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

Converting to index shifting on a 120mm rear

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.

Converting to index shifting on a 120mm rear

Old 06-17-11, 04:36 PM
  #1  
jimmuller 
What??? Only 2 wheels?
Thread Starter
 
jimmuller's Avatar
 
Join Date: Apr 2010
Location: Boston-ish, MA
Posts: 13,264

Bikes: 73 Raleigh Carlton Gran Sport, 72 Peugeot UO-8, 82 Peugeot TH8, 87 Bianchi Brava, 76? Masi Grand Criterium, 87 Centurion Ironman Expert, 74 Motobecane Champion Team, 86 & 77 Gazelle champion mondial, 81? Grandis, 82? Tommasini, 83 Peugeot PFN10

Mentioned: 179 Post(s)
Tagged: 0 Thread(s)
Quoted: 1162 Post(s)
Liked 135 Times in 90 Posts
Converting to index shifting on a 120mm rear

I've asked this C&V and gotten very little useful info. I know, it doesn't adhere to C&V principles but I have reasons to consider it. What options would there be to convert a 5-speed freewheel system to index shifting, preferable without swapping the rear hub?

Here's the way I see it. One click on the lever displaces the cable x amount. That moves the derailleur (let's say the rear) laterally y amount. Actually, y would be x times a property of the derailleur, specifically the ratio of lateral displacement per cable displacement. The cogs are spaced z amount, and as long as y = z it ought to be workable. The trouble is, those values for a variety of freewheels, derailleurs, and indexing levers aren't readily available to me, at least that I know of.

I have at least two options for freewheel, a standard 5-speed or a Suntour Ultra-6. (Re-spacing the frame(s) is not a great option.) I could whatever derailleur and shifters could be made to match either of these freewheels.

Any thoughts? Thanks!
__________________
Real cyclists use toe clips.
With great bikes comes great responsibility.
jimmuller
jimmuller is offline  
Old 06-18-11, 07:09 AM
  #2  
Homebrew01
Super Moderator
 
Homebrew01's Avatar
 
Join Date: Jul 2004
Location: Ffld Cnty Connecticut
Posts: 21,487

Bikes: Old Steelies I made, Old Cannondales

Mentioned: 10 Post(s)
Tagged: 0 Thread(s)
Quoted: 988 Post(s)
Liked 266 Times in 204 Posts
Ain't gonna work. Sounds like you already understand the problem.
__________________
Bikes: Old steel race bikes, old Cannondale race bikes, less old Cannondale race bike, crappy old mtn bike.

FYI: https://www.bikeforums.net/forum-sugg...ad-please.html
Homebrew01 is online now  
Old 06-18-11, 12:06 PM
  #3  
jimmuller 
What??? Only 2 wheels?
Thread Starter
 
jimmuller's Avatar
 
Join Date: Apr 2010
Location: Boston-ish, MA
Posts: 13,264

Bikes: 73 Raleigh Carlton Gran Sport, 72 Peugeot UO-8, 82 Peugeot TH8, 87 Bianchi Brava, 76? Masi Grand Criterium, 87 Centurion Ironman Expert, 74 Motobecane Champion Team, 86 & 77 Gazelle champion mondial, 81? Grandis, 82? Tommasini, 83 Peugeot PFN10

Mentioned: 179 Post(s)
Tagged: 0 Thread(s)
Quoted: 1162 Post(s)
Liked 135 Times in 90 Posts
Originally Posted by Homebrew01 View Post
Ain't gonna work. Sounds like you already understand the problem.
Well, in the homework assignment sense I understand the problem but I don't know if there is or isn't a solution. Won't know that for sure until I have those values for available components, old or new.
__________________
Real cyclists use toe clips.
With great bikes comes great responsibility.
jimmuller
jimmuller is offline  
Old 06-18-11, 12:37 PM
  #4  
wrk101
Thrifty Bill
 
wrk101's Avatar
 
Join Date: Jan 2008
Location: Mountains of Western NC
Posts: 22,597

Bikes: 86 Katakura Silk, 87 Prologue X2, 88 Cimarron LE, 1975 Sekai 4000 Professional, 73 Paramount, plus more

Mentioned: 78 Post(s)
Tagged: 0 Thread(s)
Quoted: 901 Post(s)
Liked 300 Times in 226 Posts
I have picked up a few five speed indexed thumb shifters that work on Shimano freewheels. I typically find them on crappy older hybrids: Huffys, Roadmasters, etc. I have not seen five speed index DT shifters.
wrk101 is offline  
Old 06-18-11, 06:44 PM
  #5  
jimmuller 
What??? Only 2 wheels?
Thread Starter
 
jimmuller's Avatar
 
Join Date: Apr 2010
Location: Boston-ish, MA
Posts: 13,264

Bikes: 73 Raleigh Carlton Gran Sport, 72 Peugeot UO-8, 82 Peugeot TH8, 87 Bianchi Brava, 76? Masi Grand Criterium, 87 Centurion Ironman Expert, 74 Motobecane Champion Team, 86 & 77 Gazelle champion mondial, 81? Grandis, 82? Tommasini, 83 Peugeot PFN10

Mentioned: 179 Post(s)
Tagged: 0 Thread(s)
Quoted: 1162 Post(s)
Liked 135 Times in 90 Posts
Originally Posted by wrk101 View Post
I have picked up a few five speed indexed thumb shifters that work on Shimano freewheels. I typically find them on crappy older hybrids: Huffys, Roadmasters, etc. I have not seen five speed index DT shifters.
Thumb shifters, or at least something on the bar, is exactly what I'm thinking of. But with what derailleurs?
__________________
Real cyclists use toe clips.
With great bikes comes great responsibility.
jimmuller
jimmuller is offline  
Old 06-18-11, 07:18 PM
  #6  
Jeff Wills
Insane Bicycle Mechanic
 
Jeff Wills's Avatar
 
Join Date: Mar 2008
Location: other Vancouver
Posts: 9,313
Mentioned: 29 Post(s)
Tagged: 0 Thread(s)
Quoted: 576 Post(s)
Liked 164 Times in 121 Posts
Originally Posted by jimmuller View Post
Thumb shifters, or at least something on the bar, is exactly what I'm thinking of. But with what derailleurs?
If they're Shimano-compatible shifters, then Shimano derailleurs. With some rare, unusual exceptions that don't apply here Shimano shifters will index Shimano derailleurs.

FWIW: here's some indexed 5-speed downtube shifters: https://www.biketoolsetc.com/index.cg...m_id=SU-137A/5 The tip says they're Shimano-compatible.
__________________
Jeff Wills

Comcast nuked my web page. It will return soon..

Last edited by Jeff Wills; 06-18-11 at 07:22 PM.
Jeff Wills is offline  
Old 06-18-11, 11:59 PM
  #7  
mrrabbit 
Senior Member
 
mrrabbit's Avatar
 
Join Date: Dec 2007
Location: San Jose, California
Posts: 3,402

Bikes: 2001 Tommasini Sintesi w/ Campagnolo Daytona 10 Speed

Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 90 Post(s)
Likes: 0
Liked 15 Times in 11 Posts
Another option:

1. Freewheel stop to outside of drive side locknut = 36.00mm
2. Center of drive side flange to outside of drive side locknut => 43.00mm
3. Fill out non-drive side IF physically possible to 120mm.
4. Re-dish wheel - the asymmetrical offsets MAY flip-flop.

Not ideal, dunno how long the drive side spokes will last IF they become the loose side after dishing. Don't know what the chainline would look like either keeping the rear at 120mm.

But at least you'd be able to install a 6 speed regular index freewheel - or a narrow 7-speed index freewheel.

=8-)

=8-)
__________________
5000+ wheels built since 1984...

Disclaimer:

1. I do not claim to be an expert in bicycle mechanics despite my experience.
2. I like anyone will comment in other areas.
3. I do not own the preexisting concepts of DISH and ERD.
4. I will provide information as I always have to others that I believe will help them protect themselves from unscrupulous mechanics.
5. My all time favorite book is:

Kahane, Howard. Logic and Contemporary Rhetoric: The Use of Reason in Everyday Life
mrrabbit is offline  
Old 06-19-11, 12:04 AM
  #8  
sooprvylyn
I suck, but you're worse
 
Join Date: Jun 2005
Location: LA
Posts: 672

Bikes: Motobecane Fantom Uno-Got rid of the rest when I moved to LA:(

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Its a steel frame no? Just stretch it a little to fit a 6/7 speed hub and get any # of indexed shimano levers.
sooprvylyn is offline  
Old 06-19-11, 01:12 AM
  #9  
fietsbob 
coprolite
 
fietsbob's Avatar
 
Join Date: Jun 2010
Location: NW,Oregon Coast
Posts: 42,627

Bikes: 8

Mentioned: 194 Post(s)
Tagged: 0 Thread(s)
Quoted: 7337 Post(s)
Liked 953 Times in 601 Posts
Internal gear hub.. Even 3 speeds are 'indexed'..
fietsbob is offline  
Old 06-19-11, 05:02 AM
  #10  
Kimmo 
bike whisperer
 
Kimmo's Avatar
 
Join Date: Dec 2009
Location: Melbourne, Oz
Posts: 8,565

Bikes: https://weightweenies.starbike.com/forum/viewtopic.php?f=10&t=152015&p=1404231

Mentioned: 14 Post(s)
Tagged: 0 Thread(s)
Quoted: 915 Post(s)
Liked 259 Times in 193 Posts
Originally Posted by jimmuller View Post
(Re-spacing the frame(s) is not a great option.)
Why not? It's quite doable...

Or how about this - I reckon you could rock Ergopower without re-spacing...

If you're prepared to rebuild the hub into on OCR, you could have a 7spd freewheel at say, 123mm OLD with maybe even a bit less dish than a normal 7spd freewheel. The 5.0mm spacing of Shimano 7spd = Campy 8spd spacing.

Jamming a 123mm hub into a 120mm frame shouldn't be too much hassle.
Kimmo is offline  
Old 06-19-11, 07:24 AM
  #11  
sonatageek
Senior Member
 
sonatageek's Avatar
 
Join Date: Oct 2006
Location: Cleveland,Ohio
Posts: 2,780
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 5 Post(s)
Likes: 0
Liked 1 Time in 1 Post
I would say a 5 speed thumb shifter matched to a Shimano/Sunrace/Falcon 5 speed freewheel with any Shimano index RD, from the low end SIS units on up. That was a very common combination on low end department store bikes of years past.
sonatageek is offline  

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 - Do Not Sell My Personal Information

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