Best front derailleur for half step plus granny
Russell Seaton
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
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=27950&item=3685486553
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&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
>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
>
>>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
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
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.
>
> 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
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
+---------------------------------------------+
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| rarely or never ride on the drops, it’s a |
| sure sign that your bike is not properly |
| fitted or is not properly adjusted! |
| See: http://sheldonbrown.com/handsup |
+---------------------------------------------+
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Phone 617-244-9772 FAX 617-244-1041
http://harriscyclery.com
Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com
pinnah
>> 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?
Sheldon Brown
>>
>>>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.
>
> 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
generalizations are false.
>>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.
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
of the cage in the granny gear.
Sheldon "Delphic?" Brown
+----------------------------------------------------------------+
| People are more violently opposed to fur than leather |
| Becaue it’s safer to harass rich women than motorcycle gangs |
+----------------------------------------------------------------+
Russell Seaton
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 <pinna...@THIS.comcast.net> wrote in message news:<qdv2e01vnl5v7g4dn...@4ax.com>...
Jeff Wills
> 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
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.
Benjamin Weiner
> 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.
Russell Seaton
> 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
>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.
Jeff Wills
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
> Benjamin Weiner <b...@mambo.ucolick.org> 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
>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?
Russell Seaton
> russell...@yahoo.com (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.
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.
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.
pinnah
>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.
Couple of things, including a retraction/correction.
1) I was able to dig out the specs from my old set up. It was (to my
astonishment) a 50/46/24, very close to your preferred 48/45. I musta
had young legs once. Note: I used it with a 13-32 6-speed cassette.
2) I'm not seeing the pit falls of the 42/39 yet, other than the
really low gearing. My casual review of the gear charts (generated
from Sheldon's very cool site) suggest that any 3 tooth jump on the
chain rings gets you really close with most off the shelf cassettes.
More important I would think, is whether or not the general size of
the chain rings is getting the basic range of gears desired. I think
your 48/45 is probably better in this regard.
3) I'm still getting my head around your desire for running a 24t
chain ring with 24 - 18 cogs. My gear charts (again, taken from
Sheldon's site) indicate this is in the gear inch range of 26 to 39
inches or so. It looks to me that this run of gears is available with
a 36t chain ring on 34 - 28t cogs. If you want something close to a
steady set of step (full, half or what have you) from a 20 inch gear
up to 100 inch gear, perhaps a more standard alpine gearing would work
for you like a 48/36/24. I just think you really beg problems as soon
as your rear cogs get to be the same size as your granny or smaller.
>Harris Cyclery carries 110mm bcd chainrings in every size. Including
>41 and 45 teeth. Both T.A. brand, expensive, and a cheap BMX brand.
Excellent. Thanks.
Russell Seaton
> really low gearing. My casual review of the gear charts (generated
> from Sheldon's very cool site) suggest that any 3 tooth jump on the
> chain rings gets you really close with most off the shelf cassettes.
> More important I would think, is whether or not the general size of
> the chain rings is getting the basic range of gears desired. I think
> your 48/45 is probably better in this regard.
I reran the numbers last night using a 42-39, 45-42, and 48-45 half
steps coupled with 14-16-18-21-24-28-32(34) seven speed off the shelf
cassettes and 12-14-16-18-20-23-26-30-34 nine speed off the shelf
cassettes. And the 42-39, 45-42, and 48-45 chainrings work pretty
well. I think the 45-42 works best for me. But my current 48-45 and
your 42-39 are just fine too. I now think I will get a 42 chainring
and go with 45-42 half step chainrings. And stay with my current
seven speed 14-16-18-21-24-28-34 cassette. And not spend the money
yet for a nine speed setup.
In answer to a post by another, off the shelf cassettes are what
appeal to me. Buy a seven speed 14-32 or nine speed 12-34 from
Nashbar and put it on the bike and ride.
> 3) I'm still getting my head around your desire for running a 24t
> chain ring with 24 - 18 cogs. My gear charts (again, taken from
> Sheldon's site) indicate this is in the gear inch range of 26 to 39
> inches or so. It looks to me that this run of gears is available with
> a 36t chain ring on 34 - 28t cogs. If you want something close to a
> steady set of step (full, half or what have you) from a 20 inch gear
> up to 100 inch gear, perhaps a more standard alpine gearing would work
> for you like a 48/36/24. I just think you really beg problems as soon
> as your rear cogs get to be the same size as your granny or smaller.
I have a 20 tooth inner chainring. 20 tooth. I love really low
gears. A 20 inner chainring gives me a 16 gear inch low when using my
34 rear cog. If I were to use a normal 24 inner chainring, then I
would only have a 19 gear inch low instead of my current 16 gear inch
low. Not as good.
I am going to run chainrings of 45-42-20. I currently run 48-45-20.
In the past I used a 24 tooth inner chainring. But the 20 tooth inner
chainring gives me even lower low gears for no extra effort.
When I run 45-42-20 chainrings with my current 14-16-18-21-24-34 seven
speed cassette cogs, I will have a high gear of 87 gear inches. Not
too high but I reckon I can live with it when touring loaded. I could
also purchase a 12-14-16-18-21-24-28 seven speed off the shelf
cassette from Nashbar for $18 to run half step and get a high gear of
101 gear inches and a low of 19 gear inches when coupled with my soon
to be 45-42-20 chainrings.