Hello People.
I'm building a hybrid bike on a 700c frame with 135mm spacing and 68mm BB shell.
I have a Dura Ace 7703 road triple which I plan to use with a 9 speed road cassette.
The obvious choice of bottom bracket seems to be the Dura Ace 7703 68mm with 118.5mm spindle.
As I understand (quite possibly wrong!) this would give me a front chainline of 45mm whilst the MTB hubs will give me a rear chainline of 47.5-50mm. Will this cause problems?
I've read Sheldon's articles on BB sizing and chainline, but as I haven't purchased all of the required parts I can't take any measurements. Any advice would be welcomed.
Cheers, Pete.

Where did you get the chainline specification for the Dura Ace triple from? My understanding is that most triples have a theoretical chainline of 46.5 mm with the correctly specified BB but that's just the spec anyway. My experience is that often the real chainline is wider than specified so I wouldn't be woried that the front chainline will be too narrow. Currently I have a triple crank that theoreticaly should be fitted to a 113 mm BB spindle for a 46.5 mm chainline but infact I have it fitted to a 108mm BB spindle with a 2 mm BB spacer for a spot on 46.5 mm chainline. So if I had fitted the specified BB the chainline would be WAY to wide.

So my best advice is that it should work just fine but you are going to have to build it and then measure it to know for sure.

Regards, Anthony

As AnthonyG says, don't assume you need to use that 118.5 mm spindle just because you are mounting a triple crank. I have built several bikes with triples, including the D/A, and some have worked fine with a double BB (what is that, 109mm?) and gave excellent chainlines. Using spacers for that extra mm or 2 can make a huge difference; just watch your centerline.

If you already have the frame and crank you can see if your LBS had a used 109mm BB you can install to measure.

FWIW, if you forgo Shimano (and therefore OctaLink) there are several "mid-size" ISIS spindles out there, in the 115mm range.