# what is the really loud clunk from the rear of my mtb when i go over small bumps coming from??



## Jakethomascampbell (Dec 1, 2021)

I recently bought the* Marin Alpine Trail 7 secondhand *and is perfect and everything runs smoothly except there is a really *annoying clank/clunk* (definitely from somewhere on the *rear of the bike*)* every-time i go off a kerb, down a bumpy track or when i go over bumpy berms.* I don't hear the noise on really slow technical rock gardens but when i get faster then fast-walking/jogging pace it starts to become really noticeable on any bumps. When going downs a fast single track or any fast trails with rocks it sounds like something is about the just fall off.

I know for a fact its not that the bushings are needing replacement on my rear shock because there is no movement near my linkage. The chain is very loose when i am in the hardest gear but gets more tight the more easier the gears, the chain isn't really stretched because the bike shop said to wait a few more months before replacing it.

My right crank-arm has a little-bit of play when in a certain position but otherwise I have no clue what could be causing this clank when i go over small bumps.

Any ideas what could be the problem? What is making the noise? What I should look out for? What I should do?

Thanks a-lot


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## TylerVernon (Nov 10, 2019)

Could be the chain growth making the cassette rotate a bit and the freehub clunks. Or the rear derailleur slapping, maybe check the clutch tension or the clutch function.


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## Jakethomascampbell (Dec 1, 2021)

TylerVernon said:


> Could be the chain growth making the cassette rotate a bit and the freehub clunks. Or the rear derailleur slapping, maybe check the clutch tension or the clutch function.


could tightening this effect anything that i don't want it too because it tightens the chain and helps stop the chain slap?


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## Sparticus (Dec 28, 1999)

That’s the B-tension adjuster.
Recommend you understand it’s function before messing with it. 
=sParty


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## noapathy (Jun 24, 2008)

There's definitely a bongo drum stuck in your hub. Just gotta learn to hit the bumps with some rhythm. I had to take a trip to Jamaica to fully understand this - I suggest you do the same pronto.


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## SteveF (Mar 5, 2004)

May be something loose in your rear suspension. Gently lift the rear end of the bike by the saddle and see if anything moves before the rear wheel comes off the ground. Find manufacturers torque/assembly recommendation and diagram of rear suspension and give it a once over, make sure that there's no play and everything is properly tight and moves freely.


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## Jakethomascampbell (Dec 1, 2021)

SteveF said:


> May be something loose in your rear suspension. Gently lift the rear end of the bike by the saddle and see if anything moves before the rear wheel comes off the ground. Find manufacturers torque/assembly recommendation and diagram of rear suspension and give it a once over, make sure that there's no play and everything is properly tight and moves freely.


yes, i have done all this and there is still a clunk!!!!! sooo frustrating!!! thanks for you help tho


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## RTM (Sep 17, 2005)

if its not the shock-mount or frame bearings this could be chain growth pulling the cassette forward. the clunk is the pawl smacking into the teeth inside the hub. with the bike sitting stationary try tugging the top of the chain forward with your hand a few times and see if you can replicate the sound.


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## Taroroot (Nov 6, 2013)

What kind of play in the cranks, thats not usually normal.


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