Excessive Steering Wheel Shimmy or Chassis Vibration

Excessive Steering Wheel Shimmy or Chassis Vibration

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Got a vehicle in your shop with a steering wheel shimmy or a chassis vibration that you feel at highway speeds and you know it’s not just a normal characteristic of the vehicle? Lots of things can cause this problem, for example: • Out-of-balance tires, rims, front wheel hubs, or front brake discs • Wrong tire pressures • Tire(s) that aren’t fully seated on the rim(s) • Excessive tire runout under load • Damaged tires (cuts, missing rubber, etc.) • Use of aftermarket parts (tires, rims, steering components, or suspension components)

• Damage This article is the first in a five-part series of articles that will look at this whole issue of steering wheel shimmy and chassis vibration and what it takes to fix the problem. We begin this series with a discussion of test-driving the vehicle. In future articles, we’ll be discussing interpreting vibrations; phase matching tires and rims; rim runout measurements and proper tire installation on rims; and finally, wheel balancers and calibration. Test-Driving the Vehicle Follow these steps and answer the questions in the order they’re asked. If possible, take someone along to write down your answers: 1. Test-drive the vehicle exactly as described on your RO. 2. Describe the vibration. NOTE: If the vibration is caused by something other than the wheels (transmission, engine, exhaust, etc.) end your test-drive right now. Check ISIS for applicable S/Bs, S/N articles, or refer to the S/M. • Where do you feel the vibration is coming from?

• Does the vibration go away after a few minutes of driving? Does it come and go? • Does the steering wheel shimmy? (It feels like it’s shaking left and right.) 3. Slow down until the vibration goes away. Now speed up in 5 mph increments, holding that speed for 15 seconds or more before speeding up again. At what speed do you start to feel the vibration again? As you continue speeding up, does the vibration get stronger, weaker, or does it just stay the same? 4. Drive for about 2 miles on straight and curved roads at the speed where you felt the vibration the strongest in step 3. • When driving straight ahead, is the vibration constant or does it come and go? • When following a curve, is the vibration constant or does it come and go?

5. Shift into neutral. Does the vibration go away? 6. Drive under the conditions that you feel the vibration the most. Speed up, applying different foot pressure to the accelerator pedal (gentle, medium, and hard). Does the vibration stay the same, or is there a specific foot pressure where it changes? 7. Climb a hill at a steady speed. • Does the vibration stay the same or does it get stronger as you climb? Apply different foot pressures to the accelerator pedal like you did in step 6. • Does the vibration stay the same or does it get stronger when you apply a particular foot pressure?