duplicate gear ratios, distributing drive train wear..

In article <[email hidden]>,

wle said:

say your gearing setup has some duplicated gears.
you can get the same thing from the big chainring or the little one,
by selecting the appropriate cog.
how do you pick which one to use?

Assuming you aren't using a half-step system:

Cogs shift faster than rings - so you shift cogs until you're about to run out,
and then change ring + cog.

I usually run 50-40-30 x 13-14-15-16-17-18-19-21-23. I start wherever I parked
it and up or down shift to maintain a comfortable cadence. If I'm going to
run out I change rings and move 3 cogs towards the middle of the cassette
unless I've just hit the top or bottom of a hill and want a big change with
the ring only.

IOW, instead of shifting from 40x14 to 40x13 I'd go to 50x17 and stay on my
big ring until wind got bad or I started up hill.

Quoted message said:

what if you thought, well i should minimize total wear..?

Cogs last long enough. Rings last longer (they have a lot more teeth).

--
<a href="http://www.poohsticks.org/drew/">Home Page</a>
Life is a terminal sexually transmitted disease.

(Drew Eckhardt) said:

Cogs last long enough. Rings last longer (they have a lot more teeth).

Really? I would expect the opposite.

I don't quite have enough data to be sure - I get about 6,000 miles
from a ring, I've never had to replace a cog (though so far I only
have about 5,000 miles on each cogset...)

Michael

In my case with 53/39 and 12-23, I try to limit myself from using the 53
with my 21 and 23 cogs and limit my 39 using the 12 and 13 tooth cogs.
How I do this is double shifting...

If I am in a big gear and the going gets steep, I gradually shift to a
larger cog until I am in the 19 tooth, then I drop down to the 16
(double shift) AND drop to the 39 ring.

Likewise, if the going gets easy in the 39, I will drop down cogs until
the 14 tooth, then I shift up to the 16 and go up to the 53 ring.

I can shift BOTH at the same time because I have a Third Eye
chainwatcher which keeps the chain from dropping. This is very important
on Campy but even Shimano Dura Ace benefits from it, especially on
rougher surfaces.

--

(wle) said:

say your gearing setup has some duplicated gears.
you can get the same thing from the big chainring or the little one,
by selecting the appropriate cog.
how do you pick which one to use?

Shoot for the combination that produces the straightest chain line.

--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Surrealism is a pectinated ranzel.

wle said:

say your gearing setup has some duplicated gears.
you can get the same thing from the big chainring or the little one,
by selecting the appropriate cog.
how do you pick which one to use?

[avoiding big/big combinations, i know that..]

what if you thought, well i should minimize total wear..?
how would you do that?
assume most of the time you are using the small chainring.
should you shift to the big one, if the desired ratio is available there?
or stay small as long as possible?

do chainrings [aluminum] wear before cogs [steel]?
if so, you would think, well use the big one when you can, to distribute the
wear.
if not, then you would try to use your smaller cogs and spread the
wear around there, but you would be using your small chainring more..

You could get a lot more duplicate combinations by adding a SRAM
DualDrive hub and Schlumpf 2-speed bottom bracket. 😉

--
Tom Sherman – Quad City Area

Tom Sherman said:

wle said:

say your gearing setup has some duplicated gears.
you can get the same thing from the big chainring or the little one,
by selecting the appropriate cog.
how do you pick which one to use?

[avoiding big/big combinations, i know that..]

what if you thought, well i should minimize total wear..?
how would you do that?
assume most of the time you are using the small chainring.
should you shift to the big one, if the desired ratio is available there?
or stay small as long as possible?

do chainrings [aluminum] wear before cogs [steel]?
if so, you would think, well use the big one when you can, to distribute the
wear.
if not, then you would try to use your smaller cogs and spread the
wear around there, but you would be using your small chainring more..

You could get a lot more duplicate combinations by adding a SRAM
DualDrive hub and Schlumpf 2-speed bottom bracket. 😉

Didn't Shimano make a 5-speed front chainring set for a while? That
would also provide a multiplier.

--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Surrealism is a pectinated ranzel.

When I had a bike with half-step gearing, it was pretty easy to utilize all
the ratios, and there were no duplicates. But, with three chainrings and
six to nine rear cogs, how would you remember which ones are duplicates--put
a chart on the handlebars? For myself, I'll continue to pedal in whatever
gear keeps me going, and avoid the "crossed" positions.

Leo Lichtman said:

When I had a bike with half-step gearing, it was pretty easy to utilize all
the ratios, and there were no duplicates. But, with three chainrings and
six to nine rear cogs, how would you remember which ones are duplicates--put
a chart on the handlebars?...

Here are the gear inch combinations of my bike with a triple crank and
SRAM 3x7 hub:

125 92 67 101 74 54 72 53 39
106 78 57 86 63 46 61 45 33
92 68 49 74 55 40 53 39 28
77 56 41 62 46 33 44 33 24
66 48 35 53 39 28 38 28 20
57 42 31 46 34 25 33 24 18
49 36 26 40 29 21 28 21 15

Needless to say, I do not have a chart on my handlebars. 😉

--
Tom Sherman – Quad City Area

Tom Sherman said:

Here are the gear inch combinations of my bike with a triple crank and
SRAM 3x7 hub:

125 92 67 101 74 54 72 53 39
106 78 57 86 63 46 61 45 33
92 68 49 74 55 40 53 39 28
77 56 41 62 46 33 44 33 24
66 48 35 53 39 28 38 28 20
57 42 31 46 34 25 33 24 18
49 36 26 40 29 21 28 21 15

Needless to say, I do not have a chart on my handlebars. 😉

Eek. That's almost a 9:1 difference between the lowest and highest.
15 gear inches would be hard to find a use for, I should think, unless
you were going to use it when pulling stuck pickups out of the mud.
(You'd need a little ballast on the front, I guess.)
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Surrealism is a pectinated ranzel.

In article <2k1gfvF13o ore..

Quoted message said:

You could get a lot more duplicate combinations by adding a SRAM
DualDrive hub and Schlumpf 2-speed bottom bracket. 😉

--

true..

wle.

Quoted message said:

Tom Sherman – Quad City Area

wle said:

say your gearing setup has some duplicated gears.
you can get the same thing from the big chainring or the little one,
by selecting the appropriate cog.
how do you pick which one to use?

I'd take the best chainline, and try to avoid more than one front shift
running through the entire gear range. Luckily these objectives are not
desperately contradictory.
--
David Damerell <[email hidden]> Kill the tomato!

Quoted message said:

Eek. That's almost a 9:1 difference between the lowest and highest.
15 gear inches would be hard to find a use for, I should think, unless
you were going to use it when pulling stuck pickups out of the mud.
(You'd need a little ballast on the front, I guess.)

I run a 20 inner chainring and a 34 rear cog on my half step plus
granny touring bike. A little under 16 gear inches. I've never
thought it was too low yet. I rarely use this combination of course.
The 20x28 or 20x24 are usually low enough. But it gives me peace of
mind to know I have a 20x34 just in case when touring loaded up a
mountain.

I sort of try to spread the wear amongst the cogs. I always wear out
the 16 and 17 and 19 cogs first on a cassette. Use the 42x15 instead
of 53x19. Or 42x14 instead of the 53x17. Roughly. But I don't lose
too much sleep at night worrying about it. Of course I use cheap
loose cog steel Campagnolo cassettes. Maybe if I used those $120 to
$160 10 speed cassettes I would be a lot more concerned.

Chainrings for the most part don't wear out. Even though they are
made of aluminum and the cogs are steel, you can run chainrings almost
forever.

[email hidden] (wle) wrote in message news:<[email hidden]>...

Quoted message said:

say your gearing setup has some duplicated gears.
you can get the same thing from the big chainring or the little one,
by selecting the appropriate cog.
how do you pick which one to use?

[avoiding big/big combinations, i know that..]

what if you thought, well i should minimize total wear..?
how would you do that?
assume most of the time you are using the small chainring.
should you shift to the big one, if the desired ratio is available there?
or stay small as long as possible?

do chainrings [aluminum] wear before cogs [steel]?
if so, you would think, well use the big one when you can, to distribute the
wear.
if not, then you would try to use your smaller cogs and spread the
wear around there, but you would be using your small chainring more..

wle.

"Russell Seaton" wrote: I run a 20 inner chainring (clip)
^^^^^^^^^^
That's what I'm LOOKING for. Are they available? When I look at my 22T, it
looks like anything much smaller would really crowd the bolt circle. I used
to have an adapter that allowed the use of rear cogs as granny gears. I'm
unable to find those now, too.

Leo Lichtman said:

"Russell Seaton" wrote: I run a 20 inner chainring (clip)
^^^^^^^^^^
That's what I'm LOOKING for. Are they available? When I look at my 22T, it
looks like anything much smaller would really crowd the bolt circle. I used
to have an adapter that allowed the use of rear cogs as granny gears. I'm
unable to find those now, too.

Dear Leo,

http://abundantadventures.com/quads.html

Carl Fogel

Leo Lichtman said:

"Russell Seaton" wrote: I run a 20 inner chainring (clip)
^^^^^^^^^^
That's what I'm LOOKING for. Are they available? When I look
at my 22T, it looks like anything much smaller would really crowd
the bolt circle.

An ordinary 58mm compact bolt circle will take a 20t chainring. There are a
number on the market, and they're cheap. Suntour and TA's 56mm circle would
allow a 19t, but I don't know of anyone currently making one.

Quoted message said:

I used to have an adapter that allowed the use of rear cogs as
granny gears. I'm unable to find those now, too.

Mountain Tamer adapters will do a similar job:

http://abundantadventures.com/quads.html

James Thomson

Werehatrack said:

Tom Sherman said:

Here are the gear inch combinations of my bike with a triple crank and
SRAM 3x7 hub:

125 92 67 101 74 54 72 53 39
106 78 57 86 63 46 61 45 33
92 68 49 74 55 40 53 39 28
77 56 41 62 46 33 44 33 24
66 48 35 53 39 28 38 28 20
57 42 31 46 34 25 33 24 18
49 36 26 40 29 21 28 21 15

Needless to say, I do not have a chart on my handlebars. 😉

Eek. That's almost a 9:1 difference between the lowest and highest.
15 gear inches would be hard to find a use for, I should think, unless
you were going to use it when pulling stuck pickups out of the mud.
(You'd need a little ballast on the front, I guess.)

An overweight, fully-faired recumbent needs a much wider gear range than
an upright road bike.

--
Tom Sherman – Quad City Area

Leo Lichtman said:

"Russell Seaton" wrote: I run a 20 inner chainring (clip)
^^^^^^^^^^
That's what I'm LOOKING for. Are they available? When I look at my 22T, it
looks like anything much smaller would really crowd the bolt circle. I used
to have an adapter that allowed the use of rear cogs as granny gears. I'm
unable to find those now, too.

The White adapter (got em here someplace) used Suntour "A"
low gear freewheel cogs as low as 18t but bolted to a 74mm
crank ( lowest gear 24t) not a 58mm crank (lowest gear 20t).

We, like most competent LBS, have 58mm x 20t, too.

--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

Get a Rohloff hub and you have no duplications...

"wle" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

say your gearing setup has some duplicated gears.
you can get the same thing from the big chainring or the little one,
by selecting the appropriate cog.
how do you pick which one to use?