Topic: Dyna beads for tire balancing?

[Stev-o]

There are certain things I don't like to do, changing tires is one of them. $70 is a fair price. I'll skip the steakhouse dinner and grill a couple good T-Bones at home for $25

[killersoundz]

There are certain things I don't like to do, changing tires is one of them. $70 is a fair price. I'll skip the steakhouse dinner and grill a couple good T-Bones at home for $25

I kind of have that feeling too. It's something I COULD do but I don't really want to do. And hopefully this guy can balance a wheel pretty good where as I may have not. (I took them in an hour close to closing so picking them up tomorrow)

[Retro Rocket]

Dyna beads    HAHAHAHA (shortened)

/

On the VFR world forum they like Dyna beads and many reports of good results.

I have already posted this here but {here we go again}   Go to the dyna beads site, look at the PDF on the site and read it thoroughly, it clearly states that they should not be used for hard cornering or racing and i can't remember the rest{ and i don't really care to go look again}, racing improves the breed with motorcycles and always has, anything that isn't recommended for cornering or speed ain't going anywhere near my bike, besides if these stupid little balls were the "ants pants" then why don't tire manufacturers recommend them at all, actually, Dunlop and i think it was Metzeler won't warranty their tires if you use the beads.....  That is good enough for me to steer clear....

All smoke and mirrors. Besides after working with and around bikes all my life, most people wouldn't have a friggin clue about most things to do with a bike. I could tell people i have fitted beads to their bike {even though i haven't} and i bet at least half would say that the bike felt better....   

[dave500]

All the Harley guys around me use the beads. I just had new tubes, tires installed and the guy that mounted them put the beads in. Have about 65 miles on them, I must say no complaints, pretty smooth..

tell the harley guys they should use them in the motor?

[andrewk]

I have already posted this here but {here we go again}   Go to the dyna beads site, look at the PDF on the site and read it thoroughly, it clearly states that they should not be used for hard cornering or racing and i can't remember the rest{ and i don't really care to go look again}, racing improves the breed with motorcycles and always has, anything that isn't recommended for cornering or speed ain't going anywhere near my bike, besides if these stupid little balls were the "ants pants" then why don't tire manufacturers recommend them at all, actually, Dunlop and i think it was Metzeler won't warranty their tires if you use the beads.....  That is good enough for me to steer clear....

All smoke and mirrors. Besides after working with and around bikes all my life, most people wouldn't have a friggin clue about most things to do with a bike. I could tell people i have fitted beads to their bike {even though i haven't} and i bet at least half would say that the bike felt better....   

If there's a PDF anywhere on the site that says that, I sure can't find it.  Can you post a link?

This is the site I went to-  http://www.innovativebalancing.com/index.php

[Retro Rocket]

I have already posted this here but {here we go again}   Go to the dyna beads site, look at the PDF on the site and read it thoroughly, it clearly states that they should not be used for hard cornering or racing and i can't remember the rest{ and i don't really care to go look again}, racing improves the breed with motorcycles and always has, anything that isn't recommended for cornering or speed ain't going anywhere near my bike, besides if these stupid little balls were the "ants pants" then why don't tire manufacturers recommend them at all, actually, Dunlop and i think it was Metzeler won't warranty their tires if you use the beads.....  That is good enough for me to steer clear....

All smoke and mirrors. Besides after working with and around bikes all my life, most people wouldn't have a friggin clue about most things to do with a bike. I could tell people i have fitted beads to their bike {even though i haven't} and i bet at least half would say that the bike felt better....   

If there's a PDF anywhere on the site that says that, I sure can't find it.  Can you post a link?

This is the site I went to-  http://www.innovativebalancing.com/index.php

I have already posted it on the forum mate, there's been a few "magic beads" threads...If i can find it again i'll post it...

[Retro Rocket]

Found it, i'll also post some more thought out reasons why they don't work...

http://www.innovativebalancing.com/LowProfileTires.pdf

Balance
First, let's first discuss theoretically what we are trying to do with dynamic balance. A dynamic imbalance is where the center of gravity (Cg) isn't around the center of rotation. This is the very similar to what we think of static balance, but the imbalance only shows up when you rotate the wheel/tire. Consider the wheel/tire on your bike, when it's sitting still, there is no dynamic imbalance. There can be a static imbalance and you can fix that pretty easily; we already do this when we manufacture a device. However, if you start spinning that wheel, there will be a dynamic imbalance if the Cg isn't right on the axial. Consider that the tire is sitting on the ground...it has a deflection which means it's mass isn't uniformly distributed anymore. That implies things like the quality of the tires, the lot, air pressure, the road surface, and even your weight all affect the dynamic balance. It should be obvious that a great many things can affect the Cg of your spinning wheel/tire and that's exactly why static balancing can't fix a dynamic imbalance.

An interesting side point is those tire balancing machines. You might ask how we can dynamically balance tires with what amounts to a static weight. We can't, at least not for all RPMs. Basically we cheat and purposefully create a slight static imbalance so as to reduce the dynamic imbalance. The dynamic imbalance is constantly changing though so static weights can only solve the problem at a given RPM. If you spin the wheel slower or faster it will become dynamically imbalanced again. Those balancing machines aren't really finding a single point solution, they are attempting to find the best compromise.

This should be even more obvious with the Hunter RoadForce machines (best commercially available AFAIK). They apply a substantial force on a roller to the tire so that it acts like the tire is rolling along the ground. A tire balanced that way is practically guaranteed to be statically imbalanced! However, it actually creates a better balanced tire because the sidewall stiffness of the tire varies (as does the rim concentricity). E.g. a high spot on the rim (which doesn't have to show up in a static balance!) on a hard part of the sidewall will give a bad ride as the resulting system isn't concentric. The point isn't to get a tire which will spin well on an unloaded axial or has good static balance, it's to get one that is properly dynamically balanced under load. You want the effective Cg to be right on the axial when in use, who cares about a test bed. As a quick side note, when using a tire balancer like the RoadForce you can actually line up the stiff part of the sidewall with a rim depression or vice versa. This usually isn't need if you have good quality rims and tires. Remember, you will never get perfect balance...engineering is the study compromises, so you can get of close enough for practical purposes.

One last thing on balance. All of this isn't to say that static balancing isn't of value. On the contrary, it's very important too, but just not for the reason most people assume. Most people are trying to achieve a dynamic balance with a static solution. As we talked about, you can't do it. However, consider this. Let's say you spend a lot of time statically balancing your rims and checking their concentricity (got to do both!). A rim is a fairly rigid system and as such, if you just spin it up there should be very little to no dynamic imbalance. Think about it. The statically balanced rim has it's Cg over the axial, unless there is a mass shift, which a rigid system like the rim really doesn't have much of, there won't be a dynamic imbalance either. The Cg doesn't magically change because you start spinning it; it changes when mass moves around in the rotating system. Of course the problem is that as the rim gets dirty or you mount something which isn't as rigid (e.g. a tire) or you put it under load (e.g. ride on it since that deflects things like the tire and even the rim a tiny amount) you've just created a dynamic imbalance. Thus, it should be apparent what a good static balance does for you...it gives you a good starting point for a mostly rigid system that doesn't experience too much mass deflection to achieve dynamic balance. That's great because it's easy to do and because it should significantly reduce the amount of dynamic balancing mass you need. As we'll discuss soon, those moving masses which allow for a dynamic balance aren't free of bad side effects; thus minimizing them with a good static balance helps.

Don't forget about concentricity either! You can have a statically and dynamically balanced system which isn't symmetric/concentric. I.e. a perfectly balanced rim which isn't concentric is going to have a very bad ride.

Autobalancers
So to fix this situation we need to figure out a way to move some mass around the rotating system so as to bring the rotating Cg back to the axial and that's what autobalancers do (and active balancers, but that's a different thread). Simply put, they exploit the physics of a rotating system so as to "perfectly" redistribute the mass and achieve dynamic balance. This is how Olsson 2004 describes it:
Another alternative is a mechanism that automatically adjust the balancing state, referred to as autobalancing. The are primarily two applications for this alternative: (1) when extreme accuracy is necessary (disk drives may be an example), and (2) when the state of balance is continuously or intermittently changed. A typical example of this is the centrifuge for a laundry machine, however fans, grinding wheels, and separators also belong to this category.
Sounds great, right? It is, but all isn't rosy.

There are several different theoretical ways to build an autobalancer. The most common is two rings/races each with a ball bearing that can freely move in them (a lubricant is often used as a dampener too).

Such dynamic imbalance has inspired the use of self-compensating, automatic dynamic balancing (ADB) mechanisms for eccentric rotors. The principal idea behind the ADB is that the balancing balls are subjected to a driving force caused by an apparent centripetal force acting from the offset centre of mass to each ball. When the speed of rotation is below the first resonance, this driving force pushes the balls towards the imbalance, thus moving the centre of mass away from the centre of rotation. However, when the speed of rotation is greater than the first resonance, the driving force pushes the balls to the opposite side of the rotor than the imbalance, thus moving the centre of mass towards the centre of rotation. Viscous damping in the ball race causes energy dissipation, allowing the balls to come to rest in asymptotically stable steady-state positions.

Let's look at some of the requirements or operating modes of the system to understand when it works well and when it doesn't. Olsson 2004 discusses the basic theory, Horvath/Flowers/Fausz 2005 discusses the theoretical, analytical, and experimental two pendulum balancer and has some good practical application, and finally Green/Champenys/Friswell/Munoz 2011 discusses the possibility of more than two balancing masses. I'll only use the first name/date from here on out.

At least two balls/rings...
You can also build this with two rotating pendulums. One ball/pendulum works too, but unless the mass of the balancer is exactly equal to the mass of the imbalance it will create its own imbalance. You must use at least two to achieve a perfect dynamic balance.
Thus far the rotor has been regarded as a point mass. All real rotors also have an extension and, consequently, a moment of inertia. This also means that they have two or more natural frequencies and dynamic as well as static unbalance. In order to balance such rotors one must have two balancing planes and in order for the auto-balancing to work there must be two balancing rings... It is obvious that a perfect balancing requires two balancing rings. If only one exists, perhaps for some practical reasons, there will be a residual unbalance.

Simple enough, Dynabeads has many balls so they shouldn't have a problem here unless it impossible/impractical for all of those balls to completely counterbalance each other out. More on that later.

"Free" balls
This article deals with the method of free balls. The basic theory includes any number of balls, but is valid only if the balls stay out of contact with each other...
This implies that for a two ball system you must have two independent rings/races for the balls to move in. I think this is because if the balls come into contact with each other they can degrade to a single ball solution under certain parameters and as we already discussed, you need at least two. Of course that means they are offset a bit and that should cause a torque around the z axis (the suspension forks). The masses should be small so it should be much though.

Dynabeads has many balls, but they are not independent of each other. Thus, under certain conditions they could degrade into a single "ball" solution. However, I don't think that is the case. The Dynabeads are small enough and are "captured" by the tire in such a way that I think they partially behave like a liquid would. I.e. the apparent centripetal force is sufficient that it will "flatten" them out and not allow a sufficient clumping like two balls in the same ring. That however brings up the next point.

Fluids as an Autobalancer
Nearly everyone cites Thearle 1932 in their papers, but only Green 2011 makes this note:
In this paper, there is also a discussion on why an ADB consisting of a fluid, in place of solid weights, would not work.
ADB is Automatic Dynamic Balancer. I do not have a copy of Thearle 1932 so I'm left only my rationale. I think the reason for this is because the apparent centripetal force is so great that unless the ADB mass can hold itself together, like a solid weight would, it gets somewhat uniformly distributed ("flattened") around the container (in our case the tire) and don't act as a true counter balance. Thus, solid masses can behave very much like a point mass solution, the liquid can't.

Dynabeads are small enough that I think they also behave partially like a liquid and partially like a solid mass solution. The liquid properties are good because it should allow them to avoid the two or more dependent masses degrading to a single mass solution (see Free Balls above), but that comes at the expense of the somewhat uniform distribution of the beads (aka liquid like), which results in most of them not acting as an autobalancer. A detailed analysis of these mechanisms should be possible, but I'm generally satisfied that the beads are a reasonable compromise at steady-state. They partially behave like an autobalancer, but require much more mass to achieve the required redistribution of the Cg than a solid mass solution would. That additional mass, above and beyond what an ideal/true autobalancer requires, has all the problems of adding un-sprung/rotational mass to your motorcycle.

I suspect that the size/material of the beads was a compromise between these two properties (or it should have been). This also implies that the liquid in tires as an autobalancer is nonsense.

Concentricity
Dynabeads takes it on the chin here...
Again we note that the ring will rotate with its center stationary, and the rest of the rotor has to adjust its motion to this. This confirms the result as obtained for the eccentric ring: the only way for the balls to be at rest is when the ring is running concentrically. This means that there is no guarantee that the rotor as a whole will run smoother, even if the balancing in itself has been successful... Deviations from a perfect ring geometry will greatly aggravate the possibility to balance. In particular, an ellipticity can cause severe residual unbalance.
Ouch. Since the tire is the dynabeads "ring" it can't be concentric...the fact is that the tire is loaded and thus deflected and not round (remember it's one reason why we have the whole dynamic balance problem in the first place). Even if the balancing sort of works, it can't become stable as the ring is eccentric! Thus, we have a perpetually unstable system, which while it may provide some level of autobalancing, it will never come close to an optimal autobalancer.
I would guess this tendency is exacerbated by bikes like cruisers which use a bias ply tire and less so by those that use a radial. The bias ply should exhibit more non-concentricity as it conforms/flattens to the road more than a radial does. I'd bet this is why wide tires are an issue more so than narrow.

Autobalancer Mass
Since at least two solid masses are required for the autobalancer to work properly, each mass should be approximately half of the total dynamic mass imbalance. Any more mass than that and you amplify the negative stability problems (which we haven't covered yet) and get even more of the usual issues with adding more rotational/un-sprung mass. If the two masses are very close to the dynamic imbalance they will take a position approximately 180 degrees from it. If they are too little they will be exactly at 180 degrees, but won't move the Cg enough to totally cancel the dynamic imbalance. If they are more than is needed they will separate and take a position between 90 and 180 degrees from the imbalance. If they are less than 90 degrees from the dynamic imbalance they will be unstable and the whole system will suffer. If this isn't quite clear take a look at Horvath 2005 as they have some good pictures you can use to increase your understanding.

The problem is this, how much dynamic imbalance do you have? I certainly don't know and its going to vary widely from bike to bike, wheel to wheel, and tire to tire. Don't forget that you actually have to add more mass than the ideal autobalancer would because some of the Dynabead mass will behave like a fluid. This is probably the biggest practical issues of implementing a Dynabead solution. I'm sure through testing you could come up with some rules of thumb, but IMHO it's a hack at best.

Supercriticality
Basically a real rotor has at least two natural frequencies and until you spin the rotor fast enough the physics involved with an autobalancer actually make the vibrations (whirl) worse, not better. In an ideal autobalancer where the balancer mass is equal to the imbalance it will be twice as bad as the autobalancer mass will "align" with the imbalance. Now that's just the rough sketch of it as in reality it won't perfectly align since the system is highly unstable in this region (if you are accelerating to get to supercritical rotation). All you need to understand is that until you spin it fast enough (aka supercritical), a system with an autobalancer will be unstable and will amplify the dynamic imbalance, not make it better.
For subcritical operating speeds, the steady-state phase delay of the displacement related to the exciting force is less than 90O. In this case, the stable pendulum position will be between 0O and 90O as measured from the horizontal axis (as shown in figure 11.a) which exacerbates the mass imbalance of the system.

Dynabeads has the same problem although the fluid mechanism of it may actually help a bit on a steady-state sub-critical rotation as a portion of its bead mass won't act like an autobalancer. However, its worse when you consider the non-stead-state system...Dynabeads should behave worse than an ideal autobalancer.
This could explain why many GS riders think it makes their bike worse, they probably ride sub-critical and Dynabeads do make it worse.

Stability and Perturbations
This is, IMHO, the absolute worst thing for Dynabeads and all autobalancers on a motorcycle. I think this is exactly why your BMW doesn't come with autobalancers from the factory. It's not that they couldn't, it's really that we probably shouldn't. Factor in that Dynabeads is a sub-optimal autobalancer in many ways which exacerbates all of the issues with autobalancers (except a minor one which I noted above) and I'm convinced not to use them. Again, YMMV.

Simply put, autobalancers have bad transition states when not in steady-state and everything you do on a motorcycle, besides cruising at a constant highway speed, perturbs them considerably. The faster you go, the less susceptible an ideal autobalancer becomes and the longer it takes to settle back to steady-state. Worse still is that based on the above analysis I don't think Dynabeads can achieve state-state stability.
Only recently have fully nonlinear analyses of the autobalancer been undertaken. Based on a Lagrangian description of the equations of motion, steady-state bifurcation studies were carried out by Chung & Ro (1999) and by Adolfsson (2001), who identified regions in parameter space where stable rotating states, whether balanced or not, are possible. By moving to a rotating frame, Green et al. (2006a) carried out a detailed nonlinear investigation in the case of two balls, by computing both isolated branches of periodic solutions and those emanating from Hopf bifurcations of the equilibrium states. Significant regions of bistability were found between these steady and periodic states, chaotic states and states in which the balls rotate at a different angular frequency than the rotor. Furthermore, perturbations were shown to result in a large growth in the vibration before subsequent transient decay. This prompted the study by Green et al. (2006b), where the authors used the concept of pseudospectra to analyse this sensitivity to perturbation. It was found there that while the completely balanced state becomes increasingly stable for high rotation frequencies, it also becomes increasingly sensitive to perturbation, with an increasingly larger transient response before settling to the steady state.

This explains why the sport bike guys generally hate them, they are constantly perturbing the system and experiencing it's very negative effects. At high speeds the transient becomes very severe. Accelerate, turn or brake and the portion of the Dynabead mass that's acting as an autobalancer is working against you. That's not my opinion, that's a know. Exactly how and how bad depends on a lot of factors.

[lucky]

I have already posted this here but {here we go again}   Go to the dyna beads site, look at the PDF on the site and read it thoroughly, it clearly states that they should not be used for hard cornering or racing and i can't remember the rest{ and i don't really care to go look again}, racing improves the breed with motorcycles and always has, anything that isn't recommended for cornering or speed ain't going anywhere near my bike, besides if these stupid little balls were the "ants pants" then why don't tire manufacturers recommend them at all, actually, Dunlop and i think it was Metzeler won't warranty their tires if you use the beads.....  That is good enough for me to steer clear....

All smoke and mirrors. Besides after working with and around bikes all my life, most people wouldn't have a friggin clue about most things to do with a bike. I could tell people i have fitted beads to their bike {even though i haven't} and i bet at least half would say that the bike felt better....   

If there's a PDF anywhere on the site that says that, I sure can't find it.  Can you post a link?

This is the site I went to-  http://www.innovativebalancing.com/index.php

Thats what I like...SOLID PROOF. RetroRocket is a good guy but I keep seeing reports of good results. Also they have a video showing how it balances an empty drinking water bottle, and it sure seems to work.

I was reading about the racing tires and Dyna Brads and it says they do not work in those gummy racing tires because the inside of the tire surface is too sticky.

Street tires and off road tires are OK.

[dave500]

instead of a water bottle i wonder why they didnt just mount a tire and wheel on a dynamic balancer machine to show how they worked?

[Gordon]

instead of a water bottle i wonder why they didnt just mount a tire and wheel on a dynamic balancer machine to show how they worked?

Stop making sense.

[BobbyR]

Here is what I suggest. If you believe in Dynabeads, put them in, if they work that is great. If they don't work you will have to probably replace your tubes unless you can get them out. If nothing else, you have learned something. 

[Retro Rocket]

Street tires and off road tires are OK.

Make sure you read the PDF entirely to Lucky, there are lots of different reasons there that they don't work or they won't in a lot of circumstances. This is the bit that gets me, its also particularly vague.
" we strongly advise against using dyna beads in any vehicle for racing, for any application involving cornering at high speeds, or in tires placed under high acceleration beyond normal highway use."

 Now considering the engine i am fitting in my K2 and F1 are capable of "high acceleration" and i still like cornering hard, i would never use these on the street, actually i would never use them period. I have NEVER had a tire that was that far out of balance that couldn't be fixed with the NORMAL lead weights, actually, the only wheel on a bike that i ever felt a vibration in, needed the spokes tightened. I now wonder how many ill fitted and balanced bikes are running round with these Placebo beads in them instead of the wheel being fixed properly....

[Stev-o]

My water bottle needs balancing, think I'll order some Dyna beads!

[Retro Rocket]

My water bottle needs balancing, think I'll order some Dyna beads!

Don't choke on them Steve....

[Stev-o]

No, I won't use it after it's done, might upset the balance!

[Retro Rocket]

No, I won't use it after it's done, might upset the balance!

You may also need a pod to filter out the magic beads.....

[lucky]

instead of a water bottle i wonder why they didnt just mount a tire and wheel on a dynamic balancer machine to show how they worked?

First off where would you find a dynamic motorcycle wheel balancer?
I live in a large California city I know of not one.

[scottly]

instead of a water bottle i wonder why they didnt just mount a tire and wheel on a dynamic balancer machine to show how they worked?

First off where would you find a dynamic motorcycle wheel balancer?
I live in a large California city I know of not one.

Since when is Guerneville a large California city??!! Fark, it's not even a large town!

[bollingball]

If I drink to much Jim Beam How many Dyna Beads will it take to walk good enough for the HP That is if I don't walk faster than normal walking speed not speed walking. Or can I just hold on to that water bottle?
Where I have my tires trued they spin them up to about 60 mph before putting the knife to the rubber. Surely they could put some weight on the wheel to make it out of balance for the before test then put in the beads. What is so hard about that. I'm with Dave500. If it works they would have done it with a tire.

Ken

[scottly]

If I drink to much Jim Beam How many Dyna Beads will it take to walk good enough for the HP That is if I don't walk faster than normal walking speed not speed walking. Or can I just hold on to that water bottle?

Ken

It depends on how many RPM you are spinning the water bottle, or the Jim Beam bottle in your case.

[lucky]

instead of a water bottle i wonder why they didnt just mount a tire and wheel on a dynamic balancer machine to show how they worked?

First off where would you find a dynamic motorcycle wheel balancer?
I live in a large California city I know of not one.

Since when is Guerneville a large California city??!! Fark, it's not even a large town!

I was speaking of Santa Rosa and Marin county motorcycle shops.
I know of one dynamic balancing machine for cars, and it is in Santa Rosa,Ca.,.
It is used for racing cars. It has a big steel cage built around it and the operator stays away from the cage behind a steel pole.

[dave500]

you dont have to organise the balancer lucky,,the dynabead place coul,,,,oh forget it.

[tomkimberly]

[lucky]

Yes... afraid so.

[scottly]

It has a big steel cage built around it and the operator stays away from the cage behind a steel pole.

Horse pucky. The steel cage in tire shops is a safety device, used when inflating tires on split-rim type wheels, such as used on big trucks. The ring that holds the tire on one side of the rim can shoot off when the tire inflates, possibly causing serious injury or death.

Balancing machines may have a guard to prevent physical contact with the spinning tire, to prevent your necktie, pony-tail, or beer-gut from getting pulled into it.