Tightening a Bosch Powertube Battery Rail


Jul 25, 2022
Dublin, Ireland
Hi lads,

Having an issue on a Cube 2022 750wh Action Team. The top bolt came loose where the bosch Powertube rail system bolts onto the downtube of the frame (worked it's way loose even with blue thread locker on the threads). LBS sorted it the first time it happened a few months back.

My issue is I can't access the bolt to tighten it as the lock mechanism is in the way. The lock mechanism is bolted to the rail system from the top so if I remove it to access the bolt I won't be able to screw it back on. Has anyone had this issue before?

I might be able to get at the bolt if I remove the barrell of the lock or if that fails, remove the forks and try access it through the bottom of the steerer tube but it looks like I'd have to get some sort of flexible extendable Allen tool for either option. Seems very finicky. Am I missing anything obvious? The bolt screws in from the bottom as you can see in pic below. Cheers



Active member
Apr 10, 2023
Glad you got it sorted, It's a common issue with this design unfortunately.

As you've found, removing the lock barrel gives enough access to the bolt.
I would keep a regular eye on the tray and bolt to make sure It's not working loose in the future, as there is potential to damage the threaded insert if it rattles loose.

If the problem occurs again you could consider using Loctite 620 retaining compound, It's a very high strength thread lock, though use with caution as it may be difficult to remove the bolt for maintenance if ever needed.

Also be mindful when tightening the bolt that the insert is bonded directly to the carbon frame, over tightening could result in a big repair bill if it broke away.

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