death wobble

[redgreen]

OK, let's think about this:
The only way that a steering head bearing will cause, or more accurately prevent, wobble is if the preload on the bearing is such that it provides mechanical dampening to the oscillating forces that are always present. Kind'a like keeping your hands on the handlebars will.

In other words, the bearings can not be the root cause of the wobbles, however they can contribute to wobble occurring by being too loose.

The root cause has to be something that is actually moving, so it is most likely caused by some part of the rotating mass of the wheel(s).

Since it is impossible to achieve 100% perfect balance on wheels, and since tires will always have some degree of imperfection, having some (small) amount of dampening in the steering head bearings would help eliminate oscillation.

If all of the front wheel variables have been checked and rechecked, then adding preload to the steering bearing may kill the wobbles. The reason a roller bearing would also work is it has more contact area, therefore more friction and more dampening for the same amount preload torque. Plus they can withstand higher preload (for even more dampening) than ball bearings, without distorting the races.

At some point too much preload of the steering bearings will result in handling issues since it will require too much effort to turn the bars to initiate steering. And, especially with balls, may cause premature wear and dimpling of the bearing races which results in notchy (varying) resistance to steering input.

So, both the "tires/wheels" group and the "steering head bearing" group may both be right here.

Very Well Stated, FredW! Best and most accurate analysis yet on our FJR's and their wobbles! I only thought our RadioHowie used the largest letters because he is such an OLD FART!

I'm wishing I would have seen this thread a few days ago when it was still warm - I'll post anyway and hope to get some feedback as well on my latest experiences. I have to agree with Fred's analysis based on my experience over the last few weeks. Got an 07 FJR - with just over 10K miles - never experienced any wobble at any speeds - smoothest bike I've ever ridden. Purchases a set of Avon StormIIs on-line since they were ~1/2 price the shop wanted. Dropped the bike off at the shop with the tires and a day later went to pick it up. Very bad front end wobble before even getting out of 1st gear in the parking lot - felt like a bent rim. Went back in - eventually discovered front tire was defective - had a bulge across 1 side. Replacement tire ordered, re-mounted, balanced, 2nd trip to pick it up. Severe wobble in between 35 & 55 - but took it home anyway - decided had enough of that shop. Got home, suspended the front end in the air, removed the calipers so the font tire would spin easily. Took a dowel, placed it on a stable base, and went across the whole surface of the tire as it spun. About all i could find was that the tire may be out of round by the thickness of a metal machinest ruler (what would that be? 1/64"??). Ended up taking wheel/tire into another shop to check balance - it was way off. They removed the weight the previous shop had put on and it was actually much better without - suspect they put it in the wrong place - this time re-balanced - supposedly correctly. Put the wheel back on, paying attention to compress the forks a few times to make sure the axle was seated properly before tightening the pinch bolts. Now the wobble is ~70% better - but still there - now confined to 40-50mph also. Back up goes the front end - I'm pissed for not checking the steering head bearings the 1st time it was up. I seem to be able to get the distance between the back of the front tire and lower fairing to change by pulling on the front tire - maybe ~1/2". Checked races, re-packed the steering head bearings, torqued the lower ring-nut to 13 ft-lbs after the initial seat to 37 ft-lbs. Put everything back together and still same results. Tried torqueing the steering head a bit tighter - ~15 ft-lbs and this actually seemed to improve things for a short period. After a couple hundred miles though - it seems to be back to it's wobble - maybe the improvement was my imagination/hopeful thinking. I also have a set of tapered bearings from Alls Balls sitting on the bench in the garage. But at this point I have to believe 1 of 2 things is going on(or maybe a combination of the 2?) 1) Tire is not true, 2) Tire is still not balanced properly. I've read on the forum that the tapered bearings may improve the situation - but I also have to believe that what they're really doing is masking the actual problem with the tire. Suppose this could be another defective tire? After the 1st defect - I asked Competition Accessories where I orded them from whether the tires were "seconds" - of couse they said no. Suppose I should call Avon CS directly? Anybody have experience with Avons - these are my first? Is it possible the tread on the Avon's could be amplifying the wobble and exagerating any out of balance/defects?

 

[FJRay]

OK, let's think about this:
The only way that a steering head bearing will cause, or more accurately prevent, wobble is if the preload on the bearing is such that it provides mechanical dampening to the oscillating forces that are always present. Kind'a like keeping your hands on the handlebars will.

In other words, the bearings can not be the root cause of the wobbles, however they can contribute to wobble occurring by being too loose.

The root cause has to be something that is actually moving, so it is most likely caused by some part of the rotating mass of the wheel(s).

Since it is impossible to achieve 100% perfect balance on wheels, and since tires will always have some degree of imperfection, having some (small) amount of dampening in the steering head bearings would help eliminate oscillation.

If all of the front wheel variables have been checked and rechecked, then adding preload to the steering bearing may kill the wobbles. The reason a roller bearing would also work is it has more contact area, therefore more friction and more dampening for the same amount preload torque. Plus they can withstand higher preload (for even more dampening) than ball bearings, without distorting the races.

At some point too much preload of the steering bearings will result in handling issues since it will require too much effort to turn the bars to initiate steering. And, especially with balls, may cause premature wear and dimpling of the bearing races which results in notchy (varying) resistance to steering input.

So, both the "tires/wheels" group and the "steering head bearing" group may both be right here.

Very Well Stated, FredW! Best and most accurate analysis yet on our FJR's and their wobbles! I only thought our RadioHowie used the largest letters because he is such an OLD FART!

I'm wishing I would have seen this thread a few days ago when it was still warm - I'll post anyway and hope to get some feedback as well on my latest experiences. I have to agree with Fred's analysis based on my experience over the last few weeks. Got an 07 FJR - with just over 10K miles - never experienced any wobble at any speeds - smoothest bike I've ever ridden. Purchases a set of Avon StormIIs on-line since they were ~1/2 price the shop wanted. Dropped the bike off at the shop with the tires and a day later went to pick it up. Very bad front end wobble before even getting out of 1st gear in the parking lot - felt like a bent rim. Went back in - eventually discovered front tire was defective - had a bulge across 1 side. Replacement tire ordered, re-mounted, balanced, 2nd trip to pick it up. Severe wobble in between 35 & 55 - but took it home anyway - decided had enough of that shop. Got home, suspended the front end in the air, removed the calipers so the font tire would spin easily. Took a dowel, placed it on a stable base, and went across the whole surface of the tire as it spun. About all i could find was that the tire may be out of round by the thickness of a metal machinest ruler (what would that be? 1/64"??). Ended up taking wheel/tire into another shop to check balance - it was way off. They removed the weight the previous shop had put on and it was actually much better without - suspect they put it in the wrong place - this time re-balanced - supposedly correctly. Put the wheel back on, paying attention to compress the forks a few times to make sure the axle was seated properly before tightening the pinch bolts. Now the wobble is ~70% better - but still there - now confined to 40-50mph also. Back up goes the front end - I'm pissed for not checking the steering head bearings the 1st time it was up. I seem to be able to get the distance between the back of the front tire and lower fairing to change by pulling on the front tire - maybe ~1/2". Checked races, re-packed the steering head bearings, torqued the lower ring-nut to 13 ft-lbs after the initial seat to 37 ft-lbs. Put everything back together and still same results. Tried torqueing the steering head a bit tighter - ~15 ft-lbs and this actually seemed to improve things for a short period. After a couple hundred miles though - it seems to be back to it's wobble - maybe the improvement was my imagination/hopeful thinking. I also have a set of tapered bearings from Alls Balls sitting on the bench in the garage. But at this point I have to believe 1 of 2 things is going on(or maybe a combination of the 2?) 1) Tire is not true, 2) Tire is still not balanced properly. I've read on the forum that the tapered bearings may improve the situation - but I also have to believe that what they're really doing is masking the actual problem with the tire. Suppose this could be another defective tire? After the 1st defect - I asked Competition Accessories where I orded them from whether the tires were "seconds" - of couse they said no. Suppose I should call Avon CS directly? Anybody have experience with Avons - these are my first? Is it possible the tread on the Avon's could be amplifying the wobble and exagerating any out of balance/defects?

I went through 3 Storms before I gave up. Avon replaced all of them. I just returned a Shinko for a refund. It looked just fine and balanced good but was getting progressively worse. Have had otheres that shook a bit on decel but it's common on this bike. head bearings are stock and have been greased once in a 100k. Tires are almost allways the culpit for these symtoms. For me the one that shakes the least is the old Pilot Road.

 

[Fred W]

Yeah, I'd be tempted to cut my losses and ditch the Avons. I know this is a small sample, and since I balance my own wheels I am pretty meticulous about getting them as near perfect as possible, but I have had 3 Pirelli Diablo Stradas (best FJR front tire known to man) and now have a PR2 on my bike and I have never had the slightest suggestion of a head shake. Granted, I'm not keen on riding around "no hands" but I often ride with just finger tips on the bars when stretching the back a little.

Even if you don't want to mount your own tires, baancing them is something anyone can do in the comfort and convenience of their own garage. Just get a Mark Parnes (or similar) static balancer and go to town.

 

[charismaticmegafauna]

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. Any ideas? I'm fairly disgusted and ... Thinking I may get rid of it.

That may be your only recourse...?

Let's review:

• Some say it's bad tires.
• Some say it's poor wheel balancing.
• Some say Yamaha put in the wrong steering-head bearings and they must be replaced with, better, after-market ones.
• Some say all bikes do it.
• Some say their bike has never exhibited any head-shake.

An enigma wrapped in a conundrum -- and, apparently, quite difficult to solve...

 

[TechJunkie]

My $0.02 worth.

Rode the Metzler's on my 08 until they had to be changed due to an upcoming trip. They were at the wear marks and my Feejer and zero head shake at any speed. I couldn't find the PR2's in time for the trip due to procrastination and my local shop had a set of the factory Metzler's for a decent price. Left the shop and within a mile I knew I had a problem. Severe head shake. I returned to the dealership and tire had balanced out well and no apparent defects. I decided to see if it would settle in. It wasn't a problem for most of my trip when on interstate but when in the Rocky Mountains in the twisties. When sweeping through the turns the front end never felt planted. Sometimes it was very unnerving.

Now with about 5k on the tires the head shake is almost gone. I personally believe it was the tire since nothing else has changed. Also since head bearing was also checked and in spec.

 

[nessundoma]

I mounted Conti Road Attack and experienced headshake on decel <40mph. Within a week I replaced the frt w/Pilot Power 2 and the headshake was gone. Prior to Conti I was running Pirelli Stradas w/o any problem.

 

[NSrider]

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

Or have her pinned wide open when shifting from 4th to 5th

 

[russperry]

<!--quoteo(post=770860:date=Aug 4 2010, 12:33 PM:name=copron)--><div class='quotetop'>QUOTE (copron @ Aug 4 2010, 12:33 PM) <a href="index.php?act=findpost&pid=770860"><{POST_SNAPBACK}></a></div><div class='quotemain'><!--quotec-->You really need to adjust those head bearings, a decel wobble in the 45-50 mph range is almost always attributable to maladjusted head bearings. The death wobble ( high speed wobble/tankslapper) is a whole different ball game.<!--QuoteEnd--></div><!--QuoteEEnd-->

Dude, perhaps you didn't hear me......

<!--sizeo:5--><span style="font-size:18pt;line-height:100%"><!--/sizeo--><b>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.</b><!--sizec--></span><!--/sizec-->

Sorry to dredge up old news, but I'm going through the same procedure right now, and in my case at least its not just "get new tires". I found the same decel wobble on the used tires on the bike when I bought it. High frequency and increasing amplitude from the moment my grip came off the bars. Never seen this kind of event in 30 years and over 100k miles of motorcycle riding with more than a few with my hands off the bars.

Reviewed many messages on this board as well as another FJR forum and saw that there were alot of suggestions for new tires, tapered bearings probably being 2nd favorite suggestion. So I decided to try the tires, and I will agree that the severity has been greatly reduced, but its still there. Maybe some of the more in-depth (hence costly) investigations may be in order, but I would say based on a statistical sample of one, that just changing the tires is not a 100% cure rate.

 

[444rose]

well, i have read and read all i can regarding this issue, but i can say this....the original bt-021 that came stock on my 2010 fjr showed major defects by 1500 miles...i managed to ride on it till 4k and at about 3K is when i noticed the wobble....i was hopeful that a simple tire change would remedy it so i had a set of Shinko Ravens purchased for a previous sport touring machine i owned at my disposal...i had the front tire installed and balanced and the wobble was still there...rode an additional 2k and i could swear the condition worsened...riding this FJR was starting to make my stomach turn...for real.. i would ride and analyze and believed that the head bearings could not be at fault because the bike was new and there was no clunk and the forks were tight when lifting the front and pulling on them, so i decided to buy a PR2. for those of you like me who don't know what a PR2 is, well its a Michelin Pilot Road 2, not a cheap tire but certainly not the most expensive either...anyway, over the course of this time i wound up getting a N0-Mar tire machine which i have used a few time already for my other bikes and friends and swaped out the Shinko, the Shinko showed absolutely no signs of wear at all w/2k on the tire by the way...wrestled to get that PR2 on that rim, i had to check the tire size twice to verify it was the correct size, finally got it on, finally filled it w/air, and then static balanced it and put the weights as close to the center of the rim as possible, re-installed and went for a ride...and here are the results, with a shinko raven tire recently installed on the rear, and the PR2 on the front the deaccel wobble is about 95% gone...i wish it was completely gone, but it isn't traceable if you keep one finger on the bar through that speed range, you will only see a slight movement when you remove your hands completely while slowing thru the 50-40 MPH range...so folks, i am satisfied w/the results! i know its not common to mix and match brands but damn that rear PR2 is costly and the machine handles much better w/the PR2, the shinko felt heavy from day one and affected the handling it had when i had the oem b-021 tires, so this is real life experience from someone who suffered this dreadful condition and nearly eliminated it w/a PR2.

What more can i say?

 

[RadioHowie]

New front tire fixes it every time

and it has always been a tire issue

New tire gauranteed to fix it

I had one front tire that wobbled right from new.....the replacement tire was perfect.

changed the tire, no more wobble

Every time a new front tire goes on it goes away and the bike has beautifully light steering

It's the tires

A new tire solved the problem

Within a week I replaced the frt w/Pilot Power 2 and the headshake was gone

Well THAT nails it....it's the bearings!!!

 

[Bounce]

Sometimes when I get drunk too early say 7am.

speaking of getting drunk. :yahoo:

i have the base done on cooking up a batch of Apple Pie Moonshine. i bought some around the time of this year's IBR and it was so good, i looked for the recipe. i found it! i have the base (flavor) cooked and it should be cooled and done steeping by the time i get home from work today. all that's left it to spike it with the right amount of moonshine and transfer it to mason jars.

then i have to wait and let it age... for TWO WHOLE WEEKS! :dribble:

best of all is that it ends up 1/3rd the price as the pre-made Apple Pie.

so the shine will have aged a week in transit, a week at home waiting, and 2 weeks as part of the Apple Pie. that's a long time in moonshine years.

 

[bernie1]

I think I have already posted this in the past! Bought a used bike,FJR, Had a terrible wobble with hands off. The front tire looked terrible, cupped all to hell! Read about timpkin bearings Replaced them with All Balls I think. Stopped all the problems!!! Put about another 5000 to 6000 on the tire before it wore out, And the cupping was almost gone. Have an additional 25000 miles on since the bearing replacement and still no shake!1 Nuff said? And the tire people over analyzed the problem then too. Replace the bearings, throw away that stupid spanner wrench that you get from the factory, and tighten them tight up to the point of being too tight. If you get them too thight you will know it and just back off a little. Don,t worry about it just do it before the thing kills you!! Bernie

 

[juniorfjr]

I've gone through many front tires. The orig Brigestones, Avons, Perelli, and PR2. All of the front tires have started out really well, but in less than 4000 miles the wobble would begin. The most recent PR2 had gone all the way from perfect to Ya don't dare let go. When I got back from WTF-0 I decided to try tightening the steering head, gave it about a half of a turn. OMG what a difference, even with the cupped PR2 the bike is perfectly mannered. Steering felt a little heavy at first, but now seems great. I'd reccomend that anyone that has a fjr that wobbles, try this first. Worked for me.

 

[Fred W]

I've posted this before, but I'll say it again:

The steering head bearings can not CAUSE head shake (or wobble, or whatever you want to call it). But, yes, they can MASK it by adding mechanical dampening (resistance to turning).

@ bernie1 The reason your cupped tires got better with continued use is because they usually will do that if you are willing to suffer through the cupped phase. Scalloping or cupping of the tread occurs due to tread block distortion during use. The blocks flex in a way that one side of the block has more pressure and friction with the road. As the blocks wear down, assuming proper inflation pressures, they will flex less as they get shorter, and tend to even out towards the end of the tire's life.

Also, as far as this killing you, I've not heard of any FJRs that have gone into a true tank slapping death wobble. The ones reported here are only when you take your hands off the handle bars. If you just keep your hands on the bars you are apt to avoid death, at least in the near term.

 

[LAF]

I have to say about the worst advise I have read on the torquing of the steering bearings.

Even on a Harley you do a fall away adjustment. If you are experimenting with torque I strongly advise you to just go up in increments on the final torque numbers and checking the fall away of your front wheel.

Very simple just jack the bike up as in removing front wheel, hold the forks strait and let go, they should fall with a bit of resistance but no clunk on hitting the stop. They should not really favor either side and may need a very light nudge to go in either direction. It is a very crude but very effective visual aid in seeing how bearing torque affects this. You can then judge what it means to steering with weight and speed on it.

Been said a million times, in all but a few cases, this is tire and or wheel condition.

And I still think people underestimate the rear of the bike and it's affect to the front. My 05 Road Glide was scarey until I put a stabilizer on the rear across the frame that essentially became a very solid 3rd link and completely took the head shake out of it at speed.

So in all this how is everyone's rear links? OEM shock and how many miles? Have you changed fork oil, know how and why you set up suspension?

Of course these are all things I would be looking at after I ruled out tires and balance.

And this is NOT a FJR specific phenomenon and was ever present on the BMW K1200 LT and my 07, it came and went and could be attributed to tire and balance combination. The only front that never gave me an issue was the Avon Azzaro which they butchered into the Storm, and then a Z6.

 

[Pete Bansen]

Funny you should mention Avon Azaros. I just finished wearing out a pair of Azaros that the previous owner of my bike reportedly installed shortly(?) before selling me the bike. I didn't think a lot about the handling of the bike until I had been riding it for a while, but last week I commented to a friend who has an '03 FJR that my '05 FJR was the twitchiest bike I've even owned and that I was going to take it to a suspension specialist so that they could look at the high-zoot Wilbers setup that the previous owner spent a lot of money on. The bike didn't want to turn, wanted to stand up while turning and required constant input to hold a consistent line while in a turn. After years of riding BMW GS'es, I was distinctly unimpressed with the handling of the FJR, although I loved the motor and ergos (mostly) and I could see the potential in the bike. If I took my hands off the bars while decelerating, they quickly started heading into one of the more violent and rapidly escalating headshakes that I've ever experienced.

So - the Avons were pretty well toast and based on what I've read here, I bought a set of Michelin PR2's. Pulled the wheels off Friday night and dropped them off yesterday morning at my local shop (Thin Air Motorsports - a shameless plug for a great shop) to have the PR2's and a pair of the Bike Effects 90 degree valve stems installed. They were done in a couple of hours and I had the bike back together for a ride this morning.

It is not a exaggeration to say that the bike is transformed with the Pilot Road 2's. Headshake is gone, handling woes are history - it turns in willingly, smoothly and predictably, holds a line perfectly - the biggest problem is that I'm going to wear out the outside edge of the soles of my boots.

These tires are what this bike is meant to be wearing. If you have headshake, wobble or handling issues, the first thing you should do is install a set of PR2's, make sure they are balanced perfectly and reassess the bike's handling. I have never seen a more dramatic improvement in the handling characteristics of a bike from one simple (and relatively cheap) change. If the wobble resurfaces as this tire wears, I'll consider working on the bearings, but the improvement in handling alone makes the change to the PR2's worth it.

Pete Bansen

Truckee, California