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Old 08-01-07, 03:07 PM   #1
mike
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Can I use an 8 speed shifter with a 7 speed cassette?

I have to replace the shifters on an older mountain bike.

The cassette is seven speed. I can get aShimano Ef28 Shifter with optical display that is for an eight speed cassette.

Will this work, but just have the eigth position on the shifter not workable?

I would use this with a Shimano Acer X derailure.
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Old 08-01-07, 03:21 PM   #2
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This wouldn't work well. The cable pull between each indexed gear is different for 7 and 8 speed cassettes/freewheels. As such, the shifter would cause the derailleur to move about 7/8 of the distance it should between gears. This would lead to incredibly sloppy shifting performance, and likely ghost shifting as well.

I would either try to find some 7-speed shifters (they're not very rare, and quite inexpensive), or replace your 7-speed freewheel with an 8-speed cassette, which would require a new, cassette-hub wheel in the rear.

Alternatively, you could experiment with friction shifters
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Old 08-01-07, 03:49 PM   #3
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It should work reasonably well. I have a friend that uses 8-speed brifters on a 7-speed cassette. The spacing is really close - 7-speed is 5.0mm and 8-speed is 4.8mm (and thus the ratio is 48/50, not 7/8). If you set up the derailer to be aligned on the middle cog, it will only be about 0.6mm off by the time it gets to the largest or smallest cog. There is usually enough "slop" in indexing systems to handle that (especially for the small cog which is controlled by the derailer stop and not an index in the lever).

If you have trouble getting it all to work, you can simply use 8-speed spacers in your cassette. You may need a 1mm cassette spacer behind the cassette if you do this.

Last edited by Gonzo Bob; 08-01-07 at 04:55 PM.
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Old 08-01-07, 04:43 PM   #4
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This question comes up about once a month. It works great for me. Sheldon Brown says it will work, too. If you compare a 7 speed and an 8 speed cassette side by side, you'll see that the difference in spacing is minute. Modern Shimano derailers can handle it easily. You can also use 7 speed shifters with 8 speed cassettes.
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Old 08-01-07, 04:52 PM   #5
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Originally Posted by Dirtdrop View Post
This question comes up about once a month. It works great for me. Sheldon Brown says it will work, too. If you compare a 7 speed and an 8 speed cassette side by side, you'll see that the difference in spacing is minute. Modern Shimano derailers can handle it easily. You can also use 7 speed shifters with 8 speed cassettes.
I agree and I disagree.

I've tried various combinations of 7-speed and 8-speed shifters and cassettes over the years. I've never been able to get them to index reliably to my satisfaction. I cen get them to work - kind of, just not to my satisfaction. The people who tell you that it works great are either better bike tuners than I am or they aren't as picky as I am.
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Old 08-01-07, 05:08 PM   #6
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The people who tell you that it works great are either better bike tuners than I am or they aren't as picky as I am.
Much less the former and a great deal more of the latter.
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Old 08-01-07, 08:09 PM   #7
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Sheldon Browns website shows an alternative cable attachment at the rear der that provides the increased pulll needed for the 7 speed cassette. I have done it and it works.
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Old 08-01-07, 08:33 PM   #8
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I run a seven speed cassette and 8 speed shifters on one of my bikes and it works just fine.
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Old 08-01-07, 08:35 PM   #9
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I have done it several times(as well as seven shifter with eight cassette, on a downtube shift road bike)

Just today I did a SRAM X-7 shifter(8-speed) with an old seven speed cassette and SRAM 3.0 derailler. It worked very nice. Tho this is different than the Shimano 7-8 conundrum.
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Old 08-03-07, 05:48 PM   #10
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You can almost guess what I did...

The 8 speed shifters were a good deal and I needed shifters so...

I bought the 8 speed shifters...

and I bought an 8 speed casette to match the shifters...

And the tool I needed to do the work...

DOH!
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Old 08-03-07, 07:14 PM   #11
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How are you going to squeeze that 8 speed cassette onto a 7 speed freehub body?
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Old 08-03-07, 07:58 PM   #12
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How are you going to squeeze that 8 speed cassette onto a 7 speed freehub body?

Probably I will jump up and down on it until it fits.
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Old 08-03-07, 08:47 PM   #13
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I am currently using 8 speed SIS mountian bike thumb shifters with 6 speed rear freewheel/cassette on 2 road bikes with trekking bars (one setup is 34 tooth mega), they shift just fine in index or friction mode. You just have to adjust the cable properly.
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Old 08-09-07, 10:19 PM   #14
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It works!

I just installed the new 8 speed shifter on the seven speed cassette. It works great.

However, I should say that I did also change the cassette. Nashbar had a great sale on both the Shimano 3X8 shifter/brake set and the cassette, so I got all the hardware for about $15.00 Really great deal.

Anyway, Dirtdrop asked how I was going to get an eight speed cassette on a seven speed hub. Of course, the answer is that cassettes usually have two sprockets that are free, so an eight speed comes with the six speed hub plus two free sprockets. I only used one of the sprockets, so the hub is actually a seven speed still. The result is that the shifter only has a range from gears 2 to 8.

I guess it isn't a rocket science approach, but anyway it got the job done with new gear for $15.00 and I'm happy.
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Old 08-10-07, 02:28 AM   #15
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Quote:
Originally Posted by mike View Post
It works!

I just installed the new 8 speed shifter on the seven speed cassette. It works great.

However, I should say that I did also change the cassette. Nashbar had a great sale on both the Shimano 3X8 shifter/brake set and the cassette, so I got all the hardware for about $15.00 Really great deal.

Anyway, Dirtdrop asked how I was going to get an eight speed cassette on a seven speed hub. Of course, the answer is that cassettes usually have two sprockets that are free, so an eight speed comes with the six speed hub plus two free sprockets. I only used one of the sprockets, so the hub is actually a seven speed still. The result is that the shifter only has a range from gears 2 to 8.

I guess it isn't a rocket science approach, but anyway it got the job done with new gear for $15.00 and I'm happy.
So, let me understand this: you actually bought an 8-speed cassette, not a 7 speed? If you have an 8-speed cassette and removed the smallest sprocket, then you shouldn't have indexing issues, as the spacing between the sprockets mathches the shifter.

As for 8-speed shifters with (genuine) 7-speed cassettes: I had that setup on an old (bought 2nd hand) MTB, and I hated the thing passionately. It would never really shift right, especially on the lowest gear. Didn't quite understand why, back then. Now I do, but I ride mostly singlespeed nowadays.
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Old 08-10-07, 03:43 AM   #16
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Quote:
Originally Posted by mike View Post
It works!

I just installed the new 8 speed shifter on the seven speed cassette. It works great.

However, I should say that I did also change the cassette. Nashbar had a great sale on both the Shimano 3X8 shifter/brake set and the cassette, so I got all the hardware for about $15.00 Really great deal.

Anyway, Dirtdrop asked how I was going to get an eight speed cassette on a seven speed hub. Of course, the answer is that cassettes usually have two sprockets that are free, so an eight speed comes with the six speed hub plus two free sprockets. I only used one of the sprockets, so the hub is actually a seven speed still. The result is that the shifter only has a range from gears 2 to 8.

I guess it isn't a rocket science approach, but anyway it got the job done with new gear for $15.00 and I'm happy.
fwiw, the seven of eight approach is the optimal solution, so long as your gear inch needs are met. congrats!
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