Tires and wobbles

[bowlesj]

I mounted a new front 880 yesterday. The 40 mph wobble has come and gone on my 04. Lately, I have noticed it so bad that I don't dare remove my hands from the bars while decelerating or holding steady speed at 35-45 mph.

So, with this new tire I am planning on testing a theory and see what results I can come up with.

Keeping in mind that my rear tire is just about wore out as well at 6,000 miles, I installed the front wheel ensuring I absolutely seated the axle in the fork as well as possible by performing at least 10 compressions while slowly torquing the axle bolt, then the pinch bolts. My theory is that the 42-46 pounds of front air pressure I have been running in order to preserve mileage may be causing an abnormal over pressure wear in the center of the tire, thus causing much of the wobble. I aired the tire to the BMW recommended 36 pounds and that is where this tire will remain.

First ride. The steering head is ridable at all speeds where the wobble was previously present. While decelerating down from 65 there is a slight wobble from 42 - 38 mph. This is more of a wiggle and not at all like the severe wobble normally experienced and may be attributed to the rear tire. The cruise can be set anywhere from 35-55 with no shake. Normally the bike is unridable in the 40 mph range with hands off. When the last tire was toast, I could feel the twitching with hands on the bars.

All this proves thus far is that I have the axle seated and tire balanced fairly well. I will monitor and report how the wobble progresses as the miles add up.

[NCrider]

I have 7000 miles on my Metzlers (08 K12LT). The rear is cupped, of course, and will be due for change, probably in less than 1k. Front is fine for a while yet and no cupping noticeable. No wobble whatsoever. I run 40 front, 44-46 rear. I don't remember any wobble ever, even on my 2000- ran several sets of tires through on it, all Metz. And of course, the tires cupped/ scalloped.

Just for your testing/ theory, fwiw.

You live in a beautiful area of NC... of course, you know that!

[adama]

I have fairly new ME880's front and rear and almost had a tank slapper last week when i was playing with my chinstrap with both hands and the bike started to slow down. Freaked me out , wont be doing that again. :eek:

[bowlesj]

I have 7000 miles on my Metzlers (08 K12LT). The rear is cupped, of course, and will be due for change, probably in less than 1k. Front is fine for a while yet and no cupping noticeable. No wobble whatsoever. I run 40 front, 44-46 rear. I don't remember any wobble ever, even on my 2000- ran several sets of tires through on it, all Metz. And of course, the tires cupped/ scalloped.

Just for your testing/ theory, fwiw.

You live in a beautiful area of NC... of course, you know that!

Thanks for the info. I bought the bike used in 2005, and the tires were slightly underinflated and severely cupped but no wobble. I have tried higher pressures and have had no serious cupping, although the howling in turns is still there and mileage has improved. I'm thinking the tire wears less across its width with the higher pressures, which may cause the wobbling effect.

We'll see.

[ironbuttwannabe]

You didn't want to try Avons? I hear mixed results about the tires and all, but have had no problem with the front end woble. The wear is perfect with 42 psi. I really love my Avon front and Metzler rear combo. :) I'm going to run and hide now because of what some people say about that.

[Rockdoc]

I don't think that it's a good comparison between a worn and new tyre. I let my Bridgestone front get lower than normal before I replaced it. The bike felt like it was under-steering and if it was wet the side-slip was really noticeable. Not only has the grip improved with the new tyre and all under-steer has gone, the whole handling of the bike is far lighter and, if anything, I'm having to sit up a bit part way through bends because I'm still mentally on the old tyre and the result is over-steering.

I had to switch from Metzelers to Bridgestone a couple of years ago, when there were no 880s in the UK, and there is a marked difference in te handling between the two manufacturers. To me the Bridgestones seem to steer qicker and it feels easier to get the bike over but the Metzelers felt more stable overall.

Keith

[MikeERideWNC]

Is this an epidemic?

I had this problem last week after I installed a new set of ME880.
I have been getting lazy and started static balancing my wheels.
After the third ride I notice my bar trembling, I let go and the thing shook like crazy.
When I got home I pulled the front wheel, removed the weight and then computer balanced it.
The tire took more weight than usual.
But once the wheel balanced 0.00 I was satisfied.
I took the bike out and any shake is now gone.

I wonder if they had a bad batch of front tires that weren't Q/C before they left the factory?

[bowlesj]

You didn't want to try Avons? I hear mixed results about the tires and all, but have had no problem with the front end woble. The wear is perfect with 42 psi. I really love my Avon front and Metzler rear combo. :) I'm going to run and hide now because of what some people say about that.

Hi Neil,

I kept thinking I would try the Avon's but just too many uncertainties there. Stuck with old reliable. What was the price of your front Avon?

[ironbuttwannabe]

I think I got the set for 220. Just checked, and you can get them at Motosport for $110 now. I went to BB's for balancing the rear Metzler. I wanted to see if it works. Makes changing tires quicker and easier. I didn't wan't to buy a balancer either.

[MikeERideWNC]

I went through a set of Avons in 1K miles.
I was completely unstatisfied with them by 500 miles.
They are not a good fit for a rider who regularly rides twisties at speed.

Not to mention there is no Q/C at the factory.

I only get 4K from the ME880. But, for extreme riding on this beast that is what we are limited to.

[NCrider]

Mike,

Are you saying a static balance isn't accurate enough? Just curious before I start changing my own tires.

[MikeERideWNC]

Static balance is fine for most instantances.

There are other variables that will effect a good static balance.
Tire composition is a main peeve of mine. If a tire as heavy as the ME880 doesn't come from the factory close to true, with a mark for the light spot then static balancing by a novice can be difficult.
Another item that throws off the balance is the steel valve stem.

A computer balance, not static on a computer balancer, but a true computer balance will place the correct amount of weight exactly where it is needed.
Right edge, Left edge in several different places to get the balance to 0.00.

I think next time I do a wheel I will post up pictures to show the difference between a static balance and computer balance.

Notice the weights on your car. They are never only on one place of the wheel.
Usually two or three places with weight.
Motorcycle wheels are no different. Just smaller weights in multiple places.
It is not as pretty as static when using stick on weights, but it does feel better.
Most shops only use ststic. It is cheaper and faster. Most riders will never be able to tell the difference.

[shadowofshoe]

I mounted a new front 880 yesterday. The 40 mph wobble has come and gone on my 04. Lately, I have noticed it so bad that I don't dare remove my hands from the bars while decelerating or holding steady speed at 35-45 mph.

So, with this new tire I am planning on testing a theory and see what results I can come up with.

Keeping in mind that my rear tire is just about wore out as well at 6,000 miles, I installed the front wheel ensuring I absolutely seated the axle in the fork as well as possible by performing at least 10 compressions while slowly torquing the axle bolt, then the pinch bolts. My theory is that the 42-46 pounds of front air pressure I have been running in order to preserve mileage may be causing an abnormal over pressure wear in the center of the tire, thus causing much of the wobble. I aired the tire to the BMW recommended 36 pounds and that is where this tire will remain.

First ride. The steering head is ridable at all speeds where the wobble was previously present. While decelerating down from 65 there is a slight wobble from 42 - 38 mph. This is more of a wiggle and not at all like the severe wobble normally experienced and may be attributed to the rear tire. The cruise can be set anywhere from 35-55 with no shake. Normally the bike is unridable in the 40 mph range with hands off. When the last tire was toast, I could feel the twitching with hands on the bars.

All this proves thus far is that I have the axle seated and tire balanced fairly well. I will monitor and report how the wobble progresses as the miles add up.

John-this type of analysis can only come from some one who has raced(outside of some engineers) & understands the dangers of a full tankslapper -I appreciate the effort and sharing results.
Having experimented w/my 05 hands off, decelerating in the 42-38 range the shake does exist.

Thanks-

Mike