If you dont know you aint had fun on a bike
s/m bikes are fast dirt bikes 45/50 bhp 120 or less kilos
150/160/60/17 rear tyre 120/60/17 super stickys massive front brakes
big wide rims minimum of every thing apart from fun tottaly unpracticul but soooo! much fun.
ace bikes race on dirt and tarmac same track speeds up to 100 mph.
you must have a meeting near you at sometime this year and you must go