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hard knocking sound while spinning rear wheel in sand?

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What can it be?  It happened to me with few bikes already while digging out from deep sand, usually on first gear.

I think it's somewhere from rear wheel but not sure and its hard, dull, metallic sound. Once I am out no more knocking and all is good.

What's that?  I must add the chain and sprockets are new.

Edited by motf

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My first guess would be chain slap against the slider from the rear wheel bouncing and going from having zero traction to some.

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7 minutes ago, Wild Alaskan said:

its the chain skipping teeth from sand clogging the sprocket, make sure your chain slack is properly adjusted. Will be much worse with worn chain and sprockets.

 

so sand clogging the sprocket can cause this?  interesting, never though about that. Maybe you're right because all my cases were in deep sand.

I guess then it's not good for a chain, as it could snap...   Any remedy for this BTW? tightening the chain I guess :)

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7 minutes ago, motf said:

 

so sand clogging the sprocket can cause this?  interesting, never though about that. Maybe you're right because all my cases were in deep sand.

I guess then it's not good for a chain, as it could snap...   Any remedy for this BTW? tightening the chain I guess :)

not really any way to completely prevent it, making sure the chain guide is in good shape will help, some manufacturers also make rear sprockets that have cutouts that allow the debris between the chain and sprockets to be pushed out more easily as it turns

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Just now, Wild Alaskan said:

not really any way to completely prevent it, making sure the chain guide is in good shape will help, some manufacturers also make rear sprockets that have cutouts that allow the debris between the chain and sprockets to be pushed out more easily as it turns

 

recently I have changed gearing (dropped 1 tooth in front and upped 3 in rear)  so maybe with different sprockets chain slack should be a bit different then stock recommendation.

 

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best way to check is to have a heavy buddy sit on your fender to compress the rear end, the tightest part of the stroke will be when the countershaft sprocket, the swing arm pivot, and the rear wheel are all in a straight line, at this point adjust The chain so it has only a little bit of play then use this tension as your measurement for future adjustments.

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22 hours ago, mlatour said:

My first guess would be chain slap against the slider from the rear wheel bouncing and going from having zero traction to some.

 

at first I thought about this too, not sure though if it would be so hard, metal sound, next time I have to put  gopro nearby to catch that moment.

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