Well, I lubed the chain yesterday and noticed that the chainring was loose!Used blue thread lock and it hasn’t moved since. No O ring.
Brilliant!I have recently got a Cube Reaction Hybrid and the the chainring got completely loose (while riding) so I have designed and 3D printed this contraption.
Seems to be fine after 30km, worse case scenario it will act like a warning, zipties broken = time to re-tighten the locknut.
View attachment 107711 View attachment 107712
I don’t think so.I have never seen anyone specifically state this but in my opinion that ring nut is single use only.
The CX motor crank is standard ISIS and the chainwheels to fit are all 3rd party with varying offsets and some with a recess for an O ring and some not. Bosch do however sell a lockring . Ensure threads are clean is always a good move on any fixing but apply grease on such a short amount of thread?? No reason, there will be little or not friction. Apply a little grease on the facing elements of the chainwheel and lockring OK but not the threads. ........... Never seen any manual from Bosch on fitting a chainwheel.....................give a link to the manual?I don’t think so.
The Bosch manual states to clean the ring nut threads, apply some grease and then re-mount the nut.
OK thanks......................page 116 to save other trawling through.@Mikerb
Only the spline dimensions of the crank shaft are standard ISIS. The whole shaft construction including the threaded part to fix the spider/chainring is an integral part of the motor and proprietary Bosch. You buy the spidernut from Bosch and not from a crank or chainring manufacturer.
The threads are not sacrificial, but of course they can become worn out over time and multiple mountings just like any other screw or nut.
Check the manual here: Bosch 2020 Dealer Manual
You wouldn’t need to clean the threads if you should use a new lockring. They come in a sealed plastic bag and are clean.yes it does say clean and lightly grease it but it does not specify anything with regard to re-use of the lockring,
....well, as I said above....and regardless of advice in the Bosch manual...........I do not believe a lockring comprising so few threads needs or indeed should have grease applied.................neither should the lockring be re-used if changing the dm chainring/spider or if the lockring has come loose. Basic understanding of how a threaded fastener works in terms of thread pitch friction and a torque setting just below the shear point tells you that. If the torque setting was somewhat less...say 10nm........I would say it would need threadlock because it infers the thread of one or other ( maybe both) elements of the fastening, are too soft for a near sheer point torque. This fastener has, for the amount of thread involved a relative high torque setting of 25nm. So I would fit it without grease and without thread lock.In shock to see how many have lose lockrings. Same here on my cx smart after 250, fully lose. Makes me wonder if its an assembly issue due to the amount of grease or there is a more structural issue in how its mounted
Thanks for the links.I used this tool: 8.95eur
Fits perfectly.
and went from 36t to 34t:
e*spec Steel Direct Mount Chainring Bosch CX Gen4
Features - e*thirteen e*spec Steel Direct Mount Chainring Chainring for 10-, 11- and 12-speed Chain line 52mm (Boost) M3 narrow-wide tooth profile eliminates chain noise and decreases overall system wear Product features...www.bike-discount.de
thanksMight put the chainring on which you can then use to lock the crank with a stick/screwdriver etc & use an adjustable wrench or mole grips to loosen the lock ring. If you're careful you might even save it!
It goes behind the lock ringWhy cant you put the chain ring back on?
Appreciate the reply but there’s nothing to put the chainring on the lock ring is at the end of the threads so nothing to grab onto if u get what I’m sayingYes but the amount of space is the same just in reverse, so you could still put the chain ring on, use it to lock the crank and find a way to knock the lock ring loose eg. a screwdriver & hammer. A lock ring is about eight quid, so even sacrificing it shouldn't be an issue.
Get two of you on it, one to hold the chain ring still & wedged against the frame with something while you knock the lock ring off & it's job done.
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