Welded chain doesn't need to have swivels, neither do bolts that have been hard twinked to prevent spin-off. However, people without spin relief are more likely to suffer other issues with their chains from accelerated gip wear to connector failure.
The physics of it are pretty simple. Your hands don't rotate while you spin, but your wicks are spinning (in relation to your hands) which creates rotational torque around the connection point to your hand. This torque has to go somewhere. If your chain doesn't have a swivel, then it causes your wicks to spin on axis where the chain connects. The weight of your wicks determines how much energy your chain has to apply to the second rotation of the wicks.
With unwelded chain, or any cheap grade, this rotational torque will twist and snap the chain, the connectors, or the grips. Someone using heavy chain and good connectors might not suffer this problem. However, the stress is still there and get applied to their grips instead. Another side effect of this is that any threaded device will tend to unscrew (eye bolts, quick links, etc) from being spun along the length of the chain.
| Results: Busted. |
They do, however, increase the life of your grips and decrease the probability of other failures.
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