# Automotive Wheel shimmy and wheel wobble difference

1. Oct 14, 2011

### monty37

what is the difference between wheel shimmy and wheel wobble?...in certain books it said they meant the same..

2. Oct 14, 2011

### Danger

I can't recall that I've ever heard the term "wobble" in reference to a wheel. To me, though, it seems to imply movement about a horizontal axis whereas "shimmy" is about a vertical one. Just my first thought, though; I don't really know.

3. Oct 14, 2011

### Ranger Mike

wheels have axial and radial run out. should not exceed 0.030" typically

4. Oct 14, 2011

### pantaz

For my personal definition, I think of "shimmy" as less intense than "wobble". (Although, I don't remember ever using "shimmy" to describe anything.)

5. Oct 14, 2011

### DoggerDan

A shimmy is when uncontrolled L/R oscillations in the front wheels cause the vehicle's direction to move left and right rapidly. It can happen in motorcycles, too. The Widowmaker, a 750cc three-cylinder bike was notorious for it: http://classicbikes.actieforum.com/t137-the-widow-maker

A wobble is merely a wheel's hub not being true. Thus, the hub's axis is not perpendicular to the directly of travel. It's often the result of hitting a major pothole or jumping a curb.

6. Oct 15, 2011

### Allenman

Being a mechanic, every wheel vibration gets dubbed as a "shimmy."... but yeah, wobble can be from a bent hub or bent rim, or on occasion someone forgetting to tighten lugnuts (i've seen it before! Yikes!) (so the axis of rotation is not perpendicular to the wheel)... Shimmy is usually from unbalanced wheels or abnormal tred wear; however, for engineering axial runout would be more probable (axis of rotation is not center in the wheel).

7. Oct 15, 2011

### monty37

That quite cleared it ,can you elaborate on axial runout?

8. Oct 16, 2011

### Ranger Mike

run out is measured with a dial indicator..where it is placed determines the axial or radial run out..place it over the axle ..ie axial or place it on the outside of the wheel on tangent to the wheel radius..ie radial

9. Jan 23, 2012

### DOsul

Could I suggest taking a look at the work of Robin Sharp ( search Robin Sharp+ motorcycle) you will find some good technical papers.