Motorcycle drive chain slack
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: Motorcycle drive chain slack
: Motorcycle drive chain slack -- srinivasanav	Post Reply	Top of thread	Engineering Forum

Posted by: RWOLFEJR ® 02/09/2011, 08:41:25 Author Profile eMail author Edit

"Does the bottom mounting point of the rear damper on the swingarm have an effect on this?" No it does not. The location of the shock or shocks will effect the leverage applied on the shock but has nothing to do with the pivot point of the swing arm as it relates to chain tension. "My problem is that I am not able to figure out the relationship between the motion of the rear swingarm when in pivot to the reduction of slack in the drive chain. Is there such a relationship?" You need to look at the center location of the front sprocket as it compares to the center location of your swing arm pivot point. If the front sprocket could be located on the same shaft as the swing arm pivot there would be no change in chain tension through the swing arm travel. It isn't that way so the way to battle that is to adjust your chain for a little slack at the point in swing arm travel where the rear sprocket center is furthest away from the front sprocket center. From that point any motion above or below that point will loosen the chain some instead of breaking it. Most bike I've dealt with are set up so that the tightest point is with the load of a rider on it and the chain should be adjusted at that point. To measure your relationship of swing arm to chain tension you just need a ruler or tape. Move your swing arm up and down and measure the distance between the centers of the front sprocket and the rear through the range of the swing arm allowed by the shocks. You could prop the bike up and remove the shocks so you aren't fighting the springs... or use a ratchet strap to compress them? Good luck, Bob

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: : Motorcycle drive chain slack
: : Motorcycle drive chain slack -- RWOLFEJR	Post Reply	Top of thread	Engineering Forum

Posted by: jboggs ® 02/09/2011, 10:04:18 Author Profile eMail author Edit

Maybe this diagram will help. The chain slack is a result of the distance between the drive sprocket and wheel axle. The distance between the drive sprocket and the swing arm pivot is fixed, as is the distance from the swing arm pivot to the wheel axle. The only variable is the angle of the swing arm. the chain should be tightened to the optimum tension at the maximum center distance. The slack at any other position is what it is. If you want to do the math its all just trigonometry based on the traingle points shown in the diagram.

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