chris2006

Hi All

I purchased a Cube C68 litening PRO 4 weeks ago and while cycling today I heard a loud crunch which I thought was my chain coming off

When I had a look the rear Derailleur has snapped off taking part of the frame with it

I cant believe how weak it is, my brother went for the felt AR5 and Rear Derailleur on it looks far stronger.

What would have caused this to happen and what way do I stand with warranty ?

alcjphil

First question always asked in these threads: What gear combination were you in when this happened? Looks as if your derailleur hanger did what it is supposed to do which is to sacrifice itself preventing damage to frame and derailleur when the derailleur shifts beyond its limits

ShortLegCyclist

Take it back to the shop ASAP.

It should absolutely be covered under warranty as a new bike.

Take care not to damage the bike while getting it there, as they will likely take it and investigate the issue and you don't want them to be able to blame you by saying you crashed it.

Most if not all makers warranty is voided by a crash as that is not considered normal usage and wear.

Homebrew01

Looks like the hanger AND frame broke .... Ouch.
Common cause is the "L" low limit screw misadjusted allowing the derailleur to shift off the largest cog into the spokes.
Another cause is a chain that's too short, so if you are in the big chainring and shift into the big cassette cog, you run out of chain and "SNAP'

What were the circumstances when this happened ? Details ?

alcjphil

After a second look, this seems to be the case. Painful. This may well be a frame integrity problem exacerbated by poor shifting adjustment, precipitated by gear selection. The first 2 are the probable causes, the third should not matter if the first 2 are good

Sangetsu

Whenever you get a new bike, make sure that the rear derailleur travel limits are set properly, and check them regularly. On new bikes the cables stretch a bit over the first miles, and the clearances on some parts changes as they break in. The bike was probably within spec when it was set up, but loosened up after some riding. With luck, the shop will probably take care of the problem, but you should be sure that you know how to check and adjust the clearance on the derailleurs, the brakes, and how to fine tune both. The mechanics at the shop can show you how.

CliffordK

Apparently this got crossposted.

Cube Litening C68 Snapped off Rear Derailleur | CycleChat Cycling Forum

Anyway, my interpretation is that this is a poor design. The derailleur hangers should be engineered to fail without also taking out the frame..

In this case, there seems to be a descending portion of the frame that is bolted to the derailleur hanger, and a failure of the hanger will necessarily also take out a chunk of the frame. It really should be designed so that the wheel primarily holds the hanger in place, and failure just rips the hanger apart.

Of course, loose bits around the rear of the bike is never good.

Anyway, take it to the shop and see what they say.