Ok, so today I was doing a recovery ride with the team, and me and a couple guys decided to do a short 200m or so sprint. So we go from whatever speed we were going and I am already in my 53-13. As soon as my cadence picked up... BAM! and my chain drops off the front!?! So of course one side comes unclipped from the jolt, and I am fuming from the near wreck. When I look at it later, it looks as if the rear derailleur was slightly crooked (the bottom pointed in towards the wheel). I know that this hanger is weak as i have a replacement sitting on my desk waiting to replaced the one that is on the bike. The one on there has been rebent several times and was getting flimsy according to my lbs, I just haven't put the new one on yet.

Soo... Why did the chainring throw? Was it that it beat up hanger bent under the force of a sprint, or did the chain being thrown bend the hanger? It is hard because they are seemingly independent of each other. Thank you

Matt

The chain comes over the top of the rear cog to the chainwheels, so a slight mis-alignment will not cause a front drop of the chain, and what kind of recovery is a 53x13 anyway?

Umm... I realize that, hence the question.

And it was a recover ride... or easy ride. Either way, a very non serious ride. We were just playing around.

When pedaling, the top of the chain determines whether or not the chain stays on the chainring. THat's why the front derailleur moves the top of the chain, not the bottom.

Likewise, when pedaling, where the chain is at the bottom of the cassette (laterally) determines where it'll go, hence the rear derailleur hanging under the cassette.

In a sprint, if the chain came off the big ring, that means the chain was not in a straight line with the rear cog (the 13 in this case). If the chainline is excessive, it can cause the chain to derail (and probably to the outside if you're in the 13).

If you have a flexy frame or crank or chainrings (or they're not tightened properly), then that is one potential cause - you torqued the stays/cranks/rings sideways, screwed up the chainline, and caused the chain to pop off.

You may have a bent tooth on the ring, but I think you'd have noticed that. Finally, your chain or rings may be worn excessively.

The hanger is independent of derailing the chain off the chainring, but it could have been bent as a result of your near fall.

hope this helps,
cdr

I had the same issue, it was a bent tooth on the ring.

Thanks a ton guys. I will go inspect it further, but as far as I know everything is in fine order. My frame is not the stiffest thing in the world, but I am really not that strong in a sprint (1500w+-)

I will use this as an excuse to buy a new bike. I love BF

Did you toss your bike into the grass? All real roadies react this way with chain issues.

I did, and I also made sure to do the awkward counterbalance that ensues when a lightweight cyclist tries shotputting a bike.

adjust your front derailer stops so that when in the big-small combo, you have minimal clearance between chain and the side plate of your derailer. Then your derailer will act as a chainguide.

Will do. I am pretty sure that is how it is set though...

Ok, I just thoroughly inspected my bike, and I am pretty positive there are not cracks or anything else. (There was a scratch on the BB that got me thinking though).

Soo..

Could the frames flexing under load be the cause of this?

anyone?

Don't know. What kind of frame?

different components, but the frame is right.

https://www.litespeed.com/2003/bikes/capella.html

Then I will forever refer to you as "Little David"

I'd agree that the hanger is not the culprit.

Check to see if any of the chainring bolts are loose or broken. Bent tooth has already been mentioned. How many miles on the chain? Is it worn and flexy?

I went over the bike very meticulously and the chainring bolts are all on there pretty tight. The chainring is straight as ever. I checked the chain, and it has some life left in it, albeit not much. I put it on last late January/early February, I think it might have 4k or so miles on it, but that is a wild guess. :/

I am tempted to just replace it to see, but I sort of wanted to wait until the season loomed closer.