11 February 2008

Darn Stick

The photo below is the result of a poorly-placed stick on my Sat arvo ride. Grrr.

My fault for not concentrating, actually I didn't even see the thing, all I heard was crack-crack-SNAP as it got flicked up into the derailleur and then broke the hanger. Great, 4km into what was supposed to be a 40km+ ride and I'm stuck on the side of the trail scratching my head.

Luckily one of my friends had a chain break, and I had a Power Link in the chain already, so I took off the derailleur, and tried the emergency single-speed conversion - as seen in photo.

Short answer - it didn't work. Despite my best efforts, I just could not find a gear that would keep enough tension on the chain. Add to this that the chain was now badly kinked, and kept dropping down the rear cassette as soon as any load was put on it. The conversion was enough to get me back to the carpark, but no further.

So now the dilemma is - what to do? Bearing in mind we are less than a fortnight away from the Otway Odyssey. This is slightly complicated by the fact that I noticed that I have torn a tooth off the 15 tooth rear ring and cannot find a replacement ring. I have a slightly worn SRAM cassette that I could install as an emergency option, so could be out of trouble there.

But can I get away with replacing just the chain, or do I need to do the whole drivetrain (front rings included). And if I have to do that, it's actually cheaper to replace the entire crankset with an XT crank rather than just change the rings.

Complicated by a possibly bent derailleur, bloody hell...

I think it will boil down to this (thanks to Sheldon Brown's Wisdom):

Check chain stretch. Get steel ruler, measure distance between rivets over 12 links. If the distance is exactly a multiple of 1 inch, all is well. If there between 1/16 and 1/8 inch stretch, can replace chain without replacing drivetrain. If over 1/8 inch, the whole lot has to go.

If the chain is ok for replacement and the derailleur still stuffed, I'll get a new derailleur locally. If the whole lot is rooted, I'll order a completely new drivetrain from .Chain Reaction Cycles and hope to God it makes it here before the OO.

Fingers and toes crossed people...


Big Mike said...

Take Sheldon's advice on measuring the chain. In future keep the chain cleaned and lubricated and change it every 4-5000km. If you do all that the cassette and chainrings should last 20000+km.

Ant said...

Thanks Mike, I ran the ruler over the chain before work this morning. Looks like it falls within the safe limits, so I'm picking up a new chain on the way home and will fit and see how we go.
Despite the look of the drivetrain in the photo, I'm pretty meticulous about cleaning the drivetrain after every ride. I think I have a heightened sense of mechanical sympathy.
The bigger concern will be the derailleur, not sure if that's going to pass muster or not.