BMW Garage BMW Meets Register Search Today's Posts Mark Forums Read
M2 Technical Topics > Mechanical Maintenance: Break-in | Oil & Fluids | Servicing | TSB | Recalls > Stiffening Plate (Belly Pan) Bolts

Post Reply
 
Thread Tools Search this Thread
      05-18-2018, 01:39 AM   #1
Nezil
Major
Nezil's Avatar
1402
Rep
1,466
Posts

Drives: LCI '18 6MT M2
Join Date: Jul 2017
Location: San Francisco Bay Area

iTrader: (0)

Stiffening Plate (Belly Pan) Bolts

Last weekend I fitted my Fabspeed Sport Cat, which required removal of the front chassis stiffening plate. I know a few people have done this before, and in the DIY threads, no-one has ever posted about replacing the bolts that hold this on, even though ISTA+ gives torque settings of 56Nm + 90 degree rotation, and states that the bolts must be replaced.

This evening I had to remove the stiffening plate again to fit an upgraded Charge Pipe, and as I was putting the plate back on, I started to get concerned that these bolts might sheer if I don't replace them. I know the torque + angle tightening sequence is designed to stretch the bolts, and that doing this is only possible a few times.

I have an upgraded FMIC on its way, and will likely need to remove the stiffening plate again... I'm thinking of getting some new bolts this time, but wanted to hear feedback from others on the forum... is this really necessary?

Thanks in advance!
__________________
2018 ///M2 LCI, LBB, 6MT...

Current Performance Mods:
CSF FMIC, ER CP, Fabspeed Cat, Aquamist WMI, GFB DV+, NGK 97506, BM3 (Stage 2 93 OTS), CDV delete, UCP, M2C/M3/M4 Strut Brace, M3/M4 Reinforcement Rings
Appreciate 0
      05-18-2018, 12:02 PM   #2
Nezil
Major
Nezil's Avatar
1402
Rep
1,466
Posts

Drives: LCI '18 6MT M2
Join Date: Jul 2017
Location: San Francisco Bay Area

iTrader: (0)

Just got a quote for these bolts from my local dealer... $8.65 each!

They offered to give me a discount to bring it down to ~$5.20 each... still very very expensive for an M10 x 33 bolt.
__________________
2018 ///M2 LCI, LBB, 6MT...

Current Performance Mods:
CSF FMIC, ER CP, Fabspeed Cat, Aquamist WMI, GFB DV+, NGK 97506, BM3 (Stage 2 93 OTS), CDV delete, UCP, M2C/M3/M4 Strut Brace, M3/M4 Reinforcement Rings
Appreciate 0
      05-18-2018, 01:07 PM   #3
greasypeanut
Second Lieutenant
230
Rep
254
Posts

Drives: F87
Join Date: Dec 2016
Location: 949

iTrader: (0)

I didn't replace my bolts but I did manage to damage the threads on one of the bolts. I am currently missing one bolt securing the belly pan lol. Need to visit the dealership and get a quote. Cheap online but shipping ruins it.
Appreciate 0
      06-01-2018, 05:28 AM   #4
cookiesowns
;)
cookiesowns's Avatar
587
Rep
898
Posts

Drives: X5 45e, 535i N54, X3 N55
Join Date: Jan 2011
Location: West

iTrader: (0)

I've done this twice already without replacing them. I'm probably going to replace them soon.. these are definitely torque to yield bolts and the belly pan acts as a lower chassis brace.
__________________
BM3, MHD, ECUTek Calibrator | N55/S58 specialist | 2023 X5 45e Frozen Marina Bay Blue
Appreciate 0
      06-03-2018, 09:37 AM   #5
nothingman
Private NumNuts
nothingman's Avatar
United_States
521
Rep
321
Posts

Drives: 2021 GT4
Join Date: May 2017
Location: Mason Dixon Line

iTrader: (0)

Garage List
Quote:
Originally Posted by greasypeanut View Post
I didn't replace my bolts but I did manage to damage the threads on one of the bolts. I am currently missing one bolt securing the belly pan lol. Need to visit the dealership and get a quote. Cheap online but shipping ruins it.
Do you by chance have the part number for them?
__________________
Appreciate 0
      06-03-2018, 11:08 AM   #6
Nezil
Major
Nezil's Avatar
1402
Rep
1,466
Posts

Drives: LCI '18 6MT M2
Join Date: Jul 2017
Location: San Francisco Bay Area

iTrader: (0)

Quote:
Originally Posted by nothingman View Post
Do you by chance have the part number for them?
33326768354
__________________
2018 ///M2 LCI, LBB, 6MT...

Current Performance Mods:
CSF FMIC, ER CP, Fabspeed Cat, Aquamist WMI, GFB DV+, NGK 97506, BM3 (Stage 2 93 OTS), CDV delete, UCP, M2C/M3/M4 Strut Brace, M3/M4 Reinforcement Rings
Appreciate 1
      07-06-2021, 11:22 AM   #7
vrooooom
New BMW owner
vrooooom's Avatar
Philippines
318
Rep
831
Posts

Drives: 2018 BMW M2 LCI
Join Date: Feb 2021
Location: Philippines

iTrader: (0)

I’m sorry but these bolts are ONE time use—Seriously?!! So I installed my CP, change. FMIC, change. Down pipe, changed?!! Isn’t that a bit extreme?

Last edited by vrooooom; 07-06-2021 at 06:48 PM..
Appreciate 0
      07-07-2021, 12:39 AM   #8
F87source
Major General
F87source's Avatar
No_Country
7178
Rep
7,342
Posts

Drives: Bmw M2
Join Date: Aug 2018
Location: .

iTrader: (1)

Quote:
Originally Posted by vrooooom View Post
I’m sorry but these bolts are ONE time use—Seriously?!! So I installed my CP, change. FMIC, change. Down pipe, changed?!! Isn’t that a bit extreme?
Yes these bolts are torque to yield meaning they are stretched. If you reuse a stretched bolt and restretch them as per bmw's torque spec you risk the bolt snapping. If you do not yield the bolt then you will not apply the correct amount of load and an even load onto the head of the bolt and threads, so chassis stiffness is not as it should be.


Also water pump bolts are single use torque to yield as well. So are strut tower bolts, differential drain bolts etc.
__________________
Click on the link below to see a compiled list of every review I have ever written:
https://f87.bimmerpost.com/forums/sh...2#post30368242
Appreciate 0
      07-14-2021, 02:46 AM   #9
vrooooom
New BMW owner
vrooooom's Avatar
Philippines
318
Rep
831
Posts

Drives: 2018 BMW M2 LCI
Join Date: Feb 2021
Location: Philippines

iTrader: (0)

I was just watching brake servicing on M2 Competition. It says 30 Nm + 90 deg.... but if re-use 110 Nm. Made me think about these one-time-use bolts. Why can't we re-use these bolts on stiffener plates but for (IMO) even more critical areas like what's holding our brake calipers or wheels are just torque to 110 or 140 and not need replacing w/ a new one.

Just throwing it out here.

Time: 17:13

__________________
2018 BMW M2 LCI BM3 Stage 2 + MPE + FTP charge pipe + MST V2 Inlet + TurboSmart DV + CSF FMIC + AA Hi-flow Downpipe + Turner Rear Shifter Bushing + Wiechers Strut Brace + Bilstein B16 PSS10 + Apex VS-5RS
Appreciate 0
      07-14-2021, 03:22 AM   #10
F87source
Major General
F87source's Avatar
No_Country
7178
Rep
7,342
Posts

Drives: Bmw M2
Join Date: Aug 2018
Location: .

iTrader: (1)

Quote:
Originally Posted by vrooooom View Post
I was just watching brake servicing on M2 Competition. It says 30 Nm + 90 deg.... but if re-use 110 Nm. Made me think about these one-time-use bolts. Why can't we re-use these bolts on stiffener plates but for (IMO) even more critical areas like what's holding our brake calipers or wheels are just torque to 110 or 140 and not need replacing w/ a new one.

Just throwing it out here.

Time: 17:13

First off some people reuse bolts that are single use because they either:

1) didn't know they must be replaced because they don't have ISTA.

2) Don't want to spend the kind of crazy price for bmw bolts.

3) Don't care.

But either way bmw says the bolts are single use so if you want to do it right the bolts must be replaced.



Well I just looked at ISTA and they do specify that both front and rear bolts must be replaced whenever removing them. Real oem says they are also the exact same bolt so despite bmw not specifying that the front bolt must be yielded as they only give a torque spec, since they are the same as the rear caliper bolts which do need to be yielded and thus stretched we know these bolts will stretch when subjected to torques past 30 nm.


This means they MUST be replaced and you really shouldn't reuse a previously stretched bolt. Because a previously stretch bolt is now weaker and is susceptible to snapping. It will also not be able to apply the same clamping load after the material is stretched (a bolt is stretched to enable it to provide a more equal clamping load along its whole thread length and prevent it from vibrating loose, once stretched its elastic properties change and clamping loads won't be the same anymore) so that bolt really shouldn't be reused.


So imo FaRKle! shouldn't have put a used bolt torque spec, he should have said new bolts are required...
__________________
Click on the link below to see a compiled list of every review I have ever written:
https://f87.bimmerpost.com/forums/sh...2#post30368242
Appreciate 0
      07-14-2021, 06:49 AM   #11
M Fifty
Banned
844
Rep
1,962
Posts

Drives: M2 & 330CI
Join Date: May 2018
Location: The Interweb

iTrader: (0)

Interestingly, BMW also recommend replacing some bolts that aren't obviously being torqued to the point of being stretched - but are being screwed into aluminium.

Made me wonder about the plating on them being some kind of passivating layer designed to prevent electrolytic corrosion, and hence the need to replace them with new each time they are removed.
Appreciate 0
      07-14-2021, 01:12 PM   #12
F87source
Major General
F87source's Avatar
No_Country
7178
Rep
7,342
Posts

Drives: Bmw M2
Join Date: Aug 2018
Location: .

iTrader: (1)

Quote:
Originally Posted by M Fifty View Post
Interestingly, BMW also recommend replacing some bolts that aren't obviously being torqued to the point of being stretched - but are being screwed into aluminium.

Made me wonder about the plating on them being some kind of passivating layer designed to prevent electrolytic corrosion, and hence the need to replace them with new each time they are removed.
Interesting point.
__________________
Click on the link below to see a compiled list of every review I have ever written:
https://f87.bimmerpost.com/forums/sh...2#post30368242
Appreciate 0
      07-14-2021, 07:44 PM   #13
vrooooom
New BMW owner
vrooooom's Avatar
Philippines
318
Rep
831
Posts

Drives: 2018 BMW M2 LCI
Join Date: Feb 2021
Location: Philippines

iTrader: (0)

1) what’s ISTA?

I tried google first but couldn’t get. One really learn something new every day about this car.
Appreciate 0
      07-14-2021, 09:28 PM   #14
F87source
Major General
F87source's Avatar
No_Country
7178
Rep
7,342
Posts

Drives: Bmw M2
Join Date: Aug 2018
Location: .

iTrader: (1)

Quote:
Originally Posted by vrooooom View Post
1) what’s ISTA?

I tried google first but couldn’t get. One really learn something new every day about this car.
Bmws dealership software which allows for full diagnostics of the car, programming, software updates, and full repair guides with step by step instructions + pictures and toque specs. Some parts of ista can brick your car if you don't know what you're doing so be careful.
__________________
Click on the link below to see a compiled list of every review I have ever written:
https://f87.bimmerpost.com/forums/sh...2#post30368242
Appreciate 0
      07-14-2021, 10:03 PM   #15
vrooooom
New BMW owner
vrooooom's Avatar
Philippines
318
Rep
831
Posts

Drives: 2018 BMW M2 LCI
Join Date: Feb 2021
Location: Philippines

iTrader: (0)

Quote:
Originally Posted by F87source View Post
Bmws dealership software which allows for full diagnostics of the car, programming, software updates, and full repair guides with step by step instructions + pictures and toque specs. Some parts of ista can brick your car if you don't know what you're doing so be careful.
Oh don’t worry I’m not thinking of touching that.
__________________
2018 BMW M2 LCI BM3 Stage 2 + MPE + FTP charge pipe + MST V2 Inlet + TurboSmart DV + CSF FMIC + AA Hi-flow Downpipe + Turner Rear Shifter Bushing + Wiechers Strut Brace + Bilstein B16 PSS10 + Apex VS-5RS
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



All times are GMT -5. The time now is 07:35 PM.




m2
Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
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