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Old 04-20-2014, 07:12 AM   #691
Taranis
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Quote:
Originally Posted by _cy_ View Post
seems on R1200GS rear caliper bolts factory spec is a super low 18ft lb .. which IMHO is a fuck up by BMW. no one else no one else in the world that I'm aware of uses 18ft lb torque that low to hold together a mission critical part like brake calipers.
I'm very careful with BMW torque specs, as I have learned the hard way. Back in 2004, I was working on a customer's brand new M3. I didn't have a manual for the car, but having done the simple task I was doing many times on many other cars, wasn't worried about it. Set the torque wrench to what I had used for the same diameter and pitch fastener in the same place doing the same job on my 1985 Toyota, and snapped the dang thing off. Had to buy a new $90 part (fastener was a pressed-in stud, not available separately) because BMW saved $0.03 on a crappy fastener. Later found a manual and saw the BMW torque spec on that fastener is less than half of the Toyota spec. On all the other cars I've worked on, the Toyota is typical. So you really have to follow the manual with German stuff.

Just to benchmark, I pulled up the manual for a K8-K9 gixxer. Its rear caliper has three different fasteners doing three different things, and these are the recommended torques:

33 N⋅m (3.3 kgf-m, 24.0 lb-ft)
18 N⋅m (1.8 kgf-m, 13.0 lb-ft)
16 N⋅m (1.6 kgf-m, 11.5 lb-ft)
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Old 04-20-2014, 08:50 AM   #692
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Quote:
Originally Posted by Taranis View Post
I'm very careful with BMW torque specs, as I have learned the hard way. Back in 2004, I was working on a customer's brand new M3. I didn't have a manual for the car, but having done the simple task I was doing many times on many other cars, wasn't worried about it. Set the torque wrench to what I had used for the same diameter and pitch fastener in the same place doing the same job on my 1985 Toyota, and snapped the dang thing off. Had to buy a new $90 part (fastener was a pressed-in stud, not available separately) because BMW saved $0.03 on a crappy fastener. Later found a manual and saw the BMW torque spec on that fastener is less than half of the Toyota spec. On all the other cars I've worked on, the Toyota is typical. So you really have to follow the manual with German stuff.

Just to benchmark, I pulled up the manual for a K8-K9 gixxer. Its rear caliper has three different fasteners doing three different things, and these are the recommended torques:

33 N⋅m (3.3 kgf-m, 24.0 lb-ft)
18 N⋅m (1.8 kgf-m, 13.0 lb-ft)
16 N⋅m (1.6 kgf-m, 11.5 lb-ft)
turns out the low 18ft lb torque value was NOT the problem for R1200GS. BMW by leaving off requirement of Loctite 243 with such low torque values was the problem.

seems KTM 690 caliper bolts are spec'd at 25 Nm or 18ft lb .. but KTM requires Loctite 243 be used at those low torque values.

_cy_ screwed with this post 04-20-2014 at 11:35 AM
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Old 04-20-2014, 09:55 AM   #693
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Quote:
Originally Posted by _cy_ View Post
turns out the low 18ft lb torque value was NOT the problem for R1200GS. BMW by leaving off requirement of Loctite 643 with such low torque values was the problem.

seems KTM 690 caliper bolts are spec'd at 25 Nm or 18ft lb .. but KTM requires Loctite 643 be used at those low torque values.
It's 243...not 643.

Having slept on this issue overnight, some of the problems very well have been the rider in the linked thread torqued to 18ft/lbs on dry threads. 18ft/lbs on dry threads is going to give a super-low clamp load that will allow the assembled part to side slip pretty easily.

This observation backs up an drives home the importance of filling in the airspace found in between the male and female threads with a liquid that turns to a thermoset plastic with thread lubricating qualities to allow a sufficient clampload to be introduced into an assembly to keep it from falling apart.

I went back and pulled a few Power Point slides directly related to the friction loss on lubricated threads vs. non-lubricated threads. Here's the talking points:

Approximately 85 to 90% of the effort used to tighten a threaded fastener is lost to friction, which leaves only about 10 to 15% of that effort is used to generate clamp load.

Another slide shows clampload (lbs.) generated on different base metals torqued to 10ft/lbs along with a calculated K Factor (Friction Factor)

The following examples are listed as:
Bolt Nut Washer K Factor Clampload

Plain Cadmium Plain 0.15 2,805
Zinc Plain Zinc 0.35 1,546
Zinc Zinc Zinc 0.55 960


The table listed above shoes that Zinc is a very sticky coating with a very high K factor. The low clampload backs up the claim that zinc plated fasteners are sticky.

Dirty
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Old 04-20-2014, 10:20 AM   #694
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I have NEVER understood the requirement of torquing fasteners dry. It makes more sense to me to specify what lubricant to use.
Could someone technically oriented explain what circumstances that REQUIRE non lubricated assembly and why, other than on applications such as oxygen service where the lubricant becomes a dangerous contaminant?

Regards....justjeff
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Old 04-20-2014, 12:06 PM   #695
_cy_
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Quote:
Originally Posted by _cy_ View Post
turns out the low 18ft lb torque value was NOT the problem for R1200GS. BMW by leaving off requirement of Loctite 243 with such low torque values was the problem.

seems KTM 690 caliper bolts are spec'd at 25 Nm or 18ft lb .. but KTM requires Loctite 243 be used at those low torque values.
Quote:
Originally Posted by dirty_sanchez View Post
It's 243...not 643.

Having slept on this issue overnight, some of the problems very well have been the rider in the linked thread torqued to 18ft/lbs on dry threads. 18ft/lbs on dry threads is going to give a super-low clamp load that will allow the assembled part to side slip pretty easily.

This observation backs up an drives home the importance of filling in the airspace found in between the male and female threads with a liquid that turns to a thermoset plastic with thread lubricating qualities to allow a sufficient clampload to be introduced into an assembly to keep it from falling apart.

I went back and pulled a few Power Point slides directly related to the friction loss on lubricated threads vs. non-lubricated threads. Here's the talking points:

Approximately 85 to 90% of the effort used to tighten a threaded fastener is lost to friction, which leaves only about 10 to 15% of that effort is used to generate clamp load.

Another slide shows clampload (lbs.) generated on different base metals torqued to 10ft/lbs along with a calculated K Factor (Friction Factor)

The following examples are listed as:
Bolt Nut Washer K Factor Clampload

Plain Cadmium Plain 0.15 2,805
Zinc Plain Zinc 0.35 1,546
Zinc Zinc Zinc 0.55 960


The table listed above shoes that Zinc is a very sticky coating with a very high K factor. The low clampload backs up the claim that zinc plated fasteners are sticky.

Dirty
thanks again for your valuable input on this issue. above agrees with my assessment that when using a low torque value like 18ft lb on a brake caliper in a vibration rich environment. use of a thread locker like Loctite 243 insures bolt will not back out from low clamploads (lbs) resulting from use of 18ft lb torque values.

seems loctite's lubricity also aids in overcoming stickiness from finish on fasteners and it's effects on final clamploads. this really points out importance of careful cleaning with low residual solvents when reusing existing bolts.

_cy_ screwed with this post 04-21-2014 at 04:47 AM
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Old 04-20-2014, 12:27 PM   #696
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Quote:
Originally Posted by KLboxeR View Post
fixed
For a KLR, tyeing fishing string around the bolt works
and is cheap
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Old 04-20-2014, 01:22 PM   #697
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For a KLR, tyeing fishing string around the bolt works
and is cheap

That's so when it falls out you don't lose it!!

jj
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Old 04-20-2014, 02:02 PM   #698
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Ok I bought an aftermarket part (starter tensioner tamer) that came with a nice little packet of Loctite 262. Unfortunately I left it in my garage over the winter, exposed to temps well below 0F.

Can I use it, or should I get a new pack? It says for industrial use only so I'm not sure I can pop down to Autozone & grab one.
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Old 04-20-2014, 02:15 PM   #699
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It'll be fine Dave.

Not a worry.

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Old 04-20-2014, 02:35 PM   #700
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It'll be fine Dave.

Not a worry.

Dirty
Thanks, didn't expect a reply that quickly!
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Old 04-20-2014, 04:07 PM   #701
dirty_sanchez
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I had foot surgery (8 screws and a plate installed) this past Wed after an off on a pre-ride of the Arkansas 500.

I'm stuck here at the house and ain't going too far from the computer for the next 8 to 10 weeks, so any questions are gonna get a speedy response.

Dirty
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Old 04-20-2014, 05:50 PM   #702
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Soooo....Are you gonna post up the Dirty details in the Face plant thread? Hope you heal up well and soon!
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Old 04-20-2014, 07:30 PM   #703
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Quote:
Originally Posted by dirty_sanchez View Post
I had foot surgery (8 screws and a plate installed) this past Wed after an off on a pre-ride of the Arkansas 500.

I'm stuck here at the house and ain't going too far from the computer for the next 8 to 10 weeks, so any questions are gonna get a speedy response.

Dirty
Sorry to hear that Dirty, I presume you advised using the stick thread lockers for surgical hardware? In all seriousness, hope you heal fast and can recruit someone cute to wait on you!
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Old 04-20-2014, 10:34 PM   #704
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Ouch you poor bloke hope you heal ok.

.....and hopefully TinyD did't say anything sarcastic.... typically my junior would have given me a lesson on how I did it wrong
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Old 04-21-2014, 04:50 AM   #705
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Yikes ... hope you heal quick ..
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