Another high gear crank/chain vibration thread
07-09-18, 09:27 AM
#1
Senior Member
Thread Starter
Another high gear crank/chain vibration thread
I'm experiencing crank/chain vibration on a recent used bike purchase and wanted to see if anyone can point me in the right direction. It's a 9-speed Specialized Tricross and I only feel it in the last 2 cogs. The highest cog does it the most.
I've swapped out the chain for a new Shimano one but that didn't make a difference. Then I swapped out the cassette for one in my spare parts bin from the original HG50 to HG70, and that helped a bit. The vibration is still there but probably half as noticeable. Some say that this is just how it is and that I should be riding at the correct speed to be in those gears, but I wonder if there is anything else that I could look at.
I have not taken a look at the bottom bracket bearings because I don't have the lock ring tool (FSA mega exo), but the cranks spin smoothly on lower gears. I will probably replace the bearings soon anyway once I can.
Any other thoughts? Thanks!
I've swapped out the chain for a new Shimano one but that didn't make a difference. Then I swapped out the cassette for one in my spare parts bin from the original HG50 to HG70, and that helped a bit. The vibration is still there but probably half as noticeable. Some say that this is just how it is and that I should be riding at the correct speed to be in those gears, but I wonder if there is anything else that I could look at.
I have not taken a look at the bottom bracket bearings because I don't have the lock ring tool (FSA mega exo), but the cranks spin smoothly on lower gears. I will probably replace the bearings soon anyway once I can.
Any other thoughts? Thanks!
07-10-18, 02:47 PM
#2
Mechanic/Tourist
That's most likely how it is, and yes you should be riding the proper gears for your speed. If you want to know more about the vibration, and some possible way to reduce it, just Google chordal action.
07-10-18, 04:45 PM
#3
Senior Member
Check your chainline
Chordal action can be increased/decreased by chainline. Putting a spacer in the BB, bringing the chainline a bit outwards helped to reduce the vibration in my bike, though not completely eliminate it.
07-10-18, 08:41 PM
#4
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Not sure this is true since chordal action is an issue of tooth count and power pulses. How the chain feeds off the cog isn't an aspect of chordal action. But really poor chain angle will induce some amount of roughness rhythmic with each tooth/link release. Andy
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AndrewRStewart
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07-11-18, 02:53 PM
#6
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Interesting. I haven't checked my chain line since everything on the bike was original. I assumed that it was set up how the manufacturer intended.
It didn't seem like anything has been modified before I purchased it, but I guess we can never be too sure. I'll take a closer look and take measurements.
It didn't seem like anything has been modified before I purchased it, but I guess we can never be too sure. I'll take a closer look and take measurements.
07-11-18, 05:16 PM
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Does it only do it while pedaling?
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07-11-18, 06:30 PM
#8
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07-11-18, 06:40 PM
#9
Senior Member
Interesting. I haven't checked my chain line since everything on the bike was original. I assumed that it was set up how the manufacturer intended.
It didn't seem like anything has been modified before I purchased it, but I guess we can never be too sure. I'll take a closer look and take measurements.
It didn't seem like anything has been modified before I purchased it, but I guess we can never be too sure. I'll take a closer look and take measurements.
07-12-18, 01:38 AM
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