vibration at certain speeds

[rh71]

what do you guys think of this person's response at another board? Seems he's saying this is somewhat expected.

At times like this when I have a problem getting tires to balance and not knowing for sure which one(s) are doing it, I just drop the air pressure a little in them one at a time until the vibration goes away.

Reason? A tire at normal inflation will bounce a little more vigorously at higher pressure and less so at lower pressure.

Now - this is for diagnostic purposes only as I don't run at lower pressure to just compensate for a bad balance. I then break the tire completely free of the rim and clock it into a different position and re-balance it again.

If you just re-balance the tire you can chase your tail for hours adding 1/4 oz here and taking 1/2 oz there and it just never ends. I never spin a tire more than two times to balance it - why? It makes no sense to move fly speck for hours when it won't make much difference except to a 200+ MPH Indy car.

Quarter ounces at 7.5 inches from epicenter at less than 100 MPH can't be felt nor will it affect the tire in the long run.

There are (kinda) rules of thumb for tire-size and road-speed imbalance factors:

13 inch tires seem to be bouncers at about 42-49 MPH
14 inch tires bounce at about 50-56 MPH
15 inch tires seem to act up around 55-62 MPH.


There appears to be a corollary to the size/speed relationship when they are out of balance. It's just a hint, not a solid rule.

I would - for good reasons - check for loose wheel bearings, bad tie rod ends or slop in any suspension/steering parts - very carefully too.