There are many different types of suspension designs in use today, one of which is a leaf spring-style system. Leaf spring suspensions are typically found on light-duty trucks (i.e., pickups, vans, etc.) and some older rear-wheel drive cars.
Although leaf springs are designed to last the life of the vehicle, they can eventually go bad, particularly when subjected to heavy loads or harsh winters and salt-covered roads. When that happens, you’ll likely notice some undesirable symptoms that you’ll want to address right away.
What is a Leaf Spring?
Leaf springs are the oldest type of vehicle suspension spring, dating back to the days of horse-drawn coaches. A leaf spring has one or more strips of layered steel (or fiberglass-reinforced plastic), referred to as leaves. The leaves have rubber or plastic insulators between them.
There is one leaf spring on either side of the suspension. Each end of the leaf spring has an eyelet with a bushing inside. A bolt runs through each eyelet to attach the spring to the vehicle.
Typically, one end of the leaf spring connects directly to a hanger on the frame, and the other end attaches to a shackle, which, in turn, connects to the frame. The shackle allows the spring to move slightly as the vehicle travels over bumps. A center bolt holds the leaves together, and a set of u-bolts and accompanying hardware attach the leaf spring to the vehicle’s axle housing.
Leaf springs are often used in the rear suspension of light-duty trucks and some older cars. Many four-wheel drive vehicles with a solid front axle also use leaf springs in the front suspension.
Symptoms of Bad Leaf Springs
Do you think your vehicle’s leaf springs might be damaged or worn out? If you notice one or more of the following symptoms, you might be right.
Note: Many other problems can mimic a bad leaf spring. You (or your mechanic) should perform a thorough diagnosis before performing any repairs.
Abnormal Noises from the Undercarriage
The most common symptom associated with a bad leaf spring is abnormal noises from the undercarriage. Depending on the problem with the spring, you might hear either a squeaking or clunking sound. The issue is usually the most noticeable while traveling over bumps.
Worn-out rear leaf springs can result in visible sagging of the suspension, causing the vehicle to sit lower than normal on one or both sides. The vehicle may also “bottom out” while traveling over bumps.
Vehicle “Dog Tracking”
If the leaf springs or related hardware are compromised, the rear axle housing can change positions, causing the vehicle to “dog track” while driving down the road. Dog tracking indicates that the wheel alignment thrust angle—the angle of the vehicle’s centerline compared to the road—is thrown off. If you’re looking at the vehicle from behind, the rear tires will appear to be moving sideways while the front tires are pointed straight ahead.
Good leaf springs usually have an elliptical shape, with the apex of the curve pointing downward. But when the spring wears out, you might notice that the curve arcs upwards or the spring becomes nearly flat.
Leaf springs can also suffer from other visible damage, such as cracks, severe rust, and dry-rotted eyelet bushings.
If you think there might be a problem with your vehicle’s leaf springs, you’ll want to perform a visual inspection, looking for obvious signs of damage, such as cracks and broken leaves. You’ll also want to check the eyelet bushings (for dry-rot and other damage), the shackles, and frame hangers.
Leaf springs are designed to last the life of the vehicle, but that doesn’t always happen. Leaf springs often fail prematurely due to rust and corrosion. Overloading the vehicle or regularly hauling heavy loads can also strain the leaf springs, causing them to fail earlier than normal. Plus, the eyelet bushings can suffer from dry rot and other damage after years of exposure to the elements.
Over time, leaf springs can become weak due to rust or hauling heavy loads. To keep your vehicle safe and reliable, you’ll want to replace any weak leaf springs right away.
Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.