Disk Brake Assembly Balancing

[JimGolden]

Hi All,

I've been reading the various threads on balancing of the running gear.

It would seem to me that the best setup would be to balance the hub assembly itself first, independantly of the wheel and tire. Then you'd spin balance the wheel and tire just like you would for your car. Since the two are balanced indendantly, it wouldn't matter how you mount the wheel on the hub.

With disk brakes, how to do this? There's really no place to drill holes in the rotor to safely remove material from the heavy side. Likewise, there's no place to add mallory metal to heavy up the light side? So what to do?

In conversations with some guys who deal in the Kodiak brake systems, they've told me that the hubs/rotors from Kodiak are very close to being balanced as-is.

The idea I had is this: If you need to only remove an ounce or so, couldn't you remove a little off the circumference of the rotor on the heavy side to balance it? This would seem like a logical way to do it. You wouldn't remove enough to get to where the disk pads swipe. You'd probably have to take less than 1/16" off the circumference of the heavy side to get it to balance. Probably more like 1/32". So you'd be left with a rotor that isn't 100% round then, it'd be a wee bit oblong, but it'd be balanced. I would think this would be fine.

Once this is done, the rotating assembly is balanced on its own and you'd not have to fool with the balancing of the wheels/tires/hubs as a single unit. It'd be a bit of work to do this, but it'd be a one time thing. Get them balanced and forget about them. Otherwise, it's a complicated task every time you change tires. And if you mount a spare out on the road, you're out of balance. I think this would really be a good solution, provided the disks weren't out of balance too badly to start with (if they are then this idea probably wouldn't work).

Thoughts?

[markdoane]

I think it's a good idea. I would probably agree that the hubs/rotors are going to be much better balanced 'out of the box' than drums.

You could use a different approach if you get separate rotors and hubs, rather than the integral design. With a little trial and error you could match the rotors and hubs so that the heavy side of the hub is opposite the heavy side of the rotor. Then if there is still any residual imbalance you could take it off the outer diameter of the rotor, or off the meat in the hub.

You'd need to mark them so they stay oriented if someone takes them apart.

[Bob Thompson]

If you haven't already considered it, you should give some thought to getting Centramatic automatic balancers. They really are the best ticket to keep your tire/wheel assemblies in perfect balance.
http://www.airforums.com/forum...s-16506-4.html

start at post #55 and read down.

[TomW]

Originally Posted by Bob Thompson

If you haven't already considered it, you should give some thought to getting Centramatic automatic balancers...

Be wary if you want to mount them on a vintage Airstream.

Tom

[JimGolden]

I've seen guys on here talk about the centramatics. I'm going to have to study up on them as I don't know anything about them, much less how they work. I've also seen some kind of beads advertised on here that are supposed to be a dynamic balancer of some type too.

I'd be all for a hub/rotor setup like is used on a car where the disk is separate from the hub. Any leads on who offers a setup like that?

[markdoane]

Originally Posted by JimGolden

I'd be all for a hub/rotor setup like is used on a car where the disk is separate from the hub. Any leads on who offers a setup like that?

Kodiak sells both the separate rotor & hub and integral one piece.

[JimGolden]

That'd be great. The only Kodiak ads I've seen showed the integral units. I'm going to dig deeper into this.

I read up on the centramatics. Looks good in theory. Looks like it works sort of like the fluidampers I've seen for engines where you've got an inner weight and an outer weight and they're allowed to "slip" to get to what's needed. I have to wonder then, if the beads that you just dump inside the tire wouldn't work about the same as the centramatics? It's the same principle anyway. At any rate, a very good idea on those things.

[markdoane]

Here's the Kodiak site: http://www.kodiaktrailer.com/redswish/disc_brakes.htm

[markdoane]

if you are interested in balancing powder or beads, search on 'Equal' (no, not the sweetener) and Dyna-beads.

[Mike Lewis]

Jim --I spent most of my automotive carreer working on front ends syspention systems, brakes etc. Here are some of my observations. It's not likely that you'll ever have a balance problem with a rotor, a drum yes, but due to the way rotors are made it's unlikely. If you take a casting as your raw material and machine all surfaces off a common center it in escence becomes balanced. There could be a difference in the density of the matterial but that would be very slight. Drums are different in that you don't machine the outer surfaces. The most accurate way to balance wheels is to spin <dynamic> balance the wheel and drum or rotor as an assembly. You then have to mark wheel stud and hole so not to loose this balance should the wheel be removed later. The second best is to balance the tire and wheel off the stud center. Most people balanceing wheels today spin the wheel off the WHEEL center which is NOT THE CENTER ON WHICH THE WHEEL ROTATES when on the vehicle. When a wheel is mounted to a hub it rotates off the center the studs create which can be different than the wheel center. There are adapters for most balances that attach the wheel to the balancer by the lug bolt holes. Imagine for example you were to balance off the wheel center then mount it on the vehilcle with the wheel tire assembly off center even a few thousands. The mass of the tire off that small amount will make a HUGE difference in balance. The only problem you'll find doing it this way is it requires more time to balance them this way and most shops don't or won't do it this way unless you insist. Having said all this there is a third way which in most cases is plenty good for trailer wheels. That is static balancing that you can do at home by yourself. Jack up a wheel, loosen brake adjustment and bearing so the wheel will freely rotate. Let the heavy spot of the wheel go to the bottom and counter balance it with weights oposite it by trial and error until the wheel will remain still anywhere you rotate it. If it takes more than a couple ounces to do this I would devide it and put half on the inside. With disc brakes its normally ness. to remove the caliper during this operation. Make sure you mark the wheel and studs so as to reinstall the wheel in the same location should you remove it. Finally and I know some will disagree but when it comes to powders liquids , bolt on balancers, etc, I have found that if it sounds to good to be true it usually is and people tend run from the truth and stand in line to be fooled!!!
Pieman

[uwe]

Originally Posted by JimGolden

I'd be all for a hub/rotor setup like is used on a car where the disk is separate from the hub. Any leads on who offers a setup like that?

Jim, Dexter's heavy duty disc brake setup is a composite system. i have installed it on my 1963 Overlander. You can see it in my thread "a 63 for me".
The discs seem to be balanced very well, with the bearing very loose, the disc stops wherever you turn it to. All my brake drums had heavy spots, they would always find a spot they would gravitate to with a loose bearing and no brake drag.
My Mercedes discs are balanced by removing material from the outside, but not all the way way across. The material is removed by a machine that is narrower than the disc's width. I have seem other rotors having metal clips installed right on the brake vents.
I doubt that a new brake rotor will be out of balance enough to warrant balancing, though.

[BigAl]

Jim,
If you remove metal from one side of the rotor would that side not tend to run hotter when braking? There won't be as large a heat sink effect on that side.
Al

[markdoane]

Originally Posted by BigAl

Jim,
If you remove metal from one side of the rotor would that side not tend to run hotter when braking? There won't be as large a heat sink effect on that side.
Al

Al,

I'm not sure I follow that. If you are removing metal from the heavy side, you are making it more balanced, from both a weight aspect and a heat sink aspect.

In other words, it may have been running cooler on that side before you balanced it.

[uwe]

Originally Posted by BigAl

Jim,
If you remove metal from one side of the rotor would that side not tend to run hotter when braking? There won't be as large a heat sink effect on that side.
Al

It is a miniscule amount of metal to begin with. More like a deep scratch between the heat fins.

[Action]

The metal removed would not come from the "side" or the machined face of the rotor. That will shorten the service life of the rotor.

Also, rotors have so much less mass on the outer edges as compared to drums, it is almost not worth the effort to "balance" the rotors. It would be like checking the tongue weight before every trip after the unit is all packed. Sure it will be different, and moving packed items around in the trailer to achieve a 8% tongue weight every trip is not going to make that much difference.

Those clips seen on the inside of rotor fins also have another purpose besides balancing. To reduce/eliminate brake noise. The rotor can vibrate and create a noise under certain conditions. Like taking a wet finger and moving your finger around the edge of a wine glass. Under certain conditions a noise will occur.

>>>>>>>>>>>Action