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

[Fire-medic]

Does anyone know how to match progressive fork springs to rider weight?

They don't. "One size fits all." You might try changing the oil weight from factory spec, and experimenting with pre-load tube lengths. P.S. front springs aren't supposed to run w/air pressure.

It may be tedious, but the best way to research this is to change 1 thing at a time.

 

[Dansmaxresto]

Do you have a fork brace on it? What tires are you running? I had bad weave running Dunlops. They seem to have a more triangular profile.

 

[Shuriken]

Do you have a fork brace on it? What tires are you running? I had bad weave running Dunlops. They seem to have a more triangular profile.

Shinko 230 at the moment. I think the ME888 would be better. The ME880s I had on it were replaced due to age but they were a much beefier tire and the 888s are being advertised as having a 15% better contact patch due to profile changes. The 230s definitely have a more triangular profile on the front. Dropping to 36psi helped calm the front down a bit but they also feel stickier by default.

No fork brace yet but I am looking for an affordable option to try. Worst case is that it doesn't do anything but even if it helps a little, I'd use one.

The step I am on now is to trade my 412 rear shocks for the same shock with a lighter spring. That's just obvious by the feel of the ride, sag, etc., but should also affect the feel of how it handles as well. As soon as I can ride test those and settle on the spring settings, I'll get another set of progressive springs for the front forks and make some educated guesses on what to put in there. While waiting for lighter springs, I will also be checking the swingarm bearings.

I am currently operating on the premise that the suspension A) hasn't been damping properly (leaking shocks) and B) has been configured for a much heavier load (heavy springs). I'm assuming that this is one reason why the handling has been so springy and unsettled. For example, when I do get the springs working, it either wants to buck me off or won't settle down. The changes I made yesterday (lower psi in tires, 0psi in front forks, 45lb backpack) noticeably settled down the speed weave quite a bit, so I believe I'm on the right track, and changing one thing at a time is definitely a better way to proceed.

Yes, everything contributes for sure. And there is tremendous piece of mind knowing that the tires, brakes, fork seals, and steering bearings are new, even if their contributions are minimal. None of this is a waste. Especially the brakes. I have legitimate 2-finger braking on a 40yr old 600lb+ bike, now, for one thing. If I can get the high speed feel settled down, I won't have anything else to complain about lol. Maybe then I can do some performance tuning...

 

[Shuriken]

Alright, finally got through to Progressive Tech Support. They said the shock I had (412-4212C) was the Standard Duty shock for the VMax that they recommend and the next lighter spring (412-4211C) is for an XS-650 and that they can't honor the warranty if installing it on the VMax. Funny, because I once had an XS-650 also.... Unfortunately, my solo riding weight is at the lowest end recommended for the 412-4212C. So I know the 412-4211C would be a lighter spring. I guess I can always eat more...

They recommended the 11-1129 springs for the front forks but unfortunately, I don't know what I have in the front end right now as is....

 

[Shuriken]

Latest test.... I had some unused spare forks with the metal spacers just under the caps. Both sets of spacers I have are around 5.5 inches long. I am not sure what pipe (PVC) diameter can be used during testing, so I decided to just cut the spare pair down to 5 inches and see if I could detect a softer front end by unloading the springs a half inch. I could not determine any significant difference during a ride test. I will probably remove another half inch and test again but for now, on to different items.

The next check will be to remove the rear wheel and test the swingarm bearings for side to side play as well as other characteristics as per the manual. I neglected to remember to do this when I changed the rear tire.

 

[Shuriken]

Good and bad news.

Swingarm is sloppy, especially side to side! Clearly not right. I may have identified the main culprit I have been chasing...

 

[Shuriken]

Good and bad news.

Swingarm is sloppy, especially side to side! Clearly not right. I may have identified the main culprit I have been chasing...

My best guess is the swingarm collar bolts were simply improperly adjusted for who knows how long. This made side to side slop in the swingarm.

Combined with blown shocks with no damping, any turn would cause an over oscillation hinging effect until springs would settle down.

With all the work I've done so far, as long as the swingarm fits properly upon reassembly and with new bearings, if I can get the slop out, combined with new rear shocks, this bike should be safe smooth and stable at all speeds.

Crossing fingers for next week when bearings show up and I reassemble...

 

[Shuriken]

Strange/uneven wear pattern on swingarm races....

 

[Fire-medic]

I suspect that the swingarm bearing was tightened excessively, causing the exterior bearing race and the bearing itself to distort dimensionally, under-load, and that's what caused your wear pattern.

You are referring to the 4 o'clock 'wrinkles?'

 

[Radioguylogs]

I haven't done the swingarm on my Vmax, so I'm imagining the bearings are tapered rollers, and not ball berarings.

A few things seem peculiar to me.

I am used to seeing the wear look like stripes where the rollers touch the race. The steering and the swingarm bearings don't rotate and they spend most of their time in the same position.

• That race doesn't have stripes where the rollers would touch it.
• The wear is in the middle, and not on the inner and outer areas.
• The wear groove has uneven thickness around the circumference.

Make me think the wear was caused by looseness.

 

[Shuriken]

Actually, I wasn't referring to the 4 o'clock pattern. I think that was a bit of grease. I was referring to what appears to be 2 wear bands: one at the deepest section of the race and one at the shallow end.

The wear I saw on the steering bearings when I did those was consistent with Radioguy's description: vertical wear stripes.

This looks to me like evidence of how the swingarm felt: sloppy side to side, like the roller bearings and cage were not fully seated into the races....

I'm expecting to reassemble and test by next weekend if rubber boot doesn't monkeywrench the job...

 

[Shuriken]

Swingarm is back together with new bearings. Torqued properly, it is rock solid and smooth.

Purposely rode it with the OEM shocks just to test and could not tell any improvement in wobble.

So then I installed the Progressive 412 suspension and tested again. For sure the progressive suspension is better at damping than OEM but it also did not sort out the wobble.

So.... back to the front end.... will start with shortening the spare fork preload spacers I have.

It's awesome to have good bearings now. No regrets.

The middle gear boot was exactly as I expected. 40yrs old, torn, and unable to reassemble to my satisfaction.

I'll work on that again another day and try to install a new one. But for now, back to the front..

 

[Shuriken]

So draining the fork oil and replacing it with 5w synthetic really softened up the front end. Damping is working. Static sag can be set. The forks are definitely working now. So I feel like I can go back to changing one variable at a time on the front end and test because the forks feel too soft, now.

However, I had hoped that softening up the front forks had to be the remaining issue in terms of causing the instability at speed but........ this change did not correct the issue during today's speed test.

The only things I haven't done on the front end:
- wheel bearings
- change wheel/rim
- rebuild forks internally (bushings/etc.)
- fork brace

Wheel bearings and rotors are next, because they are easy and relatively inexpensive. Running out of things to try but have enjoyed the process anyway.

 

[Fire-medic]

You can mix 10 wt and 5 wt 50/50 to get 7-1/2 wt, if you're close to where you need to be.

 

[Shuriken]

So.... new rotors arrived. I installed and buttoned back up and before repressurizing the brake calipers, I gave the wheel a spin and ..... dang. There is a slight drag on the pads at a spot on the rotors. I don't have a runout gauge but I can see some runout on the rim but admitttedly, I'd be quite surprised if the rim is bent close enough to the hub to affect the rotors. I'll have to do more investigation.

Nevertheless, while I don't think runout alone would cause the high speed instability, I'll be looking around at wheel options as well. If I'm not mistaken, the wheels should be interchangeable and the bike does not have the lighter 85 rims on it now; they are from another year.

 

[Fire-medic]

A sheet of glass and some old-fashioned feeler gauges should allow you to measure if the rotor is machined incorrectly. You would have to remove the rotor from the wheel though which probably would mean new rotor-retaining button machine screws.

As you mentioned, a fixture to hold a runout gauge would also work, and wouldn't require rotor removal from the wheel. I'd say, try measuring the 'hop' point, record the amount, mark it with a Sharpie, and then remove the rotor and using a piece of glass and the sheath of feeler gauges, see how that measurement compares to the runout gauge measurement.

Because of the rotor carrier and the retaining hollow rotor/carrier 'buttons,' you can't just slap the rotor onto a piece of glass, you would need to position the glass diagonally-across the rotor at the point where you found the 'hop,' being in the middle of the glass piece. Then measure the rotor to see what the out-of flat measurement of the rotor is. If you don't send the rotor back for exchange, probably a machine shop could make it flat again.

 

[Shuriken]

Ok, I got a runout gauge.

Looks like what I was hearing yesterday was probably just machining mark changes on the rotors. The gauge indicates no runout on the new rotors. Awesome.

Of course I can also use the gauge on the rims as well and it is more accurate than the eyeball method. The gauge measurement on the worst spot of the rim shows .030 of runout. Surprisingly, Yamaha says up to .080 is ok.

So wheel runout is within limits and rotors are true.

Wheel bearings spun freely don't appear to grind or catch.

So other than internally replacing fork bushings, looks like I'm about out of options...

 

[Shuriken]

Wheel bearings done.

The only things I plan to try before giving up will be possibly internal fork bushings and probably at some point I will abandon the Shinko 230s and go back to Metzlers.

 

[Shuriken]

https://www.sae.org/publications/technical-papers/content/780307/

"From the results it is very clear that the most important parameter affecting stability is lateral stiffness"

Gonna take an approach from this point of view and drop in some new progressive springs and start over on front fork tuning. This would start with a known quantity of spring length and hopefully the spring rates are consistently similar. This should help hedge against any dissimilar current fork rates and potential uneven rates between forks.

My current springs measured right about 19" in length and manual calls for 19.2 minimum, although I still don't know the length of OEM 85 springs, new....

Since the front fork oil change, the forks definitely are working but are way too soft, now, and with too much sag. When wiggling the bars on with the bike on the center stand, the forks feel a little sloppy (I know they aren't loaded with full weight), so I put some tape on the fork tubes to observe travel. Too bad I don't have a newer bike in the garage to perform the same test for comparison.

 

[Vincent Beck-Jones]

https://www.sae.org/publications/technical-papers/content/780307/

"From the results it is very clear that the most important parameter affecting stability is lateral stiffness"

Gonna take an approach from this point of view and drop in some new progressive springs and start over on front fork tuning. This would start with a known quantity of spring length and hopefully the spring rates are consistently similar. This should help hedge against any dissimilar current fork rates and potential uneven rates between forks.

My current springs measured right about 19" in length and manual calls for 19.2 minimum, although I still don't know the length of OEM 85 springs, new....

Since the front fork oil change, the forks definitely are working but are way too soft, now, and with too much sag. When wiggling the bars on with the bike on the center stand, the forks feel a little sloppy (I know they aren't loaded with full weight), so I put some tape on the fork tubes to observe travel. Too bad I don't have a newer bike in the garage to perform the same test for comparison.

I did this, put progressive springs in.. Mostly because I dropped my front end an inch and the front fender was rubbing when I braked. It changed my speed wobble a little bit in terms of what speed range it occurred. I did the "drop test" where you lift the front wheel and allow it to drop when you turn it. I ended up tightening the the steering bearing nut and it solved the speed wobble up to 120 (there's only so fast you can go down my street at 10 pm.) Then I had it in the shop getting it rejetted due to an exhaust change and they said my bearing and race were worn out. Now my slow speed wobble is back. I will try tightening the head nut again since it's new. Mine is a 2007.