Batman:
mudguard:
I wouldn't get too hung up on the weight side. It seems there are few mountain bikes being linked. Anything with actual trail tyres will be far, far harder to ride on tarseal with any speed (recently did a gravel/road road when visiting friends on a mountainbike with fresh downhill rubber, 40k in two hours with my heart rate pegged, no thanks!!)
why does a 13 year old need to pedal at 50kph to school?
Well I'm not sure about the 50KPH part, but it was about using the correct tool for the job. My analogy was a rather disgusting ride I did on a loaned mountainbike.