Some car parts are fixed, while others are flexible. Flexible parts may rotate or oscillate like wheels, tie rod ends or leaf springs. Depending on their degree of motion, the manufacturer might use bearings or bushings in their design. Exactly what are bushings on a car?
What Are Bushings on a Car?
Bushings, also called flexible or anti-vibration mountings, allow parts to move without transmitting vibration to the cabin. Limited-motion joints, like control arms and sway bar links, usually use bushings. Bushings are also used in non-moving parts, such as body mounts and strut mounts.
Some bushings are filled with oil, and others may be molded to be softer or harder in one direction. The simplest bushing consists of a metal inner sleeve bonded to an outer metal sleeve with rubber. On control arms, like those in the front end, the outer sleeve is pressed into the control arm, and a bolt affixes the inner sleeve to the frame. Neither sleeve moves, but the flexible rubber allows a limited range of motion between them. Rubber doesn’t transmit vibrations well, which prevents them from reaching the cabin.
Symptoms of Worn Bushings
Bushings do not have a replacement interval, but they do wear out over time. Dry rot, from exposure to the atmosphere, happens to all bushings, leading to shrinking, stiffening and cracking. Extreme heat accelerates this wear, particularly near the exhaust system. Oil contamination softens bushings such as those near a leaking engine or transmission. As bushings weaken, the effect may not be immediately noticeable, but it can manifest in several ways over time:
- Weak control arm bushings might manifest themselves as a pull when accelerating or braking.
- Worn control arm bushings can cause abnormal tire wear.
- If steering rack bushings are loose, the vehicle may drift or wander.
- Abnormal clunking over uneven road surfaces may indicate worn sway bar bushings.
- Weak bushings may eventually break completely, allowing more undesirable motion and noise.
For the most part, a completely broken bushing will not result in any significant collateral damage, but you should replace worn or broken bushings as soon as possible to prevent wear and tear.
Tips for Replacing Bushings
Body mounts, engine mounts, sway bar bushings, steering rack bushings and sway bar link bushings are usually replaceable without special tools. Some control arm bushings are available separately, but special tools are required. Some control arm bushings are not available separately and require a whole new control arm. Bushings that improve performance are also available in the aftermarket. For example, stiffer bushings can reduce body roll and improve stiffness.
When replacing bushings, two factors are important: First, pay close attention to the depth and orientation of pressed-in bushings. Bushings that are pressed in too shallow or deep can lead to interference and noise, and certain bushings need to be installed in a specific orientation for consistent performance. Second, for control arm, sway bar, shock and strut bushings, tighten all fasteners with all four wheels on the ground. This will prevent preloading the suspension, which can mimic alignment problems.
While bushings are a simple component, replacing them can significantly improve the quality of your ride. Whether you’re replacing bushings for wear or as an upgrade, you can enjoy a quieter and stiffer ride in just a few hours.
Check out all the steering and suspension products available on NAPA Online or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. To learn more about car bushings, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.
Photo courtesy of Wikimedia Commons.
Having been bitten by the car bug at a young age, I spent my formative years surrounded by Studebakers at car shows across Quebec and the northeastern United States. Over ten years of racing, restoring, and obsessing over automobiles lead me to balance science writing and automotive journalism full time. I currently contribute as an editor to several online and print automotive publications, and I also write and consult for the pharmaceutical and medical device industry.