Cycling and bicycle discussion forums. 
   Click here to join our community Log in to access your Control Panel  


Go Back   > >

Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

User Tag List

Reply
 
Thread Tools Search this Thread
Old 11-21-11, 12:52 PM   #1
southpawboston 
Senior Member
Thread Starter
 
southpawboston's Avatar
 
Join Date: Aug 2008
Location: Somerville, MA and Catskill Mtns
Bikes:
Posts: 4,008
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Shimano 8/9 speed compatibility

Are Shimano 9-speed derailleurs backwards compatible with 8-speed cassettes and shifters? Or is the cable pull different between the two systems? i.e., can I buy a new 9-speed Shimano RD and have it index properly with my existing 8-speed cassette and shifters?

And while I'm at it, what new medium-cage derailleurs will handle a 32T large cog?
__________________
Velo Lumino - Lighting components and integration solutions for fine hand-built and classically inspired bicycles

Riding the Catskills blog

Flickr

1971 Mercian Olympic | 1972 Jeunet 630 | 1982 Jack Taylor Tour of Britain | 1984 Shogun 1500 650B | 2013 Rawland Stag | 2014 Jeff Lyon L'Avecaise | 2015 Bike Friday Haul-a-Day

Last edited by southpawboston; 11-21-11 at 12:56 PM.
southpawboston is offline   Reply With Quote
Old 11-21-11, 01:03 PM   #2
CACycling
Senior Member
 
CACycling's Avatar
 
Join Date: Feb 2008
Location: Oxnard, CA
Bikes: '08 Fuji Roubaix RC; '07 Schwinn Le Tour GS; '92 Diamond Back Ascent EX
Posts: 4,565
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
9 speed will index fine on 8 speed. Check the Shimano web site for the level of component you are looking at to see the max cogs size for the various RDs.
CACycling is offline   Reply With Quote
Old 11-21-11, 01:37 PM   #3
AEO
Senior Member
 
AEO's Avatar
 
Join Date: Jun 2007
Location: A Coffin Called Earth. or Toronto, ON
Bikes: Bianchi, Miyata, Dahon, Rossin
Posts: 12,258
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
as long as you avoid dura ace and shadow derailers, the compatibility is fine.

There are two different medium cages. One is MTB, the other is road.
The road is specified to 27T max, but usually 30T is okay.
The MTB is specified to 34T max.
__________________
Food for thought: if you aren't dead by 2050, you and your entire family will be within a few years from starvation. Now that is a cruel gift to leave for your offspring. ;)
http://sanfrancisco.ibtimes.com/arti...ger-photos.htm
AEO is offline   Reply With Quote
Old 11-21-11, 02:33 PM   #4
southpawboston 
Senior Member
Thread Starter
 
southpawboston's Avatar
 
Join Date: Aug 2008
Location: Somerville, MA and Catskill Mtns
Bikes:
Posts: 4,008
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Thanks, I figured most mtb derailleurs are equipped to handle larger cogs. The reason I need a medium cage that can handle a large cog is because this is for a tandem with 20" wheels, so a long cage would rub the tire (not to mention risk getting eaten by rocks and curbs). But I need mtb gearing to negotiate some serious hills and heavy loads.
__________________
Velo Lumino - Lighting components and integration solutions for fine hand-built and classically inspired bicycles

Riding the Catskills blog

Flickr

1971 Mercian Olympic | 1972 Jeunet 630 | 1982 Jack Taylor Tour of Britain | 1984 Shogun 1500 650B | 2013 Rawland Stag | 2014 Jeff Lyon L'Avecaise | 2015 Bike Friday Haul-a-Day
southpawboston is offline   Reply With Quote
Old 11-21-11, 03:54 PM   #5
davidad
Senior Member
 
Join Date: Feb 2009
Bikes:
Posts: 4,853
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 10 Post(s)
Quote:
Originally Posted by southpawboston View Post
Thanks, I figured most mtb derailleurs are equipped to handle larger cogs. The reason I need a medium cage that can handle a large cog is because this is for a tandem with 20" wheels, so a long cage would rub the tire (not to mention risk getting eaten by rocks and curbs). But I need mtb gearing to negotiate some serious hills and heavy loads.
Friends who have trikes ride with 20 and 16 inch wheels and mountain derailuers with no problems.
davidad is online now   Reply With Quote
Old 11-22-11, 11:46 AM   #6
southpawboston 
Senior Member
Thread Starter
 
southpawboston's Avatar
 
Join Date: Aug 2008
Location: Somerville, MA and Catskill Mtns
Bikes:
Posts: 4,008
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by davidad View Post
Friends who have trikes ride with 20 and 16 inch wheels and mountain derailuers with no problems.
What size tires are they running? I bolted up a long cage Deore LX, and found that the cage rubbed against the 20x1.9" tire when in the largest cog. A narrower tire may allow it to clear, but then I don't want a narrower tire on a tandem that sometimes weighs over 400lb loaded up.
__________________
Velo Lumino - Lighting components and integration solutions for fine hand-built and classically inspired bicycles

Riding the Catskills blog

Flickr

1971 Mercian Olympic | 1972 Jeunet 630 | 1982 Jack Taylor Tour of Britain | 1984 Shogun 1500 650B | 2013 Rawland Stag | 2014 Jeff Lyon L'Avecaise | 2015 Bike Friday Haul-a-Day
southpawboston is offline   Reply With Quote
Old 11-22-11, 12:09 PM   #7
FastJake
Constant tinkerer
 
FastJake's Avatar
 
Join Date: May 2010
Location: Madison, Wisconsin
Bikes:
Posts: 7,574
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
If you can't use a MTB derailer I've been able to get to at 32T with a short cage road derailer, provided a long enough b-tension screw. It's not ideal but it might be your only option for running those big cogs.

Tandem with 20" wheels? Don't think I've ever seen anything like that before. Mind posting a picture?
FastJake is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

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

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -6. The time now is 12:33 PM.