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#1
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rear der adjustment
I changed out my rear wheel for my wife's, and now it won't shift to the
highest gear. Both are Shimano nine-speed. The derailer is c. 2000 Ultegra. My wheel was a low-end Mavic rim with some whatever hub. Hers is a Rolf Sestriere. Low gears are fine, and shifting is otherwise okay. I tried the H limit screw on the derailer. The derailer hanger seems aligned fine. I reviewed Sheldon's page. Any suggestions? -- JF "Here comes the lightening and here comes the thunder. Ride on the storm and take it to the sea. " - Jim Hunter |
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#2
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rear der adjustment
On 2008-03-15, Jim F wrote:
I changed out my rear wheel for my wife's, and now it won't shift to the highest gear. Both are Shimano nine-speed. The derailer is c. 2000 Ultegra. My wheel was a low-end Mavic rim with some whatever hub. Hers is a Rolf Sestriere. Low gears are fine, and shifting is otherwise okay. I tried the H limit screw on the derailer. The derailer hanger seems aligned fine. I reviewed Sheldon's page. Any suggestions? If the limit screw isn't what's limiting it then the cable may be too tight. |
#3
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rear der adjustment
Jim F wrote:
I changed out my rear wheel for my wife's, and now it won't shift to the highest gear. Both are Shimano nine-speed. The derailer is c. 2000 Ultegra. My wheel was a low-end Mavic rim with some whatever hub. Hers is a Rolf Sestriere. Low gears are fine, and shifting is otherwise okay. I tried the H limit screw on the derailer. The derailer hanger seems aligned fine. I reviewed Sheldon's page. Any suggestions? Check that it's aligned, set the limit screws and double check by shifting smartly with your left thumb before connecting the gear wire. -- Andrew Muzi www.yellowjersey.org Open every day since 1 April, 1971 |
#4
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rear der adjustment
"Ben C" wrote...
If the limit screw isn't what's limiting it then the cable may be too tight. Bingo. That, plus I opened it up half a turn. Thanks, -- JF "Here comes the lightening and here comes the thunder. Ride on the storm and take it to the sea. " - Jim Hunter |
#5
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rear der adjustment
On Mar 15, 5:29 pm, "Jim F" wrote:
"Ben C" wrote... If the limit screw isn't what's limiting it then the cable may be too tight. Bingo. That, plus I opened it up half a turn. Thanks, -- JF "Here comes the lightening and here comes the thunder. Ride on the storm and take it to the sea. " - Jim Hunter The only thing the high and low limit screws do is limit how far a derailleur can move in either direction. That adjustment can be made without a cable being attached. After that how well the indexing works is determined by cable tension. There are videos on Utube that explain the concept very well. |
#6
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rear der adjustment
Dave wrote:
On Mar 15, 5:29 pm, "Jim F" wrote: "Ben C" wrote... If the limit screw isn't what's limiting it then the cable may be too tight. Bingo. That, plus I opened it up half a turn. Thanks, -- JF "Here comes the lightening and here comes the thunder. Ride on the storm and take it to the sea. " - Jim Hunter The only thing the high and low limit screws do is limit how far a derailleur can move in either direction. That adjustment can be made without a cable being attached. After that how well the indexing works is determined by cable tension. I find that a very confusing description 'adjusting cable tension'. The tension is determined by de spring in the derailleur. You adjust the POSITION of the upper pulley with barrel adjuster. Lou |
#7
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rear der adjustment
On 2008-03-16, Lou Holtman wrote:
Dave wrote: On Mar 15, 5:29 pm, "Jim F" wrote: "Ben C" wrote... If the limit screw isn't what's limiting it then the cable may be too tight. Bingo. That, plus I opened it up half a turn. Thanks, -- JF "Here comes the lightening and here comes the thunder. Ride on the storm and take it to the sea. " - Jim Hunter The only thing the high and low limit screws do is limit how far a derailleur can move in either direction. That adjustment can be made without a cable being attached. After that how well the indexing works is determined by cable tension. I find that a very confusing description 'adjusting cable tension'. The tension is determined by de spring in the derailleur. You adjust the POSITION of the upper pulley with barrel adjuster. If the derailleur is on its lower limit screw and you turn the barrel you will be increasing tension in the cable. |
#8
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rear der adjustment
Ben C wrote:
On 2008-03-16, Lou Holtman wrote: Dave wrote: On Mar 15, 5:29 pm, "Jim F" wrote: "Ben C" wrote... If the limit screw isn't what's limiting it then the cable may be too tight. Bingo. That, plus I opened it up half a turn. Thanks, -- JF "Here comes the lightening and here comes the thunder. Ride on the storm and take it to the sea. " - Jim Hunter The only thing the high and low limit screws do is limit how far a derailleur can move in either direction. That adjustment can be made without a cable being attached. After that how well the indexing works is determined by cable tension. I find that a very confusing description 'adjusting cable tension'. The tension is determined by de spring in the derailleur. You adjust the POSITION of the upper pulley with barrel adjuster. If the derailleur is on its lower limit screw and you turn the barrel you will be increasing tension in the cable. Yeah by 0.001% or something. The main purpose is POSITIONING the upper pulley, by in- or decreasing the length of the outer cable between two cable stops. The tiny weeny in- or decrease of the tension, which you can not feel in the cable, is a side effect. Why not call by the right name instead of that voodoo bicycle tech talk nobody 'not in the business' understands. It's like calling shifting to another gear in- or decreasing cable tension. Lou |
#9
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rear der adjustment
On 2008-03-16, Lou Holtman wrote:
Ben C wrote: On 2008-03-16, Lou Holtman wrote: [...] I find that a very confusing description 'adjusting cable tension'. The tension is determined by de spring in the derailleur. You adjust the POSITION of the upper pulley with barrel adjuster. If the derailleur is on its lower limit screw and you turn the barrel you will be increasing tension in the cable. Yeah by 0.001% or something. The main purpose is POSITIONING the upper pulley, by in- or decreasing the length of the outer cable between two cable stops. Why the outer cable? The way I assume it works is like this: the shifter is clicked into the position for third gear (for example). You set the (inner) cable length to just the right length to position the derailleur nicely on third gear. You should now hit the other gears correctly as the shifter changes the cable length by the right amount for the distance between gears. The tiny weeny in- or decrease of the tension, which you can not feel in the cable, is a side effect. Why not call by the right name instead of that voodoo bicycle tech talk nobody 'not in the business' understands. Anyway if you did rack up the tension with the derailleur on the lower limit screw you wouldn't achieve anything useful. It's like calling shifting to another gear in- or decreasing cable tension. Which it isn't. As you say it's the cable length you're setting here and the tension is always the same and determined by the derailleur spring. |
#10
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rear der adjustment
tension is determined by de spring in the derailleur. You adjust the
POSITION of the upper pulley with barrel adjuster. If the derailleur is on its lower limit screw and you turn the barrel you will be increasing tension in the cable. Yeah by 0.001% or something. The main purpose is POSITIONING the upper pulley, by in- or decreasing the length of the outer cable between two cable stops. The tiny weeny in- or decrease of the tension, which you can not feel in the cable, is a side effect. Here's how I would describe the physics. You apply a torque to turn the barrel, which transmits a force to the cable and pulls it a little harder - this pull is the cable tension. The other end of the cable transmits this pull to the derailleur. As the derailleur moves, its spring lengthens, and the spring force increases to balance the increased cable tension. Look at it this way. If the derailleur spring was replaced by something like a solid rod, the derailleur would hardly move, and cable tension would have to be increased a lot for a tiny bit of movement. On the other hand, if the spring was very weak, a small increase in cable tension would cause a large movement. If you find it clearer to refer to cable length instead of tension, that's fine. But I think it's wrong to call the tension increase a "side effect," as it's the increase in tension that causes everything else to happen. Barry |
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