Compact chainsets

[MartinM]

Following on from a discussion about these; I see CW have got a whole
article about them. However none of them seem to go below 34T. This is
not that much less than the 39T on my current double. The alternative
to fitting one seems to be using the bottom two rings only of a triple,
although I can see possible issues with the front mech. Does anyone
have any experience of doing this? I only want to fit one for La
Marmotte and hopefully cascade it down afterwards. Would the top two of
an MTB one be easier?

TIA

 

[David Martin]

MartinM wrote:
> Following on from a discussion about these; I see CW have got a whole
> article about them. However none of them seem to go below 34T. This is
> not that much less than the 39T on my current double. The alternative
> to fitting one seems to be using the bottom two rings only of a triple,
> although I can see possible issues with the front mech.

I thought I had chain line problems till I realised it was the vertical
line from my 34t compact inner that was the problem. Unfortunately it
is a braze on fitting so I might have to do a bit of hunting for a new
front mech with a longer cage.

34t makes a significant difference over 39t (equiv to 28-32 jump at the
rear) IME. Of course you could bite the bullet and get a TA Vega or
Carmina which would then let you put on almost anything you want.

> Does anyone
> have any experience of doing this? I only want to fit one for La
> Marmotte and hopefully cascade it down afterwards. Would the top two of
> an MTB one be easier?

Probably. I find 48/34 to be fine and climb most anything with that and
a suitable (12-26 or 12-28) cassette in back.

...d

 

[Arthur Clune]

MartinM wrote:
> Following on from a discussion about these; I see CW have got a whole
> article about them. However none of them seem to go below 34T. This is
> not that much less than the 39T on my current double.

In practice it's a useful drop. 34x26 is a fairly low gear on a road bike
(same as 30x23 near enough)

Combine with a 13-28 cassette for a lower gear if you want. You can
always do what I did and turn a 13-up cassette into a 12-up cassette
with a jump at the top end by replacing the 13-tooth lockring with a
12. I used a Campag 9 speed block that looked like this

12-14-15 ... - 26

The gap at the top doesn't really matter since in the Alps.

> The alternative
> to fitting one seems to be using the bottom two rings only of a triple,
> although I can see possible issues with the front mech. Does anyone
> have any experience of doing this? I only want to fit one for La
> Marmotte and hopefully cascade it down afterwards. Would the top two of
> an MTB one be easier?

As I said before, I think you'll be undergeared doing this. You'll probably
have chainline issues as well since a MTB triple is designed to work on a
longer bottom bracket than a double.

Arthur

--
Arthur Clune

 

[MartinM]

Arthur Clune wrote:

> In practice it's a useful drop. 34x26 is a fairly low gear on a road
bike
> (same as 30x23 near enough)

30x23 is what I have on my Audax bike, not really low enough for last
gasp climbs

> Combine with a 13-28 cassette for a lower gear if you want. You can
> always do what I did and turn a 13-up cassette into a 12-up cassette
> with a jump at the top end by replacing the 13-tooth lockring with a
> 12. I used a Campag 9 speed block that looked like this
>
> 12-14-15 ... - 26

I used a 21-28 jump on a botched cassette a couple of years ago before
the triple; it was virtually impossible to get out of bottom gear on a
steep climb



> As I said before, I think you'll be undergeared doing this.

I know you have, the alternatives are;

compact

use the triple bike, neither give me much of an advantage over the
existing 39x26. Fortunately I have a band on front mech so can drop it
down as required. Presumably using a 28 on the back would cause chain
length issues?

what are the chainline issues? I would only be using the little ring on
the top 3 gears?

 

[Arthur Clune]

MartinM wrote:
>
> I used a 21-28 jump on a botched cassette a couple of years ago before
> the triple; it was virtually impossible to get out of bottom gear on a
> steep climb

That's why I say put the jump at the top end of the cassette. You'd not
want a large jump in the low gears anyway when climbing.

> compact
>
> use the triple bike, neither give me much of an advantage over the
> existing 39x26. Fortunately I have a band on front mech so can drop it
> down as required. Presumably using a 28 on the back would cause chain
> length issues?

Don't see why. A short cage mech is fine with a 28 and the extra chain
you need for the 28 should be compenstated for by the smaller large
ring.

> what are the chainline issues? I would only be using the little ring on
> the top 3 gears?

It may (or may not) put the little ring too close to the frame. You'd have
to see.

--
Arthur Clune

 

[Dave Larrington]

In article <[email protected]>,
MartinM ([email protected]) wrote:
> Following on from a discussion about these; I see CW have got a whole
> article about them. However none of them seem to go below 34T. This is
> not that much less than the 39T on my current double. The alternative
> to fitting one seems to be using the bottom two rings only of a triple,
> although I can see possible issues with the front mech. Does anyone
> have any experience of doing this? I only want to fit one for La
> Marmotte and hopefully cascade it down afterwards. Would the top two of
> an MTB one be easier?

IIRC road bike front mechs /can/ be a little fractious when asked to
play with MTB-size "big" chainrings and in the case of $himano, road
front mechs have different cable pull requirements to MTB ones. So
getting STI shifters to co-operate with an MTB front derailleur /may/
also be an issue.

If you can find a cheap Stronglight chainset with 86 mm BCD rings - such
as the 80 or 99 - you could assemble a 28/nn double, where nn is almost
anything you like. I used to run a 28/42 setup with a 99 years before
these so-called "compact" wossnames came onto the market[1]. This,
admittedly, was because as a Penniless Student Oaf I could not amass
sufficient credits to acquire a TA Cyclotourise, Stronglight 49D or one
of those new-fangled Red S 74/110 triples.

If you /can't/ find one, I am willing to rent out the one[2] from my
fixer for a suitable fee ;-)

1 - So /I/ invented them, and all these manufacturers must give me lots
of money immediately
2 - Though you'd need new chainrings, obv.

--
Dave Larrington - <http://www.legslarry.beerdrinkers.co.uk/>
Dead journalists make excellent objets d'art.

 

[David Martin]

Arthur Clune wrote:
> Don't see why. A short cage mech is fine with a 28 and the extra chain
> you need for the 28 should be compenstated for by the smaller large
> ring.

I'd check the mech. It isn't so much the cage length as the body
length. My Sante one is not rated above 23 (IIRC) and will not do 26
(though will do 25).

...d

 

[MSeries]

Dave Larrington wrote:
> In article <[email protected]>,
> MartinM ([email protected]) wrote:
> > Following on from a discussion about these; I see CW have got a whole
> > article about them. However none of them seem to go below 34T. This is
> > not that much less than the 39T on my current double. The alternative
> > to fitting one seems to be using the bottom two rings only of a triple,
> > although I can see possible issues with the front mech. Does anyone
> > have any experience of doing this? I only want to fit one for La
> > Marmotte and hopefully cascade it down afterwards. Would the top two of
> > an MTB one be easier?
>
> IIRC road bike front mechs /can/ be a little fractious when asked to
> play with MTB-size "big" chainrings and in the case of $himano, road
> front mechs have different cable pull requirements to MTB ones. So
> getting STI shifters to co-operate with an MTB front derailleur /may/
> also be an issue.
>

Nah, my 105 triple front mech works fine with my 48/38/28 Deore
chaniset. BUT I don't use STi or indexed front on this bike.

 

[MartinM]

Arthur Clune wrote:

> It may (or may not) put the little ring too close to the frame. You'd have
> to see.

That's exactly what I was worried about; although I could buy a wider
BB, this could also be re-cycled (as skogTM) has a good record of
wrecking these IMX despite being "sealed"

 

[MartinM]

David Martin wrote:

> Arthur Clune wrote:
> > Don't see why. A short cage mech is fine with a 28 and the extra chain
> > you need for the 28 should be compenstated for by the smaller large
> > ring.
>

breaks the rules about chain length a bit Shirley in that you won't be
able to use every front with every back cog (as if you'd ever want to).
My Ribble was converted from a double to a triple without needing a
long cage rear mech (max 50x13 min 30x23). I got a "audax specific"
50/40/30 Ofmega chainset from sjs, very pleased with it and all alloy
unlike Sora.

 

[MSeries]

MartinM wrote:
> Following on from a discussion about these; I see CW have got a whole
> article about them. However none of them seem to go below 34T. This is
> not that much less than the 39T on my current double. The alternative
> to fitting one seems to be using the bottom two rings only of a triple,
> although I can see possible issues with the front mech. Does anyone
> have any experience of doing this? I only want to fit one for La
> Marmotte and hopefully cascade it down afterwards. Would the top two of
> an MTB one be easier?
>
> TIA

I have a Deore triple with 48/38/28 rings (110mm PCD), you are
suggesting something like --/42/28 on such a device ? I use a 105 front
mech. I did have 50/36 and a 105 double front mech worked fine. Non
indexed of course, why would anyone need to index two positions, even
with three it really isn't hard to get it right.

 

[MartinM]

MSeries wrote:

why would anyone need to index two positions, even
> with three it really isn't hard to get it right.

because they have STI's? ;-) and the ratchet type as well so no use
with a triple.

 

[MSeries]

MartinM wrote:
> David Martin wrote:
>
> > Arthur Clune wrote:
> > > Don't see why. A short cage mech is fine with a 28 and the extra chain
> > > you need for the 28 should be compenstated for by the smaller large
> > > ring.
> >
>
> breaks the rules about chain length a bit Shirley in that you won't be
> able to use every front with every back cog (as if you'd ever want to).
> My Ribble was converted from a double to a triple without needing a
> long cage rear mech (max 50x13 min 30x23). I got a "audax specific"
> 50/40/30 Ofmega chainset from sjs, very pleased with it and all alloy
> unlike Sora.

Audax Specific ? Like it knows about route sheets and controls and min
and max speeds ?

 

[Dave Larrington]

In article <[email protected]>,
MSeries ([email protected]) wrote:
>
> Dave Larrington wrote:

> > IIRC road bike front mechs /can/ be a little fractious when asked to
> > play with MTB-size "big" chainrings and in the case of $himano, road
> > front mechs have different cable pull requirements to MTB ones. So
> > getting STI shifters to co-operate with an MTB front derailleur /may/
> > also be an issue.
> >
>
> Nah, my 105 triple front mech works fine with my 48/38/28 Deore
> chaniset. BUT I don't use STi or indexed front on this bike.

48 is quite large by current MTB standards, thobut. They mostly seem to
be 42 or 44 these days.

--
Dave Larrington - <http://www.legslarry.beerdrinkers.co.uk/>
Ha ha, you fool! You've fallen victim to one of the classic blunders!
The most famous is "Never get involved in a land war in Asia"

 

[MartinM]

Dave Larrington wrote:
> In article <[email protected]>,
> MSeries ([email protected]) wrote:
> >
> > Dave Larrington wrote:
>
> > > IIRC road bike front mechs /can/ be a little fractious when asked to
> > > play with MTB-size "big" chainrings and in the case of $himano, road
> > > front mechs have different cable pull requirements to MTB ones. So
> > > getting STI shifters to co-operate with an MTB front derailleur /may/
> > > also be an issue.
> > >
> >
> > Nah, my 105 triple front mech works fine with my 48/38/28 Deore
> > chaniset. BUT I don't use STi or indexed front on this bike.
>
> 48 is quite large by current MTB standards, thobut. They mostly seem to
> be 42 or 44 these days.

Thanks everyone for all the advice; still pondering. The options seem
to be;

Stronglight compact chainset (for one ride) 49.99

Buy a 105 triple groupset and fit to bike, cascade old groupset to (as
yet still in Dreamland) 2007 Audax bike

Go back to plan A, take the triple Audax bike and suffer slowly (with
secret weapon 26T cassette)

The Inland Revenue seem to be having the final say ;-( Working Families
tax credit (FSVO credit)

 

[Arthur Clune]

MartinM wrote:
>
> Stronglight compact chainset (for one ride) 49.99

You might find, like me, that you like it so much you just
leave it on all the time. I run 38/48 normally now with a
34 inner ring fitted for long and steep rides.

> Go back to plan A, take the triple Audax bike and suffer slowly (with
> secret weapon 26T cassette)

Option 3?

Put gears from Audax bike onto light bike. If you can do the
work yourself, this might be an option.

Arthur

--
Arthur Clune

 

[MartinM]

Arthur Clune wrote:
> MartinM wrote:
> >
> > Stronglight compact chainset (for one ride) 49.99
>
> You might find, like me, that you like it so much you just
> leave it on all the time. I run 38/48 normally now with a
> 34 inner ring fitted for long and steep rides.
>
> > Go back to plan A, take the triple Audax bike and suffer slowly (with
> > secret weapon 26T cassette)
>
> Option 3?
>
> Put gears from Audax bike onto light bike. If you can do the
> work yourself, this might be an option.

did think of this, it is the cheapest and easiest option, just swap
front mech/ chainset and STI unit (RX100/RSX) can restrict the Audax
bike to flat rides in the interim. Thanks

May need to use the Audax bike for a rack (depends what Caradice the
birthday fairy brings).

 

[David E. Belcher]

David Martin wrote:

> MartinM wrote:
>
> I thought I had chain line problems till I realised it was the vertical
> line from my 34t compact inner that was the problem. Unfortunately it
> is a braze on fitting so I might have to do a bit of hunting for a new
> front mech with a longer cage.
>

Campag seem to have introduced some new "compact" double front mechs
with a much deeper inner cage plate [1], presumably to take care of
efficient upshifts between rings with a wide difference in no. of teeth
like 34T to 50T, which sound as though they'd do the job well. Don't
know if there are any compatibility issues, though (e.g. suitable for
10sp chains only?).

David Belcher

[1] See, for instance, probikekit.com's full-page ads in CW for photos
showing cage design.

 

[Arthur Clune]

MartinM wrote:

> May need to use the Audax bike for a rack (depends what Caradice the
> birthday fairy brings).

It's the Marmotte. Why on earth would you need a rack?

If you really think you need a rack, you are taking far too much.

Arthur

--
Arthur Clune

 

[MartinM]

Arthur Clune wrote:
> MartinM wrote:
>
> > May need to use the Audax bike for a rack (depends what Caradice the
> > birthday fairy brings).
>
> It's the Marmotte. Why on earth would you need a rack?

only to get from the airport, will be stripping everything off at Bourg
(rack, light brackets,liposuction) although the bus is an option.