Cross shiftting

"Cross shifting", i.e., Large chain Ring/large cassette cog or small
chain ring/small cog is generally taken as a mortal sin. But with a
triple chain ring what limits are made to the shift pattern when on
the center ring? Assuming that the chain line through the center line
of the 5th cog, on a 9 speed cassette, and the center line of the
center chain ring?

It appears to me that considering the actual distance between the
three chain rings versus the actual distances on the cassette that the
center chain ring should be able to shift to any cog without problems.


John B. Slocomb
(johnbslocombatgmaildotcom)

On Jul 16, 5:30 am, John B. Slocomb wrote:
"Cross shifting", i.e., Large chain Ring/large cassette cog or small
chain ring/small cog is generally taken as a mortal sin. But with a
triple chain ring what limits are made to the shift pattern when on
the center ring? Assuming that the chain line through the center line
of the 5th cog, on a 9 speed cassette, and the center line of the
center chain ring?

It appears to me that considering the actual distance between the
three chain rings versus the actual distances on the cassette that the
center chain ring should be able to shift to any cog without problems.


A good setup should allow shifting to any combination without
problems, but for riding along you ideally want a straight chain line,
so as you shift more toward one end or the other of the cassette for
more than some brief circumstances, consider finding a combination
that moves the chain laterally at the front and rear together, rather
than shifting way back and forth at one end. (too long sentence)

On Jul 16, 8:38 am, Dan O wrote:
On Jul 16, 5:30 am, John B. Slocomb wrote:

"Cross shifting", i.e., Large chain Ring/large cassette cog or small
chain ring/small cog is generally taken as a mortal sin. But with a
triple chain ring what limits are made to the shift pattern when on
the center ring? Assuming that the chain line through the center line
of the 5th cog, on a 9 speed cassette, and the center line of the
center chain ring?

It appears to me that considering the actual distance between the
three chain rings versus the actual distances on the cassette that the
center chain ring should be able to shift to any cog without problems.

A good setup should allow shifting to any combination without
problems, but for riding along you ideally want a straight chain line,
so as you shift more toward one end or the other of the cassette for
more than some brief circumstances, consider finding a combination
that moves the chain laterally at the front and rear together, rather
than shifting way back and forth at one end. (too long sentence)

For me this amounts to two modes of operation: Outer chainring with a
few, closely spaced outer cogs for most riding, and middle chainring
with a few middle-to-inner cogs for gnarly steep climbing. (The inner
ring is for some as yet unimagined scenario, like hauling heavy loads
out from the bottom of the Grand Canyon. The inner cog is reserved as
bail-out gear and pie-plate.)

On my liesure (whjeelie) bike, the two modes are middle ring with a
couple of middle-ish cogs for riding around town, and outer ring with
a couple of outer cogs for top speed to the fire station.

On 16 jul, 14:30, John B. Slocomb wrote:
"Cross shifting", i.e., Large chain Ring/large cassette cog or small
chain ring/small cog is generally taken as a mortal sin. But with a
triple chain ring what limits are made to the shift pattern when on
the center ring? Assuming that the chain line through the center line
of the 5th cog, on a 9 speed cassette, and the center line of the
center chain ring?

It appears to me that considering the actual distance between the
three chain rings versus the actual distances on the cassette that the
center chain ring should be able to shift to any cog without problems.

John B. Slocomb
(johnbslocombatgmaildotcom)

Middle ring should shift any cogs. Large chainring avoid two largest
cogs; small chainring avoid two smallest cogs. It is that simple.

Lou

Lou Holtman wrote:

Middle ring should shift any cogs. Large chainring avoid two largest
cogs; small chainring avoid two smallest cogs. It is that simple.

Yes, but this presumes neutral chainline (middle ring aligns with the
middle rear sprocket).

Many MTBs these days have terrible chainline, where the crank is
shifted as much as two gears to the outside. This avoids much rubbing
of the chain on the adjacent sprocket when in small-small
combinations, but it means that the chainline in large-large
combinations is even more extreme.

In these circumstances, it is advisable to avoid the inner half of the
cassette when using the large ring, and the couple of largest
sprockets when using the middle ring. Not that anyone actually does
so.

Chalo

On Sun, 17 Jul 2011 01:17:20 -0700 (PDT), Chalo
wrote:

Lou Holtman wrote:

Middle ring should shift any cogs. Large chainring avoid two largest
cogs; small chainring avoid two smallest cogs. It is that simple.

Yes, but this presumes neutral chainline (middle ring aligns with the
middle rear sprocket).

Many MTBs these days have terrible chainline, where the crank is
shifted as much as two gears to the outside. This avoids much rubbing
of the chain on the adjacent sprocket when in small-small
combinations, but it means that the chainline in large-large
combinations is even more extreme.

In these circumstances, it is advisable to avoid the inner half of the
cassette when using the large ring, and the couple of largest
sprockets when using the middle ring. Not that anyone actually does
so.

Chalo

As I built this bike for this and that I was able to set the B.B.
spacers so that the center chain ring is lined up with the #5 cog of a
9 speed cassette.



John B. Slocomb
(johnbslocombatgmaildotcom)

On Sat, 16 Jul 2011 10:15:04 -0700 (PDT), Lou Holtman
wrote:

On 16 jul, 14:30, John B. Slocomb wrote:
"Cross shifting", i.e., Large chain Ring/large cassette cog or small
chain ring/small cog is generally taken as a mortal sin. But with a
triple chain ring what limits are made to the shift pattern when on
the center ring? Assuming that the chain line through the center line
of the 5th cog, on a 9 speed cassette, and the center line of the
center chain ring?

It appears to me that considering the actual distance between the
three chain rings versus the actual distances on the cassette that the
center chain ring should be able to shift to any cog without problems.

John B. Slocomb
(johnbslocombatgmaildotcom)

Middle ring should shift any cogs. Large chainring avoid two largest
cogs; small chainring avoid two smallest cogs. It is that simple.

Lou

That is what I thought but having been caught out with the "It's
obvious....." sort of thinking thought I'd ask.


John B. Slocomb
(johnbslocombatgmaildotcom)

On Jul 16, 1:30*pm, John B. Slocomb wrote:
"Cross shifting", i.e., Large chain Ring/large cassette cog or small
chain ring/small cog is generally taken as a mortal sin. But with a
triple chain ring what limits are made to the shift pattern when on
the center ring? Assuming that the chain line through the center line
of the 5th cog, on a 9 speed cassette, and the center line of the
center chain ring?

It appears to me that considering the actual distance between the
three chain rings versus the actual distances on the cassette that the
center chain ring should be able to shift to any cog without problems.

John B. Slocomb
(johnbslocombatgmaildotcom)

I always like to think that the smallest sprocket must only be used
with the outer ring and the biggest sprocket must only be used with
the smallest ring. This help reduce the strains imposed on the
derailleur pulley spring(s) and sometimes is the only way to shift
cleanly over the entire range without having a drooping chain.
Depending upon your derailleur it might be as well to limit the mid
ring off the bottom two sprockets (if its a racing type der).

On Sat, 16 Jul 2011 10:53:51 -0700 (PDT), thirty-six
wrote:

On Jul 16, 1:30*pm, John B. Slocomb wrote:
"Cross shifting", i.e., Large chain Ring/large cassette cog or small
chain ring/small cog is generally taken as a mortal sin. But with a
triple chain ring what limits are made to the shift pattern when on
the center ring? Assuming that the chain line through the center line
of the 5th cog, on a 9 speed cassette, and the center line of the
center chain ring?

It appears to me that considering the actual distance between the
three chain rings versus the actual distances on the cassette that the
center chain ring should be able to shift to any cog without problems.

John B. Slocomb
(johnbslocombatgmaildotcom)

I always like to think that the smallest sprocket must only be used
with the outer ring and the biggest sprocket must only be used with
the smallest ring. This help reduce the strains imposed on the
derailleur pulley spring(s) and sometimes is the only way to shift
cleanly over the entire range without having a drooping chain.
Depending upon your derailleur it might be as well to limit the mid
ring off the bottom two sprockets (if its a racing type der).

You are correct but there are times when you are on, say the middle
ring with a BIG hill just down the road and at the same time a bit
more speed is possible for the next few moments and rather then shift
both front and back for the next 100 M and then shift back I usually
just go up a cog on the back, if it is possible, even if it turns out
to be the little one.


John B. Slocomb
(johnbslocombatgmaildotcom)

On Jul 17, 2:22*pm, John B. Slocomb wrote:
On Sat, 16 Jul 2011 10:53:51 -0700 (PDT), thirty-six



wrote:
On Jul 16, 1:30*pm, John B. Slocomb wrote:
"Cross shifting", i.e., Large chain Ring/large cassette cog or small
chain ring/small cog is generally taken as a mortal sin. But with a
triple chain ring what limits are made to the shift pattern when on
the center ring? Assuming that the chain line through the center line
of the 5th cog, on a 9 speed cassette, and the center line of the
center chain ring?

It appears to me that considering the actual distance between the
three chain rings versus the actual distances on the cassette that the
center chain ring should be able to shift to any cog without problems.

John B. Slocomb
(johnbslocombatgmaildotcom)

I always like to think that the smallest sprocket must only be used
with the outer ring and the biggest sprocket must only be used with
the smallest ring. *This help reduce the strains imposed on the
derailleur pulley spring(s) and sometimes is the only way to shift
cleanly over the entire range without having a drooping chain.
Depending upon your derailleur it might be as well to limit the mid
ring off the bottom two sprockets (if its a racing type der).

You are *correct but there are times when you are on, say the middle
ring with a BIG hill just down the road and at the same time a bit
more speed is possible for the next few moments and rather then shift
both front and back for the next 100 M and then shift back I usually
just go up a cog on the back, if it is possible, even if it *turns out
to be the little one.

John B. Slocomb
(johnbslocombatgmaildotcom)

When I using a regiular spaced six speed block (1.1/4" wide) I was
driving 42x14 and 42x13 (smallest) a lot of the time. Without a 16 I
had difficulty using the 52 ring. Extra sprockets help, but are not
the solution to greatest efficiency. A half step setup makes front
shifts easy and the common middle gears are all near to straight.
It's also good for those who are able to accelerate quickly or need to
grab a low gear quickly because the wide range block is shifting over
fewer sprockets in usually a narrower space.