>>1251026Misunderstood your question. It does not. It helps against the same thing from the top. From the bottom, in the olden days, you would have a slider or a roller.
The thing is, that as you pedal, the bottom derailment tends to fix itsself on its own, while top derailment causes a chain drop. Bottom derailment can proceed to a full chain drop if it happens on a rough section of the trail and you are backpedalling ( in order to avoid roots, for example )
