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Old 10-01-06, 12:11 PM   #1
cuda2k
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SIS Downtube shifters: difference between 7 and 8sp sets

If memory serves me right, it has been mentioned that what makes SIS 7 and 8 speed shifters index is the design of the small plastic coverings that go on first over the shifter bosses. Is this correct?

And if so, then would it follow that in order to get my 7speed shifters to work CORRECTLY with my 8speed cassette, would be to get the correct cover to adjust the click throws?

The 7speed + friction move to the 8th gear works pretty well. But it's not perfect. I get odd phantom shifts perodically, usually when I least need them. So getting a correctly matched set of shifters on this bike sure would be nice. I did a search and not much popped up to confirm this issue.

Oh, and if my assumptions above are correct, and anyone knows where they could find me a 8speed boss cover (or full set of shifters), send me a shout!
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Old 10-01-06, 12:48 PM   #2
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Quote:
Originally Posted by cuda2k
If memory serves me right, it has been mentioned that what makes SIS 7 and 8 speed shifters index is the design of the small plastic coverings that go on first over the shifter bosses. Is this correct?

And if so, then would it follow that in order to get my 7speed shifters to work CORRECTLY with my 8speed cassette, would be to get the correct cover to adjust the click throws?

The 7speed + friction move to the 8th gear works pretty well. But it's not perfect. I get odd phantom shifts perodically, usually when I least need them. So getting a correctly matched set of shifters on this bike sure would be nice. I did a search and not much popped up to confirm this issue.

Oh, and if my assumptions above are correct, and anyone knows where they could find me a 8speed boss cover (or full set of shifters), send me a shout!
I don't know about the boss cover Cuda but why not just stake out ebay for a few weeks untils the shifters you desire come along. They shouldn't be too hard to find.
On a different subject: did you get your Flyte frame yet? I picked mine up last Thursday since I live near the warehouse, its still wrapped in foam though.
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Old 10-01-06, 12:55 PM   #3
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I've been watching for 8sp units, but honestly, like the look of the ones I have now better. Just wanted to confirm if it was the boss covers that controlled the indexing as I had read somewhere. (and if memory serves me right from when I put the levers on, makes sense from what I saw on the backside). I'm asking for another reason also: when I bought these shifters they were in a trade with a fellow BF member who got them from his LBS for me in exchange for a set of bar-end shifters I had. And this member specifically told me that they were supposed to be 8speed. On the way home with the shifters he lost one of the boss covers and returned to his shop for another one before sending them out to me. Upon installing the shifters, playing with them a bit, it was discovered that they were shifting only 7speeds. Since it worked pretty well I didn't say anything to him at the time. Now the annoyance of the ghost shifting is growing on me and would like to get it shifting the proper 8.

Flyte should arrive Tuesday. Unfortunately unless I win the lotto or my Holiday bonus from work is bigger than expected, it will be spring before I build her up. Have all the parts picked out, just don't have the $$ right now to move forward.
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Old 10-01-06, 01:30 PM   #4
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The boss covers aren't responsible for the indexing. What you want is 8sp levers. Have you checked your local shops for some cast-off 8sp levers yet?
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Old 10-01-06, 01:39 PM   #5
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Quote:
Originally Posted by cuda2k
If memory serves me right, it has been mentioned that what makes SIS 7 and 8 speed shifters index is the design of the small plastic coverings that go on first over the shifter bosses. Is this correct?

And if so, then would it follow that in order to get my 7speed shifters to work CORRECTLY with my 8speed cassette, would be to get the correct cover to adjust the click throws?

The 7speed + friction move to the 8th gear works pretty well. But it's not perfect. I get odd phantom shifts perodically, usually when I least need them. So getting a correctly matched set of shifters on this bike sure would be nice. I did a search and not much popped up to confirm this issue.

Oh, and if my assumptions above are correct, and anyone knows where they could find me a 8speed boss cover (or full set of shifters), send me a shout!
the levers detach from the shifting pods (if that's what they are called). i'm not sure if the 8sp pod will fit on the 7sp levers. you never can tell with shimano.

loose screws used to sell the shifting pods. i used to wear out a rear shifter about once a year back in the day.

ed rader
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Old 10-01-06, 03:07 PM   #6
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Originally Posted by cuda2k
If memory serves me right, it has been mentioned that what makes SIS 7 and 8 speed shifters index is the design of the small plastic coverings that go on first over the shifter bosses. Is this correct?

And if so, then would it follow that in order to get my 7speed shifters to work CORRECTLY with my 8speed cassette, would be to get the correct cover to adjust the click throws?

The 7speed + friction move to the 8th gear works pretty well. But it's not perfect. I get odd phantom shifts perodically, usually when I least need them. So getting a correctly matched set of shifters on this bike sure would be nice. I did a search and not much popped up to confirm this issue.
The problem is that the cable-pull on the 7-speed levers is longer and moves the RD more to cover the wider spacing of 7-spd cogs. No way you can get 7-spd levers to work on 8-spd cassette without putting in wider 7-spd spacers. Then the cluster will be too wide to get the lockring on, so you have to remove the smallest cog and end up with a 7-spd. Just get some 8spd levers.
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Old 10-01-06, 03:25 PM   #7
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Danno - the difference between 7sp and 8sp is actually VERY small. Mainly because 7sp was on the older 128mm hub standard, and 8sp on the newer 130mm. Yes, if you want to use a 7sp cassette on a 8/9/10sp hub there is a spacer involved (4.5mm to be exact, which is much less than the difference in spacing over all, so maybe 2.5mm difference over 7 gears?)

I've trimmed the shifter to index in gears 1-7, then move into a friction area to shift into the 8th (biggest) gear. The derailleur limit screws prevent over shifting into the spokes of course. This works fairly well. Not perfect, but much better than say 8sp shifters on a 9sp cassette (which I've also attempted to work with on a friend's mix-matched Centurion). It ghost shifts most often if I haven't kept the BB cable routing clean enough (which I need to do again apparently) because the tolerances are closer than a true 8sp setup. Was just hoping for an easy and cheap conversion, there's a set of 8sp 105 shifters coming up on ebay in a few days. Hopefully I can snag those.

edit: the difference per shift is .2mm for 7 to 8sp. So over 7 shifts: 1.4mm or a 29% over shift. If you dial the middle of the cassette's shifts in to be dead on then it's reduced by 50% at the top and bottom of the range, or a 15% over/under shift movement.

Last edited by cuda2k; 10-01-06 at 03:32 PM.
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Old 10-02-06, 03:19 PM   #8
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Problem solved by the fine folks at GVH bikes. They are sending me a set of 105 downtube 8sp shifters for less than I've been watching used ones go for on ebay. Anyone need a set of 7sp shifters?
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