Changing the SIS unit in downtube shifters
08-10-10, 09:40 PM
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Changing the SIS unit in downtube shifters
Just curious, given a Shimano Dura-Ace 8-, 9-, or 10-speed downtube shifter, could you make it shift one of the other number of speeds by changing just the SIS unit?
This Shimano tech doc for 7700 9-speed or 8-speed* downtube shifters looks a lot like this one for 7800 10-speed levers. I'm no mechanic, but it looks like the SIS units are interchangeable, and you can buy them here for $30 - $50.
*I thought 7700 was only 9-speed, so I'm a little confused about the tech doc saying 8-speed.
I don't plan on doing this, it just crossed my mind that it might be possible.
This Shimano tech doc for 7700 9-speed or 8-speed* downtube shifters looks a lot like this one for 7800 10-speed levers. I'm no mechanic, but it looks like the SIS units are interchangeable, and you can buy them here for $30 - $50.
*I thought 7700 was only 9-speed, so I'm a little confused about the tech doc saying 8-speed.
I don't plan on doing this, it just crossed my mind that it might be possible.
08-10-10, 10:08 PM
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"8/9" usu. means it'll work on either one (click-stop spacing is the same, or close enough for "government work..."), but cable tension and high/low limit are presumed to be set correnctly on an 8-er that one click-stop just won't be used.
08-11-10, 07:17 AM
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I don't think that's correct as 8 and 9-speed cassette spacing are not the same. What the shifters refer to is that they will work with 8 or 9-speed rear derailleurs. The 7700-series was 9-speed Dura Ace so the shifter index spacing is for 9-speed.
