Front derailleur socket on carbon bikes

Front derailleur socket loose or broken, rivets no longer hold, tear out

Blog article from April 2019

 front derailleur socket broken loosen detached rivet repositioning
pulled out, detached front derailleur socket befor repositioning © jostec CBS

A recurring problem are riveted front derailleur sockets, which have been resolved / detached. If this is neglected, this inevitably leads to unclean switching operations and an increase in the problem or damage.


The damage occurs due to several factors:


The most important is always a perfectly adjusted circuit to ensure smooth gear changes with the least possible resistance under all conditions. Especially on the chainrings are the "paths" in the switching operations relatively large, compared to the sprocket set / rear derailleur cassette. Smooth gear changes when changing the chainring will protect the front derailleur base. What you can do for this is described in this blog article.




The chain as the cause of caughts and hooking

Check the chain wear at regular intervals, a chain that has been overstretched by continuous use produces worn out, heavy and rough switching operations on chainrings. The increased resistance thereby directs more forces on the front derailleur socket and burdened this beyond measure. Our advice a measuring gauge for chains is easy to use and costs only a few bucks.

Check the sprocket pack / cassette

Significantly more durable than the chain is the sprocket package, but also here it comes to wear. For the passionate racing cyclist with many kilometers in the legs, a pinion wear gauge is also recommended, and with corresponding wear, a renewal of the sprocket set.

Inadequate attachment of the derailleur base by riveting

A very different factor is then still the attachment / riveting itself. Basically, the combination of carbon laminate and rivet, or rivet head technologically is not recommended, but economical. Carbon / fiber composite laminates in general are very sensitive to pressure. A fitted, tightened rivet produces the required contact pressure via the rivet head for fixation. However, this means high punctual load, which can cause the head to work through the pressure-sensitive laminate. Of course, this will reinforce the factors already mentioned above.

Chainrings wear

chainring wear briken loosen front derailleur socket base large training circumferences
Chainring wear leads to unclean switching operations and leads to unnecessary loads on the derailleur base. Source @ Saito1984 / Twitter

For extreme cyclists, drivers with very large training circumferences of course, even the large chainrings themselves are to be checked for wear. A missing tooth due to fatigue is not a rare phenomenon among frequent riders with high training scopes.


The maintenance, servicing and care of the drivetrain will thank you for the frame and keeps the enjoyment of cycling.

The repair of a loose front derailleur socket

If it comes to the demolition, detachment of the front derailleur socket a repositioning basically is no problem. However, the following must be kept in mind: In the rarest cases, a new rivet can simply be set because the core bore has been damaged by the rivet pulled out. If only the hole is affected without further tearing of the laminate, but this is also rare, all rivets are drilled out. The new fixing therefore takes place with VA bolts, prepared for form-fit, positive locking, and further glued in exclusively. Thus, the front derailleur socket load is neutral, without damaging point loads, fixed. Better than before !



As a rule, however, the surrounding carbon laminate is more extensively damaged by delamination in the case of a dissolved rivet. Therefore, the delaminations must be removed with a standard repair, sanded out. The spot is then reworked to its original contours and repainted locally to restore a solid base for mounting the front derailleur socket. Finally, then as already mentioned with bolts out of VA the front derailleur socket is re-glued.


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