Bicycle Mechanics - Help! Cyclocross drivetrain compatibilty issues
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01-20-06, 10:57 AM
I'm trying to salvage a bike-build project--see my last post about chainrings at "need help finding the right chainrings" in this section. In short, we have a cyclocross frame w/ top pull cables, to which we've been adding parts harvested from an old roadbike & other parts we've bought. After reading about chainrings on Peter White's webpage, I phoned him up to ask questions. He is of the opinion that parts of our drivetrain are incompatible. I wanted to use the STI shifters from my old Trek 1220 (which had a 7-speed cassette in back & a triple in front). Because of the top-pull cables, we've put on a Shimano Deore LX front derailleur, and in back, a 9-speed cassette w/--whoops, I'm not at home & don't have the derailleur model, but it was a top-pull Shimano of some sort. White says the top pulls wont work with the STIs and seemed to suggest that my options were to change the frame (!!!) or lose the STIs in favor of bar end shifters. ?? I looked up the Novarra cross bike I'd love to have (the Rivet) to see what they had put together, and saw that it has top-routed cables and STIs.
Does anyone understand this? Is it just the derailleurs that are the problem?
01-20-06, 11:12 AM
Peter is right. MTB front derailleurs have different geometry and require different cable pull than road derailleurs and won't work with STI shifters.
I've seen top run cables for a road front derailleur but they have to fit an anchor or adapter so the actual pull is from the bottom. Look closely.
01-20-06, 11:57 AM
What you need is a bottom pull road front deraileur, and a clamp on pulley. Like this one:
01-20-06, 04:25 PM
The Novara Rivet uses a Tiagra front derailer. The pictures on REI's website do not show the pulley, but it has to be there, because the picture of the crank shows a bottom pull front derailer mechanism.
Shimano MTB and road front derailers use different amounts of cable pull, but Shimano MTB and road rear derailers use the same amount of cable pull.
01-20-06, 07:38 PM
Oh! That clamp-on pully is brilliant! Thanks so much.
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