The tension is awesome,Daryl designed them so that if rocks or twigs get snarled they just roll right through without throwing the track or causing undue stress to the motors. Perfect correct tension at all times. I will know more when i throw her around the garden tomorrow (its like a swamp). They were a bargain too £35 inc delivery from the states. Must admit i pinched the idea of the charging socket from another website...it aint rocket science...just wiring
