Sorry if this question has been asked before, but here goes...

When converting from 4cell NiMh to 1cell Lipo, most people will have to re-gear to achieve a different rollout. The general formula is to add about 10mm for the same motor for this conversion. Eg: For a 10.5R motor: 4NiMh set @ 50mm then 1S Lipo will need to set @ 60mm.

Now my question is why?
Is it because the car is lighter, so that we can re-gear another 10mm of rollout without an increase in motor temp?OR
Is it because the voltage is less, so we need to increase 10mm rollout to match the speed of a 4cell car?

Sorry I am a little confused on this. Can someone please explain to me on this? Thanks in advance!