Go Back  Bike Forums > Bike Forums > Road Cycling
Reload this Page >

Derailleurs for Compact Drive

Road Cycling “It is by riding a bicycle that you learn the contours of a country best, since you have to sweat up the hills and coast down them. Thus you remember them as they actually are, while in a motor car only a high hill impresses you, and you have no such accurate remembrance of country you have driven through as you gain by riding a bicycle.” -- Ernest Hemingway

Derailleurs for Compact Drive

Old 09-09-04, 07:57 AM
  #1  
Sierra
Uff Da!
Thread Starter
 
Join Date: Sep 2003
Posts: 1,037
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Derailleurs for Compact Drive

Want to build a bike with 34/50 compact drive crank and 12-27 cassette. You guys told me that a front derailleur for a double should work fine with this. Now I'm wondering about the rear derailleur. I would like to use a Dura Ace 7700 for a double if I can.
The specs are as follows;

Largest cog 27t
Total capacity 29
Maximum front difference 14

I need a total capacity of 31, but I'm not too concerned with that as I plan to shift it as a crossover so will never be in the large-large, or small-small combinations.

What I'm wondering about is the Front difference spec(which I am exceeding). Why does the rear derailleur care what the difference is in front as long as total capacity is not exceeded?

Anyone else using this gearing combo? What do you use for a rear der.?

Thanks.
Sierra is offline  
Old 09-09-04, 08:18 AM
  #2  
Shadco
Resident PIA
 
Shadco's Avatar
 
Join Date: Jul 2004
Location: City of Oaks, NC
Posts: 342

Bikes: Litespeed Arenberg, Huffy Strider, Trek 4700, Gunnar Roadie

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 16 Post(s)
Liked 0 Times in 0 Posts
Originally Posted by Sierra
Want to build a bike with 34/50 compact drive crank and 12-27 cassette. You guys told me that a front derailleur for a double should work fine with this. Now I'm wondering about the rear derailleur. I would like to use a Dura Ace 7700 for a double if I can.
The specs are as follows;

Largest cog 27t
Total capacity 29
Maximum front difference 14

I need a total capacity of 31, but I'm not too concerned with that as I plan to shift it as a crossover so will never be in the large-large, or small-small combinations.

What I'm wondering about is the Front difference spec(which I am exceeding). Why does the rear derailleur care what the difference is in front as long as total capacity is not exceeded?

Anyone else using this gearing combo? What do you use for a rear der.?

Thanks.
I'm using an FSA Energy compact 50/34. I started with 105 double front and 105 rear der and I had problems not dropping the chain going big to small on the front, I had to be very deliberate making that change, I also had chain rub using the 2 smallest rear cogs when on the small ring but that's not a good combo anyway so I didn't worry about it. My normal cassette is an 11/23 DA but I do use an SRAM 12/26 if there are a lot of hills.

I upgraded to DA 7700 series FD and 7800 series RD using the same cassettes I only get a touch of rub when on the small ring on the smallest cog and the front shifting problem is a thing of the past.

I'm using an SRAM PC69 chain.

I couldn't find a 9spd rear der any cheaper than the 10spd one so I snagged it and haven't looked back. It's a 9/10 speed component.
Shadco is offline  
Old 09-09-04, 08:21 AM
  #3  
sydney
Senior Member
 
sydney's Avatar
 
Join Date: Jan 2004
Posts: 9,428
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by Sierra
Want to build a bike with 34/50 compact drive crank and 12-27 cassette. You guys told me that a front derailleur for a double should work fine with this. Now I'm wondering about the rear derailleur. I would like to use a Dura Ace 7700 for a double if I can.
The specs are as follows;

Largest cog 27t
Total capacity 29
Maximum front difference 14

I need a total capacity of 31, but I'm not too concerned with that as I plan to shift it as a crossover so will never be in the large-large, or small-small combinations.

What I'm wondering about is the Front difference spec(which I am exceeding). Why does the rear derailleur care what the difference is in front as long as total capacity is not exceeded?

Anyone else using this gearing combo? What do you use for a rear der.?

Thanks.
A short cage will work as the wrap spec is conservative, and you may not even be using the next to smallest cog when in the small ring due to possible chain rub on the big ring. The standard double front also works. The rear derailer doesn't care what rhe fronti s doing. That 14t spec just relative to the tooth difference in front.
sydney is offline  
Old 09-09-04, 08:42 AM
  #4  
-CM-
Love to Ride
 
-CM-'s Avatar
 
Join Date: Sep 2004
Location: SoCal
Posts: 201
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
I just put an FSA carbon compact crankset (34/50) on my DA equipped Merlin. With either a 12/25 or 12/27 in the back I have no problems at all, save for a bit of chain rub when in the 34 on the front and the 12 or 13 in the back, as Shadco said also.

The front der needed to be lowered a bit, and the limit screws needed to be adjusted, but it was a very easy install and setup.
-CM- is offline  
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
Santaria
Mountain Biking
0
06-22-09 01:53 PM
revolator
Foo
1
03-18-08 06:47 AM
Tracy
Touring
0
04-03-00 03:47 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.