Why do I wobble like a weeble?

[draketrumpet]

I would like to submit my circumstances to the panel of gurus to figure what exactly might be my problem.

So, I've mentioned before elsewhere that I sometimes got a wobble after riding a bit, especially at high speeds. With my old (I mean at least 5 years old) tires, I found they were filled to 40/42 psi (front/rear) and when I let them out to 36/38 the wobble went away.

I had new tires installed today about 25 miles from home, and hopped on to ride home. I had previously avoided the freeway b/c of my old tires, but now I had new tires, so I went for it on the way home. I hadn't gone 3 miles on the freeway when I was wobbling so bad I was seriously scared and got off onto the side roads to come home, still with a significant wobble, even below 40 (at least my arms got a workout ). So I get home and whip my gauge out after it cools a bit, and the guy at the shop had filled them to 42/44 , so I let them out to 38/40 and went to school, just a few miles with no issues up to 40 mph.

You also need to know I don't have the stock fender on and Yamaha fairing. The fiberglass fender that is on there serves only to keep water and dirt away and doesn't offer much bracing capabilities.

Tonight or tomorrow I'm going to go on a longer ride again now that I've let out some air and see if it wobbles, but I can't figure it out. I wonder if the problem would be fixed by going back to the stock fender, but I've never read about the front instability causing a wobble in a straight line.

Let me know any other info you need, but I sure hope it's just a matter of too much air, or at most the infamous instability.

TIA

[DGXSER]

Steering stem bearings

If it were me, I'd put the bike on the centerstand, have a friend or SWMBO or whoever lean on the back of th ebike na dput a jackstand under the frame rod or engine bolt in the front of the bike to hold the front end off the ground. Now, grab the wheel and see if your front end moves front to back at all or side to side with the wheel. You can also try setting the tension on the steering head bearings anyway. It is in the manual how to do it.

This could be wheel bearings so see if the tire and wheel move when the forks do not at all. If it moves at all, I'd replace the front wheel bearings.

Now another thing to check is wheel alignment front to back. Also look at your swing arm and see that it is properly centered in the frame. Again, the procedure is in the manual.

HTH

[motoman]

Seiously, first put the stock fender back on, see what it does. Think maybe you got something else going on in the front, a bit loose or worn steering head bearings possible. Put it on the center stand, rock it back so front wheel is off the ground, rotate front slowly back and forth feeling if it is a bit notchy rotating either direction from center straight ahead. Interesting to hear what you find in doing that.

[psycoreefer]

at least you won't fall down right?

I agree check your steering head bearings, when I got my bike it felt "loose" and "wobbly". I took the head apart and cleaned and re-greased the bearings and tightened it back up and have had no issues after that. 100% difference.

[Larrym]

draketrumpet,

I saw the last time you dealt with this and crossed my fingers hoping that the tire pressure adjustment would prove to be good enough.

My old STD with windjammer fairing didn't "wobble" but it would fail to keep a straight line. (People following behind me seriously questioned my riding skills..)

I second (third??) doing the steering stem/triple tree eval.

I did that on mine only to find no "looseness". It was tight. In fact it was too tight and the test to see if the steering would fall to either side from the center position was a "fail".


I had to take the fairing off to do the adjustment. Results were that even with the stem adjusted correctly the "fall-off" from riding a straight line persisted. In the end I concluded that the front springs were too weak/old and the fairing weight pushed the front end down. This sorta went past the "normal riding geometry" enough to make the bike misbehave.

Hopefully tightening (cleaning/repacking?) the stem will give your forearms a break. If that doesn't work then there are spacers which can raise the front springs to compensate for the additional fairing weight.

While you do have the fairing off it would be an excellent opportunity to check the stem tube-to-the-frame welds.

JAT. This wobbling just might be the primary reason the PO decided to bail on the bike. Not that hard to deal with IMO.

[Guy_b_g]

This is very good advice for troubleshooting a wobble (from a BMW site).

Testing the front wheel and swing arm bearings. Grab the front wheel in one hand and the fender brace in the other. Shake the wheel sideways. If any "play" is felt it must be in the wheel or swing arm bearings. Grab the front fender with one hand and pick it up till the wheel is off of the ground. Spin the wheel, with your other hand, and "feel" any vibration through your fender hand. It should feel completely smooth. If you feel vibration, it is from a failed wheel bearing and you are noticing the rough surfaces of rollers against the races. Replace them.

If the swing arm has some play, it must be adjusted to fix it. It is more likely that they need to be replaced. If no play is felt in the swing arm, that doesn't mean that the bearings are good, only that they haven't yet been proven to be bad. To make the next check: block up the front end and remove the wheel and shocks. The swing arm is now loose and will swing up and down freely. If it is more than a few years old, or hasn't been lubricated regularly, or both, it probably has notched bearings. Do you feel it swing smoothly or with some "tight spots?" Replace them.

With the front wheel in the air, the steering damper off (if you have one), gently and very slowly swing the forks back and forth through the straight ahead position. Does it swing completely smoothly, or with a notch in the dead ahead position? A notch can be felt while riding at low speeds by the rider noticing that the bike won't go straight. It wants to constantly curve. Notched bearings must be replaced. Loose bearings can be checked in a few ways.

1. When applying the front brakes lightly, at low speeds, did you ever feel uneven braking or a kind of resistance that was related to wheel speed? This could be loose steering bearings.

2. With engine off, push the bike and apply a bit of front brake. Do you feel a "click" or movement in the front end?

3. With the front wheel off of the ground, grab the front end by the lower shock legs, just above the swing arm, and pull gently. Don't pull if off of the center stand. A bit of "play" or a "click" can be felt if the bearings are loose. Tighten the steering bearings, as needed, and retest it for a notch or proper tightness. It is common for one to tighten up the steering bearings and only then be able to feel a notch in the bearings.
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And some of my own advice:

Also:

Correct tire air pressure.

Good shocks and mounting bushings?

Fork springs worn out and sagging? Proper air pressure in forks?

If the forks are properly aligned they won't have stiction. This can be a very important factor in wobbles, especially high speed wobbles.

Make sure the tires are properly seated all the way around the rims.

Are the tires balanced?

A bike with a large fairing can be more prone to wobble, same with saddlebags, and especially trunk bags. A last resort might be to check the bike without any one or combination of these.

If nothing else fixes it have the bike checked for tire tracking and possible bent frame, as well as taking the fork tubes apart and checking them for straightness.

Adding a steering damper can help, just don't tighten it too much or you can transfer an oscillation to the frame and actually make it much worse!

Be careful...a tank slapper can be fatal!

[Guy_b_g]

Be methodical...you'll find the cure!

PS Ignore #3 in the previous post, that is for leading and trailing link type forks. Grab the lower fork tubes and perform the same test.

[draketrumpet]

Thanks for the great suggestions.

I think my front wheel bearings are fine.

After having SWMBO get on the back, I had to hand her our 1 year old before we got enough leverage to lean it back (BIG fairing), I played with the handlebars. It is definitely rough and only half passes the fall to one side test (I think some of that may be from rubbing against the cables all around there). So, I definitely need to repack/replace those bearings.

Looking at the manual, it seems the only way to do this is to take the whole front end off, all the way down to the wheel and forks. Unfortunately that is going to be a little impossible for me (landlord is suspicious of anyone doing any work b/c he doesn't want oil spilling, and slight lack of jack).

I think the lowering the tire pressure is a decent fix to get rid of the wobble, even if I don't understand why. I'm going to go for a ride now and see if it comes back, if not, I'll put this off until I ride down to MOM in 2 weeks.

I'll also be looking hard at a fender option between now and then. There's a salvage yard in the city I need to check out, if not there, I guess there's some on eBay.

Thanks again, and I hope this ride goes wobble free.

[DGXSER]

I just feel the need to tell you the wobble is a bad thing. I REALLY would rather see you fix this before riding it again. Hate to see someone else bite it like I did over a known issue. JMO

[trbig]

If it were me, I'd look at the rear end. Put it up on the center stand with the back tire off the ground. See if you can wiggle the rear end back and forth. If it wiggles, look at where the swingarm hooks to the frame. There's a round chrome cover there on both sides. Pop those off, and under there is a nut around an adjustment bolt. Loosen those nuts on both sides, then use an allen wrench (I think a 6mm) and you can tighten those adjusting bolts. BUT... if you tighten one more than the other, it will pull that whole swingarm back and forth and cause an alignment problem. On the inside of the frame, there will be a gap between where that swing arm pivots and the frame. Adjust it to where those gaps are as equal as possible, then tighten back up those nuts and pop the caps back on.

I've ridden behind people with these out of adjustment, and the would get the wobbles pretty bad. It didn't stop them from racing Bob Jones and everybody else though at 130+... did it Hobbyman?


Tod

[draketrumpet]

Thanks Don. I do appreciate it. However, I'm not sure how I can tell if I've eliminated the wobble without getting on the bike... but I will, like tonight, make sure it's somewhere less dangerous than the lunchtime freeway traffic I was in today when it started up again.

So, I went out, and all was fine for the first 10 miles of 50+...then came the wobble and it slowly got worse. Letting more air out seemed to help some, but it did not make it go away . The more I think about it, I think the swing arm might be the culprit b/c I don't feel any jerk like it's the front tire that is wobbling, more of a reaction. I just can't figure out why I can hop on the highway, jump up to 60 and be fine for 10 miles and then it will set in

I'll pop it up tomorrow and see if I can figure out if something is up with the swing arm. I've got a bid on a fender on eBay, and does anyone have any ideas on whether or not I can get to the steering bearings without taking my wheel/forks/fairing off? I might be able to get access to someone's garage/jack, but not long enough to do all that by myself doing it for the first time freaking out I'm doing something wrong every 20 minutes and taking another 20 to talk myself through it before moving on.

[Ken Talbot]

I'll add my vote to the "steering head bearing too tight" option.

BTDT, JAT, YMMV, etc, etc.

[HobbyMan]

I've ridden behind people with these out of adjustment, and the would get the wobbles pretty bad. It didn't stop them from racing Bob Jones and everybody else though at 130+... did it Hobbyman?


Tod

No It certainly didn't. As I recall I still had the top end on you with that wobble. I am with you on the swingarm. Either that or the forks. Maby the tripple clamps are loose. Could the wheel be out of balance or deformed?

[draketrumpet]

I just had new tires put on today and he balanced the tires. I think he would have said something if they were deformed...just seems like that kind of guy.

What I don't understand is why, if it is anything besides the tires, does it never set in around town or for the first 10 miles of highway speeds. Maybe the engine, when it warms up, has just the right harmonics to make my tire oscillate funny, kinda like that bridge that twisted until it fell whenever the wind blew.

[CatatonicBug]

What I don't understand is why, if it is anything besides the tires, does it never set in around town or for the first 10 miles of highway speeds. Maybe the engine, when it warms up, has just the right harmonics to make my tire oscillate funny, kinda like that bridge that twisted until it fell whenever the wind blew.

It may be that whatever is causing the wobble (like the swingarm) is re-setting itself when you stop. It then works it's way out of allignment on the freeway, and you feel it again. JAT...