Check to see if your tires have the right pressure, underinflated tires are the most common cause of excessive tire wear on outside edge. Underinflated tires cause more stress and thus wear on outside edge compared to the center of the tire. The reason is that underinflated tires creates a bigger contact area with the road and also increasing rolling resistance. Have a look because the inner edges should be worn too then. If your tire pressure is fine but you are an aggressive driver and you like hard cornering, that could be a reason too.
Misaligned wheels could put more stress on the outside edges of the tire causing it to wear faster. Hitting a kerb could cause your wheels to misalign and speed up tire wear on outside edge. When noticing tire wear on outside and your tire pressure is fine and you are not a aggressive driver, have your wheel alignment check. These are some of the more common causes of tire wear on the outside edge, but there are several other factors that might be the culprit like worn shocks or ball joints.
