SRAM Force Front Derailleur problems, questions
06-26-11, 08:23 PM
#1
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SRAM Force Front Derailleur problems, questions
I have a fairly new SRAM Force group (~1300 miles) and front shifting is a little rough.
My LBS has had trouble dialing in the adjustment so that I get smooth shifting with no chain drops. They have a call into SRAM tech support to see if there is an issue with this derailleur. The upper limit screw is all the way out, turning it in at all prevents upshifts.
One thing that I noticed is that I have a trim adjustment on the large ring, but I never need it.
Any thoughts?
My LBS has had trouble dialing in the adjustment so that I get smooth shifting with no chain drops. They have a call into SRAM tech support to see if there is an issue with this derailleur. The upper limit screw is all the way out, turning it in at all prevents upshifts.
One thing that I noticed is that I have a trim adjustment on the large ring, but I never need it.
Any thoughts?
06-26-11, 08:52 PM
#2
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Did you check the chain line?
If you need to set the FD at the outer end of it's range, it might be because your cranks are too far outboard. This can be more of a problem if you have a steel frame with a 1-1/8" seat tube.
A smaller seat tube moves the FD inboard, it has to reach farther to reach the rings.
If you need to set the FD at the outer end of it's range, it might be because your cranks are too far outboard. This can be more of a problem if you have a steel frame with a 1-1/8" seat tube.
A smaller seat tube moves the FD inboard, it has to reach farther to reach the rings.
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FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
06-27-11, 06:56 PM
#3
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Thread Starter
Did you check the chain line?
If you need to set the FD at the outer end of it's range, it might be because your cranks are too far outboard. This can be more of a problem if you have a steel frame with a 1-1/8" seat tube.
A smaller seat tube moves the FD inboard, it has to reach farther to reach the rings.
If you need to set the FD at the outer end of it's range, it might be because your cranks are too far outboard. This can be more of a problem if you have a steel frame with a 1-1/8" seat tube.
A smaller seat tube moves the FD inboard, it has to reach farther to reach the rings.
I have Force cranks on a Trek Madone 4.7 frame with a 34.9mm seat tube.
06-27-11, 07:09 PM
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Chainline for doubles is measured from the central plane of the bike to the middle of the crankset (middle chainring of a triple, or center of the gap on a double).
Measure from the top of the teeth of the outer Chainring to the downtube. Add 1/2 the diameter of the downtube. That will give you the distance from the outer ring to the center of the frame. Now subtract 3-4mm (half the gap between the rings) to get the chainline. The target range is about 43-44mm, but there's some room.
But as I said, if you're at the outer end of the FDs travel range, you want to move the crankset in if at all possible. Look at the clearance between the inner ring and chainstay, and if it's there's room to bring it in a few millimeters do so.
Measure from the top of the teeth of the outer Chainring to the downtube. Add 1/2 the diameter of the downtube. That will give you the distance from the outer ring to the center of the frame. Now subtract 3-4mm (half the gap between the rings) to get the chainline. The target range is about 43-44mm, but there's some room.
But as I said, if you're at the outer end of the FDs travel range, you want to move the crankset in if at all possible. Look at the clearance between the inner ring and chainstay, and if it's there's room to bring it in a few millimeters do so.
__________________
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
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