Harmonics, vibrations and wobbles, WTF

[Ken Wantje]

So as with most vibrations, it can be difficult to pin point when the vibration started or did it just get gradually worse until you became aware of it. With my 2016 Audace, I noticed it as my rear tire was approaching it's time for replacement at 6500 miles and I assumed the vibration was due to the worn tire. It was most noticeable between 45 to 55 mph and felt as if there was a flat spot, it is more of a hop than a vibration, like if the wheel had bent from hitting a pot hole. So I changed the tire with the same model that was on it, a Shinko 777, and the same hop, wobble or vibration was there only it seemed worse with the new tire. It's definitely coming from the rear, I don't feel anything through the handlebars, and there is no movement of the front forks. I had not balanced the previous tire and thought that was the most obvious source, so I bought a balancer, balanced both front and rear tire with no change. Then I thought maybe the rear shocks were not properly adjusted. If the damping valve was open too far and springs were too soft this could result in the suspension "bouncing" so I firmed up the spring setting and tried various settings for the dampening valve with no change. Can anyone tell me whether the rear wheel hub is supposed to be balanced to the rear drive assembly and when I changed the tire, I possibly reinstalled it in a different location, out of balance? I plan to remove the rear wheel again, re check the balance and also check if the wheel could be bent. Any thoughts or suggestions are always appreciated. Thank you all!

 

[Moto-Uno]

I can't imagine how the rear hub is part of the balancing procedure , 40 years of doing this and that was
never a concern . Did you check where the tire beads on the rim and verify that it's the same distance all around
and on both side ? That's really critical and balancing won't correct an improperly beaded tire , good luck ! Peter

 

[Fast1400]

If you haven't already try turning off traction control.

 

[Ken Wantje]

I have inspected the bead, seems evenly fitted to the wheel. One thing to note here, I have 190-65-16 mounted where it called for a 200-60-16. This has been spoken of here and tried by others with no I'll effect but could be relevant. I did have to squeeze the tire with a ratchet strap to get it bead on the rim. This vibration was not present immediately after the first Shinko, only noticed it at the end of its life. Then it continued with the new tire which indicates it's most likely not the tire.

 

[Ken Wantje]

Traction control has always been OFF

 

[John L]

Have you checked for play in the swing arm bearings?

 

[scottmastrocinque]

You balance the tire and wheel by itself.

You gave an Audace and hence, nice chunky cast wheels.

Unless you hit a massive pothole or something else that I am positive you would remember, the odds you bent the rim out of round, is not likely. I would put it on a stand and visually look at lateral and rotational runout. I don’t expect you to find anything.

Am I correct is interpreting your synopsis as the wheel is exhibiting the same behavior with the new tire, that it was experiencing with the old one?

If so, and your wheel checks out for out of round or lateral runout, then the point of origin of your vibrational issue is not related to your tire or wheel itself.

Look elsewhere.

 

[Tonym]

Uni-Joint?

 

[Ken Wantje]

So yesterday I completely closed the dampening valve for the rear shocks to confirm my theory that it's the rear wheel hopping or bouncing, and it did cause a noticeable reduction in the severity of the problem, though I could still feel it. This would seem to confirm that either the rear wheel/tire is out of balance or out of round. I may try to locate a local shop with a speed balancer since I'm using the type that requires repeated spins to confirm that the tire is stopping at a different spot every spin after adding the appropriate weights.
Thanks to all who have chimed in with your thoughts and ideas. I will also take a look at the swing arm bushings once I have the rear wheel off again. I would be curious to hear how many clicks from the closed position you all are adjusting your rear shocks at. I ride solo and weigh 220 and typically i've been running my Audace at 12 clicks from the closed position and I have the SAG set at 1"

 

[Vagrant]

You did check the wheel bearings, didn't you?

 

[GTM®]

Ken, in my experience of mounting literally 10’s of thousands of tires (1600 in one weekend at an AMA Pro event was common occurrence, all static balanced BTW), I can assure you that static balancing is the most foolproof way to ensure proper balancing. I am often frustrated when I see spin balancers having multiple weight locations on a wheel.
In Pro racing, the wheel is ALWAYS first balanced without a tire. Machining is involved to get it right.
I suspect you may very well be experiencing a tire manufacturing issue. I am not a fan of “cheaper brand” tires for this reason. I’d suggest pull it and get it a shop that really knows tires. Even a barely visible out round tire can wreak havoc.

 

[Ken Wantje]

That's very interesting, I typically buy my tires through Revzilla, these Shinkos were $160ea, this last tire I purchased from a seller on Facebook marketplace for $140, brand new, same tire. Perhaps a blem or factory reject. Thanks for the info on balancing.

 

[Ken Wantje]

I plan to go back to the stock size and I will balance the wheel first this time. Thanks to all.

 

[scottmastrocinque]

I plan to go back to the stock size and I will balance the wheel first this time. Thanks to all.

You CANNOT balance the wheel first.

Todd was talking about having to utilize machining (millworker) to remove metal from the wheel, in order to precisely balance the rim, before ever mounting a tire on it.

This is not how your street motorcycle is done.

You just static balance a tire on a balancing stand.

 

[scottmastrocinque]

There is nothing wrong with a Shinko tire and I certainly wouldn’t call them “cheaper brand” by any stretch of the imagination.

Most every major “name brand” tire is made in China, Thailand, Indonesia, Brazil, Spain or Croatia.

I’ve had much better luck and consistent results with Korean made Shinko tires than any Michelin, Dunlop, Pirelli, Continental, etc.

Shinko was Yokohama tire before they became Shinko. Their molds, chemistry, formulations, engineering, etc is all world class.

They have been an American company for some time now. Shinko USA is wholly owned by Western Power Sports (WPS), one of the major power sports suppliers.

They are not Cheng Shin low dollar Chinese tires. Not at all.

It’s like oil, everybody has their brand favorite, but in reality, they are all really just a matter of personal choice.

 

[Ken Wantje]

I was very happy with the first Shinko 777 I purchased in the smaller size, 180/65/16. The vibration i'm feeling didn't appear until the tire was at it's end of life, about 6500 miles, and it was not as bad as what i'm feeling now. I assumed it was due to wear, but it would appear they don't make one in the stock size of 200/60/16. I think I will try the Avon Cobra Chrome, now that it's available again after a brief sell out, to eliminate all variables. I'm going to see if the seller from marketplace will take the Shinko back as a defect. Thank you for the clarification on balancing, I had never heard that before but now I understand what Todd was referring to.

 

[GTM®]

There is nothing wrong with a Shinko tire and I certainly wouldn’t call them “cheaper brand” by any stretch of the imagination.

Thanks for the reminder on Shinko formerly being Yokohama. Unfortunate name change IMO.
For the record, I wasn’t implying a “lesser brand” - simply a lower $ tire.
If he’s having an issue with vibration, I was simply suggesting to try another tire or brand… For those not able to detect a minor visible or non visible flaw.

 

[Ken Wantje]

Like I mentioned above I was very happy with the first Shinko I purchased and there was a significant improvement in handling with the narrower tire. The fact that the vibration appeared before I changed the tire would normally indicate that the tire was not the source, though it seems more severe with the new tire, it's difficult to compare from memory. I will replace the tire and see what happens. Thanks to everyone for your input!

 

[Moto-Uno]

Also keep in mind that as tires age (wear) , it's seldom exactly the same around the entire
circumference of the tire ! I'm sure I'm not the only one that has seen very over worn tires
that show the cord on part of the tire and some partial tread on other sections . There's no
way that tire is balanced , much less perfectly round ! Peter

 

[Ken Wantje]

So I finally received my new Avon Chrome Tire and after removing the wheel from my Audace I realized that it might be possible my wobble

Ken, in my experience of mounting literally 10’s of thousands of tires (1600 in one weekend at an AMA Pro event was common occurrence, all static balanced BTW), I can assure you that static balancing is the most foolproof way to ensure proper balancing. I am often frustrated when I see spin balancers having multiple weight locations on a wheel.
In Pro racing, the wheel is ALWAYS first balanced without a tire. Machining is involved to get it right.
I suspect you may very well be experiencing a tire manufacturing issue. I am not a fan of “cheaper brand” tires for this reason. I’d suggest pull it and get it a shop that really knows tires. Even a barely visible out round tire can wreak havoc.

So I received my new Avon tire in the stock size and as I was checking out the wheel with the Shinko still mounted I realized that the center hub that fits into the rubber dampers fitted in the wheel could in theory, if not properly seated or torqued, could be the cause of my wobble. Is it possible to assemble the wheel, hub, axle, spacers and bushings in such a way as to cause this wobble I feel between 47 and 55 mph?