Go Back  Bike Forums > Bike Forums > Bicycle Mechanics
Reload this Page >

Shimano M772 RD- largest cassette??

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.

Shimano M772 RD- largest cassette??

Old 05-25-18, 10:35 AM
  #1  
Tandem Tom
Senior Member
Thread Starter
 
Join Date: Dec 2011
Location: NE Ohio
Posts: 1,904

Bikes: 1992 Serotta Colorado II,Co-Motion Speedster, Giant Escape Hybrid, 1977 Schwinn Super Le Tour

Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 222 Post(s)
Likes: 0
Liked 3 Times in 2 Posts
Shimano M772 RD- largest cassette??

Have the above RD on my touring bike and would like to go up to a 36t cassette from a 34t. I know what the spec's say but I wonder if anyone has gone this route?
Thanks!!
Tandem Tom is offline  
Old 05-25-18, 11:19 AM
  #2  
Ghrumpy
Senior Member
 
Join Date: Jul 2009
Posts: 800
Mentioned: 14 Post(s)
Tagged: 0 Thread(s)
Quoted: 379 Post(s)
Likes: 0
Liked 2 Times in 2 Posts
Originally Posted by Tandem Tom View Post
Have the above RD on my touring bike and would like to go up to a 36t cassette from a 34t. I know what the spec's say but I wonder if anyone has gone this route?
Thanks!!
Can't help you specifically, but generally speaking, "cheating" a bigger cog than a derailleur is rated for requires you to factor in the total capacity rating and whether your gear combinations are within that capacity. If you are, then you can often cheat the bigger cog by running the chain a link short. Total capacity rating is a function of the RD cage length, for the most part.
So it would be helpful to provide this information:
Derailleur cage length (SGS or GS. SGS is longer)
Rear cogset (low-high)
Front chainrings (low-high)
Ghrumpy is offline  
Old 05-25-18, 11:24 AM
  #3  
Tandem Tom
Senior Member
Thread Starter
 
Join Date: Dec 2011
Location: NE Ohio
Posts: 1,904

Bikes: 1992 Serotta Colorado II,Co-Motion Speedster, Giant Escape Hybrid, 1977 Schwinn Super Le Tour

Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 222 Post(s)
Likes: 0
Liked 3 Times in 2 Posts
Cage is long, crankset is 22 low 44 high.
Tandem Tom is offline  
Old 05-25-18, 11:25 AM
  #4  
Tandem Tom
Senior Member
Thread Starter
 
Join Date: Dec 2011
Location: NE Ohio
Posts: 1,904

Bikes: 1992 Serotta Colorado II,Co-Motion Speedster, Giant Escape Hybrid, 1977 Schwinn Super Le Tour

Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 222 Post(s)
Likes: 0
Liked 3 Times in 2 Posts
Cassette I am considering 12-36
Tandem Tom is offline  
Old 05-25-18, 11:38 AM
  #5  
Ghrumpy
Senior Member
 
Join Date: Jul 2009
Posts: 800
Mentioned: 14 Post(s)
Tagged: 0 Thread(s)
Quoted: 379 Post(s)
Likes: 0
Liked 2 Times in 2 Posts
Originally Posted by Tandem Tom View Post
Cage is long, crankset is 22 low 44 high.

Cassette I am considering 12-36
Thanks, that was quick.

You started at the max, and this cassette puts you a little over. The SGS cage has a total capacity of 45t, with that cassette you're at 46t. It has a max chainring difference of 22t, you're right there.

One other factor that determines max rear cog rating and that is the derailleur hanger drop. It's not clear what drop the factory ratings are based on, unfortunately. (If I were to guess I'd say 28 or 30mm for MTB derailleurs.) Maybe your hanger is longer than what they used, maybe not. If your dropouts are horizontal, you can scoot the axle as far back as possible to get a little more gap. Or you could try screwing the B-tension in more.
Shimano's ratings tend to be a bit conservative. So you could try it, but it will take some tweaking, and I wouldn't get your hopes up too much. You'd have to make extra sure you don't cross-chain big-big.
Ghrumpy is offline  
Old 05-25-18, 11:55 AM
  #6  
IK_biker
old fart
 
Join Date: Dec 2007
Location: PA-US
Posts: 380
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 119 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
I've used a M771 (about the same geometry as M772) with a 11-36t cassette on 2 bikes, for a total of ~9,000 miles and counting.
No issue with clearance to largest cog, the B-screw is within its intended range.
IK_biker is offline  
Old 05-25-18, 02:56 PM
  #7  
Tandem Tom
Senior Member
Thread Starter
 
Join Date: Dec 2011
Location: NE Ohio
Posts: 1,904

Bikes: 1992 Serotta Colorado II,Co-Motion Speedster, Giant Escape Hybrid, 1977 Schwinn Super Le Tour

Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 222 Post(s)
Likes: 0
Liked 3 Times in 2 Posts
Thanks for the replies!!
I had heard that the shimanS spec's were a bit on the conservative side . Will order the cassette and go from there!
Tandem Tom is offline  
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
KTU
Road Cycling
3
08-18-09 01:33 PM
b_young
Commuting
24
09-20-07 02:23 PM
toThinkistoBe
Bicycle Mechanics
7
11-09-05 12:27 PM
trayer350
Advocacy & Safety
16
07-20-05 01:52 PM

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


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.