Fabian's mechanical problem E3 2016

[CPongpanich]

Hi all, I know this has been discussed in 2016 'PRO' cycling discussion. However, I think it is worth its own discussion (feel free to disagree).

Fabian was caught with a mechanical problem around 65km. to the line. He lost quite a significant amount of time but managed to get back.

If we look closely in this photo from ave that his chain appeared not to be routed properly through the pin and was outside of the pulley.



At this point, it appears to be the mechanic's false. However, JasperGr posted another photo of Fabian earlier in the race and his bike seemed perfect. The chain was routed correctly through the pin and pulley.



How did that happen? I think it is almost impossible for the chain to get outside of the pulley with the pin still intact (or perhaps, it wasn't but appeared to be)? Has anyone ever experienced this before?

The only explanation I can speculate at this point is that something, like a small rock or stick, got stuck on his chain just before it goes into the pulley and forced the chain to slip out of the pulley. With the amount of power Fabian can produce, he can easily rip the chain through the pulley and pin. However, that didn't really appear to happen as the pulley and rear mech must appear much worse.

Chanon

[JAQ1]

I know that Ashleigh Moolman (Riding for Bigla Ladies) also experienced the same thing at ladt years world champs. I was looking at a Dura-Ace RD yesterday and noticed that it is quite easy to flex the rear carbon plate by hand. I was able to open a big enough gap for the chain to be able to hook in to the gap.

[Kayrehn]

Happened to a friend twice on the same ride when he changed to using aftermarket pulley wheels, so I know it definitely happens during the ride, not sure how exactly though.

[BikeAnon]

I had it happen to me with a SRAM derailleur, carbon fiber pulley plates.

Small stick popped up from being hit by a tire, wedged between chain and pulley, and effectivly became a "derailleur" that derailed the pulley. Between the stick and the chain, there was plenty of leverage to snap the pulley cage plate.

In the first pic you show, that outer plate is not in proper working order.

[ms6073]

Happened to a friend twice on the same ride when he changed to using aftermarket pulley wheels

Similar issue occurred with my wife's bike running Di2 9070 after I swapped out the stock pulleys with Tiso alloy pulleys. The alloy 'guide' pins on the derailleur cage are only secured on one side, so when the cage flexed, the chain jumped through the gap in between the cage and guide pins and the guide pulley (lower) snapped in half which then snagged the chain. At that point the derailleur hanger snapped off and no damage was done to the derailleur cage and fortunately it happened only 1/2 mile from where we were parked. Suffice to say after that lesson, I am no longer using after market pulleys on our bikes.

[CPongpanich]

After all, this problem appears not to be too uncommon. But with great working conditions of all components on the bike and the fact that the bike was setup by one of the best mechanic in the world, it must be extremely bad luck for Cancellara to got caught up with this mechanical problem.

[TheKaiser]

I've seen this happen too, both as a result of objects getting caught in the derailleur or the chain popping off the pulley teeth and wedging between pulley and cage. Sometimes the cage tabs have broken off, but other times they simply flexed and allowed the chain to escape, preventing the chain from being returned to it proper position until the derailleur was disassembled.