Touring - Early 1990s Shimano group

[ccollins]

Hello,

Questions on Shimano road Touring groups from the early 1990s.

I have been reading Shimano history on the web for the last couple of days. Here is a questions. Shimano had what looks like road-based touring groups in the 1980s mainly the Deore. In 1989 there was Deore-II.

In 1990 it looks like Shimano made the shift to MTB groups and Road groups.

What Shimano **road** touring groups were made in the early 1990s (1991, 1992, 1993).

Was there a break during these years? From what I have read it looks like the first road touring group of the 1990's was the 1992 RX100? Is this the case? What other road groups might there have been during these early post "Deore II" days?

--Chris

 

[Ronald]

> What Shimano **road** touring groups were made in the
> early 1990s
(1991,
> 1992, 1993).

This site lists Shimano groups:
http://datenbanken.freepage.de/traut/

"ccollins" <[email protected]> wrote in message
news:[email protected]...
> Hello,
>
> Questions on Shimano road Touring groups from the
> early 1990s.
>
> I have been reading Shimano history on the web for the
> last couple of days. Here is a questions. Shimano had what
> looks like road- based touring groups in the 1980s mainly
> the Deore. In 1989 there was Deore-II.
>
> In 1990 it looks like Shimano made the shift to MTB groups
> and Road groups.
>
> What Shimano **road** touring groups were made in the
> early 1990s
(1991,
> 1992, 1993).
>
> Was there a break during these years? From what I have
> read it looks like the first road touring group of the
> 1990's was the 1992 RX100?
Is
> this the case? What other road groups might there have
> been during
these
> early post "Deore II" days?
>
> --Chris
>
>
>
> --

 

[Russell Seaton]

I have Deore DX on my 1991 Trek 520 touring bike. Its worked
just fine for many thousands of miles. Except I always hated
trying to adjust the low profile cantilever brakes and
replaced them with some Dia Compe normal cantilever brakes a
few years ago. About the only touring specific thing about
it is the half step front derailleur. I recall Sheldon Brown
writing about Shimano having a specific half step front
derailleur long ago. It was dropped a few years later. The
bike also came with RX100 brake levers and bar end shifters.
Not sure on the official name for the bar ends. They may
have been 600 or RX100 or just plain old Shimano.

ccollins <[email protected]> wrote in message
news:<[email protected]>...
> Hello,
>
> Questions on Shimano road Touring groups from the
> early 1990s.
>
> I have been reading Shimano history on the web for the
> last couple of days. Here is a questions. Shimano had what
> looks like road- based touring groups in the 1980s mainly
> the Deore. In 1989 there was Deore-II.
>
> In 1990 it looks like Shimano made the shift to MTB groups
> and Road groups.
>
> What Shimano **road** touring groups were made in the
> early 1990s (1991, 1992, 1993).
>
> Was there a break during these years? From what I have
> read it looks like the first road touring group of the
> 1990's was the 1992 RX100? Is this the case? What other
> road groups might there have been during these early post
> "Deore II" days?
>
> --Chris
>
>
>
> --

 

[ccollins]

>> What Shimano **road** touring groups
>> were made in the early 1990s (1991,
>> 1992, 1993).

> This site lists Shimano groups:
> http://datenbanken.freepage.de/traut/

Thanks, I know this site. This is the one I used to 'guess' that the RX100 from 1993 was a 'road' touring group. On that chart it shows the RX100 in the road group and it shows that these came with a long cage rear derailleur.

Anyone else know of these groups? Long cage RD, 6/7/8 speed index downtube shifters? Anyone have an opinion on if there was a *touring* road group from the early 1990s?

Thanks,

--Chris

 

[ccollins]

> Originally posted by Russell...
> I have Deore DX on my 1991 Trek 520 touring bike.

The 1991 Deore DX is listed under the MTB group. I know I am quibbling but I am looking for a Shimano *road* group if it existed.

> About the only touring specific thing about it is the half step front derailleur.

Tell me more? I have two old touring bikes with Shimano front derailuers and they are listed as "Alpine" and the other is listed as "Half step" What's supposed to be the difference? What does Half-step mean? Alpine?

--Chris

 

[Jeff Wills]

ccollins <[email protected]> wrote in message news:<[email protected]>...
> Hello,
>
> Questions on Shimano road Touring groups from the
> early 1990s.
>
> I have been reading Shimano history on the web for the
> last couple of days. Here is a questions. Shimano had what
> looks like road- based touring groups in the 1980s mainly
> the Deore. In 1989 there was Deore-II.
>
> In 1990 it looks like Shimano made the shift to MTB groups
> and Road groups.
>
> What Shimano **road** touring groups were made in the
> early 1990s (1991, 1992, 1993).
>
> Was there a break during these years? From what I have
> read it looks like the first road touring group of the
> 1990's was the 1992 RX100? Is this the case? What other
> road groups might there have been during these early post
> "Deore II" days?
>
> --Chris

Hmmm... I was stocking parts at Euro-Asia Imports in those
years (1987-1989). Before that I was a shop rat (1979-1984)
and after I was working the phones at Bike'alog (1989-1993).
I *guess* I'm qualified to answer.

"Deore-xx" parts after 1986-ish were exclusively "mountain
bike". That includes Deore, Deore II, Deore XT, and Deore XT
II. As far as I can recall, Deore II and Deore XT II
superceded Deore and Deore XT in 1987. There were only minor
changes from one to the next- all were 7-speed SIS with
thumbshifters and cantilever brakes. In 1989, Shimano
introduced the first version of Rapidfire (both upshift and
downshift activated by thumb presses) and went back to Deore
and Deore XT.

Back to your question- "road" groups of that time were Dura-
Ace, 600, and 105. There were long-cage derailleurs and
triple cranks in the 600 line and *perhaps* the 105
(memory's pretty fuzzy) in the late '80's. I think that
Shimano *did not* make a dedicated "road touring" group in
the early '90's: the few dedicated touring bikes that I
saw (Cannondales and Treks, mostly) used mongrel mountain
bike groups.

So, the short answer to your question is: no. There was no
"road touring" group before RX100.

Jeff

 

[Jeff Wills]

[email protected] (Russell Seaton) wrote in message news:<[email protected]>...
> I have Deore DX on my 1991 Trek 520 touring bike. Its
> worked just fine for many thousands of miles. Except I
> always hated trying to adjust the low profile cantilever
> brakes and replaced them with some Dia Compe normal
> cantilever brakes a few years ago. About the only touring
> specific thing about it is the half step front derailleur.
> I recall Sheldon Brown writing about Shimano having a
> specific half step front derailleur long ago. It was
> dropped a few years later. The bike also came with RX100
> brake levers and bar end shifters. Not sure on the
> official name for the bar ends. They may have been 600 or
> RX100 or just plain old Shimano.
>

There were "half-step" and "alpine" versions of the Deore II
and Deore XT II front derailleurs available at that time-
and trying to keep them all straight on the warehouse shelf
was a b***h.

The bar-end shifters were never really associated with a
particular group. They were SL-BS50 (6 & 7-speed and later
8-speed), SL-BS50-8 (works with 8-speed Dura-Ace). Nowadays
SL-BS77 is 9-speed and SL-BS78 is 10-speed.

Jeff

 

[Russell Seaton]

ccollins <[email protected]> wrote in message news:<[email protected]>...
> > Originally posted by Russell... I have Deore DX on my
> > 1991 Trek 520 touring bike.
>
> The 1991 Deore DX is listed under the MTB group. I know I
> am quibbling but I am looking for a Shimano *road* group
> if it existed.
>
> > About the only touring specific thing about it is the
> > half step front derailleur.
>
> Tell me more? I have two old touring bikes with Shimano
> front derailuers and they are listed as "Alpine" and the
> other is listed as "Half step" What's supposed to be the
> difference? What does Half-step mean? Alpine?
>
> --Chris

Physically the back cage is different between the two front
derailleurs. I don't recall which is deeper. I would guess
the alpine one is deeper. With half step gearing the front
chainrings are close in size. 5 tooth difference on my Trek
520 from the factory
(50/45). Currently I run a 48/45 in front. The half step
front derailleur is shaped so the back cage does not
hit the middle ring when you shift onto the slightly
larger outer ring. It might also have various shapes
on the back cage to allow it to shift between the
similar sized rings quicker. Which you do with half
step gearing more often than with alpine gearing.

Alpine gearing as I understand it, or as Shimano probably
meant it, is a large jump between chainrings. Like we do now
days. You basically shift all the way up or down on one
chainring without shifting the front at all. You have lots
of gearing overlap, but all of your shifting more or less is
handled by the rear shifter. I would guess the alpine back
cage is deeper to handle the bigger jump between rings and
to be able to shove the chain sideways when shifting in the
front. The deeper cage will not hit the middle ring when on
the outer ring because there is a 10 or more tooth
difference between front rings.

Hopefully Mr. Brown or others will jump in and explain the
official differences between the front derailleurs.

 

[Erik Brooks]

ccollins asked: What does Half-step mean?

Sheldon has the answer of course:

http://www.sheldonbrown.com/gloss_h.html#halfstep

I've got one bike set up this way. It shifts very well, but
it does require lots of double shifts if you feel the need
to have the perfect gear all the time. Since I started
spending lots of time riding single speed, I've lost the
need to have the 'perfect' gear, so the half step seems just
fine. It's pretty much neccessary to also have a granny gear
with it, just in case, as half step reduces the overall
range of gears available on the 2 main rings.

 

[Jeff Wills]

ccollins <[email protected]> wrote in message
news:<[email protected]>... <snip>
> Tell me more? I have two old touring bikes with Shimano
> front derailuers and they are listed as "Alpine" and the
> other is listed as "Half step" What's supposed to be the
> difference? What does Half-step mean? Alpine?
>

"Half-step" means the percentage difference between the
chainrings is half that of adjacent cogs. This means you can
make small gear adjustments with a front shift. In more
practical terms, it means the outer chainrings are 4 to 6
teeth apart, e.g. 34-44-48. The front derailleur's cage is
profiled to allow this.

"Alpine" is the nearly universal setup nowadays: large steps
on the chainrings (24-36-48) and lots of cogs. The front
derailleur's inner cage extends far below the outer cage to
make the shifts possible.

See also http://www.sheldonbrown.com/gloss_a.html#alpine
http://www.sheldonbrown.com/gloss_h.html#halfstep

Jeff

 

[Sheldon Brown]

Erik Brooks wrote:
> ccollins asked: What does Half-step mean?
>
> Sheldon has the answer of course:
>
> http://www.sheldonbrown.com/gloss_h.html#halfstep
>
> I've got one bike set up this way. It shifts very well,
> but it does require lots of double shifts if you feel the
> need to have the perfect gear all the time. Since I
> started spending lots of time riding single speed, I've
> lost the need to have the 'perfect' gear, so the half step
> seems just fine.

But that's the raison d'etre for half step!

This is one of my major objections to this obsolete system:
In practice, many people who thought it looked good on paper
don't wind up using the prescribed shifting sequence, so
they wind up with the worst features of both systems.

As to the issue of front derailers, if you are dead-set on
using a half-step-plus-granny, you'll be best off with a
"double" type front derailer.

Modern "triple" front derailers have the inner cage plate
hang way down to improve the shift from the small to the
middle ring. If you try to use such a derailer with a half-
step setup, the cage is liable to rub on the middle ring.

Sheldon "An Idea Whose Time Has Gone" Brown +--------------------------------------------------------
+
| There is no conclusive evidence of life after death. |
| But there is no evidence of any sort against it. | Soon
| enough you will know, so why fret about it? | --Robert A.
| Heinlein |
+--------------------------------------------------------+
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

 

[Gwhite]

[email protected] (Russell Seaton) wrote:
> Physically the back cage is different between the two
> front derailleurs. I don't recall which is deeper. I would
> guess the alpine one is deeper.

I would call it the inner cage plate, and yes the "Alpine"
would be deeper.

> With half step gearing the front chainrings are close in
> size. 5 tooth difference on my Trek 520 from the factory
> (50/45). Currently I run a 48/45 in front. The half step
> front derailleur is shaped so the back cage does
> not hit the middle ring when you shift onto the
> slightly larger outer ring.

Exactly.

> Alpine gearing as I understand it, or as Shimano probably
> meant it, is a large jump between chainrings. Like we do
> now days. You basically shift all the way up or down on
> one chainring without shifting the front at all.

This discription of "use them up and then shift" is really a
form of crossover shifting, not the sandwiched "Alpine" that
had been intended. And as Sheldon has keenly noted many
times, that "step and one-half Alpine" is not the original
Alpine, which more or less had a bailout at the low end.

"Crossover" (the use-em-up-and-then-cross system) is not
concerned with duplications. In fact in the strict sense, it
should have duplications. Whether or not it does in fact is
of little concern with 8-9-10 speed cassettes and triple
chainring bikes. Most folks shift "crossover" regardless of
how their gearing is designed.

> You have lots of gearing overlap, but all of your shifting
> more or less is handled by the rear shifter. I would guess
> the alpine back cage is deeper to handle the bigger jump
> between rings and to be able to shove the chain sideways
> when shifting in the front.

For practical purposes, it is similar to today's double
chainring fronts.

 

[Gwhite]

Sheldon Brown <[email protected]> wrote in message news:<[email protected]>...
> Erik Brooks wrote:
> > ccollins asked: What does Half-step mean?
> >
> > Sheldon has the answer of course:
> >
> > http://www.sheldonbrown.com/gloss_h.html#halfstep
> >
> > I've got one bike set up this way. It shifts very well,
> > but it does require lots of double shifts if you feel
> > the need to have the perfect gear all the time. Since I
> > started spending lots of time riding single speed, I've
> > lost the need to have the 'perfect' gear, so the half
> > step seems just fine.
>
> But that's the raison d'etre for half step!

Exactly.

> This is one of my major objections to this obsolete
> system: In practice, many people who thought it looked
> good on paper don't wind up using the prescribed shifting
> sequence, so they wind up with the worst features of both
> systems.

I know you don't like them, but I know the problem is more
getting the right rings, right cogs, and right front
derailleur than it is actually shifting it on a properly set
up bike. With indexing it is easy to shift the rear and
front shifts are extremely crisp due to the similar ring
size. No problems.

Also, one is not required to blindly follow the technical
sequence. There are many times when terrain changes permit
skipping a gear (and that means no double shift). Also much
riding is very casual, the sequence can often be ignored
with no import.

The system is practically obsolete from lack of "true need"
and thus a dearth of specifically designed modern hardware.
9 and 10sp cassettes do make its "need" questionable for all
but the heavily loaded tourist -- a rare bird that easily
explains the lack of manufacturer support.

I rode the system across the country. It worked great. 26 42
46 11 62.636 101.182 110.818 12 57.417 92.750 101.583 14
49.214 79.500 87.071 17 40.529 65.471 71.706 20 34.450
55.650 60.950 24 28.708 46.375 50.792 29 23.759 38.379
42.034 34 20.265 32.735 35.853

> As to the issue of front derailers, if you are dead-set on
> using a half-step-plus-granny, you'll be best off with a
> "double" type front derailer.

Even some of these will have problems. The new Campy's seem
to have a better chance when it comes to the inner plate:
they aren't as deep as Shimano's. (At least a couple years
ago that was true.)

> Modern "triple" front derailers have the inner cage plate
> hang way down to improve the shift from the small to the
> middle ring. If you try to use such a derailer with a half-
> step setup, the cage is liable to rub on the middle ring.

It _will_ rub unless it is mounted impractically high, and
may break something, if one can even get it to work.

 

[ccollins]

> Originally posted by Gwhite

> but I know the problem is more
> getting the right rings, right cogs,
> and right front derailleur than it is
> actually shifting it on a properly
> set up bike.

Yes, challenging.

> The system is practically obsolete
> from lack of "true need" and thus
> a dearth of specifically designed
> modern hardware.
> 9 and 10sp cassettes do make
> its "need" questionable for all
> but the heavily loaded tourist
> -- a rare bird that easily explains
> the lack of manufacturer support.

That be me. I discovered the joy of heavily loaded touring last summer and I am "upgrading" my equipment for this summer's tour which I am planning.

> I rode the system across the country.
> It worked great.

You had a 26x42x46 (11,12,14,17,20,24,29,34)....

> As to the issue of front derailers, if
> you are dead-set on using a
> half-step-plus-granny, you'll be best
> off with a "double" type front derailer.

So I assume someone who is doing heavily loaded tours wants front outer chainrings that are half-step with a granny third gear. This is the typical touring front? And the current mass bike setup is the Alpine-style evenly spaced front chainrings.

Thus a triple front derailer (half-step) is what would work on a touring bike triple?
The outer two rings being close would not rub, and the granny gear to middle gear jump just works slowly and the touring rider just deals with....

Funny, you would think a touring setup *would* be an Alpine style front derailer.

Thank you for the very informative conversation.

--Chris

 

[Bruce Graham]

In article <[email protected]>,
usenet- [email protected] says...
> > Originally posted by Gwhite
>
> > but I know the problem is more getting the right rings,
> > right cogs, and right front derailleur than it is
> > actually shifting it on a properly set up bike.
>
> Yes, challenging.
>
> > The system is practically obsolete from lack of "true
> > need" and thus a dearth of specifically designed modern
> > hardware. 9 and 10sp cassettes do make its "need"
> > questionable for all but the heavily loaded tourist -- a
> > rare bird that easily explains the lack of manufacturer
> > support.
>
> That be me. I discovered the joy of heavily loaded touring
> last summer and I am "upgrading" my equipment for this
> summer's tour which I am planning.
>
> > I rode the system across the country. It worked great.
>
> You had a 26x42x46 (11,12,14,17,20,24,29,34)....
>
> > As to the issue of front derailers, if you are dead-set
> > on using a half-step-plus- granny, you'll be best off
> > with a "double" type front derailer.
>
> So I assume someone who is doing heavily loaded tours
> wants front outer chainrings that are half-step with a
> granny third gear. This is the typical touring front? And
> the current mass bike setup is the Alpine- style evenly
> spaced front chainrings.
>
> Thus a triple front derailer (half-step) is what would
> work on a touring bike triple? The outer two rings being
> close would not rub, and the granny gear to middle gear
> jump just works slowly and the touring rider just deals
> with....
>
> Funny, you would think a touring setup *would* be an
> Alpine style front derailer.
>
> Thank you for the very informative conversation.
>
> --Chris
>
>
don't worry too much about this stuff. Just make sure
your bike is reliable and ride. I'm very happy with my
1997 RSX 26-36-46 low budget 7 speed 11-30 for touring.
If it was something else, I would probably enjoy the trip
about the same.

 

[Gwhite]

ccollins <[email protected]> wrote in message news:<[email protected]>...
> > Originally posted by Gwhite
>
> > but I know the problem is more getting the right rings,
> > right cogs, and right front derailleur than it is
> > actually shifting it on a properly set up bike.
>
> Yes, challenging.

I have to say I tend to agree with Bruce. Seriously consider
if it is worth the trouble when inexpensive but very well
functioning 9sp cassettes and triples are available.

> > The system is practically obsolete from lack of "true
> > need" and thus a dearth of specifically designed modern
> > hardware. 9 and 10sp cassettes do make its "need"
> > questionable for all but the heavily loaded tourist -- a
> > rare bird that easily explains the lack of manufacturer
> > support.
>
> That be me. I discovered the joy of heavily loaded touring
> last summer and I am "upgrading" my equipment for this
> summer's tour which I am planning.
>
> > I rode the system across the country. It worked great.
>
> You had a 26x42x46 (11,12,14,17,20,24,29,34)....

Yes, note the (42-46)x(12-14-17-20-24-29) is really the
half-step; the 11t and 34t are "extras" that add a 1 high
and 1 low gear.

> So I assume someone who is doing heavily loaded tours
> wants front outer chainrings that are half-step with a
> granny third gear.

Well theoretically it is the best. But ask in practice if a
9sp and "normal" triple wouldn't really do 98% of what you
"need." Is that last little bit worth the disproportionate
measure of effort for attainment? I would say no to almost
all people.

> This is the typical touring front?

Not any more. The 1/2 step w/ granny used to be the touring
standard in the 80's when Frank Berto was writing for
Bicycling Magazine. Now we have more cogs in the rear than
back then.

> And the current mass bike setup is the Alpine- style
> evenly spaced front chainrings.

As I said in another post, it isn't really "Alpine," it is
"crossover."

> Thus a triple front derailer (half-step) is what would
> work on a touring bike triple?

A modern "triple front derailer" is explicitly *not*
suitable for a
1/2 step. I don't think any new production touring bikes
use 1/2 step
w/ granny triples. They are crossover, like say a 46-34-24,
for example (as a guess). The 1/2 step front derailleur
is a special beast, not in current production to my
knowledge. Some double fronts could probably be made to
work. Conversely, a true half-step/granny front
derailleur will shift *any* system. Maybe not all
optimally, but it is universal.

> The outer two rings being close would not rub, and the
> granny gear to middle gear jump just works slowly and the
> touring rider just deals with....

There are some subtleties to setting this up today that you
are not keen to, since one cannot really purchase a
specifically designed modern 1/2 step w/ granny setup. I've
done it. It can work quite well but there some details
required to get good functional operation.

> Funny, you would think a touring setup *would* be an
> Alpine style front derailer.

These are entirely different gearing systems. Both have
similar low gears that allow hauling heavy loads over major
mountain passes. The
1/2 step has closer gear spacing across the range -- that is
its key characteristic. Both systems have similar ranges;
what you call the alpine and I call a crossover has
gearing gaps that the 1/2 step corrects for. Basically the
ranges are functionally the same but the
2/2 w/ granny has more total usable gears.

Seriously ask yourself if a 9sp cassette won't sufficiently
mitigate the gap "problem" for a tourist. I'm a gearhead and
like the 1/2 step, but even I question if it is worth the
effort, given the lack of manufacturer support and 9 and
10sp cassettes. I do have trouble generally recommending it
to anyone who hasn't tinkered with gearing quite a bit. It
might be better to just get a more standard system,
efficiently get it installed, and spend your time actually
riding and having fun.

> Thank you for the very informative conversation.

No problem. If you are still insistant on the setup, I can
give a few more tips.

 

[ccollins]

Originally posted by Gwhite

> No problem. If you are still insistant
> on the setup, I can give a few more
> tips.

Need you have asked? With my hard-head and affinity for using old stuff. Yes, this is my intent.

So, on E-bay (for $10.00) I just bought a NOS front derailuer. It is a FD-MT62 (half-step) "Deore II"

I am making a fully loaded touring bike.

The 110/74 cranks are my pallette on which I'll place good gears. From this thread it seems I am going to have the outer two be half-step distance and a bailout (For that big hill just south of Molera State Park in Big Sur).

The 170mm cranks need, I guess, 50/44 as the outers and something small like a 26.

What thought process goes into these decisions? For the rear freewheel, shouldn't I go with the Mega 7 (11,13,15,18,21,24,24)?. sheldonbrown.com writes of it as good technology and solid. The gearing is unique. Assuming it works with my shifters, and framespacing, how does this current proposed combo effect my choice of rear deraillier?

I have 7-SIS downtube shifters and the framespacing *is* 126mm.

So, I am going to jump through hoops, and search for odd old equiptment, and the result will be a good drivetrain for loaded touring. This is esoteric, but I appreciate the feedback. (and lessons).


--Chris

 

[Russell Seaton]

ccollins <[email protected]> wrote in message news:<aOndc.70248>
> The 110/74 cranks are my pallette on which I'll place good
> gears. From this thread it seems I am going to have the
> outer two be half-step distance and a bailout (For that
> big hill just south of Molera State Park in Big Sur).
>
> The 170mm cranks need, I guess, 50/44 as the outers and
> something small like a 26.
>
> What thought process goes into these decisions? For the
> rear freewheel, shouldn't I go with the Mega 7
> (11,13,15,18,21,24,34)?. sheldonbrown.com writes of it as
> good technology and solid. The gearing is unique. Assuming
> it works with my shifters, and framespacing, how does this
> current proposed combo effect my choice of rear
> deraillier?
>
> I have 7-SIS downtube shifters and the framespacing
> *is* 126mm.

Be sure to do the math to get your chainring spacing and
cogs correct to make half step plus granny work. If you have
the wrong rings and cogs, then you don't have half step plus
granny. You have a bunch of duplicate gears in a random
shifting pattern and a granny.

My loaded touring half step plus granny is 48-45-20 for the
crankset with 14-16-18-21-24-28-34 for the cogs. A nice 3 to
5 gear inch change between the main gears. Ideal for riding
into the wind fully loaded.

Bar end shifters. I would not want to try it with downtube
shifters. You need to be able to quickly and easily shift
the front derailleur with half step. Down tube shifters are
much slower and more awkward than bar end for shifting the
front derailleur. Especially if you are riding loaded with
heavily loaded low rider panniers.

As for a rear derailleur, get a long cage Shimano and it
will work. Not much choice to make.

Half step math works like this. (outer ring minus middle
ring) divided by middle ring to get percentage change. (48-
45)/45 = 6.67% The half step portion. For the full step
portion in the back it goes like this (larger cog minus
smaller cog) divided by smaller cog to get percentage
change. (16-14)/14 = 14.28% And (18-16)/16 = 12.5% And (21-
18)/18 = 16.67%. And (24-21)/21 = 14.28%. And (28-24)/24 =
16.67%. Not perfect but pretty good.

Your proposed gearing of 50-44-26 and 11-13-15-18-21-24-34
goes like this. (50-44)/44 = 13.63% for the half step
between chainrings. Full steps in the cogs are (13-11)/11 =
18.18%. And (15-13)/13 = 15.38%. And (18-15)/15 = 20%. And
(21-18)/18 = 16.67%. And (24-21)/24 =
17.5%. Not acceptable because your half step is as big or
bigger than your full steps. And your full steps vary way
too much 20% to 12.5%.

Basically your proposed gears are random gears. Its not
half step. My Trek 520 in 1991 came from the factory with a
50-45-28 and 12-14-16-18-21-24-28 setup. Apparently some
clueless idiot at Trek liked the marketing concept of half
step gearing for a touring bike but did not understand half
step gearing and specced chainrings he thought were odd,
and therefore, half step. It doesn't work that way. There
is a mathematical way to get half step gearing. If the math
does not work, you don't have half step gearing. You have
random gearing.

 

[Gwhite]

ccollins <[email protected]> wrote in message news:<[email protected]>...
> Originally posted by Gwhite
>
> > No problem. If you are still insistant on the setup, I
> > can give a few more tips.
>
> Need you have asked? With my hard-head and affinity for
> using old stuff. Yes, this is my intent.
>
> So, on E-bay (for $10.00) I just bought a NOS front
> derailuer. It is a FD-MT62 (half-step) "Deore II"

I don't know that model in particular. If it is a 1/2+granny
front, then it will be

1. "deep," so that the granny can be used. (A "shallow" one
would be okay for just a 1/2-step w/ no granny, but that
is not what you're doing.)
2. the inner plate "hangs" only scarcely lower than the
outer plate.

> I am making a fully loaded touring bike.
>
> The 110/74 cranks are my pallette on which I'll place
> good gears.

The right choice for nearly any bike in my opinion.

> From this thread it seems I am going to have the outer two
> be half-step distance and a bailout (For that big hill
> just south of Molera State Park in Big Sur).

By saying "bailout," in reference to the crank and rings, I
assume you are talking about the granny chainring. Anywhere
from 24t to 28t is fine, depending on your low gear
requirements.

> The 170mm cranks need, I guess, 50/44 as the outers and
> something small like a 26.

Hey now. No "guessing" is needed or desired. The gears are
defined by a balancing of mathematical relationship, as the
1/2-step is defined, and actual parts available. Don't
guess. Design or re-use that already designed. A 50-44 is
unlikely to meet the "half" criteria. A 50-46 is more likely
to be mathematically "correct."

> What thought process goes into these decisions?

I think this has been noted in this and countless other
threads to date. The mathematical definition of a half-step
is that the *step* between the front chainrings is *one-
half* that of the *step* between the rear cogs. Thus a shift
in the back is a "step," and that in the front is a "one-
half step." The relationship of steps is a so-called
"geometric" one. Another absolutely equivalent way of saying
this is that we strive to have certain "percent difference"
between gears.

Tooth counts are obviously integers (no 15.23 tooth cogs,
hah hah). The impact of this that one can only approximate
the ideal mathematical numbers representing the steps when
constrained by integers and the actual cogs those integers
represent. This approximation is practically unimportant:
the approximations are easily "close enough."

So the system can only be designed by understanding the
mathematical foundation. You don't have to do that because
it has already been done.

> For the rear freewheel, shouldn't I go with the Mega 7
> (11,13,15,18,21,24,24)?.

I presume (11,13,15,18,21,24,_28_)?.

We seek _equal_ geometric steps for the rear cog tooth
gradation. This is because we have only one geometric step
in the front (the granny is dismissed from design
consideration at this point because it is not a part of the
half-step system).

Computing the steps:
>> [meanStep, compavggeo] =
>> geomeanstep([11,13,15,18,21,24,28])
meanStep = .1672 .1432 .1826 .1543 .1336 .1543
compavggeo = .1559

So we would seek a chainring step of about half
"compavggeo," which is .1559/2 = 0.078 (7.8%).

Choosing some common big rings (50,48, & 46), we have

For 50 big ring middleRing = 46.2 round to 46

For 48 big ring middleRing = 44.4 round to 44

For 46 big ring middleRing = 42.5 round to 44 or 45

So let's arbitrarily test the result for the 48-44 combo:
44 48 11 106.000 115.636 13 89.692 97.846 15 77.733 84.800
18 64.778 70.667 21 55.524 60.571 24 48.583 53.000 28
41.643 45.429

For this we obtain (from low to high): meanStep = .0870
.0672 .0870 .0465 .0870 .0672 .0870 .0953 .0870 .0561 .0870
.0801 .0870

I don't like it. Note the step variance can get high.
There is a
3.65% and a 9.53% step.

Now let's look at the middle six cogs of my design and a
46-42 ring set. 42 46 12 92.750 101.583 14 79.500 87.071
17 65.471 71.706 20 55.650 60.950 24 46.375 50.792 29
38.379 42.034

For this we obtain (from low to high): meanStep = .0910
.0983 .0910 .0914 .0910 .0716 .0910 .1032 .0910 .0632 .0910

The step variance is a bit lower in this design. I think it
is superior.

If you are stuck with a 7sp freewheel, I would go with a 12-14-17-20-24-29-
34 rather than the 11-13-15-18-21-24-28. The "need" for a
heavily loaded touring gear above 100 inches is dubious --
it is easily sacrificed. On the other hand, a 34 tooth cog
will get used on tough climbs.

(12-14-17-20-24-28-34 & 12-14-17-20-24-28-32 are fine too.)

> sheldonbrown.com writes of it as good technology and
> solid. The gearing is unique.

Unique itself doesn't count.

> Assuming it works with my shifters, and framespacing, how
> does this current proposed combo effect my choice of rear
> deraillier?

It will be MTB and any modern 43t wrapup Shimano is fine.

> I have 7-SIS downtube shifters and the framespacing
> *is* 126mm.
>
> So, I am going to jump through hoops, and search for odd
> old equiptment, and the result will be a good drivetrain
> for loaded touring.

The only "odd" old part truly required is the front
derailleur. Most everything else can be had brand new.

I should note another "trouble" with this setup. The middle
and inner rings should be closer together than they are on
any other modern setup. Failure to "make this happen" will
result in occasional "bad" big-ring to middle-ring shifts in
the front. The chain will sometimes "freewheel" on the
middle ring if spaced with "normal" rings. How does one get
them closer? This is not easily done. What I did was buy a
_middle_ 46t ring and use it as the outer of my 46-42 combo.
This is the only simple way I found to solve this problem.
Rivendell did for a time have 46t "middles" for 110 cranks.
I know of no other easy and cheap solution. The "pickup
section/ramp" of "normal" outer rings places the tooth
centers too far apart. This is one of those subtleties that
makes me advise against the system.

You could make life easier you know. I still think you
should question your direction. I have some stuff you can
buy if you still insist. I have a Sachs 7sp 12-14-17-20-24-28-
32 freewheel (shimano 7sp SIS compatible) and a 126 mm
touring wheelset with a 40 spoke rear and 36 spoke front in
excellent condition.

> This is esoteric, but I appreciate the feedback. (and
> lessons).

 

[Chris Zacho "Th]

Deore started as a quality (for those days) touring group.
Since the earliest ATB's didn't have componentry of their
own, they used Touring parts, and the early frame geometry
was actually built to accommodate
it.

Eventually, ATB componentry and frames became a separate
species unto itself. And the Deore line became dedicated to
it's adopted new species. (and the tourist was once again
left behind to rot).

- -

"May you have the wind at your back. And a really low gear
for the hills!"

Chris Zacho ~ "Your Friendly Neighborhood Wheelman"

Chris'Z Corner http://www.geocities.com/czcorner