Front Wheel Oscillation-Part 3: The Resolution (merged)

[omegajim]

adjusting the suspension didn't effect the oscillation; it doesn't really surprise me.

Fundamentally, the oscillation can only occur from the two spinning masses.

I find it interesting that changing the front tire changed the speed at which the oscillation occurs.

It appears you have ruled out the front wheel.

You are now forced to review the rear wheel.

If two large weights were placed on the left side of the rear rim and one weight on the right side of the rim, it's entirely possible your rear rim was never balanced properly.

It is important to understand that the weights can't just be placed on the light side of the rim, they have to be equally balanced on either side.

Imagine the axle as a lever (or teeter totter), with the counter weights (wheel weights) effecting which side is heavier. The rim is cast and is out of balance, as you've mentioned, but now, when weight is added, you can't add it to one side or the other.

It looks like a good shop will be required, and in all likelihood, more smaller weights will be used in place of the fewer heavier weights. To avoid the out of balance oscillation that you are having.

It still concerns me that the oscillation speed changed with the changing of the front tire.

[Clint]

I still hold that it's a poorly dampened front suspension. The braking exercise would only eliminate that possibility if it was a spring preload issue, not if the damping hardware or oil are insufficient. Changing the tire changed the period of the wave pattern because of differences in sidewall stiffness and tire pressure.

This is very similar to a high-speed wobble (the kind that can lead to tank-slappers), where natural suspension rebound action and inertia set up a standing wave bounce. I'd try heavier fork oil before paying a shop for a bunch of time.

[nicocorea]

Excellent input, guys! I wanted to upgrade my rear tire to a Metzeler 200 (to match the front), so I'm gonna order it from a different dealer than I've been using and have them mount and balance it. If that doesn't take care of the problem, I'll get the fork oil changed. I'll keep the forum posted of any developments.

[Easy Rider]

Originally Posted by omegajim

It still concerns me that the oscillation speed changed with the changing of the front tire.

I don't find that too surprising since the shop admitted that the original front was out of round.

[Easy Rider]

Originally Posted by nicocorea

.... so I'm gonna order it from a different dealer than I've been using and have them mount and balance it. If that doesn't take care of the problem, I'll get the fork oil changed.

Oops, you're backsliding now !

What happened to: Leave it at the shop for a few days and let THEM figure out what the problem IS ?? ........after you get the new tire, that is.

Not that it probably has any bearing on the issue but at 155, you might want to put the rear per-load down to the first stop.......if you seldom or never ride 2-up or with a lot of gear. Can tinker with that AFTER the other problem is solved.

[nicocorea]

This is the third and last in a series of posts about a problem I've been having with the way my new 2008 M50 rides. Links to the first two posts are below.

http://www.motorcycle-journal.com/fo...cillation.html
http://www.motorcycle-journal.com/fo...-part-2-a.html

n a nutshell, the front wheel on my 2008 M50 seemed to hop in the 40-55 MPH range, as if the front tire were out of round. The problem existed from the day I drove the bike off the dealer's lot, and today I have 2500 miles on the bike. After bringing the bike in twice to the dealer to complain--and both times being told the bike was perfectly fine, the dealer finally replaced the original IRC with a Dunlop for free. But the problem was still there. So I concluded that it must be the front wheel, not the front tire. I then took the bike to another shop (unaffiliated with Suzuki) and had them check the front wheel. They verified it was good, but said the Dunlop was bad. So next I bought a Metzeler ME880. The oscillation was still there after the Metzeler install, but the speed at which the oscillation occured narrowed to 50-56 MPH.

Folks on this forum offered many hypotheses to explain the oscillation. I tested each of them and ruled each one out.

Having confirmed that there was nothing wrong with anything in my front end and that there was also nothing wrong with the drive train either, I concluded the only possible source left for my front wheel oscillation must somehow be the rear wheel/tire.

Ever since delivery, it did have two huge weights clipped on to the left side of the rim, and another large one directly across on the right side of the rim. All three weights were on the opposite side of the rim from the stem (and where the tire's dot also was). I asked this forum if anyone could imagine any way that the effects of an out-of-balance or out-of-round rear tire or wheel would be felt in the front, and the consensus was that such a thing was possible.

So my final attempt to solve this mystery was to buy a new Metzeler ME880 for the rear (I liked the front Metzeler so much I figured this would be a worthwhile upgrade even if it didn't solve the problem). Unfortunately, the cheapest price I could find on that tire was at my dealer. But I refuse to spend another dime there, so I paid $40 more to buy and install it at an independent shop.

They mounted the new Metzeler with the dot at the stem and spun it. The balance machine called for 4.5 ounces opposite the stem. Rather than putting 4.5 ounces opposite the stem, the tech re-mounted the tire with the dot opposite the stem. Now the balance machine called for 2.5 ounces opposite the stem. So that's how it was mounted: dot opposite the stem along with 2.5 ounces of weight also opposite the stem.

I drove off and held my breath as I approached the oscillation speed. The road near the shop was rough, but I didn't feel oscillation. I rode to smoother roads and still no oscillation. I really can't believe it, but the problem finally seems to be fixed--$400 later.

While I'm elated, I'm also very pissed off. Why did my dealer--who's supposed to be a professional--not figure this out? Why did they dismiss my complaints and insist that there was no problem when there clearly was a problem? Why do I have a rear wheel that is so badly out of balance that from now on I have to tell tire techs to mount my rear tire 180 degrees off from where they normally would? Unrelated question, but why did one of the bolts holding my front caliper to the fork fall out less than 500 miles after delivery? (They claimed that the normal vibration of a new bike caused the bolt to come loose. That's a ridiculous excuse for a potentially deadly mistake.)

My point is that we pay these dealers handsome amounts of money (how close did you get to MSRP?--I paid $7475 out the door for mine), and they apparently have monkeys assembling these bikes. Caliper bolts that simply fall out? Delivering a bike that requires over 4.5 ounces of weight on one side of the rim? Not being able to correctly diagnose my wheel oscillation? Ridiculous!

The only good thing I got out of this was a set of new Metzelers. But the truth is there was nothing wrong with the original tires and that's $400 I could have spent on other, more enjoyable upgrades.

Anyway, let the record reflect the fact that oscillation in the front of the M50 might be caused by a unbalanced rear wheel. This is totally counter-intuitive, but possible.

[VtWoodChuck]

Well Done succinct and on target with your explanation. Is the rear wheel out of spec to have so much weight to balance. By gosh you tried 3 rear tires, so you cannot blame the tires. Glad you have the problem solved and that you have shared it with us. The dealer should have been a better allie.

[SNAFU]

Good to know your problems solved, but man I feel for your frustration in the whole process.

Ride safe.

[Clint]

I'm glad you got it sorted. Realistically, though, the dealer doesn't make much at all off the sale of a new bike unless some sucker pays MSRP. Still, they do owe you a functional, safe bike.

[Angusdog]

Sorting out the rear wheel wouldn't have been my first thought, but now makes a bit of sense, in that when tuning suspension IIRC sensations at one end of the bike need to be dealt with at the opposite end. Like tucking in under brakes means more ride height at the back, so something like that.

I would have thought a japanese manufactured bike would have much closer tolerances than 4 ounces of wheel weights - that's bonkers. The rims are as big as a big sports bikes and you can bet they roll a bit better than that.

[nicocorea]

Originally Posted by Angusdog

...when tuning suspension IIRC sensations...

I've seen this acronym "IIRC" a couple of times now. What does it mean?

[digitalbroccoli]

If I recall correctly.

[Jay313]

Rowdy's right on that. Dealerships make their money on the back end: extended warranty sales, parts sales, service and repairs. No different at car dealerships these days, either.

[diamond_jim]

Originally Posted by Jay313

Rowdy's right on that. Dealerships make their money on the back end: extended warranty sales, parts sales, service and repairs. No different at car dealerships these days, either.

You likely picked up on this trend with computer printers a few years ago. The companies got smart. Suddenly, printers with tons of functions dropped from $250-400 dollars down to $75-100. But then the replacement ink cartridges went up in price. And they got smaller. So in the lifetime of your new printer, you're still probably paying the same amount as before you found that "great deal" on a printer, but because it's not all up front you don't quite realize it.

Dealers analyze and figure out the "X" factor. That's how much money a bike purchaser spends at their shop, in addition to the new bike, over the first 1-3 years after the purchase. Since they gave "you" a great deal by throwing in those saddlebags for free, "you" are more likely to be loyal and return to buy a Joe Rocket jacket for $220 from them. It all works outs.

[Clint]

Threads merged for archiving.

[zuphilius]

Just read this. I'm not sure if this is pertinent or not, but in cars when you have a vibration at the 40-50mph range, I was always told that was a rear tire out of balance situation. It felt like it was coming from the front, but it was from the back.

Of course, that was a long time ago with bias ply tires.

[MotoJPizzle]

Originally Posted by nicocorea

The hopping is barely noticeable below 40, but it's still there. But between 40 and 55, there's no missing it. And above 60, the bike is smooth as glass.

No, the original tire was an IRC and the new one is a Dunlop. And the Dunlop was definitely new; it had those pink lines on the treads that disappear after a couple of miles.

But thanks for the input!

Dude, I totally have the same thing - it only happens sometimes but its like a bouncy feeling and at speeds lower than 40 in 4th or 5th. it only happens when Im in a higher gear than needed for the speed Im at.

Is that what you are seeing?

[MotoJPizzle]

It is definitely coming from back for me, but I thought it was the suspension being too soft.

[Easy Rider]

Originally Posted by MotoJPizzle

It is definitely coming from back for me, but I thought it was the suspension being too soft.

It could be. Jack your pre-load up a notch or two. And check your tire pressures.

And then, if you haven't already, you might want to go back and re-read the WHOLE thread.

[MotoJPizzle]

couldnt imagine doing that - too many letters involved