7 speed to 8 speed

In article <0d5bc4a5-0f4d-4eb7-99d6-b753ce4533d6
@f47g2000hsd.googlegroups.com>, [email hidden] says...

Quoted message said:

I have an old bike out in the shed I would like to start using again.
It needs replacement shifters and rear derailleur. Currently it has 7
speed Shimano DX but there is only a limited choice in 7 speed
replacements. How much work would it be to convert to 8 speed? I am
guessing it would need a good deal of messing about with the rear
wheel which is probably more than I would want to tackle, but I
thought I would ask.

Don't know anything about Shimano DX specifically, but in general terms
you can run 8 speed shifters & derailleur on a 7 cog cassette with no
problems, because the spacing of the cogs is the same. All that happens
is that the last shift at one end of the shifter scale won't go
anywhere.

Just make sure the limit screws are set properly on the derailleur so
that you can't shift it right off the cogs.

Colin

Colin MacDonald said:

In article <0d5bc4a5-0f4d-4eb7-99d6-b753ce4533d6
@f47g2000hsd.googlegroups.com>, [email hidden] says...

Quoted message said:

I have an old bike out in the shed I would like to start using again.
It needs replacement shifters and rear derailleur. Currently it has 7
speed Shimano DX but there is only a limited choice in 7 speed
replacements. How much work would it be to convert to 8 speed? I am
guessing it would need a good deal of messing about with the rear
wheel which is probably more than I would want to tackle, but I
thought I would ask.

Don't know anything about Shimano DX specifically, but in general terms
you can run 8 speed shifters & derailleur on a 7 cog cassette with no
problems, because the spacing of the cogs is the same. All that happens
is that the last shift at one end of the shifter scale won't go
anywhere.

Just make sure the limit screws are set properly on the derailleur so
that you can't shift it right off the cogs.

Colin

That's good to know - gives the option of going to 8 speed if change
wheel in future :-)

Does it matter which end of the shifter scale is truncated?

Colin MacDonald said:

In article <0d5bc4a5-0f4d-4eb7-99d6-b753ce4533d6
@f47g2000hsd.googlegroups.com>, [email hidden] says...

Quoted message said:

I have an old bike out in the shed I would like to start using again.
It needs replacement shifters and rear derailleur. Currently it has 7
speed Shimano DX but there is only a limited choice in 7 speed
replacements. How much work would it be to convert to 8 speed? I am
guessing it would need a good deal of messing about with the rear
wheel which is probably more than I would want to tackle, but I
thought I would ask.

Don't know anything about Shimano DX specifically, but in general
terms you can run 8 speed shifters & derailleur on a 7 cog cassette
with no problems, because the spacing of the cogs is the same. All
that happens is that the last shift at one end of the shifter scale
won't go anywhere.

Just make sure the limit screws are set properly on the derailleur so
that you can't shift it right off the cogs.

Assuming the freehub (where the cassette fits) is a wider 8 speed one, with
a spacer to take the 7 speed cassette. There are (were) Shimano freehubs
which are 7 speed width and don't take an 8 speed cassette. One of the
bikes in my shed has such a freehub.

Changing the freehub isn't difficult (10mm Allen key and a bit of leverage),
though check there is enough space on the cone nuts to fit, otherwise one is
into moving cone spacers around and re-dishing the wheel. Not a costly
change, just a bit of time and skill to do it.

--
Nigel Cliffe,
Webmaster at http://www.2mm.org.uk/

icogs said:

I have an old bike out in the shed I would like to start using again.
It needs replacement shifters and rear derailleur. Currently it has 7
speed Shimano DX but there is only a limited choice in 7 speed
replacements.

I have no problem in replacing 7 speed cassettes at all on the web,
and the cheaper bike brands such as Falcon still use them so I would
expect those shops to have them. SRAM is good quality..Are the
shifters that knackered? E bay might be worth a look if necessary or
get cheap ones from the falcon shop. I f really necessary then I
think you can just put on 8 speed shifters and cassette, but I have in
the past had a problem with the 8 speed cassette being too close to
the dropout for the chain to work on the smallest sprocket on one old
bike.

Terry J

http://www.wiggle.co.uk/ProductDetail.aspx?Cat=cycle&ProdID=5360013880&N=SRAM%20PG730%207%20Speed%20Cassette
http://www.wiggle.co.uk/ProductDetail.aspx?Cat=cycle&ProdID=5360030020&N=SRAM%20SX-4%20Trigger%20Shifter

Nigel Cliffe said:

Assuming the freehub (where the cassette fits) is a wider 8 speed one, with
a spacer to take the 7 speed cassette. There are (were) Shimano freehubs
which are 7 speed width and don't take an 8 speed cassette. One of the
bikes in my shed has such a freehub.

As does my second bike, which was a surprise when I came to fit an 8
speed cassette to it.

Happily, the said 8 speed cassette had seven riveted cogs and one loose,
so it works perfectly minus the smallest cog.

-dan

"TerryJ" <[email hidden]> wrote in message

Quoted message said:

I have no problem in replacing 7 speed cassettes at all on the web

I recently used SJS for a bunch of drivetrain bits for an older bike.

http://www.sjscycles.co.uk/category-Cassettes-7-speed-72.htm

In article <caab1d08-428d-4f0a-87d2-50b3470d41c3
@n58g2000hsf.googlegroups.com>, [email hidden] says...

Quoted message said:

Colin MacDonald said:

In article <0d5bc4a5-0f4d-4eb7-99d6-b753ce4533d6
@f47g2000hsd.googlegroups.com>, [email hidden] says...

Quoted message said:

I have an old bike out in the shed I would like to start using again.
It needs replacement shifters and rear derailleur. Currently it has 7
speed Shimano DX but there is only a limited choice in 7 speed
replacements. How much work would it be to convert to 8 speed? I am
guessing it would need a good deal of messing about with the rear
wheel which is probably more than I would want to tackle, but I
thought I would ask.

Don't know anything about Shimano DX specifically, but in general terms
you can run 8 speed shifters & derailleur on a 7 cog cassette with no
problems, because the spacing of the cogs is the same. All that happens
is that the last shift at one end of the shifter scale won't go
anywhere.

Just make sure the limit screws are set properly on the derailleur so
that you can't shift it right off the cogs.

Colin

That's good to know - gives the option of going to 8 speed if change
wheel in future :-)

Does it matter which end of the shifter scale is truncated?

Not really. I chose to align the shifter's top gear with the smallest
cog, i.e. truncate the low-gear end, mostly because I very rarely make
it down to the biggest cog anyway so I'm not likely to be hunting for
the extra gear that isn't there.

Colin

In article <caab1d08-428d-4f0a-87d2-50b3470d41c3
@n58g2000hsf.googlegroups.com>, icogs
[email hidden] says...

Quoted message said:

Does it matter which end of the shifter scale is truncated?

If you set top gear on the shifter to correspond with top gear on the
derailleur then cable tension and the inner limit screw will prevent an
extra click past bottom gear, otherwise there will be an extra click and
slack cable beyond top gear.