I know it's an old thread. Went for a 200 mile run this weekend. I noticed that it gets squirrelly between 80 and 85mph. After that it seemed to smooth out past 85. Had it up to 91 but didn't care to go any faster. I've had sport bikes that would go 130mph. Did it once. Don't really care to do it again. I like twisties not long fast straights.
My strada feels squirrelly between 80 and 85, so I'm not sure you can blame the fender. no other non-aerodynamic accessories except a small (garmin quest) gps on the left handlebar.
Likewise, my strada gets to weaving between 80 and 85 as well. Stays pretty consistent up to about 105. I've got the factory extended windshield, a fandango tank bag (which at one point I thought was causing the shakes) and now a SE-540 as a tail case. None of those seem to have affected that behavior.
I went from a stocker Strada to one that has been mostly Terra and found it was all stable to 100 or so adding a windshield and changing to a Terra fender. Stability remained the same. Where it got a bit wobbly at 80-85 for me was switching the rear wheel to a spoke with a TKC 80 on it.
Just my opinion, but I think most high speed instability issues are directly related to tire choice/condition and suspension settings/set-up.
I agree completely. Nobody seems to be looking at their suspension or tires as a possible cause, and that is where most all problems start.
I'd agree with that. I've got stock tires on mine, it's always had that behavior at speed. Not really much of a concern because I rarely go above 75 on it. I've not touched the suspension, but I would imagine since it is sprung for 2 up, that could be responsible. I'm content to leave "good enough" alone on this bike tough, since weight varies so much if I have it loaded down or if it's just me.
My Strada now has 8k mles...a lot of slab running with traffic at 75-85 mph. I have a zumo 550 on the bars. Also 2 led lights from adv. monster model 60s. I have Motorsportz skid plate and just added a Hepco Becker rear rack. I have had a weave from time to time at higher speeds. I thought I had found the cause and blamed a pair of Touratech hand guards..with the added spoiler. I removed them and for awhile the weave seemed to vanish...but now it's back. I have experimented with air pressure...up and down with not much difference. I also have fiddled with the preload adjustment all to no avail. I did just add a new rear tire....that seemed to make it weave more...(I stayed with the Touarence exp) I have thought about pulling my accesories off one by one to see if it's the LEDs or perhaps the zumo? The bike has the factory available windscreen...it's quite small. There have been times when the bike seemed to be planted and didn't weave at all. After the new tire...it's pretty bad. I guess I need to slow down. That's what my wife says...lol
One of the first things I tried...I loosened my grip to the point of the throttle returning to idle...without any affect. This bike just likes to dance at speed and I'll probably just have to deal with it..or slow down. "Aero shedding"is the technical name I've come across a couple of times. Whatever you call it...I don't like it.! I still may try removing my farkles one at a time just to see if that offers any improvement.
My riding match the most of yours.. Pretty slab between 70mph and 80, but from this everything seems ok. Come to think much more to be with tires.. Somebody think about the mirrors, I will try without to see what happens.. Rear case, do not cause problems..
I have been trying to decrease or eliminate the high speed wobble on my Terra. I suspected the high front fender as a major contributor. Came across a Strada low fender on ebay, so I had to try. I used some 3/4 x 1/4 aluminium flat bar to raise the low fender above the stock mounting points I did two runs today, sporting the low Strada fender on a rough, straight, slightly uphill road in breezy conditions that always started the wobble on my Terra at about 80 mph no matter what tire, tire pressure, suspension setting and load. Big improvement !! Still twitchy but no wobble !
I did a couple high speed runs on my Terra when it was stock and had no problems. It seems like it didn't start shaking until after I put hand guards on it. Maybe they mess with the aero of the bike?
When you fitted the hand gaurds, did you put the original bar end weights back on? Also the forks can be dropped in the tripple clamp, the Strada has the forks at a different height to the Terra, this in combination with the wheel diameter will effect handling.
I don't see what bar end weights have to do with aerodynamics? Can you specify ? I always thought bar end weights were for reducing vibrations in the handlebars ?
Hey jon, quick off-topic question about your HDB risers and top clamp. I have the same setup and had to elongate/round out the holes of the risers to fit the bolt pattern of the stock triple clamp. The top clamp fit fine (after they sent the right one a second time around), but just curious if your risers were a good fit as sent.
Aerodynamics are a super complicated issue and while two separate factors might not create instability, those same two factors working together very well might. Any motorcycle has a LOT of factors and it is impossible to analyze them through any means other than a wind tunnel. (I.e., it can't be simulated by a boffin working on a computer.) A quick look at the airplane world will show a lot of smooth lines (ex. P-51 Mustang) and very few sharp edges until you get to compressible flow (ex. F-15) at the transonic barrier and beyond. Our Terra/Strada have a lot of sharp angles, probably for cosmetic reasons. The radiator shrouds. The fenders. The headlight nacelle. As you speed up the flow becomes more turbulent and the energy is dissipated by vortex shedding. The boundary layer breaks down more quickly around sharp edges leading to well-shaped vortices that carry a lot of energy. This vortex shedding is periodic and can set up oscillations. I think our TR650s lie somewhere near the transition from laminar to turbulent flow and minor changes can push it one way or another. Even air density can play a major role and is affected by temperature, humidity, altitude, and weather systems. I have one bike that I know for a fact buffets more as the air density goes down (warm/humid) but can be very quiet when it is cool and dry outside. The state of the air striking the bike will also have a major impact if it is either quiescent, like on an early morning country ride, or turbulent, if you are behind a truck. Passing through detached vortices and air with a lot of shear is an entirely different regime than passing through quiescent air which is why aerospace control systems are built with so much margin and then tested in all possible conditions. Same can be said for tires. Motorcycles are an insanely complex quasi-stable environment in which feedback plays a huge role. Aerodynamic oscillations that affect the frame can easily feed back into the dynamics of which the tires are a major part. Tire size, width, stiffness, surface roughness, heck even road characteristics, will have an effect if the bike is operating at the edge of stability. The only thing that's going to have as large an effect as tires are probably the rider, so yes, the grip is going to feeb back into the dynamics as well, along with what the rider is wearing, how much he weighs, how tall he is, where he's sitting relative to the CG, how he is leaning, how the suspension is set up, etc. In short, there is no one thing that's going to cause/uncause oscillations in all situations. Every ride on every bike is different. Ride the bike. Pay attention to the effect of mods. Be aware of how the air changes the handling characteristics of the machine. Learn when the bike oscillates and ride within the envelope you are comfortable with. Exactly as riders have been doing since motorcycles were invented. To me, this is part of what makes motorcycles such a enjoyable, challenging, rewarding experience. Bikes don't have riders. Bikes have pilots.
