Rear Mech Advice wanted

Some time ago I bought an old road bike from Ebay as I wanted something
to learn to do my own maintenance on (using other components also bought
on EBay!)

Having just replaced the freewheel and chain I'm now minded to scrap the
old, cheap and somewhat warped rear mech - A nasty looking thing
labelled Shimano SIS - with something else.

The trouble is I don't know what to replace it with as I don't know how
to tell which rear mechs are designed for MTB's and which are for road
bikes, or even if it matters?

The current setup is a 6 sprocket 14-28 with friction shifters. I might
like to change the rear, downtube shifter, to an indexed shifter at some
point in the future. I understand that Shimano and Campagnolo are not
compatible in this case.

If anyone has a moment and can point me in the direction of some
suitable products I would be most grateful.

TIA


Julesh

Julesh wrote:
Some time ago I bought an old road bike from Ebay as I wanted
something to learn to do my own maintenance on (using other
components also bought on EBay!)

Having just replaced the freewheel and chain I'm now minded to scrap
the old, cheap and somewhat warped rear mech - A nasty looking thing
labelled Shimano SIS - with something else.

The trouble is I don't know what to replace it with as I don't know
how to tell which rear mechs are designed for MTB's and which are for
road bikes, or even if it matters?

They're basically the same except MTB ones tend to cope with larger
sprockets and wider gear ranges. Same thing to a lesser extent with road
triples aka road long cage mechs.

The current Shimano road groups a Sora, Tiagra, 105, Ultegra, Dura-Ace.
MTB groups include Deore, LX and XT. They're interchangeable as far as
indexing goes.

The current setup is a 6 sprocket 14-28 with friction shifters. I
might like to change the rear, downtube shifter, to an indexed
shifter at some point in the future. I understand that Shimano and
Campagnolo are not compatible in this case.

If anyone has a moment and can point me in the direction of some
suitable products I would be most grateful.

Just about any Shimano 6 to 9 speed mech will index with Shimano 6, 7, 8
and 9 speed shifters -- so you're future options can be nice and open. A
9-speed mech's cage might be narrower than ideal for a 6/7/8sp chain
though (?).

Need some more info now: Do you want a mech able to cope with:

....Triple chainset?

....Sprockets larger than 28t?

Bearing in mind that one that can handle these will also work a double +
14-28.

Adapters are available in case your frame doesn't have a hanger for a
modern mech.

~PB

Shimano Altus is a compatible upgrade, without changing everything
else. You can use this with up to a 13/34 7 gear cog. You can also
upgrade the shifters to indexed types, SIS actually stands for
"Sequential Index System" but the 6 & 7 speed types are not compatible
with the 8 and 9 speed types as these have narrower cogs, and in fact
you will need to switch just about everything.

You can also use a standard 22/34/44 chainwheel (again, 6 and 7 speed
types).

Allthougth the tooth difference is the same, you probably cannot fit an
MTB 11/32 cog as they will not go on the freewheel that is normally
supplied with SIS type changer.

Changing to Deore/XT/XTR types requires changing everthing......buy a
new bike!

At the end of the day a 21 speed Altus setup gives you the same range
as a 27 speed, but of course with bigger gaps between ratios! On the
plus side, 7 speed systems are heavier and clunkier......read more
resilient to misuse like cross-chaining!

Roger wrote:
Shimano Altus is a compatible upgrade, without changing everything
else. You can use this with up to a 13/34 7 gear cog. You can also
upgrade the shifters to indexed types, SIS actually stands for
"Sequential Index System" but the 6 & 7 speed types are not compatible
with the 8 and 9 speed types as these have narrower cogs, and in fact
you will need to switch just about everything.

That is not strictly true. You can run a 7 speed system with 10 speed
parts. Using a 10 speed chain on a 7 speed setup is not however advised
as it could be too narrow. A 7/8 speed chain will work fine through
most 10 speed mechs (I can personally vouch for XT and Ultegra) but may
not work on 9/10 speed cassettess without issues.

You can also use a standard 22/34/44 chainwheel (again, 6 and 7 speed
types).

Any sort will do as long as the gap between chainrings is sufficiently
small to not drop a narrow chain down there. A 10-speed chainset will
be fine with a 7 speed chain.

Allthougth the tooth difference is the same, you probably cannot fit an
MTB 11/32 cog as they will not go on the freewheel that is normally
supplied with SIS type changer.
??
If by that you mean the bikes normally sold with such rear mechs tend
to have freewheels rather than cassettes then you would be right. It
may require a new wheel to upgrade the number of sprockets at the rear.

Changing to Deore/XT/XTR types requires changing everthing......buy a
new bike!
Bah!. It doesn't require changing everything. I have changed mine bit
by bit.

there are two things that have to change at the same time in an indexed
system:
the shift levers and the rear cluster of sprockets. They must both be
rated for the same number of gears or it will not work (apart from a
couple of exceptions). Everythign else is compatible.

The other thing to watch out for is the range of tooth sizes at the
back. FOr a triple front chainset and a large range at the back (more
than 28t largest rear sprocket) you will need a long cage rear
derailleur to take up the slack in the chain.

At the end of the day a 21 speed Altus setup gives you the same range
as a 27 speed, but of course with bigger gaps between ratios! On the
plus side, 7 speed systems are heavier and clunkier......read more
resilient to misuse like cross-chaining!

That is more a function of the chain. 7 speed chains are chunkier than
10 speed.

...d

Simon Brooke wrote:
http://www.wiggle.co.uk/Default.aspx...illeurs%20Rear

Oh you cruel man. Are you trying to bankrupt him?

Try the Shimano ones. The Deore should be fine for your purpose and
will be cheaper than the Campagnolo ones.

...d

Pete Biggs wrote:
Julesh wrote:

Some time ago I bought an old road bike from Ebay as I wanted
something to learn to do my own maintenance on (using other
components also bought on EBay!)

Having just replaced the freewheel and chain I'm now minded to scrap
the old, cheap and somewhat warped rear mech - A nasty looking thing
labelled Shimano SIS - with something else.

The trouble is I don't know what to replace it with as I don't know
how to tell which rear mechs are designed for MTB's and which are for
road bikes, or even if it matters?


They're basically the same except MTB ones tend to cope with larger
sprockets and wider gear ranges. Same thing to a lesser extent with road
triples aka road long cage mechs.

The current Shimano road groups a Sora, Tiagra, 105, Ultegra, Dura-Ace.
MTB groups include Deore, LX and XT. They're interchangeable as far as
indexing goes.


The current setup is a 6 sprocket 14-28 with friction shifters. I
might like to change the rear, downtube shifter, to an indexed
shifter at some point in the future. I understand that Shimano and
Campagnolo are not compatible in this case.

If anyone has a moment and can point me in the direction of some
suitable products I would be most grateful.


Just about any Shimano 6 to 9 speed mech will index with Shimano 6, 7, 8
and 9 speed shifters -- so you're future options can be nice and open. A
9-speed mech's cage might be narrower than ideal for a 6/7/8sp chain
though (?).

Need some more info now: Do you want a mech able to cope with:

...Triple chainset?

Just a double chainwheel at present. If I felt the need
to replace the chainset I'd probably feel obliged to service/replace the BB
at the same time and as I'm a mechanical klutz who is learning slowly
that's a step too far for me at present.

...Sprockets larger than 28t?

The bike has 27" wheels that can just take a 6 speed freewheel so 28t
will do at present. If I did want a larger sprocket could I use a MTB
rear mech and a Shimano Megarange freewheel or can you get road bike
equipment lower geared than I have already. I'm setting the bike up as a
sort of day/weekend fast-ish tourer. I'm quite lardy and just want
something I don't need to push up hills.

Couple of things come to mind here. I'd also like to change the wheels
to 700c at some point (when I can win some on EBay!) mainly so I can get
a better choice of tyres. If I did this I'd change to a cassette. Would
this be likely to affect my rear mech choice now? What *is* the
difference between a hybrid bike 700c and a road bike 700c - is this
just a case of tyre width or is locknut spacing also an issue? I've not
measured but I think the (steel) frame is 126mm which I believe limits
me to a 130mm wide wheel unless I fancy levering the rear traingle apart
"a la Sheldon." I'm currently running 1 1/4 tyres on the existing wheels
which feel about right for what I do.



Bearing in mind that one that can handle these will also work a double +
14-28.

Adapters are available in case your frame doesn't have a hanger for a
modern mech.

Ah, Is there a difference? I have a vague memory that when I was small
"5-Speed Racers" might have had a rear mech that bolted onto the hub.
Are all hangers the same length/thread pitch or is this something else I
need to think about.

I had a "non-exhaustive" look on the Interwebthing for indexed downtube
shifters in case this helped me decide whether I wanted to go for a
Shimano or Campagnolo mech but didn't really find any. Are these
available anywhere or does everyone now just add stops at that position
and add "Brifters"? Its not a big deal and probably just something I'd
do for the practise as friction shifters are fine for me. The present
shifters are band-on Shimano 600 if that's important.

Thanks for your help!

Julesh

David Martin wrote:
Roger wrote:


Never heard of 10 speed XT, mine is 9 speed. As the bike with the Altus
has its chain off at the moment, I just tried it for size on the 9
speed XT block. It fits....just. I think this would give a lot of
hassle in real use as it is likely to touch and catch on adjacent cogs.



You can also use a standard 22/34/44 chainwheel (again, 6 and 7 speed
types).

Any sort will do as long as the gap between chainrings is sufficiently
small to not drop a narrow chain down there. A 10-speed chainset will
be fine with a 7 speed chain.


I have no road bikes so no nothing about 10 speeds, but as far as MTB
stuff is concerned I think mixing 9 speed and 7 speed parts will always
lead to grief. The gap between cogs on the 6 the and 7 speed blocks is
around 5.5mm, on the 9 speed blocks it is around 4.5mm. Chains are
narrower as a result, and hence so are cog teeth.

Working is one thing, working well is another.



If by that you mean the bikes normally sold with such rear mechs tend
to have freewheels rather than cassettes then you would be right. It
may require a new wheel to upgrade the number of sprockets at the rear.

I mean you will not find replacement freewheel+cog units with 11 teeth
(leastways I could not find any).



there are two things that have to change at the same time in an indexed
system:
the shift levers and the rear cluster of sprockets. They must both be
rated for the same number of gears or it will not work (apart from a
couple of exceptions). Everythign else is compatible.

Strongly disagree. Firstly you can use shifters with more speeds, in
particular a 7 speed shifter on a 6 speed block, just make sure the end
screw is set right and you will not be able to go into 7th. Secondly,
in the Shimano systems the distance that the shifter cable moves is
equal to the distance between the cogs, i.e. it is different for 9
speed and 6/7 speeds. As for being 'compatible', see above, it will
never work perfectly because everything is slightly missized.

Of course the rear mech itself does not actually know how many cogs
there are, it may well be that e.g. 9 speed shifters on a 7 speed Altus
would work fine because the shifters would move the mech by the correct
distance, but of course the sprockets are still dimensioned for 7 speed
chains so once agin, it would never be quite right.


The other thing to watch out for is the range of tooth sizes at the
back. FOr a triple front chainset and a large range at the back (more
than 28t largest rear sprocket) you will need a long cage rear
derailleur to take up the slack in the chain.


What counts is the difference in the number of teeth. Most MTB rear
mechanisms are made for 21t difference as standard, with 22/44 triple
on the front. They do shorter versions of the mechanisms but you will
rarely find these in the shops as MTB'ers nearly alwys go for maximum
range. Most serious MTB bikes (Deore and up) use 11/32 cassestes
(typically 11,12,14,16,18,21,24,28,32), but as cheap axles/freewheels
can't take the 11 tooth wheel supermarket types with large range gears
go from 13 to 34. That means you get higher top gear, but it is so high
it is virtually useless.

Don't be confused by the length of the cage, the size of the sprocket
wheels is just as relevant, so you can have mechs with noticably
shorter cages (but larger sprockets) which are able to cover the same
21t range.


At the end of the day a 21 speed Altus setup gives you the same range
as a 27 speed, but of course with bigger gaps between ratios! On the
plus side, 7 speed systems are heavier and clunkier......read more
resilient to misuse like cross-chaining!

That is more a function of the chain. 7 speed chains are chunkier than
10 speed.


No doubt that the chain is the biggest issue, but also the teeth are
wider.

Julesh wrote:

Just a double chainwheel at present. If I felt the need
to replace the chainset I'd probably feel obliged to service/replace the BB
at the same time and as I'm a mechanical klutz who is learning slowly
that's a step too far for me at present.

Replacing with a cartridge bearign is easier than servicing. You will
probably need two sets of tools as the old BB will not have the same
fittings as a new one.


...Sprockets larger than 28t?

The bike has 27" wheels that can just take a 6 speed freewheel so 28t
will do at present. If I did want a larger sprocket could I use a MTB
rear mech and a Shimano Megarange freewheel or can you get road bike
equipment lower geared than I have already. I'm setting the bike up as a
sort of day/weekend fast-ish tourer. I'm quite lardy and just want
something I don't need to push up hills.

The cassettes/freewheels are interchangeable between road and MTB. Pick
the gearing to suit and don't worry about the label.


Couple of things come to mind here. I'd also like to change the wheels
to 700c at some point (when I can win some on EBay!) mainly so I can get
a better choice of tyres. If I did this I'd change to a cassette. Would
this be likely to affect my rear mech choice now?
No. It will still be compatible.
What *is* the
difference between a hybrid bike 700c and a road bike 700c - is this
just a case of tyre width or is locknut spacing also an issue? I've not
measured but I think the (steel) frame is 126mm which I believe limits
me to a 130mm wide wheel unless I fancy levering the rear traingle apart
"a la Sheldon." I'm currently running 1 1/4 tyres on the existing wheels
which feel about right for what I do.

There is little practical difference. Hybrid wheels may have wider rims
limiting the tyre width choice at the narrow end. Conversely, fitting
wide tyres on a road rim may be problematic.
The diameter of a 700c rim is about 8mm less than a 27" wheel (622mm vs
630) so ensure you have enough capacity in your brakes to move the
blocks down the necessary 4-5mm.

You should be able to spring a frame over a 135mm hub, but it will be a
pain. A 130 will go fine into a 126 rear triangle with a minor amount
of effort. Cold setting the frame is pretty easy and also easy to foul
up.

Adapters are available in case your frame doesn't have a hanger for a
modern mech.

Ah, Is there a difference? I have a vague memory that when I was small
"5-Speed Racers" might have had a rear mech that bolted onto the hub.
Are all hangers the same length/thread pitch or is this something else I
need to think about.

The cheaper rear mech have a tab that fits under the rear nut. More
expensive ones screw into a specific hole in a tab on the frame. They
are a standard thread. Adapters are available to convert frames without
the rear derailleur hanger.


I had a "non-exhaustive" look on the Interwebthing for indexed downtube
shifters in case this helped me decide whether I wanted to go for a
Shimano or Campagnolo mech but didn't really find any. Are these
available anywhere or does everyone now just add stops at that position
and add "Brifters"? Its not a big deal and probably just something I'd
do for the practise as friction shifters are fine for me. The present
shifters are band-on Shimano 600 if that's important.

Those should be quite nice as far as friction shifters go. To get
indexed DT levers (which will be *far* cheaper than STI (combined
brake/gear levers) try http://sjscycles.com/store/vIndex.htm?cat84.htm
for a selection or scour eBay.

...d

David Martin wrote:
Simon Brooke wrote:

http://www.wiggle.co.uk/Default.aspx...illeurs%20Rear


Oh you cruel man. Are you trying to bankrupt him?

Try the Shimano ones. The Deore should be fine for your purpose and
will be cheaper than the Campagnolo ones.

..d

I must admit I did rather choke - having stated my preference for buying
all the parts for this old wreck which only cost me £21 on Ebay in the
first place - at the price of the Campagnolo Record 10 Speed Rear
Derailleur which is first on the page[1]. However there are lesser mechs
below and, as much as I like Wiggle, from whom I've bought stuff in the
past this does give me an idea of what I should be looking for in t'
other place.

Having lived in Italy "per due anni" and being able to pronounce
Campagnolo without the slightest difficultly I'm minded to go that way
anyway :-)

Julesh



[1] I'm sure it's excellent value for money!

Roger wrote:
David Martin wrote:
Never heard of 10 speed XT, mine is 9 speed. As the bike with the Altus
has its chain off at the moment, I just tried it for size on the 9
speed XT block. It fits....just. I think this would give a lot of
hassle in real use as it is likely to touch and catch on adjacent cogs.

OK, it is a whatever the largest number is XT rear mech that I have
been using with a 7/8 speed chain on an 8 speed cassette.


You can also use a standard 22/34/44 chainwheel (again, 6 and 7 speed
types).

Any sort will do as long as the gap between chainrings is sufficiently
small to not drop a narrow chain down there. A 10-speed chainset will
be fine with a 7 speed chain.


I have no road bikes so no nothing about 10 speeds, but as far as MTB
stuff is concerned I think mixing 9 speed and 7 speed parts will always
lead to grief. The gap between cogs on the 6 the and 7 speed blocks is
around 5.5mm, on the 9 speed blocks it is around 4.5mm. Chains are
narrower as a result, and hence so are cog teeth.

Working is one thing, working well is another.

I was probably not careful enough to point out that it was in the
context of a 9/10speed *mech* with a 7 speed chain. 7 speed chain with
10 speed cassette is not sensible under normal circumstances.

My recommendation is to match the chain to the cassette/freewheel.
Everythign else will look after itself (except for very narrow chains
and old chainsets where the narrow chains could get between the
chainrings.)

If by that you mean the bikes normally sold with such rear mechs tend
to have freewheels rather than cassettes then you would be right. It
may require a new wheel to upgrade the number of sprockets at the rear.

I mean you will not find replacement freewheel+cog units with 11 teeth
(leastways I could not find any).

You are correct there. 11 is too small to fit on.

there are two things that have to change at the same time in an indexed
system:
the shift levers and the rear cluster of sprockets. They must both be
rated for the same number of gears or it will not work (apart from a
couple of exceptions). Everythign else is compatible.

Strongly disagree. Firstly you can use shifters with more speeds, in
particular a 7 speed shifter on a 6 speed block, just make sure the end
screw is set right and you will not be able to go into 7th.
That is one of the exceptions.

Secondly,
in the Shimano systems the distance that the shifter cable moves is
equal to the distance between the cogs, i.e. it is different for 9
speed and 6/7 speeds. As for being 'compatible', see above, it will
never work perfectly because everything is slightly missized.
?? A rear mech moves the same amount for a given amount of cable pull.
It is the indexing that determines the spacing between the gear
positions. Mechs are compatible across all SIS ranges.


Of course the rear mech itself does not actually know how many cogs
there are, it may well be that e.g. 9 speed shifters on a 7 speed Altus
would work fine because the shifters would move the mech by the correct
distance, but of course the sprockets are still dimensioned for 7 speed
chains so once agin, it would never be quite right.

Nope. It works perfectly. The difference between 7 and 9 speed chains
is in the outside, ie how much of the rivet protrudes. The derailelur
spacing between positions will still be just right. You can use the
same sprockets all the way up to 9. I think 10 may be slightly narrower
so a 10 speed chain will not work on 9 or fewer. But a 10 speed
compatible rear mech works fine on 7 speed uniglide and 7 speed
hyperglide with an 8 speed chain.

The other thing to watch out for is the range of tooth sizes at the
back. FOr a triple front chainset and a large range at the back (more
than 28t largest rear sprocket) you will need a long cage rear
derailleur to take up the slack in the chain.


What counts is the difference in the number of teeth. Most MTB rear
mechanisms are made for 21t difference as standard, with 22/44 triple
on the front. They do shorter versions of the mechanisms but you will
rarely find these in the shops as MTB'ers nearly alwys go for maximum
range. Most serious MTB bikes (Deore and up) use 11/32 cassestes
(typically 11,12,14,16,18,21,24,28,32), but as cheap axles/freewheels
can't take the 11 tooth wheel supermarket types with large range gears
go from 13 to 34. That means you get higher top gear, but it is so high
it is virtually useless.

Lower top gear, and it is quite useful when taking big loads up hills.
I was using my 28x32 in serious anger when touring. OK, you aren't
going fast but you are going. I also used the 48/11 coming down the
other side ;-)

Don't be confused by the length of the cage, the size of the sprocket
wheels is just as relevant, so you can have mechs with noticably
shorter cages (but larger sprockets) which are able to cover the same
21t range.

And the ranges given are quite conservative. You can normally get a few
more t difference if you need to. Broadly speaking they are classified
as long cage, medium cage and short cage. For the range the OP
described, a long cage will be ideal.

At the end of the day a 21 speed Altus setup gives you the same range
as a 27 speed, but of course with bigger gaps between ratios! On the
plus side, 7 speed systems are heavier and clunkier......read more
resilient to misuse like cross-chaining!

That is more a function of the chain. 7 speed chains are chunkier than
10 speed.


No doubt that the chain is the biggest issue, but also the teeth are
wider.

10 speed are narrower, everythign else is the same tooth width. The
spacing between the teeth gets smaller though.

...d