What Does Choppy Wear on the Edge of a Tire Indicate?by Chris Stevenson
Tires are the most important contact components between a vehicle's chassis and the road's surface. They control ride comfort and maneuverability. Sometimes tires develop unusual wear patterns, and these wear patterns lessen the tire's ability to provide safe and adequate traction and contact on the road. Choppy wear on the edge of a tire indicates any one of a few likely problems. Worn or misaligned suspension parts account for nearly all tire wear problems, particularly choppy or "cupped" tires.
Tire are best inspected with the wheels off the ground so they can be rotated and examined. Lift tires individually or in axle sets with a floor jack and jack stands. Choppy wear on the edge of a tire will look like cupping or scalloping, where small sections of rubber have been scuffed off the surface, showing individual indentations. This is not to be confused with "feathering," where one side of the tread line appears soft or worn while the other side of the same tread line has a sharp, feathered edge. With cupping, you can run your finger over the tire and feel the choppy dips and rises.
Suspensions Problems -- Shocks
One of the most common problems associated with cupped tires is defective shock absorbers. Hydraulic shocks, whether single-mounted or MacPherson coil-over types, hold pressurized hydraulic oil inside a tube or cylinder. The oil is restricted from sudden movement inside the tube. A worn shock, or one that has lost its hydraulic oil, will allow the tire to bounce, creating a scuffing or choppy appearance in the tread. Worn or damaged shocks will allow the vehicle to bounce more than normal, and at high speed, this loss of contact with the pavement tears sections of rubber from the tire.
Tire Problems -- Balance
Improper wheel balance can cause a choppy or cupped condition on the tire. If a tire is improperly balanced or has thrown weights from the rim, that side of the tire will be heavier than the corresponding sides. This causes skipping, or sporadic tire contact with the road. At high speeds, unbalanced tires can cause vibration, or a shimmy, that is felt in the steering wheel.
Suspension Problems -- Ball Joints and Wheel Bearings
Chopped or cupped tires can result from worn ball joints in the suspension system. Load-carrying ball joints support most of the weight of the front end, as well as allow pivoting, or an arc of travel, of the lower control arm. If the ball and socket joint is worn, excess play results, allowing side-to-side and vertical movement. The excess movement causes the tire to momentarily lose contact with the road, resulting in choppy or scalloped wear patterns. Wheel bearings with excessive play will allow abnormal tire tracking and angular lean. Wheel bearings must be packed with grease and adjusted according to manufacturer's specifications.
Suspension Problems -- Tie Rod Ends and Bushings
Tie rod ends keep the steering linkage tight between the steering box or Pitman arm and the wheel. Worn tie rod end joints will allow excessive steering play, mostly in the horizontal plane, but also in the vertical, if very worn. Worn upper and lower control arm bushings allow the wheel spindle to jump, momentarily misaligning contact of the wheel to the road surface. Broken or worn upper control arm bushings will frequently produce a harsh knocking or clunking sound when the vehicle rebounds over dips or raised surfaces. Mechanics can determine if your bushings or ball joints need replacement.
Suspension Problems -- Sagging Springs
Coil and leaf springs keep the chassis of the vehicle from contacting the body frame. Coil and leaf springs sag over time, lowering the ride height of the vehicle. Excessive sag will cause vertical bouncing, frequently setting up rhythmic up-and-down movements. This condition can cause additional wear on other suspension parts, like the ball joints, wheel bearings, tie rod ends and spindle. Excessive vehicle bounce can cause choppy or scalloped tires.
Tire Problems -- Inferior Quality
Tires have wear ratings, depending upon how much carbon black is used in the rubber compound during manufacturing. Low-quality tires will have less carbon black in their makeup, making for a softer ride, but the softer material will wear more quickly. A softer tire will show earlier signs of choppy or scalloped wear patterns over the more rigid or better quality tire in the event that suspension components are beginning to wear. Tires that have tread wear ratings of 200 and below will not last as long as those having 300 tread wear ratings and over.
Edge Wear and Choppy Tire Combination
Choppy or scalloped tires wear either on the edges of the tire treads, in the middle of the tread or both. Excessive inside or outside wear of the tire, in combination with choppy or scalloped appearance, can denote a problem with the toe-in or camber alignment adjustment. This condition shows up on one side of the tire, causing abnormal edge wear in the tread, frequently wearing down to the ply itself. When both edges of the tire are worn down, it indicates underinflated tire pressure. Inside or outside wear can also indicate worn suspension components that have caused wheel misalignment.
Tire Precautions and Safety
Consult your owner's manual for the proper tire pressure, balance procedures, and tire rotation configuration and intervals. If you see any cupping in the tire tread, first take your vehicle to a shop and have the front end suspension parts checked for wear and condition. Suspension parts must be replaced before an alignment, and this pertains to rear-wheel suspension and rear-wheel steering systems. Good suspension parts and proper alignment will not reverse an existing tire wear problem. Replace worn tires with new ones if the condition is severe enough to affect safety.
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