[lcecere]

Good afternoon.

I had a wierd thing able to me twice on a ride on Saturday. When I shifted down to the small chain in the front the crank locked up. Happy to say I was able to quickly unclip and avoid any falls.

Than after I stopped and shifted again everything was fine. When I got home put bike up on rack, but couldn't cause it to happen again. Out this afternoon and nothing went wrong. could it been user error and bad shifting?

Thanks

 

[Loraura]

If you didn't fully engage in the shift it may have caused the issue. You can trim the derailer (move the chain a little without shifting), or shift it completely. You may have been somewhere in between. If this is the case, you will get used to the feel of a complete shift and it will be second nature soon.

Also if you try to shift from the big ring to the small ring and you are in a small cog (difficult gear) in the back, the chain could have been crosschained and got hung up on the chain guide portion of the derailer.

The chain guide part (not sure what the real name is) is the part that moves the chain out and back depending on which front ring you want to be in, but if the chain is in there at enough of an angle, it won't slide through the guide, it will catch on the guide. Anything that stops the chain from moving will cause an aprupt lock up like you described.

If this is the cause, the fix is easy. Always shift down a few gears on the casette before shifting down on the front rings. You never want to shift into the big ring while in the easiest casette cog, or shift into the small ring while in the most difficult casette cog.

Have the LBS do a quick check to see if the cable tensions need any small adjustments. This should be free, or very inexpensive.

 

[PeanutButterBreath]

Sounds like "chain suck": http://www.sheldonbrown.com/gloss_ch.html

 

[Kerry Irons]

Dropped chain?

Good afternoon.

I had a wierd thing able to me twice on a ride on Saturday. When I shifted down to the small chain in the front the crank locked up. Happy to say I was able to quickly unclip and avoid any falls.

Than after I stopped and shifted again everything was fine. When I got home put bike up on rack, but couldn't cause it to happen again. Out this afternoon and nothing went wrong. could it been user error and bad shifting?

Either chain suck, as mentioned by PeanutButterBreath or your chain wedged between the small ring and the frame. A quick backpedal often fixes it, but sometimes you have to stop and push the chain out of the wedged spot with the toe of your shoe.

 

[Fredrico]

Good afternoon.

I had a wierd thing able to me twice on a ride on Saturday. When I shifted down to the small chain in the front the crank locked up. Happy to say I was able to quickly unclip and avoid any falls.

Than after I stopped and shifted again everything was fine. When I got home put bike up on rack, but couldn't cause it to happen again. Out this afternoon and nothing went wrong. could it been user error and bad shifting?

Thanks

1) Could be over shifting. If the chain ends up between inner ring and frame, inside stop screw on front derailleur is not screwed in enough.

2) But first, check derailleur cage alignment! The bolt that attaches the derailleur to seat tube often comes loose, allowing the derailleur to slip out of alignment. The cages get pulled inward from shifting, and over shift the chain inward. The cage plates right where they're joined at the pivot bushings, should be parallel with the rings.