I am having problems keeping my four year old's bike on the road. He is at the stage where he likes to ride as fast as he can and then slam on the foot brake, leaving a 3 foot skid mark behind him. It seems that when the brake is applied, it stops the back wheel in the same spot each time and it eats a hole through the tire in no time. It seems as if I am replacing the tire on a monthly basis. Any ideas on how to avoid this? Can the brake be adjusted? Can I get a tubeless tire for this size bike? Does this indicate that he may be getting to heavy for his little 12.5" cycle? I will cross post this on the Mechanics forum as well. Thanks.