Vibration Issue

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rjundi

Hi Quick q. Can well experienced mechanic with a regular balancer fix a vibration problem or do I need to seek out one of those specialty Hunter ones? My mechanic I trust has an old machine but takes the extra step of road testing the vehicle. My past experience with Hunter is besides dealer only a few tire shops have them and not convinced techs knew how to operate them properly. I went to two shops and found the print outs from a Hunter balance vastly different along with diagnosis. I know the vibration(70-77MPH) is in rear of vehicle. I am a bit afraid to rotate to the front. Vehicle was supposedly aligned, rotate/balance back when I bought it.

Originally Posted By: rjundi
Can well experienced mechanic with a regular balancer fix a vibration problem
Yes. All he needs to do is make sure the tire spins "true" before balancing. The Hunter operator needs to do the same thing, so the Hunter doesn't really buy you very much.

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You need to rotate to pin point which tire, rear or front, is out of balance.

Time for my lecture on tire uniformity. When a tire gets balanced, the balance deals with the mass distribution problem, by locating where and how much weight needs to be added. However, tires are like large ballons and they aren't the same stiffness 100% around the tire. We call this property "Unifomity" and it is a combination of "Out of Round" and stiffness. Tire manufacturers have machines that can measure this property. They are called TUG's (Tire Uniformity Graders) and if they have grinding wheels to correct the uniformity, TUO's (Tire Uniformity Optimiziers). These machines measure the amount of "Force Variation" around the tire and create a "waveform" that describes the actual variation in the form of a graph. The machine then does some mathematical manipulations and fits a series of sine waves to the waveform - once per revolutioon = 1st Harmonic, twice per revolution = 2nd Harmonic, etc. There are 3 directions when we talk about tires: Up and down (relative to the vehicle) is Radial (relative to the tire). Side to side (relative to the vehicle) is Lateral (relative to the tire). Fore and aft (relative to the vehicle) is Tangential (relative to the tire). For practical purposes, the only direction that causes problems is the Radial forces - and the first harmonic is analogous to balance - and just like you would expect, R1H (Radial First Harmonic) is the biggest contributor to vibration. The Hunter GSP9700 is an affordable tire shop piece of equipment (~\$10K) that measures the same property as the more expensive TUG machnine (~\$600K!)- albeit with less precision. So when someone has a vibration on a vehicle and it seems to be the tire and wheel assembly - and the assembly is properly balanced, the next step is to look at uniformity - and the Hunter GSP9700 is the tool for the job. It might have its faults, but it will help sort out which assembly may be the source. So, rjundi, I would suggest you start by swapping tires front to rear and see if the vibration moves. If it does, then the next step is to find a Hunter GSP9700 to confirm. FYI: It is possible to start off with a tire that has good uniformity and to wear a non-uniformity into the tire. Toe is usually the cause here - although camber sometimes plays a role.

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I appreciate the comprehensive answer. Hopefully its simple.

Capriracer pretty much covered it well. Sometimes a vibration is just a matter of imbalance because despite the mechanic doing the balancing job correctly the balancer is old and out of calibration.

Yes, he/she can. I had a slight vibration issue above 65mph. After going back to Discount Tire 3 times to have my tires balanced with no success i was about ready to buy new tires or just live with it. My last ditch effort was to go to a local shop and have all 4 tires rebalanced (traditional spin balance). They found all were exactly .25oz off. Now no more vibration.

Originally Posted By: Papa Bear
Originally Posted By: rjundi
I appreciate the comprehensive answer. Hopefully its simple.
Sooooo.......... what's happening !!
Scheduled to go in latter this week. Our other vehicle is at body shop so we need it.

rjundi- It all depends on what is wrong. Faulty tires or wheels, or a balancing problem. BTW, I have had good results with a simple old Sun gravity balancer.

Simple balance on a primitive machine with good mechanic took care of it. Thanks for replies. Went all the way to 95MPH(briefly with traffic) no vibration.

^I wonder what sort of fun going to a local tire shop for a 4-wheel balance check would reveal on their old fashioned check? F for kicks? I'm about to get the 1st 'rotation' on the Civic's new Michelin's I had installed just this fall, it includes a balance check(or is supposed to, I will be watching, lol).

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The sad truth about it all is the prior owner of Acura took to dealer and had tires rotated/balanced amongst a few other items that came up in inspection report. Basically they moved the offending tire front of vehicle to back where not quite as noticeable. He gave me a dealer receipt with some Hunter report attached of work done when I took it. I google vibration on MDX and read all sorts of issues and problems that are \$\$\$\$ to fix since out of warranty. So of course I get worried and it turns out so simple.

Acura sucks and I will never buy another one... I got taken by the dealer more then a few times and will never buy another Acura because of that. The bad trannys/rad coolers are other reasons why Acura lost my business... As you can see, I am somewhat bitter towards Acura. Oh well, LOL...

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