Shuke

So when building up my new CAAD9 last night my friend and I were having problems getting the front shifting to work. When shifting from the small to the big ring the front derailleur cage would move too far to the outside of the big chainring and then move back towards the inside. I've had this problem on another CAAD9 and was puzzled until we flipped the bike over and looked at the cable routing along the underside of the bb shell.

The cause: the plastic piece used to route along the bb shell does not sit flush against the frame, leaving approximately 3-4mm of space between it and the shell. When shifting, this plastic piece actually flexes, resulting in inaccurate shifting.

The rinkydink solution: we wedged a piece of fat bartape between the bb shell and the cable guide, essentially making it impossible for that piece to flex when under load.

I'm always bothered when somebody that's supposed to work right doesn't and requires an outside of the box solution like this. However, I'm glad that it's working better now BUT it seems like kind of a ghetto-fab solution. Are there any suggestions on how to make this less....ghetto?

waldowales

If that black part is a cable housing, that is you problem, shouldn't be there.

Burton

Yeah - not exactly what I`d expect to have to do to a new bike.

Actually I`d have to say thats the longest unsupported guide I`ve ever seen to top it off. I guess if it was my bike I`d clean the area with alcohol and use a bed of epoxy to support that record length plastic guide. No chance that the epoxy will stick to the plastic indefinately, but if the paint is clean, it`ll certainly bond to that and if you do it to cup the sides at least in the exit area - it`ll prevent sidewise movement too.

Shuke

I was thinking about that but I don't really want to start glueing things in place with high strength adhesives. I was looking more along the lines of an after market cable guide that doesn't S a fat D. Oh well this is good enough. Front D still needs tweaking.

You do not grasp the concept.

time bandit

maybe cut a few mm of the fd guide off of the end?

fietsbob

Part purchased wholesale by cannondale may have been manufactured for common diameter
BB shells , and theirs is larger diameter , and they are not going to get custom molded parts.?
Perhaps some exist for oversize BBs , i don't know.

substitute a teflon coated cable?
But since I don't run Brifters or Indexing I have not had issues with metal guides.

You can get stainless steel tubing cheaply by just getting auto parts for the hydraulic brake lines
cut off the flared ends and remove the fittings, the tube is fairly soft and will bend to shape.
then get the stuff fabricated, joined with some silver brazing, to replace the piece that is on there..

Kimmo

I'd take the guide off, and put some sort of thin tape (the clear stuff is prolly good if you can get it on without any folds) along the area on the BB covered by the poorly-fitting guide.

Then I'd re-fit the guide without the cables, letting it sit how it wants, and fill the gap underneath it with some of this stuff.

When it's set (10 min), remove the guide and tape, and clean it up with a file or blade.

DOS

I am having a hard time visualizing how a little flex in the guide would throw off shifting so much if cable tension and limit screws were set correctly.

Above said, I have same cable guide on my C'dale CAAD7 but don't have BB30 shell. I have never had an issue so perhaps fietsbob is correct and guide isn't working well with the BB30. I haven't heard that this is a common issue with CAAD 9 so maybe you just got a bad one. I would get several differnt cable guides and experiment until I found one that worked satisfactorily.

LarDasse74

I don't have that exact bike but I am surprised the small amount of lateral flex can have any noticeable effect on shifting. I think you should take another crack at it without zip ties and bar tape.

MilitantPotato

Why not heat it up and bend it into the proper shape? I've boiled/held a lighter near many plastic dohickies and bent them to various shapes

Shuke

That's actually not a bad idea.

It's not the lateral flex that is the issue. It's the flex from where the guide sits regularly to the point where it is pressed against the frame. Even though the cable tension might be right, the guide flexes enough that there is deflection there instead of pulling the derailleur. The zip tie was a little overkill. I'm fixing my other caad9 at the moment using the bartape method.

reptilezs

use the 4th hand tool to set cable tension. i doubt the bb guide can overcome the spring tension of a fd

Shuke

That's the exact issue. If the plastic wasn't so flexible then I wouldn't be having this issue.

corkscrew

He's saying that your cable tension is set to low (hence referring to the 4th hand tool to properly pull the cable). Really if something is installed correctly, the FD spring would be holding the cable guide in it's bent position.