Bicycle Mechanics - The granny gear fails to catch the chain when shifting down

When encountering an major, uphill, obstacle up ahead, I instictively shift the front gear down to the granny gear. Under such "panic maneuveur", half-of-the-time the granny gear fails to catch the chain, and I end up pedaling air. I adjusted the front deraill but this problem persisted (probably I didn't do it properly?). Is there something I can do mechanically to prevent that from happening? Or I just have to resist the urge to shift down to granny gear under such circumstances?

How old is your chain. If the derails are adjusted right most of the problems come from a worn out chain.


Bill F.

About 6 months old. I ride my bike pretty hard, but no big jumps or anything like that.

Does it derail or just miss for a few pedal strokes?

You shouldn't need to try to avoid shifting down when encountering a hill. If you are unsure about your der. adjusting abilities, you could bring the bike to the LBS, or read Sheldon Brown's (http://www.sheldonbrown.com/) carefully, then readjust the derrailleur slowly making sure to do it right. If this still doesn't seem to fix the problem, you could bring it to your LBS to make sure you aren't just missing something when adjusting it. A bad chain or worn chainrings might be the cause, but with only siz months riding, I would tend to think not. If anything, the chain might be gone, but you have to be riding a ton. If you ride enough to have worn the chainrings already, then you should be trying out with Lance. One way to keep from dropping the chain on the climbs is to shift before you put a lot of pressure on the pedals. Anticipate your shifts, and you can keep from having this happen and keep your speed up.

-Moab

Originally posted by Sailguy
Does it derail or just miss for a few pedal strokes?

The chain drops to the BB. Quite scarry sometime because I am using clipless. :eek:

Hook yourself up with one of these. (http://www.gvtc.com/~ngear/)

It will keep the chain in place.

Thank you guys!

Firebolt,

You can find many different devices to keep the chain from dropping onto the bottom bracket. Some only do this, while others just keep the chain from getting caught between the chainrings and the bottom bracket, something known as "chain suck." If you check a few sites, you should find a few different models. I think www.cambriabike.com had some last time I checked. First, I would try to ensure that the der. is adjusted right, and then go for one of these. Some bikes seem to have a reputation of have more problems with chain suck than others, so it might be necessary. Good luck!

-Moab

Getting a front der adjustment just right can be pretty difficult. Has anyone had the crank or any of the rings off? If so, it is possible that they didn't get the granny back on right, and spacing is off. If the space between the middle and granny is the same as the space between the middle and big, this isn't the problem.

Are you using standard sized chainrings for your system I pushed my Campy road triple to the extreme with a 26t granny, and it sometimes threw onto the BB.
What rear cog are you on when you attempt the change. I usually shift to the 2nd largest cog before engaging the granny. If you are in one of the smaller cogs, the chainline way be way off for the granny ring.
Check the alignment of your front mech, its rotation and its height from the large ring

Originally posted by Sailguy
Hook yourself up with one of these. (http://www.gvtc.com/~ngear/)

It will keep the chain in place.

That is cool!!!

I just put my money where my mouth was and bought a jump stop today. I will need it when I install my extra-small granny. It will truly be a throw and pray scenario with it in place.