V-Max Speed Wobble (ran it up to 115mph and...)

[Shuriken]

Most recent set of changes: tighten the steering head bolt a bit more (not the bearing nuts), swap out the front axle, spacer, and speedometer clutch with newer ones.

One or more of these changes made a slight but noticeable improvement.

I should have another wheel arrive this week, which hopefully has better intrinsic balance and less runout than my current one. Also waiting on Yamaha OEM wheel bearings and even the spacer that goes inside the wheel hub. If the wheel inspection looks good, I'll install new bearings and reassemble, probably move the Shinko tire over to the different wheel, and try things out carefully by increments.

I did a 50mile x 2 test ride yesterday and was more careful about observations.

It was windy and I notice that like the centerline on the roads, wind buffeting alone can begin to induce the wobble. I don't think having any loose clothing at all (which can be subject to buffeting at speed) does anything but contribute to the wobble. So I'm also going to figure out some solutions there. Facing into a substantial headwind and with some clothing buffeting, anything more than 85 felt iffy. However, on the return leg with more of a tailwind, there were stints to 95-100 that were more confident. I spent a lot of time on the return leg at 85-90.

Another test I performed, which I'll have to do more of, was to slide back onto the rear portion of the seat. I can reach the bars and still do this, and it felt similar to what Brian describes when carrying a passenger. I will have to carefully test this further but it may be similar to when a wobble is induced, one shouldn't grab a handful of front brake, because that may shift more weight onto the front end and can make the wobble worse (or at least that's what has been discussed before). So if this weight shift can serve to stabilize the front end, that will continue to be a clue. It will take more careful testing to decide.

Another thing I did was try to carefully observe the front forks at speed. What I observed may be normal or maybe not, but I can see fork vibrations; it looks like much of the vibration is in the forward/aft direction of travel. Almost looks like..... spaghetti forks! I'll have to borrow a more modern ride and observe and carefully compare. Hard to describe and maybe it's just doing what it's supposed to but this is where wheel balance might also come into play. Not huge vibrations coming up into the bars, but maybe worth closer investigation.

 

[Fab333]

Can you send pics or send a link to the damper you installed?

 

[brian hicks]

I notice the rear damper setting effects it greatly so have just ordered YSS shocks. I will keep you informed.

 

[Shuriken]

I notice the rear damper setting effects it greatly so have just ordered YSS shocks. I will keep you informed.

Just to be clear, spring pre-load or damping?

I tried Progressive 412s but will wait for your testing results. There are definitely more tunable shocks out there than mine...

 

[Shuriken]

Another front rim arrived yesterday. I was able to get the old tire off (k591 elite), move the new Shinko off the bent rim and over to this one. Now I have to remove the wheel bearings and use reinstall new ones as well as move my new vented rotors over and then I can try out this different rim.

I was hoping my manual tire changer would work for motorcycle as well as car and truck tires but the center post is too thick to pass through the motorcycle wheel hub without some sort of adapter. In any case, being able to work on the tires and wheels myself definitely opens up the possibility to try different tires and wheels more economically.

Hopefully my bearing puller will survive a couple of wheel bearing pulls so I can test and report today or tomorrow.

 

[Shuriken]

Bearing puller kit made easy work of the wheel bearings.

Test rode with the different wheel. The tire definitely appears more true. I can see that when I ride. Bought me just a little more stability, I think. Runs up to 95 were slightly improved.

I can try one final thing up front and that would be to install an ME888 based on the idea of the 15% flatter profile. The Shinko, as I said before, made the bike more responsive. I think the ME888 would walk that back.

For now, I will focus on the rear wheel now. Wouldn't hurt to check replace the rear bearings.

Also planning to have a friend follow at about 65 and when I do some short steering inputs, I will have said friend try to observe any wheel or suspension oscillations.

 

[Shuriken]

Some other observations. Consider these pics.

The center shaft is pinned and for a bit, I thought that however unlikely, if the pin had any slop, there could be a problem there but I've moved beyond that thought. I think the center shaft couldn't possibly be a problem and the crown nut and pin work together to keep the center shaft from spinning anyway.

It is a possibility however for the upper bridge and lower bridge to fall out of alignment under stress or steering inputs if the upper and lower fork pinch bolts are not tight, become loose, are not installed, or otherwise ineffective. In other words, when looking at the second pic at the steering stem crown nut down, if there is any slop at all between the upper tree bridge and lower bridge, there would be a steering misalignment, and under quick inputs, this could result in an elastic or springy behavior from the front end. If this occurs and the rear frame then has a delayed following response, this could definitely contribute to a wobble. The only way I can think of addressing this possibility is to simply make sure the pinch bolts are snug to spec. after properly aligning the upper and lower bridges. If anyone has any scientific or precise way of doing that, do post a response.

The fender mount is another possible area of potential easy improvement and I plan to install an actual fork brace. As I've posted before, the Yamaha fender mount leaves plenty of slop/clearance, perhaps even too much. I found a pic online of a typical fork brace and have circled in blue the areas of improvement over OEM. In the 3rd pic, you can see that the fork brace is designed to have closer tolerances. If there is any slop at all from the OEM fender mount, a brace should be an improvement just by virtue of closer tolerances alone. However, what may be happening when people install a brace and then report that it didn't solve the issue is that this might just be because making one area of the bike more solid without addressing the other areas might just transfer more of the problem to another area. So for example, if the swingarm is sloppy but then you tighten up the front end, more slop could transfer to the swingarm and the bike potentially could feel worse.

I think trying to chase the speed wobble issue on the max is like trying to iron out a bubble from a sticker: the bubble just gets pushed to a different area until you touch all areas!

 

[Fire-medic]

make sure the pinch bolts are snug to spec. after properly aligning the upper and lower bridges. If anyone has any scientific or precise way of doing that, do post a response.

The factory manual has the proper tightenting sequence for the front end and the torque values are in the suspension chapter, as well as the appendix, where all the nut/bolt sizes are listed and their torque values.

https://ia800204.us.archive.org/14/...ice-manual/yamahavmaxvmx12-service-manual.pdf

To attain best results from an aftermarket fork brace, such-as the Superbrace, go back to the factory manual, and follow the correct sequence of torque values on the nuts/bolts.

 

[brian hicks]

Just to be clear, spring pre-load or damping?

I tried Progressive 412s but will wait for your testing results. There are definitely more tunable shocks out there than mine...

I set the rebound to 2 on the left and 4 on the right and it made a difference. I have now replaced them with YSS suspension and can get to about 100MPH before the weave gets scary. The YSS only has pre-loading and no adjustable damping. The next step will be to replace the tyres.

 

[Shuriken]

I set the rebound to 2 on the left and 4 on the right and it made a difference. I have now replaced them with YSS suspension and can get to about 100MPH before the weave gets scary. The YSS only has pre-loading and no adjustable damping. The next step will be to replace the tyres.

What led to using different settings? Just curious.

I just did a 70m ride with wife and the bike is as stable as a rock with the 2 up and extra weight....

 

[Shuriken]

I set the rebound to 2 on the left and 4 on the right and it made a difference. I have now replaced them with YSS suspension and can get to about 100MPH before the weave gets scary. The YSS only has pre-loading and no adjustable damping. The next step will be to replace the tyres.

The 412 suspension I have also only has preload and no damping adjustments.

I'm beginning to think the vmx1200 was designed for 250lb riders and up. The steering head is firmly planted when 2 up and the bike feels entirely different and I'm well below that...

When 2 up, everything feels fine, with no fork brace and with shinko tires and all.

I think the extra weight just settles out the jitters. I may have to find a rear cargo box in which to add weight!

 

[brian hicks]

My 1200Vmax is more stable with my wife on the back .(She's a small girl.) Also if you try and sit further back in the seat you may see an improvement.

 

[Shuriken]

My 1200Vmax is more stable with my wife on the back .(She's a small girl.) Also if you try and sit further back in the seat you may see an improvement.

I've noticed exactly the same thing.

Our bikes must be siblings....

I wonder how the wobble would feel if one replaced the rear suspension with a couple of pieces of solid angle iron. No, not for the long term, just for testing the speed wobble. Imagine if a solid rear made the wobble disappear completely. What would that say about the rear suspension?

 

[brian hicks]

I'm beginning to think that the bike has an inherent resonant frequency causing the weave, (bit like the Tacoma bridge,) and changing tyres or suspension or engine mounts or virtually anything will effect it. To date I have 1.fitted frame braces. 2. changed front wheel bearings. 3. Changed front springs. 4. Fitted YSS rear suspension. 5. Tightened steering head nuts. My next step will be to lower yolk on the forks by about 1 inch. After that it will be a tyre change.

 

[Fire-medic]

What about solid motor mounts, delrin or aluminum? The Venture uses them.

 

[Shuriken]

What about solid motor mounts, delrin or aluminum? The Venture uses them.

I have considered that as well. It couldn't possibly make the wobble worse.

Frame braces perhaps as well, but the ones I have seen are for some reason ridiculously expensive.

Testing a solid rear would be a very inexpensive test. It should be as simple as drilling a couple of holes through 2 pieces of bar stock and swapping them in place of the rear shocks. But it would be best to test on a closed track without potholes....

However, since Brian and I have both changed the rear suspension, my next step is going to be rear wheel bearings and an inspection of the axle and spacers as well.

A test I am going to perform on the axles is to loosen axle pinch bolts and spin the axles to see if the wheels turn. This may help test for the presence of a bent axle.

 

[Woody]

I have considered that as well. It couldn't possibly make the wobble worse.

Frame braces perhaps as well, but the ones I have seen are for some reason ridiculously expensive.

Testing a solid rear would be a very inexpensive test. It should be as simple as drilling a couple of holes through 2 pieces of bar stock and swapping them in place of the rear shocks. But it would be best to test on a closed track without potholes....

However, since Brian and I have both changed the rear suspension, my next step is going to be rear wheel bearings and an inspection of the axle and spacers as well.

A test I am going to perform on the axles is to loosen axle pinch bolts and spin the axles to see if the wheels turn. This may help test for the presence of a bent axle.

Get Solid motor mounts !!!

 

[Richard Corbett]

Larger wheel, smaller profile on rear wheel.

 

[Vincent Beck-Jones]

I'm beginning to think that the bike has an inherent resonant frequency causing the weave, (bit like the Tacoma bridge,) and changing tyres or suspension or engine mounts or virtually anything will effect it. To date I have 1.fitted frame braces. 2. changed front wheel bearings. 3. Changed front springs. 4. Fitted YSS rear suspension. 5. Tightened steering head nuts. My next step will be to lower yolk on the forks by about 1 inch. After that it will be a tyre change.

I have been told the wobble is caused by the front and rear tire being slightly out of alignment due to the drive shaft. Individually the tire alignments track true but they are offset of a shared datum. This would also explain why extra weight farther back from the center of gravity would reduce the wobble. I wonder what type of experiment could be done to prove this theory? Hmm. Now I have something to spend my weekend on...

 

[Shuriken]

I have been told the wobble is caused by the front and rear tire being slightly out of alignment due to the drive shaft. Individually the tire alignments track true but they are offset of a shared datum. This would also explain why extra weight farther back from the center of gravity would reduce the wobble. I wonder what type of experiment could be done to prove this theory? Hmm. Now I have something to spend my weekend on...

I have also come across the idea regarding the offset centerline on the wheels of shaft-driven bikes. Some sources online have stated that what matters is that the rear wheel centerline conforms to the frame centerline, and that it can appear to be offset but really isn't. These sources weren't specific to the V-Max.

If you ride through some fine dust or sidewalk chalk, you can see the rear contact patch. I don't think mine has ever passed the eyeball test as far as looking like it is truly center. To be perfectly honest, it looks like the contact patch shifts a centimeter or 2 towards the driveshaft, when looking at the rear tire from behind the bike.

If this isn't an illusion, and is in fact true, this would make mechanical sense. The rear wheel hub gearing (rear pumpkin), whatever we want to call it, needs room and space to connect to the rear wheel. It would seem plausible that due to the gearing on the left side of the wheel hub that the rim and tire have to move a little off centerline towards the right side, which would indeed cause the contact patch to shift a centimeter or two..... to the left!

I think it could be plausible then, depending on the wheel profiles, for the bike to want to track more toward instability. At low speed, it might not necessarily be felt. But at high speed, slight inputs from rider, wind, bumps, etc. could exaggerate the natural instability.

So high mileage tires, which presumably might be more of a flat profile, might be slightly less prone to the problem because the contact patch, shifted off-center a centimeter or two, would still reside on a flatter portion of the tire. However, replacing worn or cupped tires with new ones, would restore the natural curved profile of the tires, making the bike feel more responsive by increasing instability.

This is all speculation and hypothesis though. It might be possible to make more accurate observations by even using the string alignment tests, in which a strings are extended between front and rear wheels.

Rear wheel alignments on shaft-driven bikes are fixed, if I am not mistaken, whereas on chain-or belt-driven bikes, the rear wheel is completely adjustable.

Speaking of tires and profiles, if anyone is willing to try the ME888 as their next tire, that could help. It will probably be the next set of tires I try but I need to wear these 230s out a bit first. Regarding the ME888 profile:

• From Metzler: "The structure and shape features a flat and wide geometry that conveys and dissipates towards the sidewall."
• From ChapMoto: "Contact patch is 5% shorter and 15% wider than the Metzeler ME880 tires for better transfers of engine torque to the ground."
• From various ride reviews: "The new structure has a multi-radius design, rounded sidewall and increased curvature. This all adds up to a wider footprint, which you may think decreases the mileage as there’s more rubber in contact with the road, but instead it does the opposite. The bigger footprint decreases stresses on certain points of the tire, increasing the high-speed stability, overall grip/performance and the mileage simultaneously. But this is far from the only area of improvement Metzeler was able to produce."
• From our own forum: "So far I love these tires. The Brigestones when new took away my confidence. Something about that profile made the bike feel like I was losing the front end sometimes. I put about 10,000 miles on those tires but never felt really confident on them. Just my feeling and I'm sure some people love that quick steering input. To me though, I was always worried on them. Now with the Metzelers and the more neutral rounded profile, I'm loving the turns again."
• Sean has stated he likes them as well: "880/888's are by far my favorite tire for all around use. The Shinko's for drag or street block to block riding."

Yes, I do regret going with the Shinko 230s but was thinking more about the budget at the time, and getting the best tire is difficult when half of your riding is, indeed, block to block riding!

I'd say the 4th bullet above really describes my ride interpretation of the Shinko 230 tires on the V-Max: I noticed immediately that the tires felt significantly more responsive. It really felt like the curve of the contact patch was increased so significantly over the ME880 tires I was using that the bike wanted to fall over much easier. Naturally, the front end became more sensitive at high speed... Of note, the 230s also have that zigzag centerline groove and the Metzlers did not.