At around 150 miles my husband's scooter on every rotation the back drive wheel would have a screeching sound but my son hopped on it and drove it full speed for about a mile in the sound stop so we believe something just got stuck in there, but so far 250 miles and everything is a go. No issues and there really fun, they will do 28mph just like it says ,and over 20 miles per charge. To help distinguish mine while walking up on them IV removed some guards and high temp painted them dark blue . Really sticks out with the fur grips . Ya I said fur grips , rabbit that is. 4 my star due to the iffy noise in the rear I just pray it stays gone .