death wobble

[muddiver]

I have an '08 fjr with 12k miles on it. If I take my hands off the bars I'll get a bad death wobble during coastdown below 50 or so. This is not a minor shake. I don't feel it with my hands on the bars. I've never had this happen with this bike before and I let go fairly often. The shop said the steering bearings were out of spec and tightened them. Helped some, but not too much. Yamaha told them to replace the swing arm bushings. Didn't help.

I smacked a deer with this bike when it had 1k on it. Probably down to 40 or 45 at impact. Still enough to kill the deer. Mostly busted up plastic and the radiator. Didn't have the death wobble until 11k (and 2 years) later. Got new tires last fall. Shop balanced and put on a different front tire (same wheel) and said there was no change. They said yamaha's only other advice is "don't let go".

Any ideas? I'm fairly disgusted and don't want to just keep replacing parts. Thinking I may get rid of it.

Thanks in advance for suggestions,

Muddiver

 

[SwollenRaccoon]

Tires.

Several times I thought I had bad steering head bearings, or something loose up there. Every time: tires. New front tire fixes it every time. Mine hasn't been in an accident, so you may have a whole different set of problems, but try a new front tire first.

Good luck.

 

[Fred W]

check the front wheel for true-ness in both axial and radial directions. Also check brake rotors for run out. Get someone else to check the wheel balance or check it yourself. Make sure that any wheel weights are centered on the wheel L-R.

I could have a "Death Wobble" on my bikes and not know it. I see no point in letting go of the bars. If it doesn't oscillate and you can't feel it with even one hand on the bars...

Is it really a "Death Wobble" if nobody dies?

 

[07fjrTom]

I've had bikes do that in the past, and it has always been a tire issue. I can't say that's whats going on with your bike, and especially since you just put on a new tire, but "Don't let go" is good advice, at least until you get to the bottom of this issue.

 

[bbdig]

I had it with the Avon Azzaros, much less with the PR2. I did not take my hands off the bars but would loosen the grip slowing down sometimes to stretch the fingers and could feel it from 50mph down.

 

[wfooshee]

As the tire wears, its actual centerline starts to wave back and forth off of the true center. When the high point moves off center, the tire pulls the steering over. Then it goes back when the high point moves the other way.

New tire gauranteed to fix it. Not a bike problem.

 

[Fred W]

He says he already replaced the front tire. I suppose it could be caused by the back one, but that is kind of a stretch.

 

[ionbeam]

If even a light touch on the bars damps the oscillations then it isn't a death wobble -- annoying yes, death no. I have had several bikes in which this wobble was inherent to the design; every one of that particular model ever made wobbled.

Since your FJR has had a front end impact I agree with Fred W, check the front wheel for lateral and radial run-out on both sides of the rim (Right & Left). When you have a new front tire installed make sure that the bead line on the front tire is exposed an equal amount between the left and right side of the rim and the bead line is concentric to the wheel (even space all the way around between the bead line and wheel rim).

I had one front tire that wobbled right from new, the tire manufacturer approved tire replacement without ever seeing my bike. The replacement tire was perfect.

Edited to add: Since this is the second tire installed, check the current tire's bead line and then have the rim run-out checked. I still think the problem is in the front wheel/tire.

 

[RaYzerman19]

I agree, it is likely tire, but check wheel runout too. Some tires more prone to this than others, i.e., z6 tread pattern likely won't whereas symmetrical patterns may, or maybe you have minor cupping starting. Inflate up to 40 and see if it gets better.

Some influence might come from the rear, but shouldn't at 50 or lower in a straight line.

 

[SnowAviation]

My 09 does the same thing, but it didn't start until about 6,000 miles and the front tire

started to show some wear. I have a small amount of scalloping on the front, I think

I ran it too long at too low of a pressure.

Not a "Death Wobble" but you can't safely let go of the bars for any length of time at

some speeds.

 

[cota95]

Same thing here, on both my 06 and 07. Much more wiggle on the 07, even pulled the wheel and checked the balance again. I will be putting on a new tire for trip to Knoxville in September and will be checking back on this thread.

 

[muddiver]

Thanks for the advice so far. If you saw how bad the bars shake after a couple seconds you'd know why I called it a death wabble. I'm a dirt biker from way back and little crap doesn't bother me. The service guy said the mechanic who rode it was pretty apprehensive about riding it back after experiencing it for himself. It's no minor issue. If I thought it was I'd just live with it. The death wabble term comes from jacked up 4wd's with suspension problems. When it happens you don't think you'll get control of it again. The tires that are on it only have about 1k on them. As I said the mechanic tried another new one. He said he balanced both tires and I assumed he checked the wheel but I call and check on it and I'll try to see for myself later.

Thanks again,

Muddiver

 

[Fred W]

If the same guy balanced both tires, that may be significant.

 

[FJRONAMISSION]

Do you have a trunk / case on the back ?? I over loaded my 08 and it fell over at 2 mph.... the

next day it had a big wobble when I let go of the bars. when I unloaded the bike, it went 98 percent away.

had my shop realign my fork tubes in the triple clamps .... all better

YMMV

B.

 

[copron]

It's the head bearings......ask almost anyone who has put a lot of miles on a VTX 1300 or a Goldwing........most riders of those bikes replace the stock ball bearings with roller bearings and the problem goes away and the wear on the front tire doesn't effect it. Both of those bikes have the exact problems you describe.

 

[RadioHowie]

It's the head bearings......ask almost anyone who has put a lot of miles on a VTX 1300 or a Goldwing........most riders of those bikes replace the stock ball bearings with roller bearings and the problem goes away and the wear on the front tire doesn't effect it. Both of those bikes have the exact problems you describe.

Nah....it's the tires.

It's Yamaha's secret, patented way of telling you it's time to change the front rubber.

Brand new Azaro...no wobble. 6800 mile Azaro, decel shake @ 50mph.

Brand new Storm...no wobble. 10,500 mile Storm, decel shake @ 50mph.

2nd brand new Storm...no wobble. 12,300 mile Storm, decel shake @ 50mph.

Brand new PR2...no wobble. 6,000 mile PR2...not worn enough yet. No wobble.

I've never touched my steering head bearings. Bad tires = wobble. Good tires = no wobble.

If it was steering head bearings, the bike would always wobble. It doesn't. So it isn't.

Ball bearings > roller bearings doesn't get rid of the problem. It simply masks it, like a poor-man's steering dampener.

The problem is, masking a worn-out or crappy tire is asking for REAL trouble.

 

[radman]

Ya wanna death wobble, take a KLR over the ton. Hell, over 90.

 

[markjenn]

If you saw how bad the bars shake after a couple seconds you'd know why I called it a death wabble. I'm a dirt biker from way back and little crap doesn't bother me.

All bikes have a resonant frequency to their front ends that is divergent at a certain key speed, typically around 40mph. It's a random thing and while new tires, perfect steering head bearings, careful suspension setup, perfect wheel alignment, correct tire pressures, and proper weight distribution, the problem is minimized but it is probably still there. If a bike appears to be steady, it is often because it decels through the critical speed fast enough for the wobble not to develop. Try throttle locking any bike at the exact resonant speed, take your hands off the bars, and they'll all develop the wobble eventually. Arms are required steering dampers.

If the wobble develops very quickly and violently, I'd bet on a defective front tire, then work down the standard checklist of stuff. Beyond this, this is something that is a lot easier to live with than to tear your hair out about.

- Mark

 

[user 213]

What I haven't read here is what pressure are you running in the front tire, what brand and model of tire is it, and have you set up the suspension or are you just running the factory defaults?