Bicycle Mechanics - Front Derailleur won't reach big ring
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I have sugino triple crank, 48-36-24, 118 bottom bracket, and a tiagra fd4503 triple FD. The limit screw is nearly backed out, it still won't get to the big ring. Sugino recommends 118-110 BB, if I back off to the 110, my cranks should clear, will that make it work?
First make sure that your problem is related to the throw of the derailleur. Activate it by either pushing down on the lever arm directly or by pulling the wire away from the downtube like a bowstring. Adjust the limit until it shifts, or you've proven it can't.
If it can shift by the bow string method, then the FD is fine and it's matter of cable length. If it cannot shift by the bowstring method, your chainrings are too far outboard, and you need to shorten the spindle (or change shims on some BBs) to bring the crank in. Don't forget to check the chainstay clearance before bringing the crank in.
It simply won't throw far enough. I should have room. If i go to a 110, that's 4mm on each side, right? Thanks for your help.
I'm assuming you're speaking of square taper spindles. If so, they're not all symmetrical and you need to check a spindle length chart (http://www.sheldonbrown.com/bbsize.html) for your best choice.
Before buying, confirm the available chainstay clearance, and how far short the FD travel is to make the decision. You might also check your chainline by measuring from the middle chainring to a frame tube, and adding 1/2 the diameter of the tube.
04-09-11, 03:59 PM
Do you for sure have a three position shifter? If you're trying to shift to a 3third position with a 2 position only shifter than it won't work since you're not pulling enough cable.
If you're pulling the cable with no issue but it just gets tight then what the others posted about the BB being the wrong length would be my next answer.
04-09-11, 08:49 PM
I use a 113 bottom bracket with that crank. 105 fd and a 28.6 seat tube.
Switched to 113 BB, problem solved.
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