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Derailleur Swing(6 posts)

Derailleur SwingDaniel
Jan 10, 2002 1:35 PM
I am in the process of rebuilding my mountain bike. Would someone please explain to me the differences between top and bottom swing for a front derailleur. Which is better? Are they interchagable?

Thanks

Daniel
Derailleur pull...C-40
Jan 10, 2002 3:51 PM
Don't you mean top-pull versus bottom-pull? A bottom pull derailleur is the type found on most road bikes and older MTB's. The draillleur cable is routed under the bottom bracket shell and pulls from the bottom. A top pull derailleur is used on newer MTB's to get the cable away from the dirty bottom bracket area. The cable is routed along the top tube and down the seat tube. The cable pulls from above, hence the term top-pull. They aren't interchangeable.
Derailleur pull...Daniel
Jan 10, 2002 4:37 PM
Thank you for your kind reply, but I do not mean top pull v. bottom pull. On some mountain front derailleurs the clamp is below the cage, on others it is above.

Daniel
Derailleur pull...Rusty Coggs
Jan 10, 2002 4:48 PM
I have diagrams of how they work,but do not know which is best or what determines which to use. You might get a better answer at the drivetrain forum at www.mtbr.com
re: Derailleur SwingTFerguson
Jan 10, 2002 4:47 PM
I believe this is in the correct order: Road bikes use bottom pull/bottom swing. They look taller than a current mtb bike. Early mtbs were modeled after road bikes and also used bottom pull/bottom swing. However, the cable routing under the bottom bracket for a bottom pull was a disaster (always full of mud) on mtbs, so they went to top pull. Top pull seems to work best with top swing so this is where current mtbs are. However, some dual suspension mtbs do not have room for the top swing cable connection so they need a top pull/bottom swing. So the answer is that most mtbs can use either top or bottom swing, but the top swing is preferred.
I'd use what was there before.nee Spoke Wrench
Jan 11, 2002 6:19 AM
You can almost never replace just one part on a bicycle.

If your bike previously had a top-swing derailleur, you're likely to find that a traditional derailleur will interfere with the water bottle braze on. If you try to do the opposite, you may find your bike has an ovalized seat tube that won't take the top swing mount.