Wheel shimmy and wheel wobble difference

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Discussion Overview

The discussion revolves around the differences between wheel shimmy and wheel wobble, exploring definitions, causes, and implications in automotive and motorcycle contexts. Participants share personal interpretations and technical insights related to these phenomena.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants suggest that "wobble" implies movement about a horizontal axis, while "shimmy" relates to vertical movement, although this distinction is not universally recognized.
  • One participant defines shimmy as less intense than wobble, indicating a personal interpretation rather than a standard definition.
  • A participant describes shimmy as uncontrolled left/right oscillations in the front wheels, affecting vehicle direction, and mentions its occurrence in motorcycles.
  • Another participant states that wobble results from a wheel's hub not being true, often due to impacts like hitting a pothole.
  • Some participants note that shimmy can arise from unbalanced wheels or abnormal tread wear, while wobble may be caused by a bent hub, bent rim, or loose lug nuts.
  • Axial and radial runout are mentioned as technical aspects related to wheel performance, with specific measurements discussed.
  • A suggestion is made to explore the work of Robin Sharp for further technical insights on the topic.

Areas of Agreement / Disagreement

Participants express differing views on the definitions and implications of wheel shimmy and wobble, indicating that no consensus exists on their distinctions.

Contextual Notes

Participants reference specific measurements and technical terms like axial and radial runout, but the discussion does not resolve the definitions or causes of shimmy and wobble.

monty37
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what is the difference between wheel shimmy and wheel wobble?...in certain books it said they meant the same..
 
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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.
 
wheels have axial and radial run out. should not exceed 0.030" typically
 
monty37 said:
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.)
 
monty37 said:
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.
 
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).
 
That quite cleared it ,can you elaborate on axial runout?
 
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
 
Could I suggest taking a look at the work of Robin Sharp ( search Robin Sharp+ motorcycle) you will find some good technical papers.
 

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