How to tell difference between Bottom & Top pull Front M — BikeRadar
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How to tell difference between Bottom & Top pull Front M
edited June 2009
As the heading says guys I know it seems stupid but can someone please advise.
All the best
A top pull front mech will be controlled by a cable running along the top-tube, then down the frame, just below the saddle and down to the mech.
A bottom pull front mech will have the cable routed via the downtube, under the bottom bracket (where the cranks are) and up to the front mech, pulling from below.
They both do the same job of shifting the front mech in & out against the resistance of the spring in the mech, just from different directions.
How the cable happens to be routed on any particular bike depends on the designers choice, but is sometimes dictated by the frame design (such as on mountain bikes where there's a gap in the seat tube to allow for rear suspension, for instance).
Alternatively, if the mech's not connected to anything and you want to check, just make the cage move and watch where the fixing bolt goes. If it moves down as the cage moves out, it's bottom pull. If it moves up, it's top pull.
some bikes with top tube routed cables still use bottom pull and have a travel changer (pulley) on the seat tube.
"Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
99.9% of road and cross bikes use bottom-pull mechs - top pull are generally used on MTBs, particularly frames with rear suspension or to avoid mud clogging the under-BB cable routing. Not many MTB mechs fit a road frame as there isn't a big enough gap between the rear wheel and the seat tube.
Make mine an Italian, with Campagnolo on the side..