On Wed, 19 Jan 2005 15:01:48 -0600, joel roth
<
[email protected]> may have said:
>I have an older Raleigh mountain bike from the late 1980's. (Elkhorn?)
>It has six speeds in back. Several years ago the LBS replaced the
>original shifter with a 7 speed index shifter. It works, but requires
>'double shifting' at times to move the chain.
>
>Can I simply replace replace the 6 speed cassette with a 7 speed? What
>would you recommend? I don't need a high end, expensive cassette.
You don't need a cassette at all, you need a freewheel. There may be
a need to add a spacer at each end of the axle to provide a little
more clarance on the left while keeping the wheel centered, but I'd
just slap the 7sp freewheel on first and try it as-is; it may work
without having to do anything else. If you need to add spacers,
there's also the issue of the rear dropout spacing to consider; if the
spacers cause you to have to force the dropouts open in order to
position the wheel, then it may be worth getting the rear of the frame
respaced to accomodate the wheel properly.
There are lots of good 7sp freewheels available for reasonable
amounts, and yes, there's a very good chance that this is all you'll
need to buy in order to make it work, provided that the largest
sprocket on the new freewheel is the same size as or not much bigger
than the current one. If you swap to a Megarange freewheel, you run
the risk of going past the limits of what the rear der can handle, and
if you increase the size of the large sprocket by much, you'll
probably need to lengthen the chain or replace it. Of course, putting
on a new chain at the same time that you replace the freewheel is
considered good parctice in any event, unless you're dead sure that
the current chain has little or no wear on it.
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