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


Go Back   > >

Classic & Vintage This forum is to discuss the many aspects of classic and vintage bicycles, including musclebikes, lightweights, middleweights, hi-wheelers, bone-shakers, safety bikes and much more.

User Tag List

Reply
 
Thread Tools Search this Thread
Old 01-13-12, 11:33 AM   #1
triplebutted
Senior Member
Thread Starter
 
triplebutted's Avatar
 
Join Date: Jun 2008
Location: SoCal
Bikes: Lemond, Gios, Fuji, Trek, too many to write
Posts: 1,886
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Why the XTRA large jockey wheels on some rear derailleurs?

May not be Vintage related but I may need to put a long cage on my Centurion so I can ride it with a 32 or 34t freewheel (doing a ride that has a 20% grade). I stripped a mtb bike of parts and there was a Shimano Acera or something with one of the pulley wheels that was twice the size! What's up with that?
triplebutted is offline   Reply With Quote
Old 01-13-12, 11:42 AM   #2
Bianchigirll 
Bianchi Goddess
 
Bianchigirll's Avatar
 
Join Date: Apr 2009
Location: Camp Hill, PA
Bikes: Too many to list here check my signature.
Posts: 22,537
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 47 Post(s)
I think it has something to do with taking up more chain for the wide spaced cassettes and compact cranks
__________________
Bianchis '87 Sport SX, '90 Proto, '90 Campione del Fausto Giamondi Specialisma Italiano Mundo, '91 Boarala 'cross, '93 Project 3, '86 Volpe, '97 Ti Megatube, , '90 something Vento 603,

Others but still loved,; '80 RIGI, '80 Batavus Professional, '87 Cornelo, '09 Motobecane SOLD, '?? Jane Doe (still on the drawing board), '90ish Haro Escape
Bianchigirll is offline   Reply With Quote
Old 01-13-12, 11:47 AM   #3
sauze
Senior Member
 
sauze's Avatar
 
Join Date: May 2010
Location: Winnipeg
Bikes:
Posts: 935
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)


Like this right?

I had always assumed it was a way to improve capacity for RD's without lengthening the cage more , but you should take everything I say with a fairly giant grain of salt.
sauze is offline   Reply With Quote
Old 01-13-12, 11:54 AM   #4
triplebutted
Senior Member
Thread Starter
 
triplebutted's Avatar
 
Join Date: Jun 2008
Location: SoCal
Bikes: Lemond, Gios, Fuji, Trek, too many to write
Posts: 1,886
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Yah, kinda looks like that. I guess I'll try it. Can't hurt right?
triplebutted is offline   Reply With Quote
Old 01-13-12, 11:56 AM   #5
rat fink
Iconoclast
 
rat fink's Avatar
 
Join Date: Aug 2009
Location: California
Bikes: Colnago Super, Fuji Opus III, Specialized Rockhopper
Posts: 3,173
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
+1 For chain-wrap.
rat fink is offline   Reply With Quote
Old 01-13-12, 03:17 PM   #6
20grit
Curmudgeon in Training
 
20grit's Avatar
 
Join Date: May 2009
Location: Rural Retreat, VA
Bikes: 1974 Gazelle Champion Mondial, 2010 Cannondale Trail SL, 1988 Peugeot Nice, 1992ish Stumpjumper Comp,1990's Schwinn Moab
Posts: 1,934
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
For more drillium room on metal wheels.
20grit is offline   Reply With Quote
Old 01-13-12, 03:42 PM   #7
balindamood 
Wrench Savant
 
balindamood's Avatar
 
Join Date: Mar 2006
Location: 61 Degrees North
Bikes: www.2nd-cycles.com
Posts: 2,202
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
I have seen some directions on 80's Suntour derailluers that swapped both the upper an lower jockey wheels sizes about based upon total teeth and cog sizes. I have never worried about it personnally, but apparently Suntour thought about it and tried to fine-tune it.
__________________
"Where you come from is gone;
where you are headed weren't never there;
and where you are ain't no good unless you can get away from it."
balindamood is offline   Reply With Quote
Old 01-14-12, 09:26 AM   #8
Glennfordx4 
Holy Spokes it's Batsman!
 
Glennfordx4's Avatar
 
Join Date: Nov 2008
Location: South Jersey
Bikes: Too many Bicycles to list
Posts: 1,691
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Shimano uses the larger jockey pulleys on all their Mega Range designed RD's that run the 34 tooth Mega Range cog. That's the only place I have seen them in use and have a few new ones in my bins, these are only used on low end RD's.
Glennfordx4 is offline   Reply With Quote
Old 01-14-12, 11:53 AM   #9
Rocket-Sauce 
Port
 
Rocket-Sauce's Avatar
 
Join Date: Jan 2008
Location: Boston
Bikes: 1990 Fuji Ace, 1990 Bridgestone RB-1, 1995 Independent Fabrications Track, 2005 Calfee Dragonfly Pro
Posts: 6,008
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 19 Post(s)
Oversized derailer pulleys were the must-have accessory in the pro peloton in 2010.

By then end of the summer, they were everywhere. Developed by Berner and then copied by everyone else, they are said to noticeably reduce drive-train friction by allowing less severe chain bends

David Millars TT bike 2010:



Frändy Schleck's Specialized Tarmac 2010:



And Lance's TT Bike:
Rocket-Sauce is offline   Reply With Quote
Old 01-14-12, 12:05 PM   #10
T-Mar
Senior Member
 
Join Date: Nov 2004
Bikes:
Posts: 12,127
Mentioned: 44 Post(s)
Tagged: 0 Thread(s)
Quoted: 235 Post(s)
FYI, only the top pulley is a jockey pulley. The proper name of the bottom pulley is a tensioner or toggle pulley. Increasing the diameter of the toggle pulley wraps wraps about 50 -66% more chain than increasing the length of the cage by the same amount. The actual percentage will vary depending on the cage geometry. Thus you can increase wrap without decreasing ground clearance as much (an issue with ATBs in off-road conditions). A dirty chain is also less likely to bind and skip on a bigger pulley. It also reduces the deflection of a longer cage. Finally, it looks different and this must not be underestimated.
T-Mar is offline   Reply With Quote
Old 12-12-12, 01:20 PM   #11
Kimmo
bike whisperer
 
Kimmo's Avatar
 
Join Date: Dec 2009
Location: Melbourne, Oz
Bikes: copy/paste links: http://velospace.org/node/36949 http://velospace.org/node/47746 http://velospace.org/node/47747
Posts: 7,099
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
I dig the larger pulleys cause they're quieter.
Kimmo is offline   Reply With Quote
Old 12-12-12, 01:25 PM   #12
clubman 
Youngman Grande
 
clubman's Avatar
 
Join Date: Jan 2010
Location: Nova Scotia
Bikes: roadsters, club bikes, fixed and classic
Posts: 3,107
Mentioned: 7 Post(s)
Tagged: 0 Thread(s)
Quoted: 61 Post(s)
Quote:
Originally Posted by balindamood View Post
I have seen some directions on 80's Suntour derailluers that swapped both the upper an lower jockey wheels sizes about based upon total teeth and cog sizes. I have never worried about it personnally, but apparently Suntour thought about it and tried to fine-tune it.
The 3 pulley Suntours had a mixed bag, 2 big and one small.

clubman is offline   Reply With Quote
Old 12-12-12, 02:55 PM   #13
T-Mar
Senior Member
 
Join Date: Nov 2004
Bikes:
Posts: 12,127
Mentioned: 44 Post(s)
Tagged: 0 Thread(s)
Quoted: 235 Post(s)
Oversize pulleys are also becoming the rage on current high end racing derailleurs on the claim that the looser chain wrap increases efficiency. I wonder if it will herald a reversal to 14T small cogs and correspondingly larger chainrings? With carbon fibre frame technology being what it is, they already have to ballast some frames to meet UCI minimum weight requirments, so marginally heavier components are no longer a big concern.
T-Mar is offline   Reply With Quote
Old 12-13-12, 04:34 PM   #14
dddd
Ride, Wrench, Swap, Race
 
dddd's Avatar
 
Join Date: Jan 2010
Location: Northern California
Bikes: Cheltenham-Pederson racer, Boulder F/S Paris-Roubaix, Varsity racer, '52 Christophe, '62 Continental, '92 Merckx, '75 Limongi, '76 Presto, '72 Gitane SC, '71 Schwinn SS, etc.
Posts: 5,069
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
When the first Dura-Ace triple gruppo debutted in the 9-speed era, they used oversized pulleys with a cage that was considerably shorter than the comparable Ultegra or 105 triple derailers had.

One thing about the pulley friction, besides how sharp that the chain bends, is that there is a ratio of diameters between the sleeve diameter (where rubbing occurs) and the working diameter (where the chain passes).

The greater is this ratio, the lower the energy losses from friction, as the frictional force at the sleeve is leveraged by the greater diameter of the pulley vs. the diameter of the sleeve.
And, with a resulting lower rotation speed, the increase in that diameter ratio further improves efficiency, now to the second power (or "x-squared").

This ratio also argues for smaller diameter sleeves or for rolling-element bearings, one reason that I somewhat dis-like most Suntour and SRAM derailers.
The Suntour pulleys I can replace with (6mm bolt-hole diameter) ball-bearing pullies (from Huret or the aftermarket), but SRAM's design uses a huge-diameter sleeve in the top pulley position that is elemental to the derailer's design.

Last edited by dddd; 12-13-12 at 09:50 PM.
dddd is offline   Reply With Quote
Old 12-13-12, 04:39 PM   #15
RobbieTunes 
Idiot Pro Tempo
 
RobbieTunes's Avatar
 
Join Date: Dec 2007
Location: NC
Bikes: at Pedal Room
Posts: 20,581
Mentioned: 9 Post(s)
Tagged: 0 Thread(s)
Quoted: 189 Post(s)
Quote:
Originally Posted by clubman View Post
The 3 pulley Suntours had a mixed bag, 2 big and one small.

I just came across one of those today in the parts box of a local bike shop....pretty cool.
__________________

Robbie ♪♫♪...☻

Friends don't let friends drink and wrench.

1985 Raleigh Competition Racing USA Series-Coleman made me do it.....
1987 Bridgestone Radac - Aluminum (sadly, the frame is toast, RD hanger snapped off)
1988 Centurion Dave Scott Ironman Master - Steel
1989 Centurion Carbon-R - Carbon Fiber

http://www.pedalroom.com/members/RobbieTunes
RobbieTunes 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 02:56 PM.