Animated Mountain Bike

Tyre susceptibility.  Tyres can be targeted separately.  They have an AC of 18, vulnerability to piercing damage, and HP of 10.  However, the tyres also have a damage threshold of 10.  Every 2 points of damage it takes, it lowers the AC by 1.

When a tyre is punctured, the bike must make a DC13 DEX save or be knocked prone.  This DC increases to 16 if both tyres are flat.

Ride by.  The bikes movement does not provoke opportunity attacks

Foot jam tailwhip slap (mounted)/Stoppie tail whip slap (unmounted). Melee Weapon Attack: +5 to hit, reach 5 ft., all targets within range. Hit:  (2d4 + 3) bludgeoning damage. 

Brake rotor slash.  Melee Weapon Attack: +5 to hit, reach 5 ft., Hit:  (1d12 + 3) bludgeoning damage. 

Movement (Costs 1 Actions).   The bike can move up to its movement.