Why tire design can cause Head Shake

[dcarver]

OK, as ya'll probably already know, I ordered a set of Avon Azarros, for cheap, and they shook CrZy8 something fierce.

I've had other tires perform with zero head shake and some with just a bit. For those, I've been able to change front end loading and get the shake removed. But after running the Azaros, I think the real cause (among other things like steering angle, rake, weight bias, etc) is simply the tread pattern.

Here's a quiz for ya'll. Which tire tread do you think is more likely to induce head shake?

I say the tire on left will cause more head shake - the tire center is transitioning between left and ride sides, causing a slight 'imbalance' meaning the tire wants to 'fall' in the direction or side that's currently in contact with the pavement. Then, it suddenly has to deal with the opposite side when it hits the pavement.

Of course, I'm not a tire enjineer or nothing, but it sure seems logical. What say you?

 

[E1Allen]

I use the cheapo shinko front tire. I think from 50-30 the bike might shake to pieces if I dont grab the steering wheel. It was the same with the first tire I had as well, not sure what kind it was. The shinko has a groove down the centerline of the tire.

 

[SkooterG]

Sure. But BFD.

What's a little tire shake when your hands ARE OFF the bars for crying out loud.

You are SUCH a girl.

But remember, tire tread pattern is just one thing affecting head shake. Oh, and I do believe that the 'cupping' a tire gets as it wears is much more a factor in head shake than the tire tread pattern. Of course, the intial tread pattern can be one that leads to earlier cupping.

That front Azaro you picture only gives me minor headshake on FJR #1 aftern it's well worn. On FJR#2, which has a different suspension and a Givi Topbox, the Azaro will give more headshake. Still not a lot, but a bit more than FJR#1. BTW, the headshake I get on either FJR maxxes out. IOW, it will only go to a certain oscillation and stop. I can still keep on riding with hands off bars while front end is doing it's shake rattle and roll. I think the Azaro is a great tire, so a little bit of headshake later on in the front tire's life is an easy trade off for me. But then I am not a whiny-gashed Bee-Otch.

So I think in your case your prolbem is not the tire, but either A) Your Fat Ass, or B) Your POS CrZy8.

Have a nice day.

:****:

 

[Ignacio]

Don,

After you've removed the offending doughnut....could you spot specific wear patterns on the tire that would correspond to the head shake? If so, did the pattern correspond to the criss-cross of the tread in some sort of pattern?

Personally, I think it's just the precise nature of Azarros with the occassional QC flier. Changing no other variables I've had dead solid Azarro fronts and one really bad one and one REALLY bad Storm. The latter was one that would actually hop off the pavement at 15 mph with about 1,000 miles on it and was definitely not related to the pattern.

 

[my2dogs]

I use the cheapo shinko front tire. I think from 50-30 the bike might shake to pieces if I dont grab the steering wheel. It was the same with the first tire I had as well, not sure what kind it was. The shinko has a groove down the centerline of the tire.

Mine did same thing with the Shinko on front if I took one hand of bars. Put some bar end weights on it and took a lot out but on next tire going with a Michelin PR2.

 

[Bustanut joker]

Sure. But BFD.
What's a little tire shake when your hands ARE OFF the bars for crying out loud.

You are SUCH a girl.

But then I am not a whiny-gashed Bee-Otch.

So I think in your case your prolbem is not the tire, but either A) Your Fat Ass, or B) Your POS CrZy8.

Have a nice day.

:****:

Bwaaaaa :rofl: :rofl: :lol2: :good:

Who the hell are you and what did ya do with Scooter??? He ain't capable of this shit.

:jester:

 

[mattster31]

I think it's more luck of the draw / bike loading / miles on the tire / riding style ....................IMO. My D220's (which have over 10K and need changing) performed great the first 5K..............but the front now has a violent head shake that would throw me off the bike if I let it. Only happens between 50 - 30mph. It's much worse with the GIVI on the back. I know................so don't take your hands off the bike right . I have only ridden one other brand (Suzuki Gamma 500) and I was starting to think headshake was a Yamaha thing. My first bike (RZ500) shook so bad I installed a steering damper (no matter the tire). I'm hoping my Azarro's work :blink:

 

[Hit the Road Jack]

Of course, I'm not a tire enjineer or nothing, but it sure seems logical. What say you?

I am an "enjineer", and was in charge of the Space Shuttle wheel and tire shop for many years. My personal opinion, regarding motorcycle tires is that you get what you pay for! The visible tread pattern is just a small part of the handling equation. What really affects the handling is the tire carcass structure and how well it is constructed. A more expensive name brand tire will have better balance and quality control built into it and thus will usually give a better ride.

Caveat:

Of course this assumes that your bike's steering head and front forks are not all outa whack from hitting deer and driving down redneck driveways and such!

 

[millride]

My two cents worth here, I get around 4,000 miles out of tires no matter what brand so I have now been getting tires soley on the front tread pattern.

Avon storms-headshake Michelin z6 headshake and all the tires i've looked at on the internet that have the pattern described like the azarro will give that pesky headshake-my opinion and it counts so there! <_<

pilot road no headshake and the dreaded mz4 had no headshake and I put up with three sets of 021's because of no headshake. I just bought a set of 020's to try strickly cause of the pattern and they are new stock made in jan 09 so i'll check those out

I do alot of riding with no hands like coming into the small towns after a section of curvy road and on the slowdown I take the hands off the bars and adjust my gloves, open facesheild, itch the nose or dig in the tank bag -whatever it adds up to no handlebar time and i like a wobble free moment :blink:

Oh yea and the tires i've run are wobble free from start to finish so there you have it, of course YMMV!

 

[DailyCommuter]

I will have to wait til later on to put up my .02 because some of the information I need to make sense is at work.I work Sunday's(sad life : ) so I'll have it later.... Prepare to be impressed.

 

[DailyCommuter]

Ok it's later. This is my theory on head shake.

The following excerpt is from Lee Parks' book Total Control, and I quote

"As a motorcycle travels down the road it actually moves in a nearly undetectable low amplitude weave. Even when the rider thinks it is going straight. This is due to a multitude of factors, like uneven pavement, tire profiles, the elastic properties of tire rubber and the constantly changing weight distribution from rider and suspension movements.

When this happens the bike begins to fall to one side and the phenomenon known as gyroscopic procession causes the wheel to turn in the direction of the fall. At this point our old friend centrifugal force pushes the motorcycle in the opposite direction, and the process of repeated over and over creating the low amplitude weave."

end quote.

That being said, some if not all of you are familiar with the properties of frequency resonance. https://www.google.com/gwt/x?source=m&u...3c31354b4cdefb3.

Resonance is the tendency of a system to oscillate at maximum amplitude at certain frequencies, known as the system's natural frequencies. At these frequencies, even small periodic driving forces can produce large amplitude vibrations, because the system stores vibrational energy.

So my theory is this: when we are riding down the road we are already experiencing a vibration resonance through the engine vibration and the frequency of the low-amplitude weave that Lee is referring to. Every tire therefore must also have its own naturally occurring frequency, which I hypothesize changes with the rubber compound and tread pattern. Normally it doesn't produce any result or visible indication. Like the wine glass that is just sitting on a table. When the tire is traveling at just the right (or wrong for us) speed, that creates a vibration which matches its naturally occurring frequency resonance it will shake violently like the wine glass having a sound matching its own frequency directed back at it at sufficient intensity can cause the glass to spontaneously shake and ultimately shatter. I'm not saying of course we are going to shatter tires but what I am saying is that the head shake is a direct result of frequency resonance occurring in a manner that speed, rubber compound, tread design, low-amplitude weave, and vibrations all come together to manifest themselves in such a way that causes the head shake.

I would be willing to bet a beer that if there were a scientific way to measure the head shake, the frequency of the head shake would be an exact match to the frequency of the low amplitude weave that we all experience without knowing it. The only difference is that the amplitude(the peaks and valleys) are much greater.

 

[DailyCommuter]

-

 

[spineman]

I have been trying to search what is happening to my bike. I have just hit 1000 miles and thus have tried to push the bike a little faster. When reaching 95-100 mph it shakes, vibrates moderately. Enough to scare me a little. I have never had a bike with saddle bags....is this due to head shake or wind turbulence. I would think this bike is designed to travel at 100 mph with the bags on???

 

[johnny80s]

PRIIs you get what you pay for.

 

[Bungie]

PRIIs you get what you pay for.

Just took off a set of lightly warn (maybe 2000 miles) Dunlop Roadsmarts and put on a fresh set of PR2's. Two observations. Neither tire exhibits any headshake on my bike, and, the PR2's sidewalls are NOTICEABLY cushier at the same inflation pressures as the RS's.

 

[SkooterG]

I have been trying to search what is happening to my bike. I have just hit 1000 miles and thus have tried to push the bike a little faster. When reaching 95-100 mph it shakes, vibrates moderately. Enough to scare me a little. I have never had a bike with saddle bags....is this due to head shake or wind turbulence. I would think this bike is designed to travel at 100 mph with the bags on???

Sounds like it is simply that one, or both, of your tires is out of balance. It has nothing to do with the aerodynamics, or having the sidebags mounted.

 

[johnny80s]

PRIIs you get what you pay for.

Just took off a set of lightly warn (maybe 2000 miles) Dunlop Roadsmarts and put on a fresh set of PR2's. Two observations. Neither tire exhibits any headshake on my bike, and, the PR2's sidewalls are NOTICEABLY cushier at the same inflation pressures as the RS's.

I ran a set of Roadsmarts and did not have any trouble either.

 

[Toecutter]

I would think this bike is designed to travel at 100 mph with the bags on???

Sounds like it is simply that one, or both, of your tires is out of balance. It has nothing to do with the aerodynamics, or having the sidebags mounted.

Now, Skooter, you sound like a person speaking from experience. Am I to believe that you've actually exceeded 100 miles per hour with bags on? I think the owner's manual recommends against doing that.

My PR2 front had a vibration that started about 85. I figured I didn't put enough beads in it, but it also acted as a governor of sorts, and I'm lazy, so I left it. Now that the tire is a bit worn (less rubber to balance), the vibes have decreased....

 

[James Burleigh]

What a pussy.