Tire balancing beads

[Keith]

Just mounted a set of new tires 19" on my sedan and for the first time over many tire changes that I have done over the years I am getting a bounce on one of the front tires. Do the glass tire balancing beads work?

[alexiskai]

They do. They're a pain to install though.

[1931 flamingo]

Yes, BUT I'd check for an out of round tire first.
Paul in CT

[Robert/Texas]

Swap the errant wheel and tire with one from the rear. I had this problem some years/decades ago and that worked for as long as I had the car.

[Kurt in NJ]

let the air out and break the beads,spin the tire a half turn and see if it is better.
A lot of times moving the tire on the rim can eliminate the need to balance.

[nkaminar]

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The tire can be out of round if part of the flap is stuck under a section of bead.

I have had good luck with the stick-on lead weights. Back off the brake adjustment and back off the bearing nut a little bit until the wheel rotates freely. Rotate the wheel twice and if it stops in the same place, add weight at the top. Add the weights at the inside rim and clean the wheel before adding the weights. If you keep track of how much you backed off the brake adjustment and bearing nut, you can easily return them to their original position. Keep adding weight until the tire stops at random places.

The balancing beads work if the tire runs true, not out of round. It works at higher speeds and not at slow speeds. It works because at higher rpm than the critical speed the light side of the tire rotates at a bigger radius than the heavy side. So the beads migrate to the light side to balance the tire.

[Y-Blockhead]

Originally Posted by Kurt in NJ

let the air out and break the beads,spin the tire a half turn and see if it is better.
A lot of times moving the tire on the rim can eliminate the need to balance.

Altho I do run balancing beads, I would do a Kurt in NJ suggests. But first check for out of round, no method of balancing is going to correct for an out of round wheel/tire.

[Keith]

Thank you all for the responses, I will first try deflating breaking the bead and rotating the tire on the rim. If no improvement than I'll try adding weights
Keith

[Bob Bidonde]

I have some concerns about glass balancing beads. (1) Do the beads wear the inner tubes making them thin? (2) How long do the beads last? I assume the beads eventually breakdown into a powder? (3) Do the beads fowl the air valve in the tubes?

[Fhane]

The better beads are ceramic. I have been selling them for 20 some years. I have never seen ceramic beads turn to dust or wear a tube. Glass bead could be a different story.

[Werner]

Originally Posted by nkaminar

... It works because at higher rpm than the critical speed the light side of the tire rotates at a bigger radius than the heavy side. So the beads migrate to the light side to balance the tire.

Guten Abend.


I don't understand that. It is clear that a tiny little bump is created at the point where the tire has the heaviest weight. To put it in an exaggerated way, the tire forms an oval.
My logical thinking would suggest that the beads would collect there on the outside in the curve of the bump. Because that is where the circumferential speed is highest and where gravity then drives the beads.


Where is my thinking wrong, please?

[nkaminar]

Werner,

Thanks for responding.

The fact that there is a phase shift above the critical speed was a real surprise to me when I took a dynamics course in college. It does not make sense to someone without the technical education.

Every dynamic system, such as a rotating tire supported by a spring system, has a critical speed where the deflection caused by the unbalance is greatest. Below this critical speed the heaviest part of the tire has the greatest radius and the balance beads will migrate to that spot and make the unbalance worse. But above the critical speed the situation reverses and the heaviest part of the tire has the smallest radius and the lightest part has the biggest radius. So the balance beads will migrate to the lightest part of the tire to balance out the heaviest part. The beads migrate due to the circumferential force. Gravity does not enter into the equation because the circumferential force is a lot greater than gravity, at least for the Model A tire.

I don't know at what speed the critical speed is in a Model A tire, but suspect it is somewhere around 30 mph or maybe higher. It will depend on the car too, such as how stiff the springs are and what condition the dampeners (shocks) are in.

I know it does not make sense from the perspective of flinging a weight around with a string, but the fact that there is a phase shift above the critical speed has been proven many times.

[Bob Bidonde]

Here is another look at the phase shift that nkaminar discusses in Post #12. When an out-of-balance wheel bounces, there is a bulge in the tire at the heavy spot that causes the wheel to bounce. When the bouncing of the wheel becomes severe, a resonance occurs that significantly increases the bouncing. The phase shift occurs at resonance, when the heavy spot and the bulge have a separation between them as the wheel goes into severe bouncing (resonance).

[Werner]

Thank you for your effort!


I must apologize, that my American vocabulary is not sufficient to fully understand the last two explanations. But it seems that the beads work, even if I don't understand why.


(In Germany, the rotary engine was invented in the 1960s by Felix Wankel + NSU car manufacturer.

The engine did not catch on. "Evil tongues" claim that this is because no one understood how it worked. But the principle still works well.)