As I work for a tire company, my thoughts.

Yes this sounds like a balance problem. There certainly are different capabilities of dynamic balancing. The Coats machine at Sam's club will not give you a fine level of balance.

Tire vibrations caused by non-uniformity are harmonic. The first harmonic at which most tires "excite" the vehicle is typically around 25-30 MPH. If you have a belt separation of other physical failure, you will sure enough feel it at this low speed. The second harmonic varies with tire OD but can hit between 65 and 75 MPH. I have never experienced a defective uniformity tire which could only be felt at high speed; they have all been VERY noticable at the 1st harmonic. Now further to checking for a belt seperation. If you have a good "feel" in your hands (some do, some don't) you can raise the tire in question on the vehicle, and turn it while you slide your hand over each tread shoulder (roll tire away from your fingers). If you have a belt sep, you will feel a very localized sinusoidal place in maybe 10-15 degrees of the circumference. This type failure is very pronounced, not something that requires a needle indicator to find. The classic OOR defect (out of round) is the one which is detected with a runout device.

One last comment on balance. I know Tire Engineers who do our vehicle dynamics testing who tell me it is possible to get a "coupling" of imbalance between 2 tires on the same axle/differential. The minor imbalance in the LH and RH tires "couple" together to excite the whole suspension system, making a molehill into a mountain. The poor mans solution which works if driving a long straight distance (interstate) is to pull off the road & drive the vehicle in a 360 degree circle once or twice. This will change the angular relationship between the 2 tires and reduce/eliminate the coupling.

If all else fails, buy a new set! (my kids need to eat). A general rule of thumb is small balance weights = good tire uniformity !


DET

• Is front-end vibration always unbalanced tires?, Nathan Work, Wed, 17 Jan 2001 10:28:55
  • Re: Is front-end vibration always unbalanced tires?, chrisx, Wed, 17 Jan 2001 14:58:52
  • Re: have you lowered your front suspension ?, Gavin, Wed, 17 Jan 2001 10:57:24
    • Re: have you lowered your front suspension ?, Nathan Work, Wed, 17 Jan 2001 16:38:01
    • Could also be inner driver problems..... n/m, Charlie, Wed, 17 Jan 2001 11:16:02
  • Almost always, Monster, Wed, 17 Jan 2001 10:46:28
    • Further to Almost always, DET, Wed, 17 Jan 2001 12:50:28 <-- Viewing This Message
      • Re: Harmonics, Monster, Thu, 18 Jan 2001 09:17:58
      • Thanks for the great info! n/m, Nathan Work, Wed, 17 Jan 2001 16:38:54
  • Re: Is front-end vibration always unbalanced tires?, Aaron Govatos, Wed, 17 Jan 2001 10:34:09

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