UmneyDurak

So this is not the first time I crashed, and probably won't be the last. Big difference is that this time it was caused by chain coming off while I was practicing sprinting. I was in 50/12 gearing. I think I shifted from 13 to 12 when that happened. Don't quite remember. Anyway it was a nasty crash. I was going all out next thing I know I am sliding on my ass at 30+ miles an hour.

I brought a bike to the shop, they adjusted a limit on FD a bit, and I guess cage as a bit bulging out. Still I don't think the chain should have came of in the first place. This never happened with my old crank.

Here is the problem. I don't have confidence in my bike. Only way to test it is to do a high effort in the same gearing, but that mean speed. I don't think at the moment I can bring myself mentally to do it. Any ideas on how to test the bike is OK, and get over the mental block? For first part I was thinking of testing on a hill so at least speed won't be that high.

I am seriously considering trying to borrow full MTB down hill armor. It will look silly as hell, but might help with the confidence.


Thanks.

rbart4506

Trainer?

carpediemracing 

Here's the issue with testing the gear combination - it may be something else that caused the chain to hop off, like a bump in the road created the perfect harmonic wave in the chain so at the peak of your power stroke the chain ended up derailling itself. Or something like that.

I've had the chain come off more than I like while sprinting in a top gear. I've eliminated shifting (I was already in the gear) but a host of other problems could cause it.

Some of my findings:
- link on chain was twisted. It may have been the result of a chain slipping off. Chain was...3 months old? Clean, properly installed, etc.
- chainring warped a bit. Changing crankarms (because the crankarm holds the ring) worked the best. Using thick chainrings also helps.
- worn components, especially chainring and/or chain.
- chain on the long side, so it bounces too much. Tighten up the b-screw or equivalent to increase tension in chain.
- chainline - with my 39 cm stays my chainline is a bit more aggressive than others. On what appears to be an otherwise perfectly good bike I've had the chain come off while in the 53 or 55x11, and the chain comes off to the outside of the ring. I even adjust my derailleur so it's super tight on the outside, for situations like this.

You can check by rolling the pedals forward slowly while the bike is on a stand/trainer/etc. Check for any link that doesn't seem "fluid". Pedal backward; use the small-small because that accentuates the link rotation in the rear derailleur. Check your chainrings. Cranks. Look down when you pedal - does the chainring move left-right more than a few mm?

I hope you were on the drops when you were doing your sprints. I've had various incidents over the years where something happened to disconnect my feet from the rear wheel - BB spindle broke, cleat broke, chain derailed (most common), pedal broke, probably others - and each time I managed to recover without falling. Most of those were at speed, 38-45 mph, at high effort. Scary, yes. Pain, sometimes. Fall, no. I attribute this to the firm grip I had to the drops and the lucky drop onto the bike.

For solutions, other than making sure your chainring/cranks are okay, is get a cassette with an 11 and don't use it much. Running the big ring with the second smallest cog will give you a better chain line than the big-little.

Hope this helps, good luck with your bike.
cdr

mattm

Try seated sprints maybe at first, or some seating uphill/bigring stuff, to get a feel for how it goes at high power.

At least you've got all winter to get used to it again. Good luck!

waterrockets 

+1 to seated, and +1 to trainer. Maybe also try out of the saddle from a standing start -- you won't be going fast if something goes wrong.

The other thing is to put it out of your mind. Don't worry about confidence, just embrace stupidity a bit. You need to focus on mechanics when doing mechanical stuff. Testing is fine, but you're never going to replicate an all-out road sprint in any test. You just getting working right to the best of your knowledge, then shift your brain into training mode, thinking only about power, and let the bike take care of itself. Our situation on the bike has always been precarious, and it's often best not to think about it... or maybe just give it all up.

UmneyDurak

Yep I was in the drops. Honestly no idea what happened. As I said one moment I was sprinting with bike "dancing" under neath me, next I am on the ground sliding.

I'll try the suggestions. Thank you. A bit hesitant to do all out standing sprints on a trainer, that can't be good for the bike... Don't get me wrong I warm up on it all the time, including seated intervals, but standing?

and yes I have whole winter to get over it. Can't believe racing season is over, it flew by so fast!