A Cycling & bikes forum. CycleBanter.com

Go Back   Home » CycleBanter.com forum » rec.bicycles » Techniques
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

Cross shiftting



 
 
Thread Tools Display Modes
  #11  
Old July 17th 11, 05:14 AM posted to rec.bicycles.tech
[email protected]
external usenet poster
 
Posts: 2,322
Default Cross shiftting

On Jul 16, 9:57*pm, " wrote:
On Jul 16, 7:30*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.


Sheldon Brown has a gear "visualizer", and there's another one called
"Gerz" that makes charting pretty easy.

It seems to me that with the 30/42/52 triple I have, run against 8sp
and 9sp cassettes with 13-23 or 14-26t cog spreads, you wind up with
gear ratios that favor running the two or three cogs most in line with
both the inner and outer rings, while the middle ring works over four
or five cogs, overlapping so to speak with the inner and outer rings
on one cog. It's been a few years, maybe I'm misremembering but I
think this "question" pretty much takes care of itself in practice if
you will.

Meaning, you're keeping the chain fairly straight while you use "same
ratios" (or close duplicates) of gears you might find by "crossing"
farther on any of the ring/cog combinations. Not to say you shouldn't
"be able" to use any cog/chainring combination without either drooping
the chain (which invites unshipping and/or dragging in the dirt) or
binding/breaking the rear derailleur due to too short a chain, but why
not use the chain in happier combinations?
--D-y


Well... I went back to Sheldon and did the numbers. The numbers don't
"work" as far as duplicate gears or even steps between chainwheel
"ranges". That part I blew out my wazoo, if that is a plain enough mea
culpa. "Way off on that one".

I did ride an 8sp triple with 30/42/52 chainrings and a 12-23 cassette
(12, 13, 14, 15, 17, 19, 21, 23) for "a season", a couple of years
ago.
I found, in use, that pairing the 30t ring with the 23 and 21,
shifting to the 42 for the middle five cogs, and using the 52 with the
last two (or maybe three) cogs worked in "real life", for my solo
riding and with "fast recreational groups".

This might be partly due to the fact that I used 42/52 or 53
chainrings for about 25 years or so before changing to the "new" 39/5x
arrangement. I didn't realize how much I missed the 42 until I had it
to use again.

I'm not even vaguely interested in a "double shift" arrangement by
whatever name, having tried one once or twice way back in the day.
Some people like them and more power, each to their taste, that's why
they make different components, etc. etc.
--D-y
Ads
  #12  
Old July 17th 11, 09:17 AM posted to rec.bicycles.tech
Chalo
external usenet poster
 
Posts: 5,093
Default Cross shiftting

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
  #13  
Old July 17th 11, 02:22 PM posted to rec.bicycles.tech
John B. slocomb
external usenet poster
 
Posts: 23
Default Cross shiftting

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)
  #14  
Old July 17th 11, 02:22 PM posted to rec.bicycles.tech
John B. slocomb
external usenet poster
 
Posts: 23
Default Cross shiftting

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)
  #15  
Old July 17th 11, 02:22 PM posted to rec.bicycles.tech
John B. slocomb
external usenet poster
 
Posts: 23
Default Cross shiftting

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)
  #16  
Old July 17th 11, 02:22 PM posted to rec.bicycles.tech
John B. slocomb
external usenet poster
 
Posts: 23
Default Cross shiftting

On Sat, 16 Jul 2011 14:11:39 -0400, "Ronsonic"
wrote:


"John B. Slocomb" wrote in message
.. .

"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.


As far as the chain and rear der are concerned all the cogs are in play from
the middle ring.

Not all setups will run without the chain rubbing the front der cage or big
chainwheel. If you can trim the front der all's good.

Both front and back are friction bar end shifters so "trimming" is not
a major undertaking :-)


John B. Slocomb
(johnbslocombatgmaildotcom)
  #17  
Old July 17th 11, 02:56 PM posted to rec.bicycles.tech
thirty-six
external usenet poster
 
Posts: 10,049
Default Cross shiftting

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.
  #18  
Old July 17th 11, 05:04 PM posted to rec.bicycles.tech
Barry[_3_]
external usenet poster
 
Posts: 111
Default Cross shiftting

Sheldon Brown has a gear "visualizer", and there's another one called
"Gerz" that makes charting pretty easy.


This one is very nice:

http://www.gear-calculator.com


  #19  
Old July 18th 11, 04:59 AM posted to rec.bicycles.tech
Michael Press
external usenet poster
 
Posts: 9,202
Default Cross shiftting

In article ,
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.


I cross chain whenever I feel like it.
When convenient I change over to a straighter run.
Do not allow guilt to poison your life. Chains are cheap.

--
Michael Press
  #20  
Old July 18th 11, 05:45 AM posted to rec.bicycles.tech
T°m Sherm@n
external usenet poster
 
Posts: 813
Default Cross-chaining

On 7/17/2011 10:59 PM, Michael Press wrote:
In ,
John B. 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.


I cross chain whenever I feel like it.
When convenient I change over to a straighter run.
Do not allow guilt to poison your life. Chains are cheap.


Indeed, occasional cross-chaining will not hurt anything, unless through
incompetence or poor judgement, your bicycle had a chain too short to
accommodate the big-big combination, in which case you can wrap the
chain and derailer into the spokes and/or bend or break the derailer hanger.

--
Tºm Shermªn - 42.435731°N, 83.985007°W
I am a vehicular cyclist.
 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
700c front wheel 2-cross lacing vs 3-cross & lateral flex kwalters Techniques 31 April 4th 07 07:58 AM
FS: Salsa cross bike just in time for cross season... Jeffrey C. Jay Marketplace 0 October 9th 05 08:39 AM
FS: Fuji Cross, 60cm, versatile road or cross bike - $600 Darrell Marketplace 0 July 12th 05 02:39 AM
3 cross or 4 cross for 24" Muni/trials? The Munieer Unicycling 2 March 3rd 04 04:23 PM
Four cross spokes for cross wheels? Dave S Techniques 17 November 1st 03 01:49 AM


All times are GMT +1. The time now is 02:57 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 CycleBanter.com.
The comments are property of their posters.