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Offline iBuchon

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A balanced debate
on: September 13, 2020, 09:40:14 PM
  Iíve heard both sides of this and looked into how major racing series prefer to do it. What do you think? To balance the wheel/tire with or without sprocket assembly?

  It looks like the majority balance without. MotoGP even does so without the brake rotors. This may be because of how the long process of tire inspection works and itís just more simple. Of course every other piece of the wheel assembly is no doubt absolutely perfectly balance so why bother.

  I saw a British Superbike video and the brake rotor was on, but not the sprocket assembly. Local level racers, same thing.

  I just got my balance stand and figured I would see what the difference was. In my case, the weight amount didnít change, but the location did. The difference in position is right at 2 inches (50/51mm).

  Knowing there is a slight difference, whatís the course now? I think Iím going with the balance with the assembly on.




  With that being said, I honestly donít think it makes a noticeable difference. My weights fell off my last set of tires completely and I only noticed when I was washing it.  :027:

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Re: A balanced debate
Reply #1 on: September 13, 2020, 10:50:51 PM
The location difference is so small its basically under the margin of error.

The reason why everyone balances without the sprocket assy is because when balancing on stand, the sprocket assy isn't fully loaded. Just pushing the carrier on the wheel may no fully seat itself and potentially introduce an error that isn't there once mounted/bolted in swing-arm.

Besides, the sprocket assy will always be neutral because how they are made and their small mass. Because how they are made, tires are rarely balanced out the mold and will almost always need correction.
Last Edit: September 13, 2020, 10:55:29 PM by Frontline

Offline Sarge

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Re: A balanced debate
Reply #2 on: September 14, 2020, 02:03:46 AM
Something else to consider is centering of the wheel with the cones on the balance shaft.  If you have the sprocket carrier inserted in the cush drive, it could be off center slightly and not center the wheel assembly to where it is perfectly perpendicular with the balance shaft.  The wheel assembly centers much more accurately when the cones are engaging press fit bearings in the wheel (not the sprocket carrier).  I take it a step further and use a digital angle finder, that has been calibrated with a perfectly level surface, to ensure that the balance shaft is perfectly level with the earth (flat).  I usually have to shim the stand to get it perfect before I mount my wheel on the shaft.

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Offline iBuchon

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Re: A balanced debate
Reply #3 on: September 14, 2020, 05:04:00 AM
*Originally Posted by Frontline [+]

the sprocket assy will always be neutral because how they are made and their small mass

Are you saying because itís near the center of the wheel or because the cush drive isnít a solid part? Or neither?

*Originally Posted by Sarge [+]
Something else to consider is centering of the wheel with the cones on the balance shaft.

I agree. The shaft provided was pretty small, so I thought there might also even be some flex in it. And thereís no way to know itís perfectly centered using the cones. I decided to just use the axle. A far as leveling, the stand has a bubble level and adjustable feet. I also checked it with another level.

Iím not looking for perfection since I know none of this will ultimately affect the stability as long as itís close. I do enjoy getting it as close as I can though and finding out if thereís actually a ďrightĒ way.

Interesting side note. I saw a R1 service manual says
ď ADJUSTING THE REAR WHEEL STATIC BALANCE NOTE:
ē After replacing the tire, wheel or both, the rear wheel static balance should be adjusted.ē
Adjust the rear wheel static balance with the brake disc and rear wheel drive hub installedĒ Granted, thatís from 2007, (Only one I could find to look at for free online) but why note that?
Last Edit: September 14, 2020, 05:06:08 AM by iBuchon

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Re: A balanced debate
Reply #4 on: September 14, 2020, 01:19:40 PM
*Originally Posted by iBuchon [+]
Are you saying because itís near the center of the wheel or because the cush drive isnít a solid part? Or neither?
Because of the low mass close to the axle and the cush, sprocket and nuts are machined so don't expect any of those to introduce an imbalance.

Except for CNC machined forged wheels (perfection), there will always be a (small) constant off-balance with cast wheels...usually so small it's rarely picked up using the tools consumers have. And in those cases, the wheel will always have the same exact heavy spot all its life. Tires...not even close. Heck, some tires will become unbalanced after they wear (due to more than just mass reduction). Moral of story, its all about the tire.

I don't have a tire mount/un-mount machine but if I did, I would balance the wheel without tire and permanently glue weight (if needed) inside wheel. This way I start off with a neutral foundation for when I'm balancing the tire - which is really the only variable in all of this.

Online 3alfa3

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Re: A balanced debate
Reply #5 on: September 14, 2020, 02:57:39 PM
*Originally Posted by Frontline [+]
....I would balance the wheel without tire and permanently glue weight (if needed) inside wheel.

What about centrifugal force?

I dont care for weight on the rims, as long it is up to 50g per wheel, if more, rotating the tire to compensate and reduce weights - if that is not helping, new tire (warranty, free of charge). But i never had that scenario, mostly is up to 30-35g, most often 10-20g but never zero, waiting for that to happen  :001: .

Here in Croatia, if i bring  the wheels, tires replacement, new valves and balancing is cheap: equivalent to 15$.
Last Edit: September 14, 2020, 03:08:30 PM by 3alfa3

Offline zed9

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Re: A balanced debate
Reply #6 on: September 14, 2020, 04:18:00 PM
Even though the rotors and Cush drive are close to the axle you are still balancing the entire rotating mass, not just the tire. So I balance with everything in place. Besides, who wants to keep R/R their rotors every time? Not me.

But here's a story. Both my brother and I have had a bike with a single sided swing arm (freaking hate them) and a 190 section tire. I don't have the proper adapter for my balancer, which is needed for a SSSA wheel.
In maybe four times mounting a new tire on these bikes we couldn't balance them (because of not having the adapter) yet they never have exhibited any signs they were out of balance. Granted, we weren't riding 150 mph everywhere nor MotoGP racing.
In fact, in over two decades of mounting and balancing motorcycle tires, only ONCE did I not require any balancing weights at all.
So I'm pretty sure all four mountings on the SSSA were out of balance yet we couldn't feel it. No hopping or vibration felt at up to 110 mph.