have excessive vibration b/w 120 and 140 mph... need help

[doug022984]

I put a new set of pilot power 2CT's on recently and notice a lot of vibration in the bike between 120 and 140 mph now. The mirrors on the front end move up and down with almost an inch of displacement and the rear wheel feels like its vibrating enough that it'll hop off the ground momentarily and lose traction.

Naturally, I thought it was the tire balancing so i had both tires rebalanced, but didn't notice any change (better or worse). Runs smooth at lower speeds. What else could cause the vibration only in a certain speed range and in straight lines? Suspension setup?

 

[updated]

I had the same problem last year on my GSXR.
Brand new set of PP's mounted and balanced at dealer.
They were fine till 120MPH.
Had them rebalanced, but same problem.
I e-mailed Michelin thinking may-be these tires were factory defects. They e-mailed me back saying "only 100% perfect tires leave the factory"
Tried to loosen and re-tighten forks thinking they were mis-aligned, same problem.
Tried adjusting suspension settings and tire pressure, same problem.
I realized the bike got smooth again above 150MPH.
After around 500 miles or so the problem just went away.:dunno:
I now have about 1500 miles on them and they are solid at all speeds.

 

[rugbymook]

First off, i'm a die hard Pirelli guy. I go through about 25 sets a year and have done so without issue for 4 years.

I'd try and swap out the tires again. Despite what Michelin says about 100% perfect, something seems fishy.

It could be a belt or lamination issue, either which you don't want to fail.

If you have specific technical issues with Michelin, you might try Quentin Mize. He might be able to help.
http://mizemotors.com/

(now might be the perfect time to grab a set of DC3's from Moon!)

 

[zangman]

I agree with the Michelins having issues. I used to run them until I had two sets of the Pilot Race with different build dates that were crap. BOTH the fronts AND the rears were junk. Impossible to balance. Michelin will not EVER take the blame and therefore they have lost my business.

Switched to Dunlops and not one problem at all. I like the Pirelli's too, but I LOVE Dunlops. AND, both the Dunlops and Pirelli's give you SO much more feedback for track riding.

 

[BLARNEY]

Hmmm...


I have run 50+ Sets of Michelin without issues.... event the recalled 2CT was fine while I used it.


Would start with re-balance and go from there


Tom

 

[Meat]

I have never had the issue you are describing on a bike but I have experienced exactly what you are describing in a car before and it was due to a separated belt.

That’s all I've got...sorry.

 

[barry38]

What tires were on the bike prior to these?

 

[under100crowd]

I just put on a set of Dunlops sportmax- UK version, and the first time i was able to use them was on 9/13 at summit point. i was getting headshake at high speed down the front stretch- i dont know what the problem is. they were put on and balanced by the manufacturer at a track day in July this year, does anyone have a clue as to what the problem could be?

 

[barry38]

under100crowd;16903 wrote: I just put on a set of Dunlops sportmax- UK version, and the first time i was able to use them was on 9/13 at summit point. i was getting headshake at high speed down the front stretch- i dont know what the problem is. they were put on and balanced by the manufacturer at a track day in July this year, does anyone have a clue as to what the problem could be?

My bet would be the geometry of your suspension set up is way off. The 209 rear is a very tall tire, so your rear ride height is now higher than it was before. You have to be careful when switching tires from on manufacture to another. Just because a tire is the same "size" doesn't mean they are the same.

 

[under100crowd]

thanks for the info-- the person doing my suspension setup hopefully will address this issue this coming week- i gotta get ready for the next rack day-- thanks again for the info... cant wait to ride with you guys again!!.

 

[Maryland998]

Thinking out loud...

What kind of shape is your chain and sprokets in? When you rotate the rear wheel does the tension vary dramatically. If the sprockets are fishooked or the chain gets to whipping it can feel like an out of balance wheel. Also the steering stem bearings being loose can make things feel strange. No vibration while braking? These are things I would be looking at if I ruled out the tires. Hope this helps. Ken

 

[doug022984]

Maryland998: I do notice the chain tension vary at low speeds when i glance down at it. I don't think I'd be comfortable looking at it going 130 mph though to see if it's whipping, but it sounds like this could be the cause.

Barry38: I had stock tires on before and didn't notice the problem, but I also had this same set of 2CT's on earlier in the year and don't recall experiencing the problem then. I switched them out with the front stock tire again and a cheap Shinko rear while i knew i'd only be doing more straight line riding and no track days to save tread. The shinko rear was visibly out of round though and caused vibration at all speeds so i sent it back and put put the 2CT's back on. The vibration at all speeds went away, but now i notice this head shake only at the high speed.

Could riding on the out of round tire for a couple weeks have caused some other problem?

 

[under100crowd]

Still shaking

thanks for all the good information. I had my suspension guy setup my bike- he lowered the front forks to just below tripletrees. I went to Beaverun on Fiday 9/26 and still had headshake especially when going over some bumps out of turn 10. then down the straights. so i am still at a loss- should i lower the rear?? any help would be greatly appreciated..

 

[under100crowd]

the chain and sprokets are nearly new-- less than 200miles on them- chain is like new. no noticable chain tension/slcak issues either..

 

[CoolTall1]

You may need to check the front wheel bearing. It could be bad. With the front tire off the ground will it move if you pull of push on it?