FRONT END VIBRATION...part III

[BUSA_CHeMiST]

Ok, so I went to the track day, everything went well, but the vibration was still too much to really explore the full potential of the Busa as a cornering machine.
If unfamiliar with this vibration issue, refer to the link below..

PREVIOUS THREAD LISTING PROBLEM....CLICKY

Yeah, vibration is still between the ranges of 40-60mph, mainly noticed on decceleration, but prominent in that range when accelerating and holding constant speed there.

Went to a local shop today and we pulled the front wheel off and put a dial indicator on both the wheel and the rotors...here are ther results.

Wheel...Everything straight and OK
Right rotor...off 10/1000 th's
Left rotor...of 9/1000 th's

My question to the masses is, what, if any, is the allowable amount for a rotor to be "off" before you notice problems?  i mean, is this like a no room for error type of problem?  Any deviation gonna cause this?  

Like before, under braking, i DO NOT notice any vibration, unless in those ranges, and the intensity is the same in that range whether braking or just deccelerating without hands on the bars.  

Guy at the shop says that the wheel/tire is "almost" balanced, but it is just ever so slightly off.  Would this cause the head shake?  Should i take it tomorrow and have a reputable shop just check and see how far out of balance it is, if any?

I am very tempted to remove the brake pads and brake lever and take off down an empty street, and just see if it does it.  If the vibration goes away, I guess we will know the rotors were to blame.  if NOT, back to square one!

Just spinnin my wheels here guys/ladies...
Open to suggestions once again.

 

[rubber2burn]

Man I spoke to the guys at the shop and they are at a loss as well Man I told them every thing you had done and they were like well thats is every thing we would have done. Quick question though that just popped into my head are you running actual wheel weights or you still running the beads?

 

[Mrs.Rubber2Burn]

Hey Jerry, this is coming from a person with absolutely NO knowledge of bike mechanics.....However, I read your post, and it reminded me of when my car did almost the exact same thing you are describing! The same 40-60 mph range and everything. I had to get my tires balanced, and that fixed the problem! It was like magic!! Like I said, I by no means have knowledge of mechanics, just experience with my car.

I hope you get your bike fixed soon, I know it has to be frustrating!!

 

[BUSA_CHeMiST]

I am using wheel weights right now, we dumped those damn DynaBeeds as soon as we found out they were in there.

I am planning on taking it to The local Honda shop since they have a true wheel balancer, and see how out of balance it is.

 

[rubber2burn]

Have them do both wheels Jerry if that does not cure the problem I am empty as far as any more idea's of what it could be

 

[BUSA_CHeMiST]

Will do adam, i'll haul em both up there tomorrow and check em

 

[69chevydr]

Busa-CHeMIST I too am having the exact same problem and am starting to try to eliminate possible causes .If I find anything I will surely let you know.It's a real headache trying to find whats causing that shimmy.Mine is cruising between 40-55 mph. on a flat open road, and starts to shimmy ever so slightly.

 

[BUSA_CHeMiST]

When did it start Chevy? What was the last mod/service/maintenance you had done right before you noticed the shimmy?

 

[Dart451]

My first guess is the tire is out of round. Had it happen on cars and trucks.

My second guess is that one side of fork is screwed up and not compressing the same as other side, so when load goes to front the one side is try to compress more then other side.

 

[BUSA_CHeMiST]

My first guess is the tire is out of round. Had it happen on cars and trucks.

My second guess is that one side of fork is screwed up and not compressing the same as other side, so when load goes to front the one side is try to compress more then other side.

Well, can't be the tire, we have installed 3 different front tires and all three did it. One of the three was a brand new Dunlop Qualifier.

As far as the fork theory, not sure how I would go about checking that. Any ideas? I was told by one shop mechanic that it was due to the fork oil being bad and the fact that the forks hadn't been serviced in a while.

I changed fork oil, seals and washers in the forks, complete service. If anyone has any way to check the simultaneous compressing/rebound of the forks, let me know!

 

[Dart451]

Was just reading your other thread, and saw you switched tires. Mot sure how to check the fork theory. Not even sure its a good theory. Could get two bathroom scales and remove rim then put each fork on a scale to see what the load is. Switch scales from side to side to make sure the read the same.
Seeing it happened all at once I wouldn't think it would be forks.
What are the odds he put the wrong spacers back on the rim?

Let me reread other thread to see what else you tried so you don't need to repeat yourself

 

[BUSA_CHeMiST]

afte reading the manual, Looks like the MAXIMUM ALLOWED RUNOUT for the front/rear rotors is 0.3mm (0.0118 inches)

My runout on the right rotor is 0.01 inches (10/1000th inch)

Its a theory, but can it be that the rotor is causing the vibration, but the runout is not severe enough to cause it under braking??

 

[GMbusa]

Check your spring preload on the forks. Maybe one is set different than the other.

 

[BUSA_CHeMiST]

All suspension settings are the same GMBusa, checked and rechecked it.

Well, i think I ruled out the rotors. Pulled the front brake pads, rolled down the road, and still same vibration in that same range of speeds, no change in intensity.

Takin in to shop tomorrow to check balance. I'm gonna crap if this whole time, these guys that have been calling this "balanced" is the problem.

God this is really getting to me!

 

[Spudley]

Ummmm....errr....uhhhh..."HMMMMMMMM".........

Vibration can be generated from moving-mechanical, air pressure, or spinning items. You're talking a head-shake-like symptom.....hmmmm.......can you feel it in your butt, or just in your hands, or possibly in the crotch

....I'm not being funny, I'm just asking....occurs accelerating at that speed, holding at that speed, or decelerating through that speed

......wheel balance, axles (do you load the front , on a rear stand, a few times before torquing axle-clamp nuts ?), spacers, tires...rear chain sprocket alignment (bent ?), the rotors, out of round, would be noticeable on braking. I've had them, it feels like a bucking bull. Have you checked your stabilizer ?......although it's shouldn't be working that hard.......

Tire pressure pushes out, while spinning, HMMMM.......rear tire ?, cush-rubbers (one disintegrating ?), spacer misaligned, or pressed in wrong ?, or missing ?, ......HMMMM....rear sprocket loose ?, dog bones tight (check for movement/slop at pivot locations)

.....HMMMM...got to go to the chiropractor.....to be continued.....

Forks

?.....possibly, but that would cause a lean-component....

 

[BUSA_CHeMiST]

Wow Spud, now thats a list that can keep me busy!!

I know a few peeps in the last thread stated that it might be something to do with the rear.

As far as the head-shake, i can feel it only in my hands, thru the bars. I can feel it on accelerating thru that range, holding a constant speed in that speed range and deccelerating thru that range.

I will pull he rear orr as well tonight to take to the shop to have balance checked, and I will make sure all is well with the hub back there. I know im close to needing some new cush rubbers cause the hub just BARELY stays in the wheel, ya know, wanting to fall out once removed.

 

[cougar19]

Just a shot in the dark here - I noticed in your previous post that you put 75W oil in the damper. That seems pretty thick. Could this be too high of a viscosity and over restricting the handle bars?

 

[Powers739]

Ok, I give up... what's causing the probelm...












Keep us posted... I'm just wondering what I am going to do when the suspense is over...

 

[helofltmech]

When you find out what the problem is...let me know too!!! I have a 07 blue busa and it's been doing that since I got it. I figured when I get new front tire, I'm hoping it will go away. I have a fried that has an R1 that did the same thing, when he got a new front tire everything went away.

I have 9500 miles and no wear problems...just the front end wobbles between 40-55 mph.

Thanks

 

[69chevydr]

BUSA-CHeMIST I just checked runout on my wheel and rotors left rotor was.007" right was .009" runout /wheel has about .008" runout.Then Itook notice of my front tire which is a Dunlop Qualifyer it has a serrated type pattern on it if I run my hand with tread I feel it is kinda bumpy.Put my stock tire and rim and stock rotors back on this evening,but it started to storm out so I'll test ride tommorrow.Pics of tire with only about 2k on it,RED arrow shows low area Blue shows raised area kinda serrated.VERY obvious when you run your hand across it.