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


Go Back   > >

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.

User Tag List

Reply
 
Thread Tools Search this Thread
Old 03-11-11, 08:19 PM   #1
Seaners
Member
Thread Starter
 
Seaners's Avatar
 
Join Date: Jan 2004
Bikes:
Posts: 30
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
tourer chain won't back pedal

i dug my tourer out from underneath a thick layer of dust and set about tuning it up for spring only to remember it had a really annoying problem with the drivechain.

whenever i backpedal something won't reverse fast enough and the chain ends up getting sucked downwards on top and the derailleur gets pulled forward. the chain isn't thrown off and normal forward cyclin doesn't seem to be affected.

i have replaced both the chain and the freehub body to no avail and am feeling stumped.

set up is eight speed shimano, LX hub, deore chainset, sram pc 830 chain 9 speed XT derailleur front and rear (reverse rise)

two further thoughts are the chain rings are worn out which doesn't seem to be the case and the rear derailleur wheel pulleys are clogged somehow. of course one of the small pulley screw heads has stripped on me

any thoughts appreciated.
Seaners is offline   Reply With Quote
Old 03-11-11, 08:32 PM   #2
FBinNY 
Senior Member
 
Join Date: Apr 2009
Location: New Rochelle, NY
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
Posts: 29,660
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 217 Post(s)
OK, it's a case of divide and consider. Start by pedaling forward and getting the rear wheel up to a decent speed. Stop suddenly and watch the top loop. If it doesn't sag from the wheel pushing chain forward then the freehub is OK, and you need to move on.

If it isn't the freehub, my best guess is friction in the RD pulleys, or simply a sticky chain, from dried lube, or dirt. Shift to high fear and push the cage forward to get some slack, and lift the chain from the pulley and check each for free spinning. If they're sticky, remove them one at a time, field strip, clean and oil them.

Next check the chain by back-pedaling slowly while watching the chain unspool from the lower pulley. Push the cage forward to get a bit of slack in the lower loop. If the chain doesn't straighten immediately as it leaves the pulley, it needs oil, or a bath then oil.

Last, and maybe should have been first, make sure the RD trims well and pedaling forward is smooth and quiet. Poor trim can add friction and bind the chain when you back pedal.

So, you have 10 minute of diagnosis ahead of you. Come back afterward if it's none of the above.
__________________
FB
Chain-L site

An ounce of diagnosis is worth a pound of cure.

“Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin

“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

WARNING, I'm from New York. Thin skinned people should maintain safe distance.
FBinNY is offline   Reply With Quote
Old 03-11-11, 10:07 PM   #3
fietsbob 
coprolite
 
fietsbob's Avatar
 
Join Date: Jun 2010
Location: NW,Oregon Coast
Bikes: 7
Posts: 19,561
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 416 Post(s)
derailleurs are a go forward scheme, as above if the chain wont go slack coasting,
chainsucking into the wheel.. Its good to go.

maybe if chain is in the best chainline .. central combinations
and the shift mech has the pulley dead on under the cog
then Back pedaling may work , but why? its not a fixie or a unicycle.

forward is the direction..
fietsbob is offline   Reply With Quote
Old 03-12-11, 10:50 AM   #4
Seaners
Member
Thread Starter
 
Seaners's Avatar
 
Join Date: Jan 2004
Bikes:
Posts: 30
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
seems like sticky pulley wheels are the thing. much better now after a liberal dousing of chemicals. still seems like the rear mech needs be further back to apply a little more chain pressure and the B screw isn't helping out much. more chemicals and perhaps a internal spring cleaning. pun intended.

fietsbob - you'd be surprised at how annoying it gets, coasting down a hill and wanting to reposition your pedals for a corner and it gets all weird on you and you have a 'dead space' before your pedalling cycle starts giving power. it's not right at all.

thank you
Seaners is offline   Reply With Quote
Old 03-12-11, 10:59 AM   #5
fietsbob 
coprolite
 
fietsbob's Avatar
 
Join Date: Jun 2010
Location: NW,Oregon Coast
Bikes: 7
Posts: 19,561
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 416 Post(s)
You could always purchase pulleys with a sealed bearing in the center..
The ones made with ceramics instead of steel is probably overspending


Just realize if 'cross chaining', back pedaling may also change the gear
or mess up things , partially, at least.
consider bringing crank around forward a half turn,
to bring up that inside pedal, rather than backwards..


Last edited by fietsbob; 03-12-11 at 11:03 AM.
fietsbob is offline   Reply With Quote
Old 03-12-11, 01:51 PM   #6
Jeff Wills
Insane Bicycle Mechanic
 
Jeff Wills's Avatar
 
Join Date: Mar 2008
Location: other Vancouver
Bikes:
Posts: 7,942
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 15 Post(s)
Quote:
Originally Posted by Seaners View Post
seems like sticky pulley wheels are the thing. much better now after a liberal dousing of chemicals. still seems like the rear mech needs be further back to apply a little more chain pressure and the B screw isn't helping out much. more chemicals and perhaps a internal spring cleaning. pun intended.

fietsbob - you'd be surprised at how annoying it gets, coasting down a hill and wanting to reposition your pedals for a corner and it gets all weird on you and you have a 'dead space' before your pedalling cycle starts giving power. it's not right at all.

thank you
It sounds like you need to remove and clean the derailleur pulleys. This is quite easy- just don't mix them up. The upper and lower pulleys are different. Some help is here: http://www.parktool.com/blog/repair-...lleur-overhaul
__________________
Jeff Wills

Comcast nuked my web page. It will return soon..
Jeff Wills 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 02:41 AM.