Dyna Beads?

[JOHNNYMEZZ]

Has anyone had any experiences, good or bad, with this product? I'm riding a '02 K1200LT and I have noticed a fairly heavy vibration when traveling at lower speeds (30 - 40 mph). My local dealer believes that the front rim may be bent slightly which is causing this vibration through the bars; however, there isn't any vibration noticeable at any other speed range. Before spending the $ on a new rim, I thought this may be a more economical attempt. Looking for any feedback or recommendations.

[RoboRider]

There are MANY posts about Dyna beads here. You'll find people that swear they work, and others who swear they don't. I've only seen anecdotal evidence. The fact that they don't have a good independent lab test makes me skeptical. I tried them and I didn't have any issues, but my tires didn't wear better or longer than before. I'm not certain that I would have had an issue if I didn't use them either.

I use a static balancer by No Mar now and it is excellent. Works very well.

Dyna beads didn't get a fantastic write up in MCN:

http://www.marcparnes.com/MCN_DB_Review.jpg

Also, if you have a vibration that can't be balanced away by the dealer, I would suspect a bad wheel also.

Robo

[Polarbear]

My buddy just put them in his Yamaha and says they work. The physics of it all seems a little wierd though, as its seems the beads would find the heavy spot in the tire and make it worse? Quite the phenom these days, as many are asking about the beads. I know one thing in recent years, many tires I've mounted have needed NO balance at all and I find myself riding the bike first, without doing a balance job. I'm riding two new tires right now on my GSA that have NO balance issues and the balance job was ignored. Go figure. Tires are coming out of the factories a lot better than yesteryears. Many still have heavy spots marked right on the tire sidewall and putting this at the valve stem helps a lot, I would say. You may want to try it. Randy PS; I have found even my BMW Dealer ignoring the heavy spot markings and I wonder why, as they added weights! Hmmmm?

[marchyman]

The valve stem is assumed to be the heavy spot of the rim. The markings on the tires are either the light spot (often a yellow dot) or the point of maximum radial force (sometimes a red dot). The rule-of-thumb is to place the yellow dot, if present, at the valve stem.

However, on my bike the valve stem is not the heavy spot. The addition of a tire pressure monitor sensor inside the rim doesn't help. When I realized that I hadn't seen a tire light spot marking in quite a while and was usually putting the new weights at the same place I'd removed the old weights I finally saw the light.

I balanced my rim. Now I mount tires without removing the old weights and check the balance when done. So far I've not needed to make any changes.

As for dynabeads.... I don't use them because of the hassle and cost, especially now that I've balanced my wheel. I do understand (I think) how they work. The beads react to the complex motion of an out of balance wheel in a system where the axle is NOT fixed. They will not work on a spin balancer (or in the rear of a hard-tail bike, I think) as the axle in those systems doesn't have the necessary freedom to move. That's where MCN's test failed. It only proved that they did not understand how the beads could work. It's too bad as there are questions that a good test could have answered, such as:

• How much axle movement is necessary for the beads to be effective?
• What is the minimum wheel RPM for the beads to be effective?
• Are the beads effective against dynamic (side-to-side) imbalance?

// marc

[MOTORRADMIKE]

Johnny:

Have you checked the rim(s) with a dial indicator?

Also, it seems to me that an unbalanced wheel would show up at another speed(say 60-80). If you haven't tried that beware it might be severe.

Maybe someone has experience with a vibration on this bike that was NOT due to wheel imbalance.

One last thing:
I use Dynabeads, they work very well(off track). The principle is counter-intuitive though so difficult to explain.

One more last thing:
Wheel balance is not that critical, you just have to be close. Otherwise, single point weights and mounting new tires on balanced rims would not be good enough.

[testinglogin]

The valve stem is assumed to be the heavy spot of the rim. The markings on the tires are either the light spot (often a yellow dot) or the point of maximum radial force (sometimes a red dot). The rule-of-thumb is to place the yellow dot, if present, at the valve stem.

However, on my bike the valve stem is not the heavy spot. The addition of a tire pressure monitor sensor inside the rim doesn't help. When I realized that I hadn't seen a tire light spot marking in quite a while and was usually putting the new weights at the same place I'd removed the old weights I finally saw the light.

I balanced my rim. Now I mount tires without removing the old weights and check the balance when done. So far I've not needed to make any changes.

As for dynabeads.... I don't use them because of the hassle and cost, especially now that I've balanced my wheel. I do understand (I think) how they work. The beads react to the complex motion of an out of balance wheel in a system where the axle is NOT fixed. They will not work on a spin balancer (or in the rear of a hard-tail bike, I think) as the axle in those systems doesn't have the necessary freedom to move. That's where MCN's test failed. It only proved that they did not understand how the beads could work. It's too bad as there are questions that a good test could have answered, such as:

• How much axle movement is necessary for the beads to be effective?
• What is the minimum wheel RPM for the beads to be effective?
• Are the beads effective against dynamic (side-to-side) imbalance?

// marc

I know I've talked about it in another thread, but really, the statement the "the beads don't work in a spin balancer because the axle doesn't have freedom to move" is ridiculous. The axle on my two Airheads is surely "fixed". It doesn't move. The rear on my GSPD even more so, since there isn't really an "axle" with the single-sided swingarm. For the front, the forks can move up and down with suspension travel, but that is it. The axle doesn't move. A spin balancer allows for this type of movement - it's required so the machine can sense the out of balance condition.

As it is, sometimes there isn't a lot of balancing required. I mounted two TKC80's to my GSPD and rode it for a week before I got it down to have the tires balanced before a long trip. The difference was hardly (if at all) noticeable, and it was "off" about 1/2 oz.

Balancing "beads" have been around a very long time. This is just the same "technology" with a fancy marketing campaign in front of it. After all these years, if they really improved tire wear and handling, why wouldn't auto companies switch to this instead of using wheel weights? They could save a ton of money in balancing machine and in the personnel who have to do the balancing. Think how easy it would be to have the people mounting the tires throw in some magic beans... I mean beads.

[MOTORRADMIKE]

The axle on my two Airheads is surely "fixed". It doesn't move.

Hey JD:

If the axles on your bikes don't move, how do you go over a bump? Or up a hill? Or down the street for that matter?

What we mean by "Fixed axle" is that it is not free to move in any direction and that describes a dynamic balancer axle.

I'll buy you a beer someday and we can discuss it face to face!

[testinglogin]

Hey JD:

If the axles on your bikes don't move, how do you go over a bump? Or up a hill? Or down the street for that matter?

What we mean by "Fixed axle" is that it is not free to move in any direction and that describes a dynamic balancer axle.

I'll buy you a beer someday and we can discuss it face to face!

I'm all for the beer - I'll buy the second round!

The axle moves up and down, but the axle itself doesn't move. The front wheel of my bikes moves, but it runs on bearings which rest against the axle. The axle is clamped in place so it can't spin, and the up-down motion is covered by the suspension. The spin balancers allow for that same "up-down" type movement - it's how they detect the wheel being out of balance as it "pulls" towards the heavy spot.

Until I can see a verified independent study on them from a reputable source (say a University or respected lab), I won't believe they work, and I don't think physics backs it up. I get especially suspicious of things that can't be verified except by "feel". They say spin balancers don't work, so how is one to verify aside from "seat of the pants" where a placebo effect could come into play?

We will probably have to agree to disagree - not that there is anything wrong with that.

[marchyman]

The axle on my two Airheads is surely "fixed". It doesn't move.

OK. Perhaps I should not have used the word axle. How about this: the axis of the rotating wheel moves up and down with the suspension. Do you prefer it stated that way? A spin balancer detects the force caused by an out of balance wheel against an axle, but the actual wheel axis movement is minimal to non existent. No movement and the beads can't work.

An out of balance tire will cause shocks to the suspension, causing it to move up and down (the only direction it can go). At some combination of wheel RPM, spring rate, and suspension damping the forces can combine, causing the wheel to actually hop off of the road. The beads counteract the up/down movement through inertia. See, for example, this paper: http://bobrutherford.com/kb/getattac...A2LnBkZg%3D%3D (pdf) which describes an enhancement to using beads. (Note: One of the authors works for a company selling such beads).

I don't use beads. I've never used them. I don't have any plans to use them. That doesn't mean that they don't work. I understand how they could work in theory. I don't know what the operational parameter are, though, so I don't know how well theory translates into practice.

// marc

[kgadley01]

Ok, you guys have got away from the mans problem. here's what I recomend... go to Harbor Frieght and purchase a motorcycle balanceing kit. you can also use it to check the runout on your rim. While your at it check the balance of your tire. at $ 50.00 this rig will pay for itself quickly.

[JOHNNYMEZZ]

Looks like this brought up some good discussion and I really appreciate everyone's input. It would appear that my next course of action should really be to check the wheel run out and based on my findings take the next step. As far as using the beads??? Maybe a little more research. I may also have to post on the K side to see if anyone else with a LT has experienced this horrific vibration; it's so bad that you can forget trying to lift one hand for a stretch! I just can't imagine that an out of round wheel can cause this at the indicated speed (30-40) without a similar effect at highway/cruising speeds.

Thanks again and happy motorcycling!

[SweetT]

Dynabeads are fantastic. I've used them in the last 6 tire changes and even run them in my antique car. They are much easier than using a spin balancer since you just dump them in the tire before you seat the bead. Easy! I have a food scale that I bought at a grocery store and I weigh out the proper amount each time. I bought a big bag of them that will do about 10 tire changes for $24. Now I dont have to deal with any of the local bike shops who cant balance a shaft driven wheel.
And yes they DO work, but be warned! If you dont have an advanced degree in physics these beads wont be able to balance your tires!!

[krpreston]

I first put Dyna Beads in my Airhead last year and I swear they make a difference. It kicks in at about 30 mph and the bike just smooths out.

JD: I reads your posts a couple of time trying to figure out where the hell you're coming from. You seem to admit that as you are travelling down the road the axle IS moving horizontally relative to the earth and is oscillating VERTICALLY due to road variations, but you repeat over and over your axle does not move! Of course it's moving. As for the statement that your bike does not have a rear axle, how could it rotate otherwise? The axle is in the final drive housing.

[sibud]

I first put Dyna Beads in my Airhead last year and I swear they make a difference. It kicks in at about 30 mph and the bike just smooths out.

JD: I reads your posts a couple of time trying to figure out where the hell you're coming from. You seem to admit that as you are travelling down the road the axle IS moving horizontally relative to the earth and is oscillating VERTICALLY due to road variations, but you repeat over and over your axle does not move! Of course it's moving. As for the statement that your bike does not have a rear axle, how could it rotate otherwise? The axle is in the final drive housing.

I read it to mean his axle doesn't rotate.

[MOTORRADMIKE]

JD:
A spin balancers axle is as solid as bedrock. The machine measures force, not movement.

Marchyman:
Nice explanation, but still not good enough I fear!

Kgadley:
Good point, and good suggestion but I think runout could be measured on the centerstand.

Johnny:
Consider this thread hijacked.

Dr SweetT:
Can you present us with a simple explanation, perhaps referencing a similar natural phenomenon, so we'll all have a better understanding of dynamic balancing? Or are you not that sort of physicist?

Sibud:
You're just causing trouble.