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

BMX crank sounds

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.

BMX crank sounds

Old 10-12-17, 09:18 PM
Thread Starter
Join Date: Oct 2017
Posts: 1
Likes: 0
Liked 0 Times in 0 Posts
BMX crank sounds

I'm having a problem with my BMX that hopefully someone can help with. I got it as a "do-up" bike as it needed some work so I was just going to rebuild the whole thing while I was at it. As I was riding it for the first time I heard a loud "clink" noise coming from the drive side crank that didn't happen every time I pedaled but when I applied force to go a bit faster and it sometimes happens when I'm just pedaling. The chain was worn, the sprocket was bent, the bottom bracket sealed cartridge bearings were a bit rusty so I thought maybe since the sprocket is bent its stressing the chain out when the chain goes around the bend. All of what was listed was replaced. I installed a brand new fiction savage bottom bracket, stolen 25-T sprocket and a gold KMC 1/8" chain. I took it for a test ride and it was still making that sound, just not as frequent. Everything has been greased and installed properly. I even thought maybe the bolts were too tight, I backed them off a bit to see if that was the problem but sure enough it wasn't. The next thing I'll be changing is the cranks and pedals since I'm doing a total rebuild of this bike but since I'm still going to be riding this in the mean time I want the problem sorted. I've tried everything I can think of. I'm a beginner bicycle mechanic so it's really infuriating when I can't solve the problem. Has anyone else experienced this problem? I need someone else's brain to help me solve this problem lol thanks!
TK18 is offline  
Old 10-12-17, 10:54 PM
Senior Member
Join Date: Apr 2009
Location: New Rochelle, NY
Posts: 39,255

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

Liked 3,104 Times in 1,709 Posts
Just to make sure. Is the chain tensioned properly?

Before you answer ------- the right tension is NO TENSION.

Proper chain tension is sightly slack, and a tight chain can produce the kinds of noise you're hearing.

So, turn the cranks slowly observing the lower loop to make sure there's always some sag. The sag will vary as you turn the crank, and you want roughly 1/4" (1/2" total free up and down movement) of sag middle of the lower loop at the tightest place.

If after confirming that there's chain slack, it still makes noise, then we can look at other possibilities.
Chain-L site

An ounce of diagnosis is worth a pound of cure.

Just because I'm tired of arguing, doesn't mean you're right.

“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 online now  
Old 10-13-17, 07:50 AM
Senior Member
Join Date: Nov 2009
Posts: 1,177
Liked 86 Times in 76 Posts
Going along with the chain tension theory, is it a standard BMX sprocket in that it has one bolt holding it in place? Those can vary quite a bit in how they locate themselves on the spindle. Depending on the combination of parts and if it uses an adapter bushing you might have to play around to get it truly centered.

The other obvious culprit would be the center sleeve between the bottom bracket bearings. Very common to need a little custom fitting to get the length perfect, shimming a longer one or cutting/filing one down. I know some folks sort of set the crank tension with the bolts, but in my opinion if you can't tighten them down fully you got that center sleeve length wrong to begin with.
wesmamyke is offline  
Old 10-13-17, 12:58 PM
Senior Member
canopus's Avatar
Join Date: Mar 2009
Location: Kingwood, TX
Posts: 1,574

Bikes: Road, Touring, BMX, Cruisers...

Liked 173 Times in 111 Posts
So it wont make the noise all the time but only when force is applied? Is it one "clink" per revolution? Is it a clink or a thunk?
I've found that one clink per revolution is usually something loose or broken... for example from the poster above, a loose spyder or spyder bolt on the crank, or a loose pedal, or a bolt that wont tighten correctly because it is rusty and not lubed. You say you've replaced the bottom bracket. Is there any chance the bottom bracket could be shifting in the frame under torque? How are the pedals? worn? dry?
Parts are easy and usually noises go away when threads are lubed and tightened correctly. Not to be a downer but did you inspect the frame good? Ive also seen cracked frames make a noise on a pedal stroke also.
1984 Cannondale ST
1985 Cannondale SR300
1980 Gary Littlejohn Cruiser
1984 Trek 760
1981 Trek 710
canopus is offline  
Old 10-15-17, 11:48 PM
Thread Starter
Join Date: Oct 2017
Posts: 1
Likes: 0
Liked 0 Times in 0 Posts
Thanks for your reply's everyone. I did check the frame good before I installed the bearings as usual and everything was fine, the chain isn't tight and has slack. It is the standard one bolt sprocket. The sound doesn't happen for every revolution, it happens, I would say every 5-10 revolutions (I cant be sure with that number but it doesn't happen with every revolution. It is a loud CLINK sound coming from the drive side crank area
TK18 is offline  
Related Topics
Thread Starter
Last Post
10-17-18 12:05 PM
Bicycle Mechanics
09-15-17 05:57 AM
Bicycle Mechanics
06-10-13 07:59 AM
Bicycle Mechanics
07-30-12 04:21 PM
Bicycle Mechanics
07-20-11 12:19 PM

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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Your Privacy Choices -

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.