adapter, Technic harness, JL XD 6/600.
'02 E46M3, Imola/Black, 6MT, CWP, no sunroof, Ohlins, Eibachs, PFC DD rotors, PFC pads! HAT Clarus/Legatia speakers, 2 big amps in the back.
'05 X5 4.4i, Imola/Black, Premium, Cold, HAT Imagine 6.5's, Intravee iPod adapter
Appreciate 0
      01-23-2015, 06:30 PM   #21
BLKLYZ
Brigadier General
BLKLYZ's Avatar
United_States
61
Rep
3,033
Posts

Drives: E90 M3 AW
Join Date: Aug 2010
Location: FT. Bragg, NC.

iTrader: (19)

Garage List
2007 335i  [4.50]
Quote:
Originally Posted by admranger View Post
Except the ride height argument is wrong...

The bearing rides on the shaft collar. The tightening of the nut serves to hold the strut in position in the collar. It does nothing to the ride height unless your car sits with the shocks fully extended, which it doesn't...

I'm not even sure the torque number is correct. I'll have to look at the manual to be sure.
I was just referring to tightening the nut to the shock. My friend and I installed my springs after removing my sleeve overs. The position of the nut sat at a different height when my s/o were installed. We did not tighten the nut that much once the springs were installed to mimic the look of the s/o. I received the clunking noise when driving as well but after reading this post, I just tightened the 2 strut nuts and the clunking went away. I guess it had to do with different spring rates. Either way, the car rides like a champ now!
__________________
ModeCarbon V1 CF lip/Platte Forme AG CF Side Skirt ext./OSS/B&G Springs/CF Hood Vents/Performance Spoiler/LCI Tails
Appreciate 0
      01-23-2015, 06:44 PM   #22
admranger
Captain
admranger's Avatar
18
Rep
604
Posts

Drives: 2002 M3, 2005 X5, 2011 M3
Join Date: May 2011
Location: Las Vegas

iTrader: (0)

Quote:
Originally Posted by BLKLYZ View Post
I was just referring to tightening the nut to the shock. My friend and I installed my springs after removing my sleeve overs. The position of the nut sat at a different height when my s/o were installed. We did not tighten the nut that much once the springs were installed to mimic the look of the s/o. I received the clunking noise when driving as well but after reading this post, I just tightened the 2 strut nuts and the clunking went away. I guess it had to do with different spring rates. Either way, the car rides like a champ now!
Great! You do have to tighten that nut down or the shaft will thunk around (up and down motion) in the strut bearing. I've had them loosen up before in my old race car (that's what I get for re-using nylock nuts).

If you ever have to do this again, make sure you don't spin the shaft of the strut when you are tightening the nut. In some shocks this can damage the valve body. Not saying you did this time, but sometimes people get carried away tightening things!
__________________
'11 E90 M3, Mebourne/Black/Fox Red/Black, 6MT, PP2, heated seats, moonroof, split folding rear seats, iPod/USB adapter, Technic harness, JL XD 6/600.
'02 E46M3, Imola/Black, 6MT, CWP, no sunroof, Ohlins, Eibachs, PFC DD rotors, PFC pads! HAT Clarus/Legatia speakers, 2 big amps in the back.
'05 X5 4.4i, Imola/Black, Premium, Cold, HAT Imagine 6.5's, Intravee iPod adapter
Appreciate 0
Post Reply

Bookmarks

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -4. The time now is 11:21 AM.




m3post
m3post
Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2015, Jelsoft Enterprises Ltd.
1Addicts.com, BIMMERPOST.com, E90Post.com, F30Post.com, M3Post.com, ZPost.com, 5Post.com, 6Post.com, 7Post.com, XBimmers.com logo and trademark are properties of BIMMERPOST