New Front Tire - 40 MPH vibration

[Guest]

I had a new Shinko 712 installed a couple of weeks ago.

The old 712 had about 7500 miles on it and was installed tubeless.

The dealer I took the tire to this time put in a tube because he said that's what the service manual called for.

He also added this number of wheel weights (pictured) each weight square is 1/4 ounce.

Now I notice a vibration near 40 MPH every time.
In all kinds of road conditions, it's still there, I have put over 400 miles on the new tire and the problem still persists. Which really sux because that's about the typical (twisty) cornering speed and it feels almost as if there's "wheel hop" occurring.

It's fine up to 40 and it's fine after about 43....

Any known causes, advice, & most importantly fixes?

Any help is greatly appreciated.

I plan to call the dealer tomorrow (they're closed today) but would like to be a bit more armed with possible causes.

[tkent02]

That is a huge amount of weight. The tire is very out of balance which is odd for a Shinko, Shinko is Yokohama, which usually needs no weight at all on car tires, they are very well made and symetrical.

I would take the wheel off and set it on it's axle on a pair of jackstands to check the balance myself, and see if it's out of round somehow, or just take it back to whoever mounted and balanced it and ask for a new tire.

40 is an odd speed for a balnce issue to show up, usually it's 50 something.

[Guest]

Is the mark on the tire (a white circle) aligned with the valve stem hole on the rim? If not, it should be. Have them rebalance the tire. Might add a bottle of RIDE ON tire sealant as well, helps with the tire balance and yes, you can use it with a tube. Check the rim for trueness just for the heck of it. If all that fails, you might have a slight defect in the tire.

[Griffin]

I usually double check wheel balance by simply unbolting the brake calipers and rotating the wheel in place. that also helps to see if something is wonky in how your wheel is mounted in your forks.

My guess is the wheel is out of balance and rpms at 40mph are in the sweet spot to amplify the wavelength that is being emitted by the vibration.

[Guest]

The circle (RED in this case) is near the valve stem, but not exactly aligned with it.
Within a 1/2 inch though.

Is a slight defect worth going through attempting to return the tire through Amazon/Motorcycle Superstore, shipping, waiting and then having them telling me it has wear and therefore is unreturnable? I dunno, I guess the more important question here is.....it it dangerous? If so, then cost be damned, it's coming off.


I too thought it was an awful lot of wheel weights being the last tire only had 1.

I did the unbolt and wheel rotation, looked well within reason, I then put a marker on a stick and each side rotated to see if the rims where somehow tweaked, that was within acceptable limits as well. I rechecked, re-torqued to spec and even did the string wheel alignment...I suppose I'll try some of the Ride-On magic goo and see if that doesn't help before I just discard the tire and get another.

[posplayr]

I usually double check wheel balance by simply unbolting the brake calipers and rotating the wheel in place. that also helps to see if something is wonky in how your wheel is mounted in your forks.

My guess is the wheel is out of balance and rpms at 40mph are in the sweet spot to amplify the wavelength that is being emitted by the vibration.

It might be more subtle than that. The wheel was probably balanced statically as indicated by all the weights. However if under dynamic load something changes (more likely rubber than lead ) the balance is suddenly lost and a dynamic imbalance appears. I would guess that the recommendation that the circular is not at the valve stem is a more likely culprit .

[posplayr]

Is the mark on the tire (a white circle) aligned with the valve stem hole on the rim? If not, it should be. Have them rebalance the tire. Might add a bottle of RIDE ON tire sealant as well, helps with the tire balance and yes, you can use it with a tube. Check the rim for trueness just for the heck of it. If all that fails, you might have a slight defect in the tire.

This would be a real test for dyna beads as well.

[allojohn]

Dyna Beads - and........forget it.

[Guest]

It might be more subtle than that. The wheel was probably balanced statically as indicated by all the weights. However if under dynamic load something changes (more likely rubber than lead ) the balance is suddenly lost and a dynamic imbalance appears. I would guess that the recommendation that the circular is not at the valve stem is a more likely culprit .

Would this position be cause enough for a remount and rebalance ?




Also for those of you who have used such products which do you prefer?

RIDE-ON
or
Dyna-Beads

[tkent02]

NO, not a problem. That dot is close enough. How is it balanced now? Axle on jackstands or remove the brake, both methods are fine, but does it always stop spinning at the same place or does it stop randomly which indicates it is balanced?

It seems more likely to me that the installer made a mistake when balancing it than the tire was that far out of balance.

[Griffin]

NO, not a problem. That dot is close enough. How is it balanced now? Axle on jackstands or remove the brake, both methods are fine, but does it always stop spinning at the same place or does it stop randomly which indicates it is balanced?

It seems more likely to me that the installer made a mistake when balancing it than the tire was that far out of balance.

I agree, that's a lot of weight on one side.

I spin the wheel and log the position of the valve stem as if it were a clock. one o'clock, six o'clock, etc.... I'm looking for the wheel to gradually stop (and not spin backwards) with the valve stem at random spots.

Usually if it is out of balance enough to cause a wobble, then it will be pretty obvious once you free spin it a few times, and the valve stem stops in the same place multiple times. If the wheel stops and spins backwards, then swings back and forth like a pendulum to come to a rest, it's WAY out of balance.

[posplayr]

NO, not a problem. That dot is close enough. How is it balanced now? Axle on jackstands or remove the brake, both methods are fine, but does it always stop spinning at the same place or does it stop randomly which indicates it is balanced?

It seems more likely to me that the installer made a mistake when balancing it than the tire was that far out of balance.

It would appear obvious that it is a matter of variable imbalance. If there was a static imbalance then the imbalance would simply cause an increasing level of whampum as the speed increased.

Because there is no noticeable whampum at higher or lower speeds, but only at one particular speed, the imbalance is only occurring at that speed.

Balance is exactly that matching two sides of a scale. In this case the wheel balance is for moment of inertia which has to do with equalization of the sum of the products of mass times distance from a center of rotation.

According to the principle of conservation of energy, mass can not be created nor destroyed. It therefore stands to reason that a change in moment of inertia is likely to do with a change in incremental distance rather than incremental mass. In other words the total sum of all of the smallest incremental pieces of the tire times each of it's respective distances has been altered by a change in incremental distance.

Change in distance implies flexibility, of the two items that are in static balance, the tire is most likely to flex and create an imbalance at that particular speed.

I would recenter the reference mark to the valve stem , properly air the tire and and test. If that doesn't work then the only logical conclusion is that the tire is defective.

[tkent02]

An inch movement of the dot will have next to zero effect, that huge mass of lead weights is MUCH bigger that any imbalance on any Yokohame or Shinko tire I have ever mounted.

Something is seriously wrong, a 1/4 ounce of weight is a lot on a Shinko.

I just looked at the Jeep in the driveway, with it's new Yokohama tires. Two of them have 1/4 ounce, two of them have none. This is how Yokohamas and Shinkos roll, they take pride in making very symmetrical tires.

Haven't had to use much if any weight on any Shinko yet, certainly never more than an ounce. Usually closer to none.

Out of balance tires always have a certain speed at which they shake the most, usually it's around 55 mph or so. Having it happen around 40 means it is very badly out of balance. Again, there is some strangness here, if it were that badly unbalanced, you would expect little bit of shaking at other speeds too.

If it were a physical lump of some sort in the tire, it would do it at any speed.

Very curious to find out what the actual cause is.

[Guest]

I had it on the centerstand with handlebars braced evenly and calipers removed. I rotated (spun) the tire and like Griffin said used the valve stem for reference and it seemed to stop in various spots with no backspin. The overall spin looks smooth, nothing out of place to the eye.

I just don't want to go back there and have the shop manager tell me everything is normal and that it's my imagination - which it isn't. I did some parking lot figure 8's and put a few hundred miles on it to see if somehow that would smooth things out. Nope.

I'll go in tomorrow and point out the "0" in relation to valve steam alignment, AND all the weights and see what they are willing to do.

It wouldn't be such an issue if it were at a different speed, say 10 or 90, but 40 is right there in that most visited range and it's become quite annoying.

I'll post back with the outcome & thanks for the possible remedies, insights & edification.

[posplayr]

An inch movement of the dot will have next to zero effect, that huge mass of lead weights is MUCH bigger that any imbalance on any Yokohame or Shinko tire I have ever mounted.

Something is seriously wrong, a 1/4 ounce of weight is a lot on a Shinko.

I just looked at the Jeep in the driveway, with it's new Yokohama tires. Two of them have 1/4 ounce, two of them have none. This is how Yokohamas and Shinkos roll, they take pride in making very symmetrical tires.

Haven't had to use much if any weight on any Shinko yet, certainly never more than an ounce. Usually closer to none.

Out of balance tires always have a certain speed at which they shake the most, usually it's around 55 mph or so. Having it happen around 40 means it is very badly out of balance. Again, there is some strangness here, if it were that badly unbalanced, you would expect little bit of shaking at other speeds too.

If it were a physical lump of some sort in the tire, it would do it at any speed.

Very curious to find out what the actual cause is.

Your probably correct in that the magnitude of the number of weights does not correlate with the small offset of the alignment mark. Either the tire is bad, or perhaps a fold over in the tube?