>>1558124depends on if you are riding though sand, and how deep and dry the sand is
for the beach yu might want two inch thick tires, it helps a bit to bike over to top of the sand
to bike though sand for a long distance lower gears ratios are better, something like a 28 or 34 tooth chain ring with a 28 tooth sprocket
so you dont have to count the teeth instead measure the diameter and times it by 3.14159 then divide by 12.7
on some bikes the gears have the teeth count stamped into them
your mtb should have sufficient gearing and tires
the cruiser has good enough tires but the gearing might be slightly tall