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FSA SLK Loose Crank Arm

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FSA SLK Loose Crank Arm

Old 04-20-07, 06:22 PM
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VT Biker
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FSA SLK Loose Crank Arm


To anyone with information on FSA MegaExpo bottom brackets and tightening crank arms:

I have only been riding on my new crank set for approximately 200 miles. Already, the crank arm is loose (which was installed by a large local bike shop, so this is not a self-generated issue.

I am wondering how to (a) Tighten the crank arm (i.e. - what tool do I need, as I cannot figure this out; (b) Has anyone on this forum been experiencing the same problems and found out how to clear this issue?

(c) Is this a symptom of manufacturer defect, or is this typical for newly installed BB's?
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Old 04-20-07, 06:56 PM
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I believe it takes an 8mm hex wrench to tighten the bolt on the non-drive side.

This is a known problem with the FSA SLK cranks. Last summer, a friend of mine had his left crank arm fall off his 2 week old '06 Specialized Roubaix Comp when the bolt backed out completely on a ride. In an earlier thread, someone said the problem was that the fixing bolt is alloy and flexes under force causing it to work itself loose. The fix is supposedly to switch to a steel bolt. Talk to your LBS about it.
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Old 04-20-07, 07:18 PM
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Thanks. I guess I am not too concerned if all it takes is a little adjustment here and there. But I am concerned about over-tightening, and damaging the BB.
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Old 04-20-07, 07:55 PM
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If I understand the FSA web site, this also uses the MegaExo BB, right?
I installed a Team Issue Mega Exo BB/crankset on my Spectrum Ti touring bike over this past winter.
While reviewing the instructions on the FSA website, I noticed an amendment from October 2006 referring to a requirement that an "installation compound" (aka Loctite 641) be used on the splined portions of the BB axle and crank arm. (note that this is not the Loctite threadlocker as we know it; it different stuff.)
Anyhow, this was not supplied to the LBS in the crankset package I purchased, so I called FSA and they shipped me a small tube, no problem.
Proximo makes a good point about the steel crank arm fixing bolt.
Suggest you get this stuff from FSA and pull the crank arm and reinstall. Use a torque wrench and folow the specs. My experience was that you cannot get to the needed torque with one of those basic L shaped allen wrenches.
My install has about 250 miles on it after 4-5 rides. I have re-torqued the crank arm fixing bolt after each ride. After the first couple of rides, it took a couple of turns to acheive the torque spec, but now maybe 1/8 turn.
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Old 04-20-07, 08:01 PM
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Originally Posted by VT Biker
Thanks. I guess I am not too concerned if all it takes is a little adjustment here and there. But I am concerned about over-tightening, and damaging the BB.
Search around here and you'll probably find the other thread I was talking about. You can also read the reviews on roadbikereview.com. Some of the folks there said that even loctite wouldn't hold the bolt in. When you tighten it, cranking on it really hard isn't going to help because it will still work itself loose. Best to just firmly tighten it by hand and check it frequently. I believe FSA has a PDF doc on their web site that gives torque specs for all their products. In the end, though, the only solution is to replace the bolt with a steel one.
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Old 04-21-07, 07:49 PM
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Just to clarify, this is not a bolt issue, but an axle/crankarm issue.
From observing my bike, it does not appear that the bolt is loosening, per se, but the crank arm is "settling" onto the axle, thus the bolt seems to have loosened.
The recommended so-called installation compound / Loctite 641 is not a thread locker, but is applied to the splines on the crank arm and axle. FSA's installation instructions do not recommend the application of a threadlocker to the crank arm fixing bolt, only grease.
Since my instruction sheet used different definitions of torque (foot pounds here, kgf-cm there) I found the Maryland Metrics site to have a nice tool to convert these.
If you have installed the bearings with the correct spacers, I suspect it will be very difficult to damage the bearings by overtightening the crank arm fixing bolts. The crank arm should "bottom out" on the axle splines before that happens. But I guess, never say never.
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Old 11-23-14, 12:08 AM
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I have problems with tightening down the crankarm fixing bolt to proper specs (40 nm), because the crankset ends up too tight up against the bottom bracket and the crankset won't spin effortlessly inside the BB. Slackenening off the fixing bolt will loosen the tightness, but then the crankarm isn't on tight enough and will likely eventually fall off while riding. What am I doing wrong. I have the wavy washer on the crank spindle before the crankarm, washers on both sides of the fixing bolt etc.....
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Old 11-23-14, 12:37 AM
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Originally Posted by albees View Post
I have problems with tightening down the crankarm fixing bolt to proper specs (40 nm), because the crankset ends up too tight up against the bottom bracket and the crankset won't spin effortlessly inside the BB. Slackenening off the fixing bolt will loosen the tightness, but then the crankarm isn't on tight enough and will likely eventually fall off while riding. What am I doing wrong. I have the wavy washer on the crank spindle before the crankarm, washers on both sides of the fixing bolt etc.....
At first glance (not that any of can really look at the bike) it would seem like the after tightening of the arm results in too much bearing preload. So if one started from the beginning... is the Bb shell within the right width range and the seats square with each other? Are the proper size and count of spacers/washers in place? Do you, or a friend/shop, have another LH arm of the same spec to sub? Are the bearings fully pressed/threaded in place? How about the brand, model, BB spec? Andy.
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