MT09 (FJ) Tracer Steering Wobbling

[wessie]

Ok, so I called Givi and no, there isn't an official speed limit on the cases but he did say that yes, they used to mold a "don't exceed speed" into the lid and that if they don't anymore, 75mph should be considered that advisory limit. "I personally ride faster than that and haven't had a problem". 
So, to your point @wessie, I wasn't saying "YOU'RE GONNA DIE" but that you should think good and hard because you're opening yourself up to the aerodynamics making everything go pear-shaped in a real hurry.

I've been riding bikes for decades with full luggage on German autobahns quite legally at speeds greater than 140mph. I know what it feels like when a bike gets out of shape due to inappropriate speed for the conditions, with or without luggage.
 
I'll do my own risk assessment based on the conditions on the day. As ULEWZ says, in crosswinds one has to be mindful of the effect of the luggage on handling especially a topbox which has a leverage effect in a crosswind. In relatively still air, or with a tail wind there is little adverse effect. In fact, the additional mass added by the luggage will counteract the effects of lift. This is simple physics. 
 
Givi's warning are set by their lawyers not based on the laws of physics. They put a "no more than 10kg" label on a rack, then make a case that weighs nearly 10kg when empty. Go figure.
 
Why does Yamaha have a 115mph limit in the USA but no limit in the UK? Merely because people in the USA are more litigious. In the UK we are more likely to admit we got it wrong, not look for a design flaw in the bike and phone our lawyer. 
 
The difference in our perception of the risks of going at speeds over 75mph with luggage fitted is cultural, not based on the laws of physics. 

[pattonme]

I eagerly await your experience riding a luggage equipped FJ09 at 140mph with accompanying video footage of the fork action. With or without a stabilizer.

[wessie]

I eagerly await your experience riding a luggage equipped FJ09 at 140mph with accompanying video footage of the fork action. With or without a stabilizer.

You have veered off on a tangent. You are claiming the handling of the bike is suspect at speeds over 75mph with luggage fitted. Please stay on topic if you want to have a coherent debate.
 
What you suggest won't happen. If you read other threads in the forum you will see my views about the high speed stability of the Tracer. Possibly scroll back a few posts in this thread.
 
To reiterate my views, the Tracer is absolutely fine, cruising all day at 100mph with 2x Kappa K40 side cases on a French autoroute. Each case is 40 litres in capacity and weighs about 10kg with contents. I have accelerated up to 120mph for brief periods to get past traffic without any terrors. Above 120mph the aerodynamics of the upright riding position make the bike an unpleasant place to be so I will not be exploring the upper speed limit of the bike which is around 138mph according to a few Youtube videos.
 
The fastest I have been on my Tracer is an indicated 134mph, hitting the rev limiter in 4th gear. This is the only time the handling got truly unruly. That was more about the rev limiter cutting power and then reapplying power when I backed off. Fortunately the unruly behaviour was a relatively mild tankslapper, not severe enough for me to consider a steering damper.
 
So, if you wish to continue to insist the bike is inherently unstable at speeds over 75mph with luggage fitted then I will, based on my real world experience, continue to press the bullshít buzzer. 
 
 
 
 
 

[Guest dmizer]

Why does Yamaha have a 115mph limit in the USA but no limit in the UK? Merely because people in the USA are more litigious. In the UK we are more likely to admit we got it wrong, not look for a design flaw in the bike and phone our lawyer.

Completely unrelated, but the Japanese are not litigious at all, yet have a limiter. I believe (not positive) the Australian model is also limited. Litigation culture in the US has nothing to do with the limiter.

[pattonme]

It was the Givi rep's suggestion that the advisory be drawn at 75mph, not mine. You're misreading my posts to somehow conclude I said the FJ was necessarily unstable at 75mph with luggage. The closest statement I made to that figure was that I doubted the bags were certified for anything higher than 70 (certified != disaster if you exceed), and that if going 90+ it's a bad idea to do so with luggage. And if you're going to ride like that anyway, that one needs to make sure the bike is balanced and suspension adjusted to compensate properly for the weight, and that you can probably help matters by getting rid of the panels that are trapping air.
 
Well, at least we now know that dual Kappa 40's on your bike are fine up to 120mph. Speed away!

[wessie]

Why does Yamaha have a 115mph limit in the USA but no limit in the UK? Merely because people in the USA are more litigious. In the UK we are more likely to admit we got it wrong, not look for a design flaw in the bike and phone our lawyer.

Completely unrelated, but the Japanese are not litigious at all, yet have a limiter. I believe (not positive) the Australian model is also limited. Litigation culture in the US has nothing to do with the limiter.

Odd really. Perhaps Europeans are riding gods? It must be a nurture thing as many North Americans and Australians are European by DNA. 
 
 
 

[suncoaster]

The Australian model is not limited.
Top speed has been quoted at an estimated 280km/h in AMCN Vol 64 No 18, (I'm not likely to go that high).

[pattonme]

In Japan if it's not class-based licensing limits (ie bikes between 600 and nana-han), general certification limits, I'm sure it's nationally imposed top-speed limits. I don't know why the limiter in the USA aside from the fact that unlike every rational country, we don't have mandatory and rigorous rider training.

[skipperT]

Interesting stuff. For the most part.
 
Couple things I'm wondering about:
-I've experienced slight head shake on multiple FZ 09's as well. Usually when accelerating hard from 80-105 mph. Based on that, I feel that this particular chassis design/set up is prone to head shake. Could be the rake/trail numbers and height of the bike, (I'm no engineer.)
 
My point is, that yes aerodynamics could lift the front forks slightly at speed on the FJ 09 but how do you explain the FZ 09 as its a naked bike without the FJ fairing?
 
-secondly, I still feel that better steering head bearings are the answer. This is the fix on all GL1800 goldwings, all years, even after multiple suspension and tire changes have been attempted and failed to correct the decel-wobble.
 
-skip

[skipperT]

Oh, and IIRC the instruction sheet that comes with the Yamaha hard cases has a maximum speed suggested of either 75 or 85 mph (forget which one).
 
-S

[pattonme]

head stock bearings could very well be a contributing factor - it's not like there haven't been other 'huh?!?' headscratchers. The FJ/FZ have shorter wheelbases than Ducati Monsters but longer than the SV650 and CBR600 but I don't know the relationship of the swing-arm length. There's also chain angle to consider. If you have a copy of Tony Foal's chassis dynamics software, we could punch those numbers in and see what it says.
 
Anyway the point is these factors and the torque of the motor, many owners have first-hand experience with the front to get light/wheelie-prone, more so than many bikes currently on the market. It makes for lively, responsive handling around town but not a good thing for high-speed stability or when under heavy acceleration. If you moseyed from 85-105 I expect you wouldn't get so much as a twitch unless the rider trying to hang on while being blown about was introducing steering inputs.
 
Yes, I agree Yamaha purposely designed it to be wheelie-friendly - who doesn't like to hoon, right? And the press will make a big point of selling that to all the "young kids" who think that's how you earn your coolness badge. Or maybe they assigned the design to a young, inexperienced team (the FZ07 just reeks of neophyte engineers getting their first crack at design, and sourcing crap metallurgy parts from cut-rate suppliers) that has no hard-earned knowledge about designing in stability. I'm slightly tempted to chalk it up to the latter. The -09 engine, however, was clearly done by guys who know what they are doing.
 
 
This series of Yam FZ/FJ07 and 09 have IMO such badly done suspension both front and rear such that somebody over in Japan Inc. should be banished into the mountains for bringing such 'haji' to the company. Even with revised suspension, properly torqued headstock bearings, and proper balance, I doubt the headshake tendencies at 100+mph and earnest throttle application will change that much. For the FJ I'd rip that plastic out because I expect that will make a perceptible difference. And put a longer swing-arm on it.

[captainscarlet]

This bike has a big 'pocket' for air pressure to build up at speed (80mph+) and Yamaha has blocked off spillover on the sides and upward flow. If you look at the Z1000 tourer, the old FZ1 and a bunch of others that can (and are) ridden pretty fast, they don't have the shrouds and they have noses that are canted downward. The FJ has it's 'mouth' open wide and angled upward to catch as much wind as possible. What you need at speed is downforce and the Yamaha is designed for lift; never a good idea.

 
I'm sorry but surely that's bollocks isn't it. The Tracer has no more of a gaping mouth than virtually any fully faired of half faired bike. In fact if you look carefully (actually you don't need to look carefully) there are huge amounts of daylight between the forks and the fairing which allow air to pass up through the area where the triple trees are. Also there's loads of gaps between the top of the radiator and sides of the tank. The Tracer could never be described as aerodynamic and I don't find it credible that the front end is generating lift. The bike has far too many angles and (as far as airflow is concerned) messy details that disturb airflow.
 

As to the forks, this is what contributed mightily to my Triumph's stability issues. I had 10mm more preload in one leg than I had in the other. At 80mph even with 50lbs of luggage on the back it was no problem. Just steered a little odd - left was easier to initiate over right. With the shock not sufficiently preloaded for the bag contents I was running nose-light which set up and then quickly escalated the head shake once aerodynamic forces had built up enough.

 
Hang on a minute I'm not sure I follow your logic here. As I read what you've written above your suspension was wrongly adjusted and the bike got out of shape. Surely that should tell you that it is always prudent to check your suspension and adjust it according to the type of riding you're going to be doing. The situation with your Triumph has to my mind nothing whatsoever to do with the Tracer.
 
I have been following this thread with some interest and it seems to me that most people have "solved" their difficulties by adjusting the suspension correctly and not holding onto the bars for grim death whilst riding. I was out for a fairly spirited ride during the week and barrelling along some extremely bumpy Swedish roads at around the 150-160 km/h mark. The bike never once got into a wobble. At one point I touched 200 km/h and still nothing. As others have noted if you hold the bars too tightly your own arm inputs and wind on the upper body can induce oscillating steering inputs that could be interpreted as a wobble. Of course I too have watched the videos where people have got a wobble on and would suggest that like any powerful, quick steering bike, when the front end gets light, for whatever reason things can start moving around.
 
What is it I'm trying to say? I'm at odds with the idea that the Tracer is fundamentally flawed or dangerous or that people should "start ripping plastic off to make it safe". To my mind this is simply not true.
 
All IMHO of course.
 
CS
 
 

[wessie]

 
What is it I'm trying to say? I'm at odds with the idea that the Tracer is fundamentally flawed or dangerous or that people should "start ripping plastic off to make it safe". To my mind this is simply not true.
 
All IMHO of course.
 

 
I'm glad it's not just me smelling high amounts of speculative bullshit and dubious application of the laws of physics in this thread.
 
I've been riding a naked MT/FZ09 for the last 2 days as my dealer didn't get my 6000 mile service finished yesterday. The bike has a reputation of being a bit wild. Unfounded in my view.
 
Both variants of the MT09, naked or Tracer/FJ, are good bikes that anyone can enjoy. There are niggles but nothing that makes the bikes inherently dangerous. As you say, if people relax when riding they will enjoy the ride. The problems are mostly in the rider's head, not the bike.
 
 

[pattonme]

the issue with lift isn't that the fairing is "flying" or acting as a foil. I don't have access to a 120+mph wind tunnel but there isn't "huge amount of daylight" between the forks and the bodywork - Yamaha put blanking panels in there to keep the cockpit area calm but the side-effect is it traps air. It is my contention that the lift is coming from what amounts to a 'ball' of high-pressure air trapped in the nose to radiator section. Look at the FZ1, the FZ8, the versys 1000, sv1000. Only the FJ has such large vertical distance between fender and fairing nose. The others also have downward sloping noses which helps to reduce the build-up. The 1st gen FZ6 has an upward angled fairing like the FJ and modest side-curtains so from an aero perspective it probably has similar tendencies.
 
I'm not sure how my words got twisted into that the FJ was dangerous to ride. ANY bike ridden at the edge of it's stability envelope and with objects producing dirty-air is no longer safe. I could put side or top cases on a CBR600 and the results at 120mph+ probably wouldn't be pretty. The point was that over 100mph aero forces really start to assert themselves. It is therefore no wonder that introducing hard cases, top boxes, or unbalanced suspension that things can go from just fine, to iffy or worse in a moment of time.
 
I mentioned the triumph situation simply to point out that had I been running clean, I probably wouldn't have crashed. Yes the bike was inherently unstable. But without the bags, the turbulence coming off the side cases would not have induced shakes into the chassis, nor the weight caused rear squat nor some degree of weight transfer fore and aft. All of it combined to lead to a nasty crash. Perhaps my word of caution is over-blown. Take it or ignore it.
 
The reason I chimed in in the first place was that it one shouldn't mask handling and chassis dynamics problems with a steering stabilizer.

[captainscarlet]

the issue with lift isn't that the fairing is "flying" or acting as a foil. I don't have access to a 120+mph wind tunnel but there isn't "huge amount of daylight" between the forks and the bodywork - Yamaha put blanking panels in there to keep the cockpit area calm but the side-effect is it traps air. It is my contention that the lift is coming from what amounts to a 'ball' of high-pressure air trapped in the nose to radiator section. Look at the FZ1, the FZ8, the versys 1000, sv1000. Only the FJ has such large vertical distance between fender and fairing nose.

 
Sorry to keep banging on about this but what you've stated in my opinion simply isn't correct. If you look at the bike from side-on the radiator is angled downwards and backwards. This means any air striking the front of the bike is mostly directed downwards towards the downpipes and engine.
 
Any air channelled upwards can easily escape in the space around the steering head and up through the cockpit area.  Below is a picture looking down through the handlebars. As you can see there is plenty of space to allow air to be funnelled up through the gap. In fact on full lock I can get my arm through that gap.  The second image shows how it looks with the bars straight.  I simply can't understand where air would get trapped, sufficient to lift the front end/extend the forks.  The more likely cause of the forks extending in the video you referred to is that the rider's weight shifted backwards as speed increased. Likely combined with them pulling on the bars in the process of holding on as the speed increased thereby causing the forks to extend somewhat.