QuestionQUESTION: How does an automobile-service shop measure road-force variation? Why would the numbers (cold) of the four tires vary from a single digit to more than 30? What would a shop do to bring the numbers under 18? Thank you.
ANSWER: Robert,
Sometimes it's best to refer folks to places where there may be more than is needed to answer the question, but these 2 links I think will address the subject:
Here's how Road Force Variation is measured:
http://www.gsp9700.com/
And here's an explanation of force variation, balance and match mounting:
http://www.geocities.com/barrystiretech/unifandbal.html
If you have something that seemed unclear or these lead to additional questions, don't hesitate to post a followup.
---------- FOLLOW-UP ----------
QUESTION: Thank you. The articles provided good information.
Are you able to answer my question about what a service shop would do to change the four tires from non-uniform and greater than 18 (which I am told is the highest acceptable number) to uniform and less than 18? The tires have been driven under 3,000 miles.
Thank you.
AnswerRobert,
A summary from those links:
They would measure the assembly high point and location, then measure the rim low point and location, then match those 2 points. The result is a lower value.
No, 18 is not the highest acceptable number. The number varies considerably across the country (how rough the roads are) and also depends on the sensitivity of the vehicle (driver, too!). Some places claim they need 10, but I have also seen 30 give an acceptable ride.
