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 11-12-10, 10:50 AM   #1
granto
Member
Thread Starter
 
Join Date: Sep 2010
Location: Pittsburgh, PA
Bikes: '88 Specialized Hardrock, '82 Centurion Le Mans
Posts: 42
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Rear deraillieur tension pulley popping

Only when I'm on my highest front cog, my rear tension pulley (the lowest one) seems to get jerked by the chain at random (seems I don't even have to be peddling) and makes a horrible noise like the whole drivetrain is about to shear off. I guessed it was poor lubrication in the tension pulley but lubing its pivot point didn't seem to help much. Other suggestions?
granto is offline   Reply With Quote
Old 11-12-10, 10:54 AM   #2
DannoXYZ 
Senior Member
 
DannoXYZ's Avatar
 
Join Date: Jul 2005
Location: Saratoga, CA
Bikes:
Posts: 11,600
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
If you're not pedaling and the chain's not moving through the derailleur, where's the popping motion coming from?
DannoXYZ is offline   Reply With Quote
Old 11-12-10, 10:57 AM   #3
Al Criner
Senior Member
 
Join Date: Aug 2007
Location: NorCal
Bikes: 2009 Surly Cross Check Frankenbike
Posts: 544
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Are you sure your freehub is OK? Can you replicate this problem on the repair stand?
Al Criner is offline   Reply With Quote
Old 11-12-10, 10:58 AM   #4
granto
Member
Thread Starter
 
Join Date: Sep 2010
Location: Pittsburgh, PA
Bikes: '88 Specialized Hardrock, '82 Centurion Le Mans
Posts: 42
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
not sure.. maybe it does require pedaling, like if I pedal backwards through my freewheel, normally the chain would just be going through the lower pulley, but every once in a while it yanks it forward... Let me take a ride and be sure of that
granto is offline   Reply With Quote
Old 11-12-10, 10:59 AM   #5
LarDasse74
Guest
 
Join Date: Jul 2008
Location: Grid Reference, SK
Bikes: I never learned to ride a bike. It is my deepest shame.
Posts: 3,769
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
I agree with DannoXYZ - if you are not pedlling and the derailleur is doing a dance, the problem is comeing from somewhere else.

If while you are coasting your derailleur jerks forward occaisionally it is most likely a problem with the ratchet mechanism in the freewheel/freehub. THis is somethign you shoudl fix soon as freewheels and freehubs generally get worse if left alone, not better. And you will be left either not being able to coast (loss of freewheel function) or not be able to pedal (loss of forward motion).
LarDasse74 is offline   Reply With Quote
Old 11-12-10, 11:00 AM   #6
granto
Member
Thread Starter
 
Join Date: Sep 2010
Location: Pittsburgh, PA
Bikes: '88 Specialized Hardrock, '82 Centurion Le Mans
Posts: 42
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Have not tried on a repair stand, because I don't have one I'll throw it up at the local co-op and tell you what I see
granto is offline   Reply With Quote
Old 11-12-10, 11:04 AM   #7
granto
Member
Thread Starter
 
Join Date: Sep 2010
Location: Pittsburgh, PA
Bikes: '88 Specialized Hardrock, '82 Centurion Le Mans
Posts: 42
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
(because I know nothing about freewheels), why would it only happen when I'm in the highest front gear?
granto is offline   Reply With Quote
Old 11-12-10, 11:05 AM   #8
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: 29,382
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 70 Post(s)
I suspect that your problem isn't with the pulley itself but in the chain, or the point of chain/pulley engagement.

Like Danno, I assume that despite the "seems that I don't have to be pedaling" it only happens when the chain is moving. If it happens while coasting it's another ball o' wax altogether.

It's easy to check the chain first. Backpedal while holding a bit of pressure against the lower pulley until the chain just begins to sag. Watch the chain as it comes off the pulley for any links that don't straighten immediately, and feel for any tugging on the cage. Either indicate stiff links, which can usually be solved with chain lube.

If the chain is OK, use a stand or have someone hold the rear wheel off the ground. Put the bike in the problem combination, pedal forward and watch carefully as the chain engages the lower pulley. You're want to see if it's trying to come off the side of the pulley. If so, that's your problem, and the solution may lie in checking the RD and hanger alignment.

Note, some RD pulleys are more prone to the problem than others, so if all checks out but it still does this when the chain feeds from an angle (outer chainring, middle and inner cassette sprockets) you might want to find a lower pulley with deeper teeth (more like a sprocket) as these do a better job keeping the chain in the groove.
__________________
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 11-12-10, 11:18 AM   #9
LarDasse74
Guest
 
Join Date: Jul 2008
Location: Grid Reference, SK
Bikes: I never learned to ride a bike. It is my deepest shame.
Posts: 3,769
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by granto View Post
(because I know nothing about freewheels), why would it only happen when I'm in the highest front gear?
Sorry I missed that detail in the OP. It could also be, as FBinNY says, an issue with derailleur alignment. Using the big chainring up front might be putting the chain at an angle the derialleur cannnot accomdate. But you need to see if this is happening when you coast or just when the chain is moving.
LarDasse74 is offline   Reply With Quote
Old 11-12-10, 11:19 AM   #10
granto
Member
Thread Starter
 
Join Date: Sep 2010
Location: Pittsburgh, PA
Bikes: '88 Specialized Hardrock, '82 Centurion Le Mans
Posts: 42
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
OK, well the chain is very new, but here's my observation when backpeddling- If I do it slowly enough, the cog on the lower pulley does not spin until I pull it far enough and it finally spins. So it seems like I may just do a slight backpedal while riding and this happens. But I lubed the heck out of that cog to no avail. I could try loosening it, or... replacing it?
granto is offline   Reply With Quote
Old 11-12-10, 11:23 AM   #11
DannoXYZ 
Senior Member
 
DannoXYZ's Avatar
 
Join Date: Jul 2005
Location: Saratoga, CA
Bikes:
Posts: 11,600
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Does the lower-pulley spin freely by hand? There is typically a stationary bushing on the inside that the pulley spins around. Some pulleys have ceramic bushings that can be cracked by overtightening the bolt, leading to a binding pulley. Or if the bushing is too narrow (like it was swapped from another pulley), then the washers on the side would bind up the pulley.
DannoXYZ is offline   Reply With Quote
Old 11-12-10, 11:29 AM   #12
granto
Member
Thread Starter
 
Join Date: Sep 2010
Location: Pittsburgh, PA
Bikes: '88 Specialized Hardrock, '82 Centurion Le Mans
Posts: 42
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
It spins, but not for long. It's an old bike, but it's been OK for months so far. I have made no adjustments to the pulley (and haven't wrecked the bike)... it just appeared. Maybe just worn out bushings?
granto is offline   Reply With Quote
Old 11-12-10, 11:39 AM   #13
granto
Member
Thread Starter
 
Join Date: Sep 2010
Location: Pittsburgh, PA
Bikes: '88 Specialized Hardrock, '82 Centurion Le Mans
Posts: 42
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
OK, looks like it's probably the hub. While backpedelling, the top of the chain goes slack and the rear pulley is pulled forward, and the tension is held in by the freewheel and not the pulley. Guess it's time for me to learn about freewheels
granto is offline   Reply With Quote
Old 11-12-10, 12:02 PM   #14
granto
Member
Thread Starter
 
Join Date: Sep 2010
Location: Pittsburgh, PA
Bikes: '88 Specialized Hardrock, '82 Centurion Le Mans
Posts: 42
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
OK one more question, I forgot that I just installed a new threaded freewheel on this bike a few months ago. (Still not understanding how the freewheel/hub works), could the backpedal resistance come from the hub itself? In other words I thought it was a mechanism in the freewheel, and not the hub, that allowed it to "click" when coasting or pedaling backwards....
granto is offline   Reply With Quote
Old 11-12-10, 05:00 PM   #15
granto
Member
Thread Starter
 
Join Date: Sep 2010
Location: Pittsburgh, PA
Bikes: '88 Specialized Hardrock, '82 Centurion Le Mans
Posts: 42
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Alright now that it's clear that I was waaaay off, here was the real problem: there was a chunk of metal on the face of one of my chainring's teeth, which was catching on the chain, and the lower pulley was sticking enough to be pulling forward during the process (the lube finally took to the pivot point and it no longer pulls forward when backpedaling). Filed it off, back to normal. Thanks for everyone's help.
granto 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 10:57 AM.