> Doesn't a derailleur have to have a spring in it? Indeed, a lot of them now have batteries and electric motors. I was surprised how easily electronic shiftin

> Doesn't a derailleur have to have a spring in it? Indeed, a lot of them now have batteries and electric motors. I was surprised how easily electronic shifting was allowed into the sport. So yes, many pro-racing bikes already have battery power, even though it's not directly driving the bike. It could be argued that some kind of KERS would be a natural evolution of this.