# Thump in drivetrain when I stop peddling. Canyon Hardtail SX Drivetrain



## FatalMISTER_Z (Aug 15, 2021)

I have a Canyon Grand Canyon 7 with a SRAM SX Drivetrain. I have noticed when I stop peddling there is a thump like every thing stopped but the back wheel. I have a couple older mountain bikes and they don't do this. Is this normal for this drivetrain? Do I need to repair it or work with Canyon on the warranty? I have been searching the internet trying to find a post of someone having a similiar problem and I just havn't found anything. Any help is appreciated. 

Thank you.


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## Cleared2land (Aug 31, 2012)

Well...I think we need a bit more detailed information. Internet folks will provide answers all over the map with what has been provided.


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## Hit Factor (Apr 7, 2021)

I believe my bikes do the same thing. I think it's just the tension function of the rear derailleur dealing with momentum when you stop pedaling.


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## Cleared2land (Aug 31, 2012)

^^^ Say what?


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## Pisgah (Feb 24, 2006)

Pay attention to the chain when the thump happens. If the chain gets slack, your problem could be freehub pawls malfunctioning (which is a bad thing).


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## Reaperactual (Apr 20, 2020)

I get the same thing but only in the *two highest gears* and as above the chain goes a little slack at the same time.

In my case it's the chain slightly rubbing on the side of the next biggest cog. Not a problem that happens when pedalling forward so I don't see it as a big deal. Easy enough to spot as it's just as obvious on a workstand. Worth checking out if this is a similar thing that's happening to your drivetrain.


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## p1nhead (Sep 3, 2013)

Pisgah said:


> Pay attention to the chain when the thump happens. If the chain gets slack, your problem could be freehub pawls malfunctioning (which is a bad thing).


Yep, this is usually what is happening when you stop pedaling and feel a little bump on the pedals. The bike doesn't want to freewheel for an instant when you stop pedaling, and the cassette keeps turning, causing the chain to slack momentarily. The pawls in your freehub are probably sticky. Usually you can grease them and it's fine.


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## nayr497 (Nov 9, 2011)

Just learned something new about pawls! Have thankfully never had this issue.


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## FatalMISTER_Z (Aug 15, 2021)

Thanks for all the input. I suspected it was the freehub. Just odd that it is sticking in less than 2 months of only paved path riding. I will tear it down clean and grease it this weekend. Thanks again!


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## Cleared2land (Aug 31, 2012)

You do have Shimano hub and freehub do you not? Maybe a MT-400? Is that correct?


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## FatalMISTER_Z (Aug 15, 2021)

Cleared2land said:


> You do have Shimano hub and freehub do you not? Maybe a MT-400? Is that correct?


nailed it, that is what I have.


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## Cleared2land (Aug 31, 2012)

The Shimano Hub is not your typical 'pawl freehub' like you will find with I-9, DT Swiss (not Star Ratchet) or any number of other pawled freehubs where you easy access to the pawls. Your Shimano freehub can be serviced, it's just more challenging.


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## FatalMISTER_Z (Aug 15, 2021)

Cleared2land said:


> The Shimano Hub is not your typical 'pawl freehub' like you will find with I-9, DT Swiss (not Star Ratchet) or any number of other pawled freehubs where you easy access to the pawls. Your Shimano freehub can be serviced, it's just more challenging.


Good to know, thanks!


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