I think it's a combination of things.
For some of us, it has to be.
For others, one thing will solve the problem and they declare that the source of all speed wobbles/instability is the thing that resolved it for that person. This can make things very confusing to a person who is just casually working on the problem.
If there were an organized ride where 20 guys show up and swap rides for a mile, I think it would be much easier to find results. If all 19 bikes handle fine except mine, for example, then I suspect a bent frame or some other completely anomalous cause.
I've done enough ride testing now and one-at-a-time changes that if I were to ride any other vmax bikes for even a mile at a speed of only 60mph, I would be able to distinguish any differences right away... immediately. I've ridden other bikes recently (and at least 40 different bikes over the years), such as a friend's BMW and also even a Buell. The BMW front end felt slightly noodly given quick oscillating steering inputs but it immediately settled down; the inputs didn't translate through the frame from front to rear. That is an noticeably obvious difference right away. His bike is stable to 140.
My feeling on my own ride is that the wobble begins entirely at the front end and then translates backward. Trying to swap shocks and swingarm bearings and rear wheels and tires should help it settle down or maybe help with severity but after all the repairs and experiments that I've done, I'm just right back at the beginning - the front end.
If any of you have ridden basic bicycles on the road, let's say a road bicycle, you may know the feeling of having quick steering combined with large diameter rims with narrow tires and a shallow rake/trail angle: steering inputs, especially at low speed, make the bike feel like it wants to fall over into turns. However, if you then ride the same bike or similar but instead with fat tires (i.e., fat tire bikes), the feel may be quite noticeably different just with a tire change alone.
Since I'm refocusing back on the front end, I'll be trying to learn how much difference the front tire can make regarding the wobble. The 3 most obvious things to consider regarding the front tire would be:
- air pressure
- I've experimented with this but with the current brand of Shinko 230 tires, lowering the PSI has increased stability and increasing PSI has reduced stability. This makes me wonder if the lower pressure makes the profile flatter and contact patch larger, which leads to the next thing.... profile!
- tire profile
- The Shinko 230 felt entirely more responsive vs the worn ME880s that were on the bike. The profiles feel more curved and the in-town handling was immediately improved. However, high speed steering sensitivity also improved, making the front end feel less stable at speed.
- tread pattern
- The Shinko 230s also use a wavy center groove tread pattern and the ME880s and ME888s do not. I don't know if this is translating negatively in my situation but my gut is telling me that it might.
Sean has stated that he feels the ME880/888 tires are the best all around tires for the Max. Unfortunately, they are on the expensive side for tires. Additionally, some have also reported wobble with these tires as well as manufacturing defects. Many reviews I've studied indicate that they are less performant overall and definitely stick less in the rain. So yes, there are tradeoffs. Do you want to put your max into the curves or ride it fast in a straight line? The Shinko 230s feel outstanding from block to block and general riding. On my bike, they feel twitchy at high speed, despite their higher speed rating.
The ME888s are advertised as having a different contact patch and a 15% flatter profile for the heavier cruiser style bikes. By personal experience, when I removed the ME880s and replaced with Shinko 230s, I cut the ME880 front tire with a cutting disk and examined the profile mold and sidewalls. What was immediately apparent was that the ME880 front tire was much stiffer and had a thicker sidewall and tread base overall than the Shinko 230. The ME880 tire felt heavier and stiffer and stronger overall. My first impression was that I had made a mistake by buying a cheap Shinko of lesser material and thus lesser quality. Indeed, I can flex the Shinko tires right on the rim as they sit at full inflation pressure with my bare hands. I feel like the 230 tires are indeed softer, probably stickier, and definitely cheaper. But the bottom line is that might make them more performant for general use and curves and more twitchy at load on the freeway and at speed. Take with a grain of salt, these are just my observations and opinions. I am not a tire scientist.
So.... despite the cost of the ME888s, I am planning to swap out the Shinkos soon and mount up a set of ME888s anyway. That's a great (albeit expensive) way to be able to describe the difference between the inexpensive tire and the expensive tire, I guess. My hypothesis is that eliminating the wavy center groove, increasing the weight and stiffness of the tire sidewall, and flattening the profile further should settle down the front end a little more at speed. It will also give me the opportunity to reassess tire and wheel balance.
On a similar note, check out this Quora article regarding the speed wobble. This is an interesting take. Does the addition of more weight/passenger simply serve to keep the front tire more on the ground? Does more weight simply settle down the front springs, reducing bounce and increasing tire contact?
I have actually never found an example of a vmax owner who has done a swap to a modern (R1, hayabusa, etc.) front end and who has later reported a speed wobble. Maybe someone can find an example but, a front end swap would give you a modern fork, modern damping, larger fork diameter, better brakes, and of course, far more tire options. Or... in other words, a completely different set of engineering to keep the front tire on the ground and aligned straight ahead!
