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Torque spec for rear underbody chassis braces?

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MrPT
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Torque spec for rear underbody chassis braces?

Post by MrPT » Sun Sep 17, 2017 10:57 am

Hi,

Been looking for torque values for the rear diagonal chassis brace bolts. Does anybody know?

I've got a bit of a clunk at the rear, so just checking rear ARBs, struts etc, one at a time. Pretty sure it's the KW shocks - they are only one click from full "soft" at the moment - but thought it worth checking the braces while she's up in the air.

Cheers!

P.
2008 Z4MC: heavy wheels | crap suspension | skittish rear end | wobbly engine | not enough induction noise | underwhelming turn in | inconsistent braking | lardy battery | chubby steering wheel
2006 Z4 2.5si: gone

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Torque spec for rear underbody chassis braces?

Post by Smartbear » Sun Sep 17, 2017 11:02 am

Hi, reading this made me wonder if the z4m suffered from the diff mount becoming detached as the z3m/m3 have been known to fail?
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Torque spec for rear underbody chassis braces?

Post by VRSteve » Sun Sep 17, 2017 11:09 am

MrPT wrote: Sun Sep 17, 2017 10:57 am Hi,

Been looking for torque values for the rear diagonal chassis brace bolts. Does anybody know?

I've got a bit of a clunk at the rear, so just checking rear ARBs, struts etc, one at a time. Pretty sure it's the KW shocks - they are only one click from full "soft" at the moment - but thought it worth checking the braces while she's up in the air.

Cheers!

P.

Can't find values for them on TIS
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Torque spec for rear underbody chassis braces?

Post by Scooba_Steve » Sun Sep 17, 2017 11:33 am

The lower ones that meet at the diff?
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Torque spec for rear underbody chassis braces?

Post by VRSteve » Sun Sep 17, 2017 11:54 am

Smartbear wrote: Sun Sep 17, 2017 11:02 am Hi, reading this made me wonder if the z4m suffered from the diff mount becoming detached as the z3m/m3 have been known to fail?
Rob
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Torque spec for rear underbody chassis braces?

Post by MrPT » Sun Sep 17, 2017 1:34 pm

Scooba_Steve wrote: Sun Sep 17, 2017 11:33 am The lower ones that meet at the diff?
Yep.
2008 Z4MC: heavy wheels | crap suspension | skittish rear end | wobbly engine | not enough induction noise | underwhelming turn in | inconsistent braking | lardy battery | chubby steering wheel
2006 Z4 2.5si: gone

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Torque spec for rear underbody chassis braces?

Post by Scooba_Steve » Sun Sep 17, 2017 3:07 pm

MrPT wrote: Sun Sep 17, 2017 1:34 pm
Scooba_Steve wrote: Sun Sep 17, 2017 11:33 am The lower ones that meet at the diff?
Yep.
From TIS:
51 71 482 is the process, don't drive without them fitted. The nut is the one in the middle, screws at each end.

51 75 5AZ: Replace screws
59 Nm + 90 degrees

51 75 7AZ: Replace nut
24 Nm
3.0si Sport: F10 Illuminated ZHP, Retrofit Cruise, OE Stubby, Gaptech RCH+, Kenwood BT73DAB + Handsfree, HIDs, LED Sidelights, OE LED Number Plate Lights, Custom LED strip bootlight.

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Torque spec for rear underbody chassis braces?

Post by MrPT » Sun Sep 17, 2017 8:39 pm

Scooba_Steve wrote: Sun Sep 17, 2017 3:07 pm
MrPT wrote: Sun Sep 17, 2017 1:34 pm
Scooba_Steve wrote: Sun Sep 17, 2017 11:33 am The lower ones that meet at the diff?
Yep.
From TIS:
51 71 482 is the process, don't drive without them fitted. The nut is the one in the middle, screws at each end.

51 75 5AZ: Replace screws
59 Nm + 90 degrees

51 75 7AZ: Replace nut
24 Nm
Nice one, thanks Steve. :thumbsup:

Looks like it's the same procedure for loads of models. I'm taking the "don't drive without them fitted" to mean they don't do nothing and are worth re-torquing every few years!
2008 Z4MC: heavy wheels | crap suspension | skittish rear end | wobbly engine | not enough induction noise | underwhelming turn in | inconsistent braking | lardy battery | chubby steering wheel
2006 Z4 2.5si: gone

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Torque spec for rear underbody chassis braces?

Post by Scooba_Steve » Sun Sep 17, 2017 9:34 pm

Welcome, ref is only so you know I'm not guessing! I think they're always worth a check, though after 6 months if they don't work loose I doubt they would.
3.0si Sport: F10 Illuminated ZHP, Retrofit Cruise, OE Stubby, Gaptech RCH+, Kenwood BT73DAB + Handsfree, HIDs, LED Sidelights, OE LED Number Plate Lights, Custom LED strip bootlight.

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Torque spec for rear underbody chassis braces?

Post by MrPT » Tue Oct 03, 2017 11:12 am

Well, the "Screws" are definitely single-use. Sheared @ 30Nm!

Just a heads up to anybody who wants to try this. The car is parked up now while I get a replacement bolt/screw. :cry:
2008 Z4MC: heavy wheels | crap suspension | skittish rear end | wobbly engine | not enough induction noise | underwhelming turn in | inconsistent braking | lardy battery | chubby steering wheel
2006 Z4 2.5si: gone

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Torque spec for rear underbody chassis braces?

Post by Steve84N » Tue Oct 03, 2017 5:19 pm

Almost certainly been off and overtightened before as I've had mine off at least once with no problem.
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Torque spec for rear underbody chassis braces?

Post by GuidoK » Tue Oct 03, 2017 7:42 pm

^with mine at least 20 times :rofl:

But they are stretch bolts and the more you use them the stiffer they get. So be sure not to use that 90deg if you have used them multiple times.
I do it mostly by feeling, but its usually around 30-45deg

Maybe I'll change all underside bolts sometime.


But if it shears at 30Nm, something is wrong.
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Torque spec for rear underbody chassis braces?

Post by MrPT » Tue Oct 03, 2017 11:27 pm

Ok, cheers fellas. That’s actually reassuring - probably should have lefty loosey’d before I righty tightey’d.
2008 Z4MC: heavy wheels | crap suspension | skittish rear end | wobbly engine | not enough induction noise | underwhelming turn in | inconsistent braking | lardy battery | chubby steering wheel
2006 Z4 2.5si: gone

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