Automotive Wheel shimmy and wheel wobble difference

[monty37]

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

 

[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.

 

[Ranger Mike]

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

 

[pantaz]

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

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

 

[DoggerDan]

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

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.

 

[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).

 

[monty37]

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

 

[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

 

[DOsul]

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