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

Changing chainrings on XT M770 crankset

Notices
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.

Changing chainrings on XT M770 crankset

Old 10-21-15, 02:10 PM
  #1  
Junior Member
Thread Starter
 
Join Date: May 2015
Posts: 130
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 30 Post(s)
Likes: 0
Liked 2 Times in 1 Post
Changing chainrings on XT M770 crankset

When I decided to upgrade my stock crankset, I picked up a Shimano M770. Unfortunately, however, the largest ring is 44T (was 48) and I discovered I couldn't get the front mech low enough (chain stay in the way). Being more willing than able, I hadn't anticipated that. D'oh!

Is there any reason why I couldn't substitute M771 chainrings (48/36/26, which match my original setup) as opposed to the 44/32/22 on the 770?

I did a little research on other chainrings, but even when they were drilled in the same format, I kept reading there was some issue with "tabs" being the wrong size. Or sumpin'.

Thanks for the help.
cloozoe is offline  
Old 10-21-15, 03:42 PM
  #2  
Senior Member
 
dsbrantjr's Avatar
 
Join Date: Sep 2010
Location: Roswell, GA
Posts: 8,320

Bikes: '93 Trek 750, '92 Schwinn Crisscross, '93 Mongoose Alta

Mentioned: 30 Post(s)
Tagged: 0 Thread(s)
Quoted: 1439 Post(s)
Liked 1,094 Times in 724 Posts
Perhaps an appropriate front derailleur is the solution.
dsbrantjr is offline  
Old 10-21-15, 03:47 PM
  #3  
Senior Member
 
Shimagnolo's Avatar
 
Join Date: May 2008
Location: Zang's Spur, CO
Posts: 9,088
Mentioned: 11 Post(s)
Tagged: 0 Thread(s)
Quoted: 3401 Post(s)
Liked 5,582 Times in 2,896 Posts
Only issue I've ever had with putting a 48T on an XT crankset is that there is a post on the backside of the 48T which lines up with the crank arm, (apparently to prevent the chain from getting wedged between the arm and the large ring). I always need to take about 1/4" off that post with a hacksaw, else it hits the arm, preventing installation.
Shimagnolo is offline  
Old 10-21-15, 04:27 PM
  #4  
Mad bike riding scientist
 
cyccommute's Avatar
 
Join Date: Nov 2004
Location: Denver, CO
Posts: 27,432

Bikes: Some silver ones, a red one, a black and orange one, and a few titanium ones

Mentioned: 153 Post(s)
Tagged: 1 Thread(s)
Quoted: 6254 Post(s)
Liked 4,280 Times in 2,398 Posts
I suspect that you have a top swing/low clamp front derailer. A bottom swing/high clamp derailer might solve your problem and allow you to use the 44 ring. However, there's no reason you couldn't substitute a 48 tooth ring for the 44. You might be able to use the current 34 as well. I certainly wouldn't change out the 22 without a good reason. It will work just fine with a 36 tooth middle.

On the other hand you could split the difference and use a 46 tooth outer like this one from Blackspire. That would definitely work with the 32 middle. I did the same with an XT crank on my touring bike this spring and never had a problem with shifting in 1500 hard miles.
__________________
Stuart Black
Plan Epsilon Around Lake Michigan in the era of Covid
Old School…When It Wasn’t Ancient bikepacking
Gold Fever Three days of dirt in Colorado
Pokin' around the Poconos A cold ride around Lake Erie
Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!



cyccommute is offline  
Old 10-21-15, 05:48 PM
  #5  
Junior Member
Thread Starter
 
Join Date: May 2015
Posts: 130
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 30 Post(s)
Likes: 0
Liked 2 Times in 1 Post
Thanks, cyccommute, for the suggestion about the 46T. As to clamp configuration (listen up, oh snide Mr. dsbrantjr) I'm hip to all the top-swing/bottom-swing/top-pull/bottom-pull stuff; there is no "appropriate front derailleur" for this particular chainset with this particular frame. Got plenty of seat tube to adjust the derailleur clamp downward, but the chainstay gets in the way of the derailleur cage before edge of said cage is within 3/4" of edge of top ring, much less a mm.

Shimagnolo- doesn't sound too bad, if I'm picturing it correctly. Thanks.
cloozoe is offline  
Old 10-21-15, 07:22 PM
  #6  
Senior Member
 
dsbrantjr's Avatar
 
Join Date: Sep 2010
Location: Roswell, GA
Posts: 8,320

Bikes: '93 Trek 750, '92 Schwinn Crisscross, '93 Mongoose Alta

Mentioned: 30 Post(s)
Tagged: 0 Thread(s)
Quoted: 1439 Post(s)
Liked 1,094 Times in 724 Posts
A derailleur sized for the smaller 42 big ring will likely have the tail not hang down so far as one sized for 48 teeth, thus may clear your chain stay. Here is an example: microSHIFT -The best control system specifically designed for 42-32-22 which may work in your application. I have had good luck with Microshift products and find that they offer good performance and value and are compatible with Shimano components.

When you respond to a post you might consider that you are asking strangers to take their time and trouble to give you free advice.

I hope that your project works out for you.

You are welcome.
dsbrantjr is offline  
Old 10-22-15, 12:54 AM
  #7  
Junior Member
Thread Starter
 
Join Date: May 2015
Posts: 130
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 30 Post(s)
Likes: 0
Liked 2 Times in 1 Post
Originally Posted by dsbrantjr
When you respond to a post you might consider that you are asking strangers to take their time and trouble to give you free advice.
And when it is offered without smugness or condescension it is much appreciated. If I misread the tone of your first reply, my apologies.

Also can't help but pointing out that I was hardly walking around interrupting people on the street and asking for "free advice"; many people --clearly you are one-- like frequenting forums like this (which is why they exist) and like to answer questions -- either out of altruism or a desire to demonstrate how much they know. I'll leave it to you to evaluate which camp you fall into. In any event, glad I could give you an opportunity to indulge yourself. You are welcome.

Last edited by cloozoe; 10-22-15 at 06:10 AM.
cloozoe is offline  
Old 10-22-15, 07:48 AM
  #8  
Mad bike riding scientist
 
cyccommute's Avatar
 
Join Date: Nov 2004
Location: Denver, CO
Posts: 27,432

Bikes: Some silver ones, a red one, a black and orange one, and a few titanium ones

Mentioned: 153 Post(s)
Tagged: 1 Thread(s)
Quoted: 6254 Post(s)
Liked 4,280 Times in 2,398 Posts
Originally Posted by cloozoe
Thanks, cyccommute, for the suggestion about the 46T. As to clamp configuration (listen up, oh snide Mr. dsbrantjr) I'm hip to all the top-swing/bottom-swing/top-pull/bottom-pull stuff; there is no "appropriate front derailleur" for this particular chainset with this particular frame. Got plenty of seat tube to adjust the derailleur clamp downward, but the chainstay gets in the way of the derailleur cage before edge of said cage is within 3/4" of edge of top ring, much less a mm.

Shimagnolo- doesn't sound too bad, if I'm picturing it correctly. Thanks.
You might want to look at a bottom swing anyway. Some of them have a different cage profile from bottom swing units that are a little bit higher. I'd also suggest a Sram Xseries derailer over a Shimano. They have a different profile as well. And they work better than Shimano.
__________________
Stuart Black
Plan Epsilon Around Lake Michigan in the era of Covid
Old School…When It Wasn’t Ancient bikepacking
Gold Fever Three days of dirt in Colorado
Pokin' around the Poconos A cold ride around Lake Erie
Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!



cyccommute is offline  
Old 10-22-15, 09:07 AM
  #9  
Junior Member
Thread Starter
 
Join Date: May 2015
Posts: 130
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 30 Post(s)
Likes: 0
Liked 2 Times in 1 Post
Thanks again. I'll look into it.
cloozoe is offline  
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
richas
Cyclocross and Gravelbiking (Recreational)
3
02-06-19 11:27 AM
kuroba
Bicycle Mechanics
23
04-27-17 07:59 AM
goldfinch
Bicycle Mechanics
6
08-16-14 06:28 PM
corwin1968
Bicycle Mechanics
5
02-26-12 08:06 AM

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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread

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

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.