Balance Question

Lynnmor wrote:
Here is a perfectly balanced tire/wheel that I had to add two ounces of weight to bring it into balance when mounted.



Here is the video before adding weights:
Video

Any guesses to the cause?

A question, when you say the tire and wheel was perfectly balanced, can you describe:

1. The tire and wheel assembly balancing process?
2. What part of the wheel was used to hold the assembly?
3. What was used declare the center of rotation of the wheel?

I have found several out of balance conditions that can exist on the standard trailer setup, maybe you found a new one. I have found on brake drums, the brake shoe surface diameter and grease seal diameter show they run true to each other as turned in the same setup. And on the same drum, the inner and outer bearing bores are machined true to each other as they where bored in the same setup, but the brake shoe and seal diameter are on different centerlines the the bearing bores. Some are off center greater then 0.015" TIR and some over 0.020" TIR.

I have not yet measured the lug stud centerline to sort out what centerline that spin true to, but would really surprise me if it ran true with the bearings. The drum wheel face can be out of square with the bearings bores also creating wheel wobble.

Trailer wheels many times have stamped center bores that are not very accurate to the center of the wheel rotation, as the center bore is not machined in relation to the tire bead area. "Standard" trailer wheels are called "lug centric" on most travel trailers/fifth wheels and small utility trailer as they spin by the lugs studs/lug nuts. There is no machined brake drum center pilot to mate with the wheel center bore. If a wheel balancer used the center bore to balance a tire to, that could affect wheel balance as the wheel assembly could not run true with the lug nut holes that mount on the brake drum.

Sadly, all that above could be made very accurately like the auto industry has done for years, but yet, standard trailers fall into cheaper made versions. If you happen to look close at what U Haul uses on their rental cargo trailers, they spent the extra money to have piloted wheels on brake drums (hub centric), and they do not use cheap nylon spring pin or shackle plates in the suspension. U haul does not want to have to deal with the suspension failures while the miles add up.

John