This could indicate wheel misalignment, improper inflation pressure, the need for tire rotation, or all of the above. Regardless of the specific reason, uneven tread wear is a sign that you need to take your car in for servicing.  If uneven tire wear is extreme or if tires wear out much faster than expected, have a competent tire workshop check your suspension and correct it as necessary before replacing tires. Improper alignment or worn suspension parts can dramatically shorten a tire's life. Rotate your tires from front to rear in pairs to avoid irregular tread wear. Take both front tires and move them to the rear and vice versa. The sidewall is the tire surface outside the rim that faces you when the car is parked. A bulge indicates that the rigid internal frame of the tire has been damaged and cracked, allowing air pressure to reach the flexible outer layers of the tire. Any tires with sidewall bulges should be replaced immediately, regardless of the tread status.  Such damage could be caused by driving through a large pothole, driving over a curb, or by driving with low tire pressure. Never continue to drive on a tire that has a sidewall bulge. This indicates that the structural integrity of the tire has been significantly reduced, which greatly increases the likelihood of a sudden failure or blowout at highway speeds. If your tires are worn unevenly, you may feel a vibration in the steering wheel when you are driving. If the vibration starts at 40 to 50 mph (64.37 to 80.47 km/h) and intensifies as you increase your speed, you probably need to balance your tires. If that doesn't stop the vibration, the tire is most likely damaged and needs a full replacement.  If you experience vibrations in the absence of tread damage, try balancing and aligning your tires' shock absorbers. If you notice tire vibrations along with other tire damage indicators like abnormal bulges and irregular tread wear, you probably have to replace your tire. If you notice that your tires are cupped—meaning they have a cupped or scalloped appearance around the tire—they likely aren't being rotated enough. If you see little cracks all over your tires, it means that the rubber is breaking down. Tires with dry rot can fall apart and separate from the steel belt, which causes damage to the exterior of the car. In some cases, your wheels might start rotting before the tread starts to diminish—you should still bring them in to be inspected or replaced.  Inspect for dry rot before heading out on any longer trips and bring your car in for a check-up regularly. Degrease your tires to prevent dry rot, especially if your tires are exposed to a high degree of sunlight. Check the 4-digit code on the wall of the tire for its age. Regardless of your country, most governmental transportation departments place 4-digit numbers on the wall of each tire. The first 2 numbers represent the week it was made and the last 2 represent the year. For example, 12/08 means your tire was made in the 12th week of 2008. If the tire is more than 6 years old, replace it.  If you're having trouble finding the number, look for the initials DOT, followed by other letters and numbers. The code should appear following dot and will not contain any letters. Remember that although 10 years is the maximum service life for tires—which means since the date they were manufactured—this should never be used as the maximum drive time. Always err on the side of caution if you suspect your vehicle has tires that are over 6 years of age. Always change your tires if the tread is below the minimum depth recommendation, which is often 2⁄32 inch (0.16 cm).

Summary:
Bring your car in for maintenance if you notice irregular tread wear. Check for any abnormal bulges or bubbles in the sidewall. Balance your tires if you feel steering wheel vibration. Check for dry rot and have affected tires inspected or replaced. Replace your tires at least every 6 years.