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      05-31-2020, 12:01 PM   #1
frankc
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Flex Disc / Guibo Torque Spec

I would like to get confirmation on the torque spec for the E9x M3 flex disc bolts. The car has M12-10.9 fasteners.

The "torque specs" thread (https://www.m3post.com/forums/showthread.php?p=20922983) states:

(6) Giubo (aka Flex Disc) Screw and Nut (BMW TIS Link) - 55 NM (41 ft lb) plus 90 degrees

When I pull up the BMW TIS page for the E9x M3, there is no E90 entry specifically for the M3 (like there is for the E36 & E46), but there is an entry for the E90 with M12-10.9 fasteners that matches the above spec, but the description for that entry states "ZNS screws and nuts, Shiny zinc coating, All versions". My concern with this description is the "Shiny zinc coating" part. The bolts on my E90 are not shiny. In fact, the three that that bolt the disc to the transmission output flange are the normal dull zinc, and the three that bolt the disc to the driveshaft flange are painted black. The six new locking nuts are also a dull zinc.



Perhaps I'm being too pedantic when reading the TIS, but there are M3/M5 entries on the TIS page for M12-10.9 bolts that do not have "Shiny zinc coating" in their description. These entries list a torque spec of simply 115Nm (no angle) - see below. The E36 Bentley manual also states 115Nm for the M12-10.9 bolt in this application (matching the TIS). I realize this I am asking about an E90, not an E36, but same bolt spec in same application. However, note that E60 TIS entry has the same M12-10.9 bolt, but with the 55Nm+90 torque spec, and other models have the same bolt with simply 100Nm torque.



Can someone please confirm which flex disc torque spec is correct for the E9x M3 for the (dull) fasteners that I have? Thanks.
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      05-31-2020, 01:35 PM   #2
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I can’t but for what it’s worth, I just used the industry standard TAF, german equivalent of gudentight
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      05-31-2020, 02:51 PM   #3
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TAF. You'll never get a torque wrench on it.
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      06-01-2020, 12:23 AM   #4
frankc
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For those interested, I used the 55Nm + 90* method, and then looked at the log on my torque wrench to see what the final actual torque values were. Only 5 values were recorded because I didn't quite hit 90* on the first one.

Angle Torque
90 129.6 Nm
90 134.4 Nm
92 143.5 Nm
90 126.6 Nm
90 137.4 Nm

Btw, I don't know how one would do this torque sequence for this part without a wrench that is capable of measuring accumulative angle values, since there is room to turn the nut only about 20 degrees at a time. Fortunately, my Snap-On allows me to ratchet back and forth, and adds up all the angles while torquing.
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      06-01-2020, 09:02 AM   #5
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The BMW TIS says to, "Grip mounting bolts of flexible disc at propeller shaft flange at nuts and tighten down at bolt heads." No accumulative angle torque wrench required when following the TIS.

"Shiny zinc coating" is poorly translated from German to English, "dull silver zinc coating" is a better description, but in their defense, they did identify the bolts and nuts they were referring to as "ZNS screws and nuts." The ZNS label is used by BMW to identify their "dull silver zinc coating" bolts and nuts.
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What I Wish I Knew When I First Bought My E9X M3 Can Be Found Here
E9X M3 Exact Original Equipment (OE) Equivalent Parts Can Be Found Here
E9X M3 Common Torque Specs Can Be Found Here
E9X M3 "Factory" Tools Can Be Found Here

Last edited by Theodore; 06-23-2020 at 04:19 PM..
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      03-18-2021, 02:18 PM   #6
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Quote:
Originally Posted by frankc View Post
For those interested, I used the 55Nm + 90* method, and then looked at the log on my torque wrench to see what the final actual torque values were. Only 5 values were recorded because I didn't quite hit 90* on the first one.

Angle Torque
90 129.6 Nm
90 134.4 Nm
92 143.5 Nm
90 126.6 Nm
90 137.4 Nm

Btw, I don't know how one would do this torque sequence for this part without a wrench that is capable of measuring accumulative angle values, since there is room to turn the nut only about 20 degrees at a time. Fortunately, my Snap-On allows me to ratchet back and forth, and adds up all the angles while torquing.
Have just done a DIY of the solid subframe bushings, and driveshaft was envolved on that.

Torquing up things back on installation, those 90 degrees required a huge amount of force to do, specially as the car was on jacks, and the space is really tight below it.

To be honest, I wasn't able to make to 90 degrees. I think 70 is what I got
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      03-18-2021, 04:49 PM   #7
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      03-18-2021, 05:11 PM   #8
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