rear wheel jumpy at speed

Domagoj · March 28th, 2011, 10:44 PM

I have this problem, pretty annoying.

At speeds greater than 70 mph, or close, when leaned to the right, bike becomes very unstable in the rear.
Steering is fine, I feel no shaking in my hands.
Rear starts shaking in an up-down and slightly-left right motion, which increases in frequency and intensity with more speed, and more lean. I feel this in the seat, it starts to wobble quite violently. With passenger on board, the wobbling is still present, but damped to at least half the value or even more.
If the bike goes straight, or if it leans to the left, there are no problems.

This is more or less with me since I switched to BT45 from BT90. I had both wheels balanced twice, and they really are fine. No weights have been lost.

My rim is ok, there are no dents, no damage, it's just very dirty

Rear suspension was not tampered with and it is on factory setting, never had problems before.

Does anyone have any ideas what to do?

Cuongism · March 28th, 2011, 10:58 PM

Have you done a wheel alignment?

Domagoj · March 28th, 2011, 11:45 PM

Quote:

Originally Posted by Cuongism

Have you done a wheel alignment?

Yes I have. Using strings.
If I was terribly wrong (which I doubt, but it is possible), could that result in this behavior?

SteveL · March 29th, 2011, 12:47 AM

You might just have a bad tire; I have had this on a car where above 160Kph the whole car shook. Wheel alignment usually makes the bike go around say a left bend Ok but not want to go around right bend.

Steve

kkim · March 29th, 2011, 01:28 AM

yes, it could be a bad tire. post some pics of the right side of the rear tire.

also, check your suspension linkage bolts for tightness. If the linkage is okay, check the shock mounting bolts and the swing arm bolt for proper tightness.

min nin · March 29th, 2011, 03:02 AM

Tire pressure?

I bought a bike that had lumps on the sides of the tread, I think from running low too long. It sounded like a knobby in corners.

Domagoj · March 29th, 2011, 03:51 AM

Quote:

Originally Posted by kkim

yes, it could be a bad tire. post some pics of the right side of the rear tire.

also, check your suspension linkage bolts for tightness. If the linkage is okay, check the shock mounting bolts and the swing arm bolt for proper tightness.

Quote:

Originally Posted by min nin

Tire pressure?

I bought a bike that had lumps on the sides of the tread, I think from running low too long. It sounded like a knobby in corners.

I will check what I can later today when I get home, thanks for the ideas!
Another interesting thing I noticed just now, left side of rear fender is covered in dirt, and the right side is significantly more clean. That seems strange, they should be equally dirty. Is this another indicator that something is wrong with the tire? Will post pictures later.

Domagoj · March 31st, 2011, 12:33 AM

I checked the screws and checked wheel alignment again. No problems there.
I also did a track day yesterday, and had no problems at all

No shaking whatsoever. I honestly do not understand this.

Today on a ride to work, same old story. Maybe it's the road surface, not the bike...

ztrack157 · March 31st, 2011, 09:22 PM

I use to get that effect on the track here. I cranked up the rear suspension

March 28th, 2011, 10:44 PM	#1
Domagoj ninjette.org guru Name: Domagoj Location: Rijeka, Croatia Join Date: Aug 2010 Motorcycle(s): Ninja 250r 2009 Posts: 396	rear wheel jumpy at speed I have this problem, pretty annoying. At speeds greater than 70 mph, or close, when leaned to the right, bike becomes very unstable in the rear. Steering is fine, I feel no shaking in my hands. Rear starts shaking in an up-down and slightly-left right motion, which increases in frequency and intensity with more speed, and more lean. I feel this in the seat, it starts to wobble quite violently. With passenger on board, the wobbling is still present, but damped to at least half the value or even more. If the bike goes straight, or if it leans to the left, there are no problems. This is more or less with me since I switched to BT45 from BT90. I had both wheels balanced twice, and they really are fine. No weights have been lost. My rim is ok, there are no dents, no damage, it's just very dirty Rear suspension was not tampered with and it is on factory setting, never had problems before. Does anyone have any ideas what to do?

March 29th, 2011, 12:47 AM	#4
SteveL old git Name: Steve Location: Geneve Switzerland Join Date: Mar 2009 Motorcycle(s): BMW K1300S Posts: 479	You might just have a bad tire; I have had this on a car where above 160Kph the whole car shook. Wheel alignment usually makes the bike go around say a left bend Ok but not want to go around right bend. Steve __________________________________________________ Some mistakes are too much fun to make only once.

March 31st, 2011, 09:22 PM	#9
ztrack157 The Sportisi Master Name: Matt Location: Chico Join Date: May 2009 Motorcycle(s): 2008 Ninja 250 Posts: A lot.	I use to get that effect on the track here. I cranked up the rear suspension __________________________________________________ Sportisimoto USA is born.

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March 28th, 2011, 10:58 PM	#2
Cuongism ninjette.org certified postwhore Name: Cuong Location: San Diego Join Date: Jul 2010 Motorcycle(s): 2008 Ninja 250r, 2007 Daytona 675 Posts: A lot.	Have you done a wheel alignment?

March 29th, 2011, 01:28 AM	#5
kkim Join Date: Nov 2008 Posts: Too much.	yes, it could be a bad tire. post some pics of the right side of the rear tire. also, check your suspension linkage bolts for tightness. If the linkage is okay, check the shock mounting bolts and the swing arm bolt for proper tightness.

March 29th, 2011, 03:02 AM	#6
min nin ninjette.org member Name: terry Location: SW fla Join Date: Sep 2009 Motorcycle(s): 2007 250r Posts: 94	Tire pressure? I bought a bike that had lumps on the sides of the tread, I think from running low too long. It sounded like a knobby in corners.

March 31st, 2011, 12:33 AM	#8
Domagoj ninjette.org guru Name: Domagoj Location: Rijeka, Croatia Join Date: Aug 2010 Motorcycle(s): Ninja 250r 2009 Posts: 396	I checked the screws and checked wheel alignment again. No problems there. I also did a track day yesterday, and had no problems at all No shaking whatsoever. I honestly do not understand this. Today on a ride to work, same old story. Maybe it's the road surface, not the bike...