Touring - Early 1990s Shimano group

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

(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.

Sheldon Brown wrote in message ...
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.

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



--

In article , usenet-
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.

ccollins wrote in message ...
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
1/2 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.

Originally posted by Gwhit

No problem. If you are still insistant on the setup, I can give a fe
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
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. Fro
this thread it seems I am going to have the outer two be half-ste
distance and a bailout (For that big hill just south of Molera Stat
Park in Big Sur)

The 170mm cranks need, I guess, 50/44 as the outers and something smal
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.co
writes of it as good technology and solid. The gearing is unique
Assuming it works with my shifters, and framespacing, how does thi
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 i
esoteric, but I appreciate the feedback. (and lessons)

--Chri


-

ccollins 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 =
12.5%. 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.

ccollins wrote in message ...
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 =
0.1672
0.1432
0.1826
0.1543
0.1336
0.1543
compavggeo =
0.1559

So we would seek a chainring step of about half "compavggeo," which is
0.1559/2 = 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 =
0.0870
0.0672
0.0870
0.0465
0.0870
0.0672
0.0870
0.0953
0.0870
0.0561
0.0870
0.0801
0.0870

I don't like it. Note the step variance can get high. There is a
4.65% 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 =
0.0910
0.0983
0.0910
0.0914
0.0910
0.0716
0.0910
0.1032
0.0910
0.0632
0.0910

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).

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