Throwing the chain

[phuufme]

So, I need some help. For background, I have ultegra components (including the front deraillier), with a 53/39 front chainring, 12 - 27 rear cogs. I just bought my new Calfee with the ultegra components and I am throwing the chain at least 2x on every 25 mile ride. It occurs when I shift down from the 53 to the 39. I have been to the LBS and he says "the screws are properly adjusted so it must be operator error".

I went to his shop and he was nice enough to let me sit on my bike on a trainer in the store as he watched me shift. He "corrected" my operator error but I am still throwing the chain. I cannot recreate the problem when I am not on the bike (i.e. it shifts cleanly on the stand).

In the past I had an ultegra triple and I NEVER threw the chain. This LBS built up a bike for my good friend last year (53-39 & 12-25), and he NEVER throws the chain. So, is it me?

Any ideas? Its getting frustrating and I am now reluctant to make shifts without carefully watching the chainring, so I am very inefficiently shifting right now. Help!!

Thanks.

 

[dhk]

Steve: Not sure what "operator error" means, but since your old triple bike never threw the chain, don't think it's you.

First, do you have the correct 9 sp chain and chainrings? Believe the 9 sp inner ring is machined to mount up closer to the outer ring (vs the older 7/8 sp) to accomodate the thinner chain.

What is happening when the chain throws? Does it come off the inside of the 39, and end up sitting on the BB shell when you do a fast shift? If so, I'd think the limit screw on the front derailleur still may need small adjustment.

Did the LBS check chain length/tension also? If your chain is correct length, I am told the rear deraileur pulley axles should be vertical when you shift up to high gear (53/12).

Dan

 

[phuufme]

Originally posted by dhk
Steve: Not sure what "operator error" means, but since your old triple bike never threw the chain, don't think it's you.

First, do you have the correct 9 sp chain and chainrings? Believe the 9 sp inner ring is machined to mount up closer to the outer ring (vs the older 7/8 sp) to accomodate the thinner chain.

Well, the LBS ordered it and since it is new stuff I am assuming its the right stuff.

What is happening when the chain throws? Does it come off the inside of the 39, and end up sitting on the BB shell when you do a fast shift? If so, I'd think the limit screw on the front derailleur still may need small adjustment.

Yes it comes off the inside of the 39 and ends up sitting on the BB shell when I do a fast shift, that is exactly it. Which limit screw do you think I need to adjust? I have sort of played with the inside one a bit and moved it towards the outside. Do you think I need to adjust the outer limit screw a little more outside? Or is it the inner limit screw?

Did the LBS check chain length/tension also? If your chain is correct length, I am told the rear deraileur pulley axles should be vertical when you shift up to high gear (53/12).

Dan

I will check this.

Thanks, Dan.

 

[daveornee]

Originally posted by phuufme
Well, the LBS ordered it and since it is new stuff I am assuming its the right stuff.

Yes it comes off the inside of the 39 and ends up sitting on the BB shell when I do a fast shift, that is exactly it. Which limit screw do you think I need to adjust? I have sort of played with the inside one a bit and moved it towards the outside. Do you think I need to adjust the outer limit screw a little more outside? Or is it the inner limit screw?

I will check this.

Thanks, Dan.

Check chain length, FD height, FD angle. inner limit on FD should be set such that when the chain is in 39 front and largest back cog and under load it just barely clears the inside of the cage.
You might also check the "B" screw on the RD for correct adjustment.
You can see the adjustment information on the Shimano web site at URLs:
http://bike.shimano.com/product_images/FD/si_images/FD_6500_SI.pdf
http://bike.shimano.com/product_images/RD/si_images/RD_6500_SI.pdf

 

[phuufme]

Originally posted by daveornee
Check chain length, FD height, FD angle. inner limit on FD should be set such that when the chain is in 39 front and largest back cog and under load it just barely clears the inside of the cage.
You might also check the "B" screw on the RD for correct adjustment.
You can see the adjustment information on the Shimano web site at URLs:
http://bike.shimano.com/product_images/FD/si_images/FD_6500_SI.pdf
http://bike.shimano.com/product_images/RD/si_images/RD_6500_SI.pdf

Wow, David, thanks. I have some reading to do.