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Chain Stabilisation Device in conjunction with SickBikeParts, SBP, Sick Bike Parts, shift kit

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Chain Stabilisation Device in conjunction with SickBikeParts, SBP, Sick Bike Parts, shift kit

Post by Fabian on Tue Nov 29 2011, 12:16

Finally i've fixed the problem of chain suck when riding on heavily potholed roads.
From my experience (and it doesn't matter if it's SRAM or Shimano) rear derailleurs (as i've tried them all) do not have enough spring tension to control the chain when the bicycle is slamming into potholes or heavilly rutted roads at a reasonable level of speed.

With the chain stabilisation device working in conjunction with the double idler wheel system and chain loop enclosing the idlers, the problem of chain bounce and chain suck has been successfully resolved, with the device effectively dividing the length of unsupported chain returning to the rear derailleur (when on the smallest cassette sprockets); also isolating chain bounce from making it's way to the front chain wheel when chain links are disengaging the sprocket teeth.

A side benefit is the elimination of ghost shifting, which would occur when the chain gained excessive lateral velocity overcoming the derailleur pantograph spring tension causing a ghost upshift, followed by the resultant downshift to the preselected gear, usually tearing out a chain side plate or tearing off a sprocket tooth under power.
With the device installed the chain can only move approx 1 3/4 inches laterally but in practice (and when running on the smaller cassette sprockets) the chains lateral movement is insignificant and chain bounce is also insignificant.
Since the modification there is a maximum of 6 inches of unsupported chain in top gear; best shown in the last two photos.
Prior to this modification the chain would have around 12 inches of vertical travel, wildly whipping about on seriously bad road surfaces, resulting in chain suck; usually tearing out the rear derailleur and sometimes the front derailleur.
For general travel on well paved surfaces this modification is not necessary but is beneficial for severe duty riding conditions



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It's only when fitting a small video camera to capture the action that a person realises how weak and ineffective the spring tension is on modern "higher" end derailleurs. It seems the more money you spend on a rear derailleur, the weaker the spring tension becomes, and i've tried both SRAM and Shimano with equal disgust.
In coming weeks i'll post an easy modification to significantly increase spring tension for rear derailleurs which will also increase the pantograph spring tension making downshifting to the smaller sprockets on 9 and 10 speed rear derailleurs significantly better, especially if the selector cable is sticking due to dirt or a plain weak pantograph spring.

A good point is not to leave a conventional "top normal" derailleur in 1st gear (largest sprocket) when the bike is not in use as the pantograph spring is stretched to it maximum. This is a sure fire way to weaken spring tension (over time), making it harder to engage the smaller sprockets when the derailleur tries to pull the inner cable through the outer cable.
If you have a "low normal" derailleur the reverse is true: never leave the bike in top gear (smallest cassette sprocket) when the bike is not in use.

Fabian
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