Go Back  Bike Forums > Bike Forums > Singlespeed & Fixed Gear
Reload this Page >

Chain problem - single speed mountain bike

Notices
Singlespeed & Fixed Gear "I still feel that variable gears are only for people over forty-five. Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

Chain problem - single speed mountain bike

Old 06-24-15, 07:15 PM
  #1  
Harcati
Junior Member
Thread Starter
 
Join Date: Jan 2013
Posts: 21

Bikes: Fuji Roubaix 1.0, Fuji Absolute 1, Rocky Mountain Element, Wal Mt Cruiser

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Chain problem - single speed mountain bike

Got a fixed gear hardtail mountain bike about a week ago. I have a problem with the chain. During crank rotation, it varies from too tight to too loose.

I changed some cog spacers to better align the chain; problem still there.

The dealer sent replacement cranks, chainring, and bottom bracket in case those components were defective. Put them on this morning; problem still there.

The cog and rear wheel are straight, and the rear wheel is properly aligned.

I can't think of anything else to look at....any ideas?
Harcati is offline  
Old 06-24-15, 07:22 PM
  #2  
john4789
Senior Member
 
john4789's Avatar
 
Join Date: Aug 2011
Location: Chicago, IL
Posts: 437

Bikes: Surly Steamroller FG, Trek 800 SS MTB, Omega Tandem Sport

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 3 Times in 2 Posts
No expert, but it might be the frame alignment then. If the BB shell is and chainstays are not aligned it may not ever be perfect.

Are you dropping your chain when it goes loose? If not maybe it is just too tight in the first place. Post photos. Try the mechanics sub forum.
john4789 is offline  
Old 06-24-15, 08:34 PM
  #3  
taras0000
Lapped 3x
 
taras0000's Avatar
 
Join Date: Dec 2004
Location: 43.2330941,-79.8022037,17
Posts: 1,720
Mentioned: 13 Post(s)
Tagged: 0 Thread(s)
Quoted: 324 Post(s)
Liked 20 Times in 17 Posts
Sounds like the chainring is out of round/machined off center. Cheap chainrings do this.
taras0000 is offline  
Old 06-24-15, 08:54 PM
  #4  
john4789
Senior Member
 
john4789's Avatar
 
Join Date: Aug 2011
Location: Chicago, IL
Posts: 437

Bikes: Surly Steamroller FG, Trek 800 SS MTB, Omega Tandem Sport

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 3 Times in 2 Posts
Originally Posted by taras0000 View Post
Sounds like the chainring is out of round/machined off center. Cheap chainrings do this.
Sounds unlikely as OP says dealer sent a new chainring and the problem persists. Could be two bad rings but doesn't seem likely to me. Could be...
john4789 is offline  
Old 06-24-15, 09:02 PM
  #5  
hardboiled718
Senior Member
 
Join Date: Nov 2014
Posts: 516
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 71 Post(s)
Likes: 0
Liked 12 Times in 10 Posts
How much is the difference between slack and tight spots? If the slack has about a 1/4" of wiggle room and the chain's not binding in the tight spots that it should be fine.
hardboiled718 is offline  
Old 06-24-15, 09:29 PM
  #6  
ThermionicScott 
7-speed cultist
 
ThermionicScott's Avatar
 
Join Date: Aug 2011
Location: CID
Posts: 20,093

Bikes: 1991 Bianchi Eros, 1964 Armstrong, 1988 Diamondback Ascent, 1988 Bianchi Premio, 1987 Bianchi Sport SX, 1980s Raleigh mixte (hers)

Mentioned: 88 Post(s)
Tagged: 0 Thread(s)
Quoted: 2792 Post(s)
Liked 737 Times in 517 Posts
Originally Posted by john4789 View Post
Sounds unlikely as OP says dealer sent a new chainring and the problem persists. Could be two bad rings but doesn't seem likely to me. Could be...
If the crank/chainrings in question weren't really designed for fixed-gear use (Harcati, what brand/model?), they might be out of round, yet within spec. My fixed-gear, of course, has always featured mid-level road cranks and cheap chainrings, so I'm used to finding the tight spot in the chain and using that to set the slack. Works fine.
__________________
Originally Posted by chandltp View Post
There's no such thing as too far.. just lack of time
Originally Posted by noglider
People in this forum are not typical.
RUSA #7498
ThermionicScott is offline  
Old 06-24-15, 11:54 PM
  #7  
taras0000
Lapped 3x
 
taras0000's Avatar
 
Join Date: Dec 2004
Location: 43.2330941,-79.8022037,17
Posts: 1,720
Mentioned: 13 Post(s)
Tagged: 0 Thread(s)
Quoted: 324 Post(s)
Liked 20 Times in 17 Posts
Originally Posted by john4789 View Post
Sounds unlikely as OP says dealer sent a new chainring and the problem persists. Could be two bad rings but doesn't seem likely to me. Could be...
OP also doesn't say what rings and cranks they are using. Cheap replacements are still cheap equipment and susceptible to the same tolerances. In my 15 years of track racing and SS/FG riding, this has been the mostly likely reason for thus happening. Sometimes the differences in the tight/slack differences can be mitigated my trying to match the "high" spots in the ring with the "low" spots on the crankarm spider. Just keep rotating the chainring on the spider until the problem goes away or is minimized.
taras0000 is offline  
Old 06-25-15, 06:16 AM
  #8  
nripin
Senior Member
 
Join Date: Nov 2011
Posts: 72
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 5 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by Harcati View Post
it varies from too tight to too loose.
Originally Posted by hardboiled718 View Post
How much is the difference between slack and tight spots? If the slack has about a 1/4" of wiggle room and the chain's not binding in the tight spots that it should be fine.
it is normal to have minor difference in roundness of chainring. i agree with hardboiled, define your tight and loose, how many inch of slack at the loosest point?

Last edited by nripin; 06-25-15 at 06:17 AM. Reason: spelling
nripin is offline  
Old 06-25-15, 06:27 AM
  #9  
Mumonkan
Brown Jersey Winner
 
Mumonkan's Avatar
 
Join Date: Apr 2012
Location: The Bad Woods.
Posts: 8,806
Mentioned: 14 Post(s)
Tagged: 0 Thread(s)
Quoted: 243 Post(s)
Likes: 0
Liked 1 Time in 1 Post
cogs can be out of round just like chainrings

try centering your chainring as explained here, see if that helps.

otherwise do like ThermionicScott sez and set the tension at the tightest spot
Mumonkan is offline  
Old 06-25-15, 07:08 AM
  #10  
Harcati
Junior Member
Thread Starter
 
Join Date: Jan 2013
Posts: 21

Bikes: Fuji Roubaix 1.0, Fuji Absolute 1, Rocky Mountain Element, Wal Mt Cruiser

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by nripin View Post
it is normal to have minor difference in roundness of chainring. i agree with hardboiled, define your tight and loose, how many inch of slack at the loosest point?
Tight: 1/4" at the loosest point, virtually no play at the tightest point with serious binding.
Harcati is offline  
Old 06-25-15, 07:12 AM
  #11  
Harcati
Junior Member
Thread Starter
 
Join Date: Jan 2013
Posts: 21

Bikes: Fuji Roubaix 1.0, Fuji Absolute 1, Rocky Mountain Element, Wal Mt Cruiser

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by ThermionicScott View Post
If the crank/chainrings in question weren't really designed for fixed-gear use (Harcati, what brand/model?), they might be out of round, yet within spec. My fixed-gear, of course, has always featured mid-level road cranks and cheap chainrings, so I'm used to finding the tight spot in the chain and using that to set the slack. Works fine.
The bike is a Nashbar Bees Knees 27.5 single speed.
Harcati is offline  
Old 06-25-15, 07:12 AM
  #12  
Harcati
Junior Member
Thread Starter
 
Join Date: Jan 2013
Posts: 21

Bikes: Fuji Roubaix 1.0, Fuji Absolute 1, Rocky Mountain Element, Wal Mt Cruiser

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by john4789 View Post
No expert, but it might be the frame alignment then. If the BB shell is and chainstays are not aligned it may not ever be perfect.

Are you dropping your chain when it goes loose? If not maybe it is just too tight in the first place. Post photos. Try the mechanics sub forum.
Yes, the chain drops when it is loose.
Harcati is offline  
Old 06-25-15, 10:46 AM
  #13  
SquidPuppet
Calamari Marionette Ph.D
 
SquidPuppet's Avatar
 
Join Date: Dec 2013
Location: Coeur d' Alene
Posts: 7,862

Bikes: 3 Chinese Gas Pipe Nerdcycles and 2 Chicago Electroforged Boat Anchors

Mentioned: 74 Post(s)
Tagged: 0 Thread(s)
Quoted: 2356 Post(s)
Liked 20 Times in 17 Posts
Originally Posted by Harcati View Post
Tight: 1/4" at the loosest point, virtually no play at the tightest point with serious binding.
Your chain is WAY too tight. You should have at least 1/4" slop in the tight position.
SquidPuppet is offline  
Old 06-25-15, 10:49 AM
  #14  
SquidPuppet
Calamari Marionette Ph.D
 
SquidPuppet's Avatar
 
Join Date: Dec 2013
Location: Coeur d' Alene
Posts: 7,862

Bikes: 3 Chinese Gas Pipe Nerdcycles and 2 Chicago Electroforged Boat Anchors

Mentioned: 74 Post(s)
Tagged: 0 Thread(s)
Quoted: 2356 Post(s)
Liked 20 Times in 17 Posts
Originally Posted by Harcati View Post
Yes, the chain drops when it is loose.
He means "does it fall off?".

It's common to have snug and loose spots. Find the tightest position and adjust your slack while it's there.
SquidPuppet is offline  
Old 06-25-15, 10:52 AM
  #15  
ThermionicScott 
7-speed cultist
 
ThermionicScott's Avatar
 
Join Date: Aug 2011
Location: CID
Posts: 20,093

Bikes: 1991 Bianchi Eros, 1964 Armstrong, 1988 Diamondback Ascent, 1988 Bianchi Premio, 1987 Bianchi Sport SX, 1980s Raleigh mixte (hers)

Mentioned: 88 Post(s)
Tagged: 0 Thread(s)
Quoted: 2792 Post(s)
Liked 737 Times in 517 Posts
Originally Posted by Harcati View Post
The bike is a Nashbar Bees Knees 27.5 single speed.
So we're looking at a square-taper double crank that is being set up with just the inner ring... for the problem to recur with a new bottom bracket, crank, and chainring makes me think that it could be a chainline issue, not the parts themselves. "Serious binding" should not be necessary to keep the chain from jumping off, and will prematurely wear your bearings -- my chain is a little flappy all the way around, and I have never ONCE dropped a chain.

Could you measure the chainline for us? And does the chainring have noticeable wiggle from side to side as you turn the crank?

EDIT: @SquidPuppet asks the important question!
__________________
Originally Posted by chandltp View Post
There's no such thing as too far.. just lack of time
Originally Posted by noglider
People in this forum are not typical.
RUSA #7498
ThermionicScott is offline  
Old 06-25-15, 10:59 AM
  #16  
SquidPuppet
Calamari Marionette Ph.D
 
SquidPuppet's Avatar
 
Join Date: Dec 2013
Location: Coeur d' Alene
Posts: 7,862

Bikes: 3 Chinese Gas Pipe Nerdcycles and 2 Chicago Electroforged Boat Anchors

Mentioned: 74 Post(s)
Tagged: 0 Thread(s)
Quoted: 2356 Post(s)
Liked 20 Times in 17 Posts
Originally Posted by ThermionicScott View Post
So we're looking at a square-taper double crank that is being set up with just the inner ring... for the problem to recur with a new bottom bracket, crank, and chainring makes me think that it could be a chainline issue, not the parts themselves. "Serious binding" should not be necessary to keep the chain from jumping off, and will prematurely wear your bearings -- my chain is a little flappy all the way around, and I have never ONCE dropped a chain.

Could you measure the chainline for us? And does the chainring have noticeable wiggle from side to side as you turn the crank?

EDIT: @SquidPuppet asks the important question!
To me it just sounds like the infamous (but understandable when new) "I'm trying tighten this up and get rid of all this nasty sag and slop." syndrome.

A droopy chain is a happy chain.
SquidPuppet is offline  
Old 06-26-15, 12:17 PM
  #17  
Harcati
Junior Member
Thread Starter
 
Join Date: Jan 2013
Posts: 21

Bikes: Fuji Roubaix 1.0, Fuji Absolute 1, Rocky Mountain Element, Wal Mt Cruiser

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by SquidPuppet View Post
To me it just sounds like the infamous (but understandable when new) "I'm trying tighten this up and get rid of all this nasty sag and slop." syndrome.

A droopy chain is a happy chain.
I tried turning the crank 90degrees on the bottom bracket and rechecking chain tension. I tried all four faces on the bottom bracket spindle. This did not solve the issues I'm having; the chain still oscillates from 1/4" to too loose.

My chain does come off either the cog, chainring, or both; usually when I am climbing or going over rough terrain.

I did get the chain to the point where it has 1/4" play at its tightest , but still more than 1" play at its loosest, but with no binding. Still comes off however.

Do you have a recommendation for a single speed crank replacement? Would square taper BMX cranks work? The bottom bracket is JIS standard 68mm wide shell ,British threading. Also, I'd like to fine tune my chainline but am limited to the spacers that came with the bike. Are spacer kits available with spacers in a wide range of thicknesses?
Harcati is offline  
Old 06-26-15, 12:36 PM
  #18  
SquidPuppet
Calamari Marionette Ph.D
 
SquidPuppet's Avatar
 
Join Date: Dec 2013
Location: Coeur d' Alene
Posts: 7,862

Bikes: 3 Chinese Gas Pipe Nerdcycles and 2 Chicago Electroforged Boat Anchors

Mentioned: 74 Post(s)
Tagged: 0 Thread(s)
Quoted: 2356 Post(s)
Liked 20 Times in 17 Posts
Originally Posted by Harcati View Post
I tried turning the crank 90degrees on the bottom bracket and rechecking chain tension. I tried all four faces on the bottom bracket spindle. This did not solve the issues I'm having; the chain still oscillates from 1/4" to too loose.

My chain does come off either the cog, chainring, or both; usually when I am climbing or going over rough terrain.

I did get the chain to the point where it has 1/4" play at its tightest , but still more than 1" play at its loosest, but with no binding. Still comes off however.

Do you have a recommendation for a single speed crank replacement? Would square taper BMX cranks work? The bottom bracket is JIS standard 68mm wide shell ,British threading. Also, I'd like to fine tune my chainline but am limited to the spacers that came with the bike. Are spacer kits available with spacers in a wide range of thicknesses?
If you have 1/4" slack at the tight point and over an inch at the loose point, that certainly is an extreme variance.

Qs

What brand crank and chain ring is it?
What brand chain and is it new or old?
What brand cog?
You mentioned working on the chainliine. What was the final result front and rear?

Do this test to examine your chainring/crank. Put a zip-tie around the down tube, Line up the excess "finger" with the teeth of the ring and cut the tie off where it meets the teeth. Use it as a feeler indicator. Rotate the cranks and watch the feeler/tooth intersection and see how much deviation there is. All my bikes have a deviation, but its super tiny. I can see it but it is almost unmeasurable. If yours has big gaps, that's for sure part of the problem.
SquidPuppet is offline  
Old 06-26-15, 12:46 PM
  #19  
Harcati
Junior Member
Thread Starter
 
Join Date: Jan 2013
Posts: 21

Bikes: Fuji Roubaix 1.0, Fuji Absolute 1, Rocky Mountain Element, Wal Mt Cruiser

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by SquidPuppet View Post
If you have 1/4" slack at the tight point and over an inch at the loose point, that certainly is an extreme variance.

Qs

What brand crank and chain ring is it?
What brand chain and is it new or old?
What brand cog?
You mentioned working on the chainliine. What was the final result front and rear?

Do this test to examine your chainring/crank. Put a zip-tie around the down tube, Line up the excess "finger" with the teeth of the ring and cut the tie off where it meets the teeth. Use it as a feeler indicator. Rotate the cranks and watch the feeler/tooth intersection and see how much deviation there is. All my bikes have a deviation, but its super tiny. I can see it but it is almost unmeasurable. If yours has big gaps, that's for sure part of the problem.
The crank and chain ring are generic (Alloy square taper 104mm bcd with 32t ring). They are made for Nashar in Taiwan (the bike is a Nashbar Bee's Knees Single speed 27.5").
The chain is new; KMC Z410.
No name 18 tooth steel cog.
Front and rear chainline is 3mm off; I am using the measuring technique described by Sheldon Brown.
Harcati is offline  
Old 06-26-15, 12:52 PM
  #20  
SquidPuppet
Calamari Marionette Ph.D
 
SquidPuppet's Avatar
 
Join Date: Dec 2013
Location: Coeur d' Alene
Posts: 7,862

Bikes: 3 Chinese Gas Pipe Nerdcycles and 2 Chicago Electroforged Boat Anchors

Mentioned: 74 Post(s)
Tagged: 0 Thread(s)
Quoted: 2356 Post(s)
Liked 20 Times in 17 Posts
Originally Posted by Harcati View Post
The crank and chain ring are generic (Alloy square taper 104mm bcd with 32t ring). They are made for Nashar in Taiwan (the bike is a Nashbar Bee's Knees Single speed 27.5").
The chain is new; KMC Z410.
No name 18 tooth steel cog.
Front and rear chainline is 3mm off; I am using the measuring technique described by Sheldon Brown.
3mm off on the chainline shouldn't be causing this. Eliminate that as a cause.

KMC z410s are good so I doubt that's the problem,

Check the crank as I suggested. Also inspect the cog in the same way to check for roundness. If you find that either, or both are wonky, you can proceed from there.

Watch the BB spindle too. If it's bent it'll cause wobble. It's new so it shouldn't be bent, but worth a look.
SquidPuppet is offline  
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
Files
Singlespeed & Fixed Gear
10
09-05-18 03:43 PM
sirtirithon
Bicycle Mechanics
12
07-17-13 07:57 PM
ETN612
Singlespeed & Fixed Gear
3
01-05-13 04:24 AM
EssEllSee
Bicycle Mechanics
2
07-07-11 09:18 PM
sundersledge
Singlespeed & Fixed Gear
7
06-28-10 11:10 AM

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 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.