he looked down at the gears and the chain and gearbox of the mountain bike. the gear chains are very washable and greasy, and the

back background bicycle bike black brake chain change close closeup cog cogwheel cogwheels component copy detail dirt dirty disc disk drive engineering force gear gearing gearshift gearwheel grass greasy green hardware hydraulics industry machine machinery mechanics mechanism metal mountain oil out overhaul part power ratchet reparation ride service set shift space speed sport sprocket steel structure teeth tire transmission wheel worn yellow