Blast from the past post…
I’ve had two derailleurs on my Hilsen self destruct. The first on a 300k keeping me in the big ring for the 2nd half of the ride. The second on a commute home. Different manufacturers, same bike and crank/chainrings. Strangely, they both broke in August – exactly one year apart. The other strange thing here, I have the exact same crankset on my Vélo Routier, and have never had an issue. It uses an older derailleur – Suntour XC Pro, however.
I’ve gotten advice from “ignore it – probably just unlucky” to “need a stronger derailleur”. Something is going on here. I have always been careful to align the derailleur within 2-4mm of the outer chainring. Perhaps this bike just needs a 1×10? I’ve never had another bike destroy even one front derailleur, so I was suspicious of the following:
- Chainring 16 tooth spacing (44t – 28t) too great a jump
- Chainring thickness (chain seemed to stick to big chainring)
- Derailleur construction
On to the specifics:
The first one let go on a 300k brevet on August 4th, 2013. It was a Shimano CX-70. Luckily it happened after my big climb for the trip up to Artist’s Point on Mt. Baker.
As you can see, the outer cage popped out at the top with a fairly clean break. To be fair, I had several instances of chainsuck over the prior year that spread the derailleur apart. To fix, I would just push the cage back into the normal shape after I re-railed the chain. I assume it finally fatigued to the point of failure after the last chainsuck.
I then mounted a Campagnolo Centaur CT that had worked well on other bikes. This lasted for approximately 1 year, but then self destructed in much the same way on August 12, 2014, breaking on the upper inside plate.
At this point, it was clear that the shifting pressure was too much for these modern derailleurs. I decided to swap the big ring from a 44t to a smaller 42t so the gap was not as great. With an inner ring of 28t, I dropped the spread from 16t to 14t with the hope that it would not be as much distance to push, however, the problem always happened when dropping the chain from the large ring to the small. I had an extra CX-70 that I put on this bike. It came from the Hunqapillar, which had never mis-shifted or chain-sucked while it was mounted.
A year and a half later, and all is well. No sign of problems with the new CX-70, and no further instances of chain-suck. I have a feeling it was the large chainring causing the problems. C’est la vie. One of the more frustrating things about biking (and food/diet) is the sparse amount of useful information out there. Anyone else had front derailleurs go boom on a road bike?
Ah, the simple days of not having to worry about shifts. Tech will get us there again, soon. Can’t wait for the variable ratio belt drive bike that you can control with your embedded chip.