Rear end sagging in a car: causes, repair options

You may notice that the rear end of your vehicle is sitting lower than the front, even with no extra load. Often it's one side that could be lower in the back. If all the suspension parts in your car are original and have not been modified It could happen for several reasons:

1. One or both rear coil springs at the back could be broken; see the photo.
2. "Sagging" of the rear coil or leaf springs.
3. If the vehicle has leaf springs, one of the leaves could be cracked or broken.
4. In trucks with rear leaf springs, the shackle mount could be broken.
5. Problems with the rear suspension.

The first step is to have your vehicle inspected. Your mechanic can check your vehicle during an oil change or tire rotation when your car is lifted on the hoist. If all the suspension parts are intact and nothing is broken or damaged, the issue could be caused by sagging springs.

If needed, your mechanic can measure the ride height of your vehicle at all four wheels and compare them to the specs. The wheel alignment can also show if the rear coil springs are sagging. If the rear wheel camber angles are out of specs (negative camber) and cannot be adjusted, in most cases it's caused by weak or sagging rear springs.

Why do springs sag?

Over time, under constant load, the structure of the spring metal changes and the springs become "weaker." Springs tend to sag more if the back of the vehicle is often loaded with extra weight, for example, when the car is parked with some load at the back for extended periods of time.

What are the problems caused by sagging coil springs?

When the rear of the vehicle is sagging it not only makes the vehicle look old, but often causes rear tires to wear out sooner. If the vehicle has an independent rear suspension like this BMW in the photo, the rear tires will wear unevenly, more on the inside. It might even be noticeable that the top of the rear wheel is tilted inward, which in technical terms is called "negative camber."

You may also notice that the rear of your vehicle is bottoming out when driving with a load over bumps. This can damage suspension components over time.

The handling will likely suffer too: the rear of the vehicle is more likely to shift side-to-side when driving on a patchy road or when one of the rear wheels ends up on the unpaved shoulder. You may notice that the car feels less stable and doesn't hold the road as good as when it was new when driving on the highway.

Another problem is when the back of your car sits lower, your headlights are pointing higher blinding oncoming drivers.

Is it safe to drive if the rear of the car is sagging?

Only your mechanic can tell you this after inspecting your vehicle. If nothing is broken or loose and tires are not rubbing against anything, the vehicle could still be safe to drive. Have your vehicle inspected to be sure.

What are the repair costs?

The repair will depend on what your mechanic's diagnosis is. If just the coil springs need to be replaced, in an average car it may cost 2-4 hours of labor for both rear coil springs plus the parts. Aftermarket parts are often cheaper than OEM. Some additional parts, like sway bar links, may need to be replaced if they are seized. The wheel wheel alignment might need to be done too.

If only one coil spring is broken and the vehicle is not too old, replacing one spring might be enough, provided it's an OEM part. If the vehicle is more than 5 years old and one spring is broken, changing both rear springs makes more sense.

If you have a truck that needs new rear leaf springs, replacing both rear leaf springs will cost on average 3-5 hours of labor plus the cost of parts plus the wheel alignment.