Well, I checked the balance on the front wheel and it was a bit off. Kind of imbarrasing I started from scratch and re-balanced and had another guy double check my work this time. I won't get a chance to test it out for a few days but I'm hoping that that was the problem. Thanks to all for the suggestions and help!!! Would the weight being off by just a little bit, cause that severe of a vibration?
The placement of the weights was wrong initially. I guess it could have been alot rather than a little.
The vibrations started aproaching 100mph and got worse as I went a bit faster. The vibrations continued under braking from those speeds. By the time I would turn into T1 it would feel fine. I didn't feel any vibration at lower speeds even if I was on the brakes hard.
have you checked to see if it repeats at the same speed (indicating wheel problem) or at the same rpm (indicating engine problem)
Good idea Jig. It is a speed issue for sure. Now that the front wheel is properly balanced I'll give it another try.
It was a stick on weight and I used the same weight after removing the double sided tape and replacing with fresh tape then putting this as close to the center line as possible. Head shake (not vibration) was gone. This was only a ¼ ounce weight. If you think about what the off-set weight was doing while spinning you will see it was alternately trying to turn the wheel left then right then left again. Consider a plane through the wheel which is defined by the forks. As the off-set weight spins in front of the fork the weight trys to center itself so the wheel turns a little to the left. When the weight reaches the fork plane (near the ground) the weight tries to move the wheel but because it is now resisted by the forks and the whole bike the effect is practically removed and the wheel returns to neutral. When the weight moves the back side of the forks it again tries to center itself which results in the wheel turning right. As it reaches the top of the fork-plane it again approaches a near zero effect. Some trivia; I don't recall if it is a ½ ounce or 1 ounce out of balance average car tire (225/65R15) but this tire is out of balance enough to lift off the ground at 55 mph. Consider that even the typical sportbike rear tire assembly is about half the mass of the car's.
I didn't know they used those to balance motorcycle tires. I have not seen a motorcycle balancing machine yet, though I expect to this weekend at Grattan. I wonder if they check for the couple imbalance that you refer to in your earlier post? Your little trivia tidbit is a good example of just how sensative an imbalance we should be concerned with, a question brought up earlier in this topic, especially since cars don't travel at 150mph like bikes do on the track. The higher the speed, the better the balance needs to be. probably why quick6R's vibration issue only hits at higher speeds, his balance may have been pretty close, but not close enough. Course he may have something resonating like jig was getting at. Inquiring minds want to know...
I'll test out the properly balanced front wheel this weekend and let you know if that was the culprit. I hope it's that simple!
Finally got the chance to test out a properly balanced front wheel. WOW that made a world of difference LOL. It wasn't the smoothest pavement on earth but the front end felt much better.
Awesome, glad you were able to get by with the cheap fix quick6r! Anyone know if it is typical to use a machine to balance motorcycle tires or if the tire/wheel assy is usually just balanced with a stand like STT uses trackside when you purchase the michelin tires? I saw them done this way at the last Grattan event and was curious if pretty much everyone does them that way. Jigmoore, sorry I didn't get a chance to look you up after tech review on the 5th, that beginner group really kept me busy! (My instructor Jeff did a great job too) I'm still hoping to spend some time with you on the 18th though...
it was good meeting you in tech...sorry it was so short. i'm looking forward to the 18th also. all trackside balancing that i've ever seen is done on a static balancer. i've never seen a problem with the results from those. a static balancer assumes the wheel is of uniform density and all mass is equally and uniformly distributed about the center and side to side. then the weights adjust for the very minor differences that are left. a dynamic balancer accounts for any of the non-uniform problems and balances for that. if a wheel will not static balance but will dynamic balance...i would look to see why. it probably means that the wheel is way out of balance and has something odd going on with the tire or wheel. more likely than not, what i've seen in this case is that it just wasn't properly static balanced in the first place...and just re-balancing fixes it. i actually have no problem only balancing the wheel...and then not having to balance when you put a new tire on. tires are usually quite balanced...especially if you use the same brand and put the balancing dot on the tire in the same point on the rim each time. jmo.
I didn't know that they were matchmarked like that. Also didn't notice the balancing dot on the tires when I was checking out the Michelins, I'll check that out and keep it in mind when I get my first new set! Which will be fairly soon...
Of possible interest to this topic, I had my rear tire spin on the rim Monday while working with the California Superbike school at Pocono. How do I know? I placed a mark on the tire side wall inline with the valve stem and that dot is now 1/3 the way around the wheel.
Used to mark tires and rims the same way prior to road testing autos. This is very common on cars, especially when driving hard. I used to think that only happened after the tire was lubed for mounting, but not so!
The lube from mounting the tire probably wasn't completely dry or gone. An identical tire on the same rim last year didn't move.
The lubes we used were designed to dry in 10 minutes, much less time that it took to get the car on the road prior to testing. It was surprising to me at the time, but they do move around. Lube was a water base.