6 speed shifter...7 speed block.....

LaoFuZhi said:

Plan to change the rear cogs from a 6-speed sis type to the 7 speed
14-34 megarange type. Obviously I'll need to change the rear mech
(old one's past it anyway) but do I really need to change the front
shifter? OK so it's not going to 'index' properly but that's of
little interest to me so long as I can shift from one end of the set
to the other....

Anyone see any problems with me keeping the original shifter?

You will not be able to use a 6 speed shifter with a 7 speed cassette/block
in indexed mode. It will constantly rub against adjacent sprockets unless
you are very very lucky with the adjustment. You may not need to change the
rear mech. but if its past it .... In friction mode you shifter ought to be
OK. Why not change the shifter ?

LaoFuZhi said:

Plan to change the rear cogs from a 6-speed sis type to the 7 speed 14-34
megarange type. Obviously I'll need to change the rear mech (old one's past
it anyway) but do I really need to change the front shifter? OK so it's not
going to 'index' properly but that's of little interest to me so long as I
can shift from one end of the set to the other....

Anyone see any problems with me keeping the original shifter?

Hi,

you may find that the 7 speed block won't fit on your 6 speed hub. Also
a wheel with a 7/8/9 speed hub won't fit into your frame. This is
because the 6 speed hub is slightly narrower.

At least, that was my experience when trying to upgrade a six speed bike
from 1989. Frames can be stretched through a process known as cold
setting so that 7/8/9 speed hubs can be fitted.

Rob Horton yahoo.com@mr_horton opined the following...

Quoted message said:

LaoFuZhi said:

Plan to change the rear cogs from a 6-speed sis type to the 7 speed 14-34
megarange type. Obviously I'll need to change the rear mech (old one's past
it anyway) but do I really need to change the front shifter? OK so it's not
going to 'index' properly but that's of little interest to me so long as I
can shift from one end of the set to the other....

Anyone see any problems with me keeping the original shifter?

I suspect that a 7 speed shifter may need to pull more cable than a 6
speed. Consult Sheldon.

Quoted message said:

At least, that was my experience when trying to upgrade a six speed bike
from 1989. Frames can be stretched through a process known as cold
setting so that 7/8/9 speed hubs can be fitted.

Cold setting is a steel thing. I don't know that anyone recommends cold-
setting Aluminium.

Jon

Rob Horton said:

you may find that the 7 speed block won't fit on your 6 speed hub.
Also a wheel with a 7/8/9 speed hub won't fit into your frame. This is
because the 6 speed hub is slightly narrower.

At least, that was my experience when trying to upgrade a six speed
bike from 1989. Frames can be stretched through a process known as
cold setting so that 7/8/9 speed hubs can be fitted.

My tourer, frame dating from 1984, got upgraded from 6 to 7 last year.
Block fitted OK; I just had to put a washer about 1mm thick on each end of
the axle to sprong the frame out a little.

--

Dave Larrington - http://www.legslarry.beerdrinkers.co.uk/
===========================================================
Editor - British Human Power Club Newsletter
http://www.bhpc.org.uk/
===========================================================

Rob Horton said:

LaoFuZhi said:

Plan to change the rear cogs from a 6-speed sis type to the 7 speed
14-34 megarange type. Obviously I'll need to change the rear mech
(old one's past it anyway) but do I really need to change the front
shifter? OK so it's not going to 'index' properly but that's of
little interest to me so long as I can shift from one end of the set
to the other....

Anyone see any problems with me keeping the original shifter?

Hi,

you may find that the 7 speed block won't fit on your 6 speed hub.
Also
a wheel with a 7/8/9 speed hub won't fit into your frame. This is
because the 6 speed hub is slightly narrower.

At least, that was my experience when trying to upgrade a six speed
bike from 1989. Frames can be stretched through a process known as
cold
setting so that 7/8/9 speed hubs can be fitted.

I think a 7 speed cassette will be OK on a 6 speed hub, you may be right if
the OP is using a screw on block though. I have test fitted a 7 speed
cassette on my 6 speed hub OK, the wheel fits into the frame perfectly. I
actually changed to 8 speed by using 9 speed sprockets and spacers which
gives a total width near enough the same as 7 speed. I used a 9 speed chain
and 9 speed levers too of course.

Martin 'MSeries' Newstead said:

LaoFuZhi said:

Plan to change the rear cogs from a 6-speed sis type to the 7 speed
14-34 megarange type. Obviously I'll need to change the rear mech
(old one's past it anyway) but do I really need to change the front
shifter? OK so it's not going to 'index' properly but that's of
little interest to me so long as I can shift from one end of the set
to the other....

Anyone see any problems with me keeping the original shifter?

You will not be able to use a 6 speed shifter with a 7 speed cassette/block
in indexed mode.

.....except if you're shifter is a Suntour and you're cassette is
Shimano. I have an old Schwin road bike in Sacramento that came with
Suntour stem mounted shifters and a Suntour 6 gear freewheel. The
Suntour shifters pull a different ratio of cable compared to Shimano
shifters, slightly less in fact, and this prves to be just dandy for a
standard 7 speed shimano freewheel. Works fine.

Chances are the shifters are not Suntour though :-)

Garry

Quoted message said:

It will constantly rub against adjacent sprockets unless
you are very very lucky with the adjustment. You may not need to change the
rear mech. but if its past it .... In friction mode you shifter ought to be
OK. Why not change the shifter ?

garryb59 said:

....except if you're shifter is a Suntour and you're cassette is
Shimano. I have an old Schwin road bike in Sacramento that came with
Suntour stem mounted shifters and a Suntour 6 gear freewheel. The
Suntour shifters pull a different ratio of cable compared to Shimano
shifters, slightly less in fact, and this prves to be just dandy for a
standard 7 speed shimano freewheel. Works fine.

Chances are the shifters are not Suntour though :-)

OP said SIS so I presume it was Shimano

Thanks to all for the responses........

I should perhaps have said that the new block was already attached to a
replacement wheel which fitted the frame with no problems. Given the
apparent likliehood of the shifter not being suitable I may as well order a
replacement with the rear mech ...I was merely hoping to make the job a tad
simpler (lazy sod that I am <g>😉