Replacing Front Mech
 

Hi,

I have a Bianchi Sempre Pro 2013 with Ultegra groupset.

I need to source a new front mech (can't spell that french word) as the cage is bent on the existing one. It's the FD-6700 band-on type. I'm struggling to figure out the diameter I need. I don't have calipers so trying to do it with a piece of string and a tape measure. My best attempt is the circumference of the seat tube is 120mm, which would equate to a diameter of 38mm. So I'm thinking I probably need the 34.9mm version?

Did Shimano do different product codes for the different diameters? My googling has so far drawn a blank. I.e. if i take the existing one off can I locate a product code somewhere that will confirm what diameter it is?

Thanks,

Alan

I cannot answer your question, but you can call it an 'FD'

I'll help you with the spelling. D e r a i l l e u r. Not hard.

You can buy an exact replacement on eBay right now. Plenty of them. Is your set-up top or bottom pull? There's also a shim kit to help with various tube sizes.

Also, why not simply straighten the cage on the one that you have?

Also, why not purchase a digital caliper for these measurements? It's a pretty basic tool for a mechanic. Useful for inner and outer dimensions, plunge depth, etc.

In many cases, the diameter will be stamped on the derailleur clamp, often on the inside. Remove the current derailleur and check. Then buy a replacement with the same diameter.

Look inside the band clamp of your current derailleur, the diameter should be engraved on it. (Whoops, John typed faster than I did)

You don't need a "digital" caliper. Dial calipers are just as accurate, les expensive and more rugged. Even a very cheap plastic caliper is adequately accurate for what you are likely to need it for.

Also, you don't need an exact match to that derailleur. A "braze-on" version with a separate adapter clamp will also work and may be more easily found.

Yep, it's stamped on the inside - 34.9.

Thanks a lot.