Dyna Bead Issue?

[AdamK]

Ya, I've seen that demo before. My bike has a wheel with a tire on the back, not a pop bottle. The weight of the beads relative to a wheel and tire are far different than compared with a pop bottle.

A video of an out of balance tire in a dynamic balancing machine before and after bead installation, running at different speeds, would be more convincing. I'd like to see if it can compensate for the imbalance at any speed/rpm.

 

[Fred W]

"I'd like to see if it can compensate for the imbalance at any speed/rpm."

It can't. In fact, as someone else already mentioned, the only way that any balancing media (beads, liquid, goo whatever) can dynamically balance an out of balance wheel and tire is if it can freely move inside the tire.

Here's the Centramatic Balancer spiel that shows a (greatly exaggerated) imbalanced wheel and how their version of balancing beads in a tube work their way around and balance out the vibration.



Notice while you are watching that the wheel is out of balance initially each time it starts spinning. Only after it has shook and vibrated the wheel for a period of time do the balls move to where they need to be to counteract the wheel's imbalance.

I think that is a clue as to how the beads move inside the tire. The beads, or balls, or whatever have a mass, and an inertia. When the imbalanced tire and wheel shake the heavy part of the tire goes further out from the center of rotation and the lighter side stays closer to the center. The inertia of the beads prevents them from moving further with the heavy part, so they tend to accumulate at the lighter end.

So until it has already vibrated and shook, it won't, or can't balance it.

This seems to be in sync with how Dyna Bead describes their beads' action. They claim it is the vibration motion that causes the beads to move to the light spot.

 

[AdamK]

Interesting. Thanks for posting that one.

So you'd feel the imbalance for a second or two before the beads took effect. That is unless the static effect keeping them in place someone mention actually works. This example had beads in a viscous fluid which would move every time you slowed down or stopped. I could see why a MotoGP rider wouldn't want to come off the start line and have to wait for the wheels to balance as he was approaching the first turn!

I can see how this would be useful for truckers driving through snow and picking it up on their wheels. Not sure why I'd want this over a simple static balance on a bike?? My static balanced wheels start out balanced every time I start moving.

 

[Gitbox]

That Centramatic video seems to show an out of balance wheel after he removed the magnet. The ball bearings are not evenly distributed as the narrator said either. It evens sounds out of balance. It sure would not sell me on them.

Maybe the key there is that they will counteract a huge imbalance but not a slight one. What about bumps from the road surface? Does that knock the beads silly again and then have to resettle to their sweet spot?

Another thing, at the rate that wheel was spinning the vehicle would have to be doing 200 MPH. Well maybe not but it was cranking.

 

[Fred W]

What about bumps from the road surface? Does that knock the beads silly again and then have to resettle to their sweet spot?

That right there is an excellent question. Since they claim that the beads move to where they "need to be" from vibration, why wouldn't road forces cause the beads to move too? I suppose because the road forces are generally transient and the vimbalance vibration will be repetitive and synchronized with the wheel rotation.

 

[Gitbox]

Bringing back my old thread for an update:

I finally got around to buying a manual tire changing stand and static balancer. I removed the beads from the front and rear tires and static balanced both. HUGE IMPROVEMENT! Not quite perfect but I think running them so long unbalanced may have caused them to wear unevenly. A good portion of the beads were stuck to the center line of the tires. I had to use a brush to knock them loose and vacuum them out. It took 28 grams on each wheel to balance them.

 

[Auburn]

Bringing back my old thread for an update:
I finally got around to buying a manual tire changing stand and static balancer. I removed the beads from the front and rear tires and static balanced both. HUGE IMPROVEMENT! Not quite perfect but I think running them so long unbalanced may have caused them to wear unevenly. A good portion of the beads were stuck to the center line of the tires. I had to use a brush to knock them loose and vacuum them out. It took 28 grams on each wheel to balance them.

That sounds about average for the amount of weight I usually put on a tire. When you do the static balance, the wheel can have a slight rotation (very slow when the weighted area is put at the 3 o'clock position) and be OK. If it moves more than very slowly, then you might want to start the balancing process again and re-check the light spot on the wheel. It happens sometimes.

You may find after some miles that you need to re-balance the tire again since you are starting with a used tire with some abnormal wear. Don;t be surprised if you run across a tire that just doesn't seem right. I have found a couple over the years that were not round, be it manufacturing or in one case, the way the shipper bound the tire so tight it screwed up the tire.

 

[redzgrider]

Which static balancer? The Harbor Freight unit works well -- until the grease in the bearings starts to gel. Then you need a new set of high quality 608 skate bearings to put it back in service. Drag -- any drag -- on the axle will throw the balance off a bit.

 

[PhilJet09]

Yea, you have to be smarter than the tools you're using.

 

[Gitbox]

It's a GoPlus static balancer from Amazon. The rod is aluminum so I might replace it at some point with drill rod. The tire changer is from the same maker. I'm sure they are just rebranded items but they both worked very well for me - actually a lot better than I expected.

 

[FJRay]

I finally read the whole thread. Put me in the camp that doesn't like the beads. I probably mount and balance 50 tires a season and if someone wants beads and they supply them I'll put them in but I tell them if I have to take them out it's another mount and balance charge. I don't get comebacks with basic static balance.

The other thing I hate about beads is when removing the tire if you don't know the beads are there they go everywhere. I have to clean them out of the machine and walking on the damn thins is like ice skating.