Bicycle Mechanics - My Chain Flicks Off

I have a problem when shifting down while pedaling. My chain flicks off to the right. I am using a single used 39 tooth chain ring at the front, with a new 9 speed derailleur, new 9 speed chain but old cranks which I believe to be only 7 - 8 (?) speed. See below...
I do have a 9 speed set of cranks but am waiting for the compatible BB to come. Would this solve it?
Thanks Steve.
http://i6.photobucket.com/albums/y214/giantcfr1/My%20Bikes/zzzzgiant003.jpg

By "shifting down", do you mean move the chain to the right on the rear cogs into higher (tougher) gears? Could be a chainline issue where the rear cogs aren't aligned with the chainring in front.

I have a problem when shifting down while pedaling. My chain flicks off to the right. I am using a single used 39 tooth chain ring at the front, with a new 9 speed derailleur, new 9 speed chain but old cranks which I believe to be only 7 - 8 (?) speed.

Apparently that is common when using a rear derailleur without the front. Shifting in the rear sends a wave forward along the chain, the effects of which would have been stabilized by the front derailleur cage.



I do have a 9 speed set of cranks but am waiting for the compatible BB to come. Would this solve it?

Why don't just change the chainring, if you're concerned?

^^^.....Doesn't happen with any of mine,and what good does changing a chainring do?

^^^.....Doesn't happen with any of mine,and what good does changing a chainring do?

The pedaling is likely a contributing factor. Another may be a tendency to shift by more than one gear. Since it is the chainring thickness that matters for the speeds, what is the point in chainging the whole crankset+BB?!

Tensioner. The chain jumps when on the small cluster cogs?
Or when curb jumping?
Also if you are running the same length chain to do a bigger ring =too long.
http://www.bikeforums.net/showthread.php?p=1612076

Cranks don't have speeds. Chainrings fine I'd say.
I run similar though 7 spd, offroad. Lower speed -larger chain to avoid it breaking.
There are many guides\tensioners to choose from. Mines kinda cheap and brutal looking.
Works GREAT!

Thankyou for the advice.
The Tensioner looks like a good idea.
DannoXYZ yes, that's what I meant.
I was thinking about moving the chain ring to the inside of the cranks and putting a thingy where the larger ring would normally sit. (Help Sydney, the ring that I see on older style bikes which helps prevent the chain slipping off and from getting grease on your daks) I saw a guy use a large chain ring with the teeth grinded off.
Steve.

Consider fitting a front derailleur and adjust it so the cage sits centered over your single chainring by using the inner limit stop screw. You won't need a cable or shifter and it will be no heavier than a "ring guard".

Remember a rider (David Millar?) who lost the Tour de France Prologue because his chain came off a single chainring? His team mechanic had removed the front derailleur to save a few grams.

BTW, the chainring you are using looks like a modern design with ramps and other shifting aids. That is exactly what you don't want. A flat, old style chainring may be less of a problem.

Since it is the chainring thickness that matters for the speeds, ...........That's nonsense.

Consider fitting a front derailleur and adjust it so the cage sits centered over your single chainring by using the inner limit stop screw. You won't need a cable or shifter and it will be no heavier than a "ring guard".

Remember a rider (David Millar?) who lost the Tour de France Prologue because his chain came off a single chainring? His team mechanic had removed the front derailleur to save a few grams.

BTW, the chainring you are using looks like a modern design with ramps and other shifting aids. That is exactly what you don't want. A flat, old style chainring may be less of a problem. Looks like an unpinned unramped inner 39 to me. My setups all do use old flat rings tho.

Well I'm pretty sure I can get my hands on a flat chain ring and I also have the old front derailleur. I'll start experimenting.
Thanks Steve.

The Tensioner looks like a good idea.


The devices sold as tensioners for standard bikes operate on the return side, while your problem appears to be on the drive side. What you need is usually referred to as the chainguide, though the tensioner term may be also used somewhere in the device description. In any case, this should have a guiding pulley on the drive side. An alternative, already mentioned, is to put a front derailleur.

The devices sold as tensioners for standard bikes operate on the return side, while your problem appears to be on the drive side. What you need is usually referred to as the chainguide, though the tensioner term may be also used somewhere in the device description. In any case, this should have a guiding pulley on the drive side. An alternative, already mentioned, is to put a front derailleur.


This particular contraption:

http://www.cambriabike.com/shopexd.asp?id=16907

with figure enclosed, having a guiding cage on the drive side and few other shown at Cambria might be good.

The devices sold as tensioners for standard bikes operate on the return side, while your problem appears to be on the drive side. What you need is usually referred to as the chainguide, though the tensioner term may be also used somewhere in the device description. In any case, this should have a guiding pulley on the drive side. An alternative, already mentioned, is to put a front derailleur.

I run a lower pulley return -stops all chain slip -offroad...?
Chainguides are noisy. Effective, but the tensioner adds drive effectiveness.
I pull 4 more teeth at all time, less wear, more torque. No derailer mis-fires, no derailer hitting the frame -no chainslap.
Now that the mech is put on -I can adapt the design as I need to -box guide plastic easy, make one.
The mech requires the bb to be pulled? Threaded and bolted to the bb.
The chain tension systems I think must be bb mounted.

I took the easy way out and put the front derailleur on (without cables etc) and it is working like a dream.
Looks silly, but I looked more silly on the side of the road putting the chain back on.
Thanks everyone,
Steve.