Best front derailleur for half step plus granny

[Russell Seaton]

I am transferring my touring bike parts to a new frame. The
new frame needs a 1.25" clamp on front derailleur. So my old
1991 Shimano Deore DX half step specific 1.125" clamp on
front derailleur won't fit.

My chainrings are 48-45-20. Half step plus granny. Rear cogs
will be 9 speed 12-34 cassette.

1. Which current front derailleur will best handle the 3
tooth difference between the 48 and 45 chainrings and
still allow the use of the 20 tooth granny with the
largest 4 or 5 rear cogs without dragging the chain on
the derailleur cage?

2. I know a double front derailleur will handle the half
step very well. But how would it work with the 28 tooth
difference in chainrings?

3. Is there any way to change clamps on my old front
derailleur? Can I buy any cheap Shimano front derailleur
and easily change clamps?

 

[Frank Miles]

In article <[email protected]>,
Russell Seaton <[email protected]> wrote:
>I am transferring my touring bike parts to a new frame. The
>new frame needs a 1.25" clamp on front derailleur. So my
>old 1991 Shimano Deore DX half step specific 1.125" clamp
>on front derailleur won't fit.
>
>My chainrings are 48-45-20. Half step plus granny. Rear
>cogs will be 9 speed 12-34 cassette.
>
>1. Which current front derailleur will best handle the 3
> tooth difference between the 48 and 45 chainrings and
> still allow the use of the 20 tooth granny with the
> largest 4 or 5 rear cogs without dragging the chain on
> the derailleur cage?
>
>2. I know a double front derailleur will handle the half
> step very well. But how would it work with the 28 tooth
> difference in chainrings?
>
>3. Is there any way to change clamps on my old front
> derailleur? Can I buy any cheap Shimano front
> derailleur and easily change clamps?

I feel your pain. If you can't find something from, say,
Rivendell, then my recommendation is to get a road front
that doesn't have the deep inner plate, and extend the
plates toward the rear. Most derailleurs have steel plates
(IIRC) so it's fairly easy to braze or weld extensions.

There will probably be some that argue against the 1/2+Gr
arrangement, but I'm with you -- there are nice things about
this arrangement.

Good luck -- and let us know how it works out!

-frank
--

 

[Gwhite]

Russell Seaton wrote:
>
> I am transferring my touring bike parts to a new frame.
> The new frame needs a 1.25" clamp on front derailleur. So
> my old 1991 Shimano Deore DX half step specific 1.125"
> clamp on front derailleur won't fit.

This, I think, is what really screws you when it comes to a
half-step.

> My chainrings are 48-45-20. Half step plus granny. Rear
> cogs will be 9 speed 12-34 cassette.
>
> 1. Which current front derailleur will best handle the 3
> tooth difference between the 48 and 45 chainrings and
> still allow the use of the 20 tooth granny with the
> largest 4 or 5 rear cogs without dragging the chain on
> the derailleur cage?
>
> 2. I know a double front derailleur will handle the half
> step very well. But how would it work with the 28
> tooth difference in chainrings?

If it weren't for the clamp issue, these work great just
like your Deore DX:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=2795-
0&item=3685486553 http://cgi.ebay.com/ws/eBayISAPI.dll?View-
Item&category=27950&item=3685712205

> 3. Is there any way to change clamps on my old front
> derailleur? Can I buy any cheap Shimano front
> derailleur and easily change clamps?

I doubt it. Many of the f-ders have half the clamp as part
of the derailleur itself. You could look for the model of
Suntour Cyclone f-der with the totally removable clamp.
Maybe you could replace it with a custom clamp. I don't know
if I've ever seen a 31.8 Suntour Cyclone. All I've seen were
28.6. My Cyclone is not the removable clamp model.

Let me know if you have trouble. I have a cheapo Suntour
front der that I bent (modified) the cage on that I would
sell you if you got desparate. It would probably work for
you. It has a 31.8 clamp. I use it with a 46-42-26 front. It
works, but is not perfect. (This is not the Cyclone.)

 

[Pinnah]

[email protected] (Russell Seaton) wrote:
>My chainrings are 48-45-20. Half step plus granny. Rear
>cogs will be 9 speed 12-34 cassette.
>
>1. Which current front derailleur will best handle the 3
> tooth difference between the 48 and 45 chainrings and
> still allow the use of the 20 tooth granny with the
> largest 4 or 5 rear cogs without dragging the chain on
> the derailleur cage?
>
>2. I know a double front derailleur will handle the half
> step very well. But how would it work with the 28 tooth
> difference in chainrings?

Help me out here. I thought the biggest difference
between a double and triple front changer was the range
of motion (side to side) available. That is to say, I
don't think there would be any difference between a front
derailleur for a half-step granny and any other triple
set-up. Am I mistaken?

It's been a few years since I ran a half-step granny, but
doesn't the half-step make things better, not harder? I
mean, with only a 3 (I used to run a 4 t diff back in the
day), you can mount the changer lower and closer to the
center ring without the outer cage hitting the the outer
ring like you would if you had a 10 t or 12t diff, no?

-- Dave
==============================================
"It is impossible, or not easy, to do noble acts without
the proper equipment." Aristotle, <<Politics>>, 1323a-b,
trans Jowett
==============================================

 

[Sheldon Brown]

Russell Seaton wrote:
>=20
>>My chainrings are 48-45-20. Half step plus granny. Rear
>>cogs will be 9 speed 12-34 cassette.
>>
>>1. Which current front derailleur will best handle the 3
>> tooth difference between the 48 and 45 chainrings and
>> still allow the use of the 20 tooth granny with the
>> largest 4 or 5 rear cogs without dragging the chain on
>> the derailleur cage?

Virtually any modern "double" type front derailer will work
for=20 half-step-plus-granny.

>>2. I know a double front derailleur will handle the half
>> step very well. But how would it work with the 28
>> tooth difference in chainrings?

This may require some experimentation, may also require some
surgery to=20 the cage.

See: http://sheldonbrown.com/derailer-adjustment

An anomymous poster asked:

> Help me out here. I thought the biggest difference between
> a double and triple front changer was the range of motion
> (side to side) available. That is to say, I don't think
> there would be any difference between a front derailleur
> for a half-step granny and any other triple set-up. Am I
> mistaken?

Yes, you are.
>=20
> It's been a few years since I ran a half-step granny, but
> doesn't the half-step make things better, not harder? I
> mean, with only a 3 (I used to run a 4 t diff back in the
> day), you can mount the changer lower and closer to the
> center ring without the outer cage hitting the the outer
> ring like you would if you had a 10 t or 12t diff, no?

Modern "triple" front derailers have an inner cage plate
that hangs down =

much lower than the outer one. This is to facilitate the
upshift from=20 the smallest ring to the middle.

They also generally have a more 3-dimensional outer cage
plate to reduce =

rubbing when clueless riders cross chain the small/small
combinations.

Sheldon "There Is A Difference" Brown +---------------------------------------------
+
| If your bike has drop handlebars, but you |
| rarely or never ride on the drops, it=92s a |
| sure sign that your bike is not properly |
| fitted or is not properly adjusted! |
| See: http://sheldonbrown.com/handsup |
+---------------------------------------------+ Harris
Cyclery, West Newton, Massachusetts Phone 617-244-9772 FAX
617-244-1041 http://harriscyclery.com Hard-to-find parts
shipped Worldwide http://captainbike.com
http://sheldonbrown.com

 

[Pinnah]

>I asked:
>> Help me out here. I thought the biggest difference
>> between a double and triple front changer was the range
>> of motion (side to side) available. That is to say, I
>> don't think there would be any difference between a front
>> derailleur for a half-step granny and any other triple
>> set-up. Am I mistaken?

Sheldon replied:
>Yes, you are.

So, do all (most) modern double and triple FDs have the same
range of motion side to side? I would have expected that
some double FDs wouldn't have enough travel for a triple.

Sheldon continues:
>Modern "triple" front derailers have an inner cage
>plate that hangs down much lower than the outer one.
>This is to facilitate the upshift from the smallest
>ring to the middle.

Ah.... so do I understand correctly.... This lower inner
cage plate would become the limiting factor for how low you
can mount the FD so it will clear the middle chain rain when
the cage is over the outer chanring. And given the huge
difference in the lower edges of the inner and outer cage
plates, this would leave you with the FD too high for
effective shifting from the outer to middle chain rings. Did
I get that right?

-- Dave
==============================================
"It is impossible, or not easy, to do noble acts without
the proper equipment." Aristotle, <<Politics>>, 1323a-b,
trans Jowett
==============================================

 

[Sheldon Brown]

pinnah asked:
>>
>>>Help me out here. I thought the biggest difference
>>>between a double and triple front changer was the range
>>>of motion (side to side) available. That is to say, I
>>>don't think there would be any difference between a front
>>>derailleur for a half-step granny and any other triple
>>>set-up. Am I mistaken?

I replied, in part:

>>Yes, you are.
>=20
> So, do all (most) modern double and triple FDs have the
> same range of motion side to side? I would have
> expected that some double FDs wouldn't have enough
> travel for a triple.

I have never found this to be a problem with normal
chainline, but all=20 generalizations are false.

>>Modern "triple" front derailers have an inner cage plate
>>that hangs dow=
n=20
>>much lower than the outer one. This is to facilitate the
>>upshift from =

>>the smallest ring to the middle.
>=20
> Ah.... so do I understand correctly.... This lower inner
> cage plate would become the limiting factor for how low
> you can mount the FD so it will clear the middle chain
> rain when the cage is over the outer chanring.=20

Yep.

> And given the huge difference in the lower edges of the
> inner and outer cage plates, this would leave you with the
> FD too high for effective shifting from the outer to
> middle chain rings. Did I get that right?

Yes, and also this would likely lead to the chain draggin on
the bottom=20 of the cage in the granny gear.

Sheldon "Delphic?" Brown +-------------------------------------------------------
---------+
| People are more violently opposed to fur than leather |
| Becaue it=92s safer to harass rich women than motorcycle
| gangs |
+-----------------------------------------------------------
-----+ Harris Cyclery, West Newton, Massachusetts Phone 617-244-
9772 FAX 617-244-1041 http://harriscyclery.com Hard-to-find
parts shipped Worldwide http://captainbike.com
http://sheldonbrown.com

 

[Russell Seaton]

No. The problem with using regular triple front derailleurs
with a half step setup is that the inner cage on the triple
front derailleur drops down very deep. Much deeper than the
outer cage. The outer cage will be half inch deep and the
inner cage will be 1 inch deep.

If you position the front derailleur so the outer cage just
clears the outer chainring, then the inner cage will hit the
middle chainring when shifting the chain to the outer
chainring. I only have 3 teeth difference between my
chainrings, so they are the same size practically. I really
need a front derailleur shaped like a triple, to handle the
capacity between the outer and inner chainrings, but the
inner and outer cages shaped like a double derailleur so
they are the same height and will not hit the middle
chainring when shifting between half steps.

pinnah <[email protected]> wrote in message
news:<[email protected]>...
> [email protected] (Russell Seaton) wrote:
> >My chainrings are 48-45-20. Half step plus granny. Rear
> >cogs will be 9 speed 12-34 cassette.
> >
> >1. Which current front derailleur will best handle the 3
> > tooth difference between the 48 and 45 chainrings and
> > still allow the use of the 20 tooth granny with the
> > largest 4 or 5 rear cogs without dragging the chain
> > on the derailleur cage?
> >
> >2. I know a double front derailleur will handle the half
> > step very well. But how would it work with the 28
> > tooth difference in chainrings?
>
> Help me out here. I thought the biggest difference between
> a double and triple front changer was the range of motion
> (side to side) available. That is to say, I don't think
> there would be any difference between a front derailleur
> for a half-step granny and any other triple set-up. Am I
> mistaken?
>
> It's been a few years since I ran a half-step granny, but
> doesn't the half-step make things better, not harder? I
> mean, with only a 3 (I used to run a 4 t diff back in the
> day), you can mount the changer lower and closer to the
> center ring without the outer cage hitting the the outer
> ring like you would if you had a 10 t or 12t diff, no?
>
>
>
>
> -- Dave
> ==============================================
> "It is impossible, or not easy, to do noble acts without
> the proper equipment." Aristotle, <<Politics>>, 1323a-b,
> trans Jowett
> ==============================================

 

[Jeff Wills]

pinnah <[email protected]> wrote in message
news:<[email protected]>... <snip>
> Help me out here. I thought the biggest difference between
> a double and triple front changer was the range of motion
> (side to side) available. That is to say, I don't think
> there would be any difference between a front derailleur
> for a half-step granny and any other triple set-up. Am I
> mistaken?
>

Yes. Most recent front derailleurs have inner cage plates
that extend far below the outer cage plate in order to
facilitate shifting across the 10-tooth jumps common in
"alpine" gearing. These downward-projecting inner cages
run into the middle chainring on the "half-step plus
granny" setup.

To the OP: I recall that the Shimano Deore and Deore XT
front derailleurs came in both "half-step" and "alpine"
versions in the late 80's. I *think* there was one that
featured an endless-band clamp that was adaptable to 1 1/4"
seat tubes. I can't recall if there was one with *both* a
half-step cage *and* an endless band clamp... but I'd bet
that one of the old-guard bike shops could get one from Euro-
Asia if they ever existed. I can't say for sure, though.

Jeff

 

[Pinnah]

Russel and Sheldon, can you guys reconcile the following?

Russell Seaton wrote:
> I really need a front derailleur shaped like a triple, to
> handle the capacity between the outer and inner
> chainrings, [snip...]

Sheldon wrote:
>Virtually any modern "double" type front derailer will work
>for half-step-plus-granny.

Russell, I'm assuming that you are concerned about:
a) the chain draging on the connector bolt that runs between
the 2 sides of cage when on the granny or
b) clean shifts from the granny up to the middle

Sheldon, thanks for the clarification in your other post.

-- Dave
==============================================
"It is impossible, or not easy, to do noble acts without
the proper equipment." Aristotle, <<Politics>>, 1323a-b,
trans Jowett
==============================================

 

[Benjamin Weiner]

Jeff Wills <[email protected]> wrote:

> To the OP: I recall that the Shimano Deore and Deore XT
> front derailleurs came in both "half-step" and "alpine"
> versions in the late 80's. I *think* there was one that
> featured an endless-band clamp that was adaptable to 1
> 1/4" seat tubes. I can't recall if there was one with
> *both* a half-step cage *and* an endless band clamp...

Yes (I had the Deore 31.8mm variety on a Cannondale touring
bike) but it looks a lot like a typical road double front
derailler.

> but I'd bet that one of the old-guard bike shops could
> get one from Euro-Asia if they ever existed. I can't say
> for sure, though.

 

[Russell Seaton]

pinnah <[email protected]> wrote in message news:<[email protected]>...
> Russel and Sheldon, can you guys reconcile the following?
>
> Russell Seaton wrote:
> > I really need a front derailleur shaped like a triple,
> > to handle the capacity between the outer and inner
> > chainrings, [snip...]
>
> Sheldon wrote:
> >Virtually any modern "double" type front derailer will
> >work for half-step-plus-granny.
>
> Russell, I'm assuming that you are concerned about:
> a) the chain draging on the connector bolt that runs
> between the 2 sides of cage when on the granny or
> b) clean shifts from the granny up to the middle

I know the double front derailleur will shift the half step
very well. But a double front derailleur won't handle the
granny worth a darn. Especially not a 28 tooth difference
between outer ring and inner ring. Dragging on the
connector bolt is what I am concerned about. But I think I
have an old Superbe double front derailleur I can fit to
see how badly it drags. I want the biggest 4 or 5 cogs to
not drag when using the inner ring. Welding on extra long
cages to the derailleur is not what I really want to do but
may be forced to.

Shifting from the inner ring to the middle is not a concern.
I can always overshift to get out of the granny or if it
takes a few seconds, no big deal. I am never in a big hurry
when leaving the granny ring. That would be at the top of a
mountain getting ready for the downhill. No rush.

 

[Pinnah]

[email protected] (Russell Seaton) wrote:
>I know the double front derailleur will shift the half step
>very well. But a double front derailleur won't handle the
>granny worth a darn. Especially not a 28 tooth difference
>between outer ring and inner ring. Dragging on the
>connector bolt is what I am concerned about. But I think I
>have an old Superbe double front derailleur I can fit to
>see how badly it drags. I want the biggest 4 or 5 cogs to
>not drag when using the inner ring.

You and I might have very different desires for a half-step
granny that are leading to different gearing choices
(neither good nor bad). I suspect that your gearing prefs
may be complicating the FD issue though.

I used to run a 44/40/20 front crank and my old Suntour DL
double FD handled the 20t drop just fine. However, I alway
ran this with a 32t rear cluster and never used (or wanted
to use) the granny on anything smaller than a 28t rear cog.
As I contemplate setting up a new Half-step rig, I'll
probably shoot for 42/39/?? to get the 3t diff with commonly
made chain rings.

Note, I don't ride big gears so I can live with smaller
outer and middle chain rings. More to the point, I
associate big chain rings with racing and fast sport riding
where shifting performance counts. For that, I think alpine
gearing makes more sense as it favors faster single rear
shifts. For the touring and long-distance riding I like, I
want to find the exact right gear for that long grind into
the head wind. But this is slower speed riding and a
result, lower geared than I think your large chain rings
would provide.

-- Dave
==============================================
"It is impossible, or not easy, to do noble acts without
the proper equipment." Aristotle, <<Politics>>, 1323a-b,
trans Jowett
==============================================

 

[Jeff Wills]

Benjamin Weiner <[email protected]> wrote in message news:<40e218f2$1@darkstar>...
> Jeff Wills <[email protected]> wrote:
>
> > To the OP: I recall that the Shimano Deore and Deore XT
> > front derailleurs came in both "half-step" and "alpine"
> > versions in the late 80's. I *think* there was one that
> > featured an endless-band clamp that was adaptable to 1
> > 1/4" seat tubes. I can't recall if there was one with
> > *both* a half-step cage *and* an endless band clamp...
>
> Yes (I had the Deore 31.8mm variety on a Cannondale
> touring bike) but it looks a lot like a typical road
> double front derailler.
>
> > but I'd bet that one of the old-guard bike shops could
> > get one from Euro-Asia if they ever existed. I can't
> > say for sure, though.

Ah, so... I kind of figured it would be used on a
Cannondale. As to it "looking like a typical road double
front derailleur"... whaddaya wanna bet the cage is longer?

Jeff

 

[Benjamin Weiner]

Jeff Wills <[email protected]> wrote:
> Benjamin Weiner <[email protected]> wrote in message
> news:<40e218f2$1@darkstar>...

> > Yes (I had the Deore 31.8mm variety on a Cannondale
> > touring bike) but it looks a lot like a typical road
> > double front derailler.

> Ah, so... I kind of figured it would be used on a
> Cannondale. As to it "looking like a typical road
> double front derailleur"... whaddaya wanna bet the cage
> is longer?

I managed to dig it up, and I think we're both wrong. The
cage is about the same length as a road double, and oddly,
the inner plate is deeper than a road double. It looks
similar to the type of FD that came on early mountain bikes
with 48-38-28 rings.

 

[Russell Seaton]

> You and I might have very different desires for a half-
> step granny that are leading to different gearing choices
> (neither good nor bad). I suspect that your gearing prefs
> may be complicating the FD issue though.
>
> I used to run a 44/40/20 front crank and my old Suntour DL
> double FD handled the 20t drop just fine. However, I alway
> ran this with a 32t rear cluster and never used (or wanted
> to use) the granny on anything smaller than a 28t rear
> cog. As I contemplate setting up a new Half-step rig, I'll
> probably shoot for 42/39/?? to get the 3t diff with
> commonly made chain rings.

You will have a very hard time getting your cassette cogs to
work in a half step pattern if you go with 42-39 chainrings.
42-40 will work a bit better. One of the reasons I am using
48-45 chainrings is because they work wonderfully with the
very common 14-16-18-21-24-28-32 7 speed cassettes. And also
work wonderfully with the very common 12-14-16-18-20-23-26-30-
34 9 speed cassettes. Your 42-39 proposed gearing will not
provide the half step with any available cassettes. You will
not have half step gearing.

With half step gearing, you have to pick chainrings and
cassettes that work together to give the mathematically
correct percentage changes.

My low gear on the middle ring will be 45x30 or 45x34,
assuming I get the 9 speed cassette to work. 41 or 36 gear
inches. My next lowest gear on the granny ring would be
20x18. 30 gear inches. I really need the front derailleur to
work with the top 5 cogs on the cassette without dragging on
the connecting bolt.

 

[Pinnah]

[email protected] (Russell Seaton) wrote:
>You will have a very hard time getting your cassette cogs
>to work in a half step pattern if you go with 42-39
>chainrings.

Interesting. I'll have re-run my numbers tonight. My first
cut at it showed a perfect interleave with the stock 12-28 7
speed cassettes. I'll take a second look. Glancing at my
numbers, my suggested 42/39 combo isn't very happy as it
doesn't give me enough high gear choices. My prefered choice
for a 7-speed cassettes would be a 44/41 and I think it will
work for most common cassettes. But, I can't seem to find
41t middles for a 110mm bolt pattern.

>One of the reasons I am using 48-45 chainrings is because
>they work wonderfully with the very common 14-16-18-21-24-28-
>32 7 speed cassettes.

Where are you finding a 45t middle ring? My current
cranks have a
110/74 bolt pattern and 39 is one of the few odd numbered
chain rings I've been able to find (Salsa and Sugino
both make 'em).

>My low gear on the middle ring will be 45x30 or 45x34,
>assuming I get the 9 speed cassette to work. 41 or 36 gear
>inches. My next lowest gear on the granny ring would be
>20x18. 30 gear inches. I really need the front derailleur
>to work with the top 5 cogs on the cassette without
>dragging on the connecting bolt.

Hmm.... What I like for loaded touring is to have big enough
jump that I can sit and spin on a granny during a climb and
then shift to the middle to climb out of the saddle (to
stretch the legs). When the jump is just right, this can be
done with only a front shift no rear shifts. For this I only
needed the top 2 or 3 rear cogs with my granny, which
resulted in a higher chain line.

I'll look in my notes but I'm pretty certain my old (6
speed) set up was a 44/40/24. I think I would find your
proposed 45 middle to create too high of a gear, even on the
larger rear cogs. That's what I was trying to say earlier...
if you can go lower on your middle, you don't need to go as
far into your rear cassette with your granny.

I'm struggling to see the advantage of a half-step with 9
speeds though. At that point, doesn't wide range alpine
gearing make more sense with fewer double shifts?

-- Dave
==============================================
"It is impossible, or not easy, to do noble acts without
the proper equipment." Aristotle, <<Politics>>, 1323a-b,
trans Jowett
==============================================

 

[Russell Seaton]

pinnah <[email protected]> wrote in message news:<[email protected]>...
> [email protected] (Russell Seaton) wrote:
> >You will have a very hard time getting your cassette cogs
> >to work in a half step pattern if you go with 42-39
> >chainrings.
>
> Interesting. I'll have re-run my numbers tonight. My first
> cut at it showed a perfect interleave with the stock 12-28
> 7 speed cassettes. I'll take a second look. Glancing at my
> numbers, my suggested 42/39 combo isn't very happy as it
> doesn't give me enough high gear choices. My prefered
> choice for a 7-speed cassettes would be a 44/41 and I
> think it will work for most common cassettes. But, I can't
> seem to find 41t middles for a 110mm bolt pattern.

I've run the numbers on my spreadsheet using my existing 14-16-18-21-24-28-
34 7 speed cassette and a 42-39 did not work well. 42-40
worked better. The best chainring setup I've found with the
above 7 speed setup is the 48-45 half step. The 42-40 setup
just did not produce enough jump between successive gears.
Your 12-28 7 speed cassette is the same as the above
cassette except you have a 12 instead of a 34 or 32.

Harris Cyclery carries 110mm bcd chainrings in every size.
Including 41 and 45 teeth. Both T.A. brand, expensive, and a
cheap BMX brand. Also look at your local bike shop's Quality
Bicycle Products catalog. They will list every tooth in the
110mm bcd pattern. Or a tandem shop. Tandem shops carry lots
of chainrings.

>
> >One of the reasons I am using 48-45 chainrings is because
> >they work wonderfully with the very common 14-16-18-21-24-28-
> >32 7 speed cassettes.
>
> Where are you finding a 45t middle ring? My current
> cranks have a
> 110/74 bolt pattern and 39 is one of the few odd numbered
> chain rings I've been able to find (Salsa and Sugino
> both make 'em).
>
> >My low gear on the middle ring will be 45x30 or 45x34,
> >assuming I get the 9 speed cassette to work. 41 or 36
> >gear inches. My next lowest gear on the granny ring would
> >be 20x18. 30 gear inches. I really need the front
> >derailleur to work with the top 5 cogs on the cassette
> >without dragging on the connecting bolt.
>
> Hmm.... What I like for loaded touring is to have big
> enough jump that I can sit and spin on a granny during a
> climb and then shift to the middle to climb out of the
> saddle (to stretch the legs). When the jump is just right,
> this can be done with only a front shift no rear shifts.
> For this I only needed the top 2 or 3 rear cogs with my
> granny, which resulted in a higher chain line.

I'm not a stand up and pedal person when touring loaded. I
sit and spin. Or grind depending. With the 20 tooth granny,
its spin. I like to have a good progression with the granny
ring when I hit a slightly less steep section. I can shift
in back and not have to jump from the granny to the middle
ring. When the granny is a 20 tooth, it takes quite a shift
to get it from the 20 tooth granny up to the 45 middle ring.

>
> I'll look in my notes but I'm pretty certain my old (6
> speed) set up was a 44/40/24. I think I would find your
> proposed 45 middle to create too high of a gear, even
> on the larger rear cogs. That's what I was trying to
> say earlier... if you can go lower on your middle, you
> don't need to go as far into your rear cassette with
> your granny.

My 48x14 high gear is 93 gear inches. High enough for a
loaded touring bike. With the 45 middle ring, I have 12
nicely spaced gears between 93 and 43 gear inches. Just
right for loaded touring.

>
> I'm struggling to see the advantage of a half-step with 9
> speeds though. At that point, doesn't wide range alpine
> gearing make more sense with fewer double shifts?

There is no advantage going to a 9 speed half step gearing
pattern. But I'm getting a new loaded touring frame so I
thought it would be nice to change over to 9 speed. And the
12-14-16-18-20-23-26-30-34 Shimano 9 speed cassette is
actually a very good full step cassette when coupled with
48-45 half step chainrings. And if it does not work out,
I'll convert back to 7 speed. The 9 speed cassette just adds
the 12 on the bottom and an extra cog at the top end. Not
much different than my current 7 speed cassette. Except it
will be new to go with my new frame. It will add a little
extra fun to the parts swap since I will have to redish the
rear wheel and change hub bodies.

>
>
> -- Dave
> ==============================================
> "It is impossible, or not easy, to do noble acts without
> the proper equipment." Aristotle, <<Politics>>, 1323a-b,
> trans Jowett
> ==============================================

 

[Gecwhite]

Sheldon Brown wrote:
>

> Virtually any modern "double" type front derailer will
> work for half-step-plus-granny.

I find the cage screw is too low on Shimano f-der's.

 

[Gecwhite]

Russell Seaton wrote:

> You will have a very hard time getting your cassette cogs
> to work in a half step pattern if you go with 42-39
> chainrings.

39 42 11 93.955 101.182 12 86.125 92.750 14 73.821
79.500 17 60.794 65.471 20 51.675 55.650 24 43.063
46.375 29 35.638 38.379 34 30.397 32.735

Not so hard, and not so bad. The middle six cogs are the
half step. The 11t & 34t are extras. The cassette is
made from 2 available Shimano 7sp cassettes. The 11-12-
14 cogs can be had from a Performance cassette too, the
last I checked.