help with chain falling off

chemgirl

Well-Known Member
I got a new Cannondale Synapse, and I have only about 6 rides on it so far. I'm doing my first triathlon next week and will be riding this bike, but I'm having problems shifting. I don't know if it's the bike or me:hmmm: I am very new to the road world.

If I'm pedaling slow, I can shift up into the big ring just fine. If I'm moving at 20+ mph and I shift up into the big ring, the chain moves onto the ring and then keeps going and falls off the outside of the ring. This happened everytime I shifted on my ride yesterday. I'm in a middle cog when I shift so it's not an issue of crossing the chain.

Anyone know why this is happening? I need to get it straightened out by next week. Is it something I'm doing or do I need my derailleur tweaked?
 

MixMastaMM

Team Bulldog Rider
I got a new Cannondale Synapse, and I have only about 6 rides on it so far. I'm doing my first triathlon next week and will be riding this bike, but I'm having problems shifting. I don't know if it's the bike or me:hmmm: I am very new to the road world.

If I'm pedaling slow, I can shift up into the big ring just fine. If I'm moving at 20+ mph and I shift up into the big ring, the chain moves onto the ring and then keeps going and falls off the outside of the ring. This happened everytime I shifted on my ride yesterday. I'm in a middle cog when I shift so it's not an issue of crossing the chain.

Anyone know why this is happening? I need to get it straightened out by next week. Is it something I'm doing or do I need my derailleur tweaked?

Bring it back to the shop where you bought it. Sounds like the cables have stretched a bit.
 

Norm

Mayor McCheese
Team MTBNJ Halter's
You need a tweak. The chain is just being thrown too far to the right (looking down) when you shift.

When you shift up, are you pulling the front derailleur as far to the right as it will go, letting the chain get on, and then releasing? If so, you can probably avoid this in the short term by just shifting and not pulling the derailleur that littlee xtra bit further than it will setlle at. You probably still need a tweak, but this may be able to help of you're wrenching it as far as it will go.
 

BiknBen

Well-Known Member
While cable stretch is often an issue on new bikes, this issue has to do with the limit screws of the Fr Der.

Front Derailleur Limit Screw Settings
Limit screws stop the inward and outward travel of the front derailleur cage. Limit screws are marked "L" and "H". The L-screw will stop the motion of the derailleur toward the smallest chainring. The H-screw will stop the motion of the derailleur toward the largest chainring.

The rest of the How-To can be found here:
http://www.parktool.com/repair/readhowto.asp?id=75
 

chemgirl

Well-Known Member
I feel incompetent. I'm definitely a chemist and not an engineer. Of course, my husband is away fishing in Alaska for 10 days, so the only help I have is from a 6 yr old.

I followed Bens tutorial. Screws aren't labeled L and H, but I tried to figure it out. The derailleur appears to be positioned perfectly but the chain is stilling coming off, and now the back seems to be skipping gears - ughh.

JDog, if you are reading this, I'll be at your shop on Monday with all three kids in tow:getsome:. I hope you can squeeze in a few minutes for me.

I was planning to do my first group road ride on Sunday...hopefully it won't involve shifting.
 

jimvreeland

Endurance Guy: Tolerates most of us.
If it doesn't have an L or H written on the derailleur, the bottom screw is usually "high"

-Jim.
 
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