small gap in the left crankset

What I have seen is 2 Nm for the included plastic bolt, but an aftermarket aluminum bolt can be a little more.  Proper order is to loosen the crank arm clamp bolt with a 5mm hex key, tighten the plastic crank bolt to 2 NM, and then re-tighten the clamp bolt (I have seen differing torques from 15 Nm to 22 Nm for this).

5382224, My plastic bolt actually stripped its threads and fell off prior to the crank arm loosening up fully.  I attempted to tighten the clamp bolt without the crank bolt but I could not get it tight enough to hold.  Only after adding the threaded rod "clamp" was I able to keep the crank arm from loosening back up.  Last night's Zwift ride was flawless after struggling with it the previous ride before my fix.

Update. Tried to swap with an aluminum bolt and srew it on on tight. Was okay for about 4hours then fell off again - stripped this one too.

However i did not check exactly how much nM was it. Seriously considering the lock tight glue option. Really dissapointed, but i don't want to loose the setup for a month just before the season waiting for the repairs. 

Only for alignment of the crank, the crank should be fastened with the crankbolts, if still slipping try stripp of the grease, clean with some detergent/cloth to get rid of the grease and be careful not to get any detergent in the bb. 

Then slide on crank and put one or two locktite dots inside of the crankarm and then slide on and make fast again. Maybe re-apply locktite to the bolts of the crank also.

Hi. I followed Garmin instructions to sort out the plat in the left hand crank. I was riding tonight in a team time yrial and the left hand crank arm almost fell off. I found on another site how to replace and secure this type of crankset. Its called shimano Hollowtech II. The plastic threaded insert appears only to preload the bb bearings before you tighten the crank arm bolt. Have a look on youtube for vids re hollowtech II. 

Resurrecting this thread as I'm having the same problem myself - and this is my THIRD bike (others replaced for different reasons). Was riding the other day and I started to notice a 'swooshing' sound under load like the drive belt rubbing. Then I felt a lot of float in the left pedal, next thing I knew the crank arm had fallen off (glad it wasn't a real ride!)

I remounted the crank-arm but noticed that the spindle didn't protrude all the way through the arm, so there was still a few mm of the threaded section of the arm visible. I tightened the Allen bolt and everything seemed good, even the noise had stopped. However, a few rides later and the float in the left pedal returned, and I was able to pull the crank arm off by hand, I hit the right crank arm with a rubber mallet to make sure the spindle was sticking out on the left as far as it would, but when I remount the left pedal, the spindle still seems to be too short.

FWIW, I've also noticed seem black swarf on the floor below the bottom bracket, but that could just be dirt from somewhere else in the garage.

I've contacted Garmin Support UK who have been very good in the past, just waiting to see what they say, and hoping that by now they've come up with a proper fix for this as it's clearly a known issue.

In the meantime, could people tell me if there left crank arm connection is actually meant to look like mine, i.e. with the gap between the end of the spindle and the threaded section? [I was going to add a photo here, but can't find an option to do so]

Thanks,

Neil

EDIT: Re-reading this thread, is there actually meant to be a pre-load cap over the spindle end? I guess that would explain the spindle not reaching the edge of the crank arm.

Hi Neil. My problem has been completely resolved by properly securing the left crank arm. The central plastic plug screws into the end of the spindle and is intended to pull the crank arm on to the spindle after the crank arm bolt has been loosened. If you try to tighten the central plastic plug without loosening the arm you will strip its thread. I loosened the crank arm pinch bolt, pushed through the spindle from the right, as far as it would go, and pushed on the left arm. I tightened the plug without using very much torque and tigtened the pinch bolt. Have a look on youtube for fitting shimano hollowtech 2 crank arms. Best of luck. Alan 

Thanks Alan, so my problem seems to be that I don't actually have a pre-load cap! (the plastic plug) I don't know if I've never had one, or if it's come off unnoticed at some point (which I think is more likely given that I've cycled several thousand km before this happened). I suspect even if I do find it somewhere in the garage, the swarf under the bike is probably the thread from it so it'll need replacing. Let's see if Garmin Support will provide a replacement, and hopefully a better quality one!

Yes there should be a pre-load crank bolt threaded into the spindle.  The crank is similar to the Shimano Hollowtech design, but only has 1 pinch bolt instead of 2 like the Shimano.  My solution has been working since I had the issue this winter.  I purchased an aluminum (M18) crank bolt from Amazon to add a little more thread engagement than the plastic OEM bolt that stripped it's threads.  I also torqued the pinch bolt on the crank to at least 22 N-m.  My Hollowtech cranks have less material in the clamping zone and 2 bolts with a12-14 N-m recommended torque so 1 bolt with a thicker crank arm cross section needs significantly more in my opinion.