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Old 05-25-11, 07:07 PM   #1
Sirrus Rider
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8 speed hub configured as a 6 Speed.. Is it possible?

I recently replaced the wheel set on my 1988 Specialized sirrus with an 8 speed Ultegra wheelset by flipping to friction. It works well enough; however, it very sensitive. So I'm wondering is it possible to drop the number of cogs in the cassette so I can turn indexing back on???
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Old 05-25-11, 08:04 PM   #2
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You have 6 speed index shifters? See Sheldon's chart on spacing: http://www.sheldonbrown.com/gloss_sp-ss.html#spacing It doesn't have a listing for 6 speed Shimano, but I've read that 6 speed is slightly wider than 7 speed.

The way I see it the only to get it to index would be to:

a) Get some 8 speed shifters
b) Buy a cassette and tear it apart to get at the plastic spacers. File them down to whatever you need to add in between the gears of your 8 speed cassette so it will index. Note that you might not be able to do anything about the last couple cogs as they have built in spacers. This will probably be a tedious job and may not work too well.

You might find with a 7 speed cassette it will index ok. How bad is it now?
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Old 05-25-11, 08:18 PM   #3
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So it sounds like your original wheel was a 6 speed freewheel. And you were using a 6spd thumb shifter.
Now replaced with an 8spd cassete wheel, and switched the thumbshifter into friction mode.
Is that the correct assesment?

So the thing is, the spacing between the cogs in a 6spd is going to be different from with an 8spd.
So the position of the 'clicks' in your old shifter will not match.

In theory, you could dissasemble the 8spd cassete by drilling out the rivits holding the cogs together.
Then choose 2 cogs to throw away (probably the largest 2 will be simplest).
Replace the plastic spacers between the cogs with wider ones so the remaining 6 cogs are at old style 6spd spacing.
then the old shifter can be used.

Thats a lot of work though, the hardest part will be getting spacers the right size. 6spd cassettes(non-freewheel) with removble cogs and spacers did exist, but are now obsolete, so finding spacers from one will be extrememly difficult. You'll also probably need to finagle something for the spacing of the smallest lockring cog since it uses an iintegrated spacer not the plastic ones.

So yeah, it is possible, but will be cheaper and less work to just upgrade your shifter to an 8spd one.
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Old 05-25-11, 11:29 PM   #4
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Quote:
Originally Posted by xenologer View Post
So it sounds like your original wheel was a 6 speed freewheel. And you were using a 6spd thumb shifter.
Now replaced with an 8spd cassete wheel, and switched the thumbshifter into friction mode.
Is that the correct assesment?

So the thing is, the spacing between the cogs in a 6spd is going to be different from with an 8spd.
So the position of the 'clicks' in your old shifter will not match.

In theory, you could dissasemble the 8spd cassete by drilling out the rivits holding the cogs together.
Then choose 2 cogs to throw away (probably the largest 2 will be simplest).
Replace the plastic spacers between the cogs with wider ones so the remaining 6 cogs are at old style 6spd spacing.
then the old shifter can be used.

Thats a lot of work though, the hardest part will be getting spacers the right size. 6spd cassettes(non-freewheel) with removble cogs and spacers did exist, but are now obsolete, so finding spacers from one will be extrememly difficult. You'll also probably need to finagle something for the spacing of the smallest lockring cog since it uses an iintegrated spacer not the plastic ones.

So yeah, it is possible, but will be cheaper and less work to just upgrade your shifter to an 8spd one.
After dwelling on it I scored the last OEM 8 Speed Shimano 600 Downtube shifters off E-pay. Even on friction it works well; however, not so much when I'm in a hurry.
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Old 05-26-11, 12:11 AM   #5
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If your rear derailleur is Shimano, it should be possible to get it indexing properly.
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