Rear wheel wobble - how to recover?

 The thread on rear wheel wobble this week got me thinking... remember
the link to the clip someone posted here last year on the flat-track
racer whose bike went into that rear wheel wobble? The guy looked for
sure like he was going to crash, but somehow dismounted the bike as it
was moving (almost like road skiing), gained control over the bike,
remounted it and went on as if nothing happened.

I have never experienced the rear wheel wobble (henceforth referred to
as RWW) thing and I've seen instances of it on Youtube featuring sport
bikes.

I assume from the discussion here that RWW can be cause by:

1. braking in a corner - would you have to lock up the back tire?

2. slowing/braking in gravel or some other substance that would
alternatively rob and then restore traction

3. chain malfunction that locks up the rear wheel

4. ???

So how do you pull out of it? I'd guess most folks would instinctively
throttle down and/or brake like crazy.

What should you do?

Greg

 

If you try this, please videotape it and post it here.

Done a LOT of high speed wobbling on my Brits. I always was able to hold on
and recover.

Thumper

 

A rear wheel wobble would be caused by a mechanical  problem with the
wheel/tire.  I am not sure if  you are referring to a  "high sided" or  "tank
slapper."



Tank slappers



High side

 

I see a common thread on most of the tank slappers... the
feet have left the pegs, at least somewhat.  When your feet
leave the pegs, you no longer have butt-grip to help you
dampen and control the handlebars.  A tank-slapper is
an undamped oscillation of the fork and frame.  Misaligned
rear wheel would exacerbate the situation (you're already
stepped out to one side).

Keep your feet on the pegs!  If the rear breaks loose, don't
panic (easy to say, hard to do), just do a little less of what
you were doing (accelerating/rear braking)... and remember,
low side is better than high.
__
Steve
'06 FXDI
KI5YG
#0627
.

 Stephen Cowell wrote:


You don't even know the difference between a *speed wobble* (tank slapper)
and a "speed weave* (wahoo!).

Since a "tank slapper" takes place at such a high frequency, the rider
doesn't have time to respond it it.

Afterwards, he might claim that he let go of the bars, or say that he
*wished* that he'd let go of the bars before his thumbs were broken hitting
the gas tank, but the simple fact is that a "tank slapper" is over before the
rider has time to react.

Tank slappers happen after the front tire contact patch is unweighted, going
over railroad tracks or a sudden crest in the road or over small bumps. The
speed wobble is around the steering axis, it doesn't involve the rest of the
motorcycle's chassis.

The motorcycle continues to go in the approximate direction it was headed,
the rider's feet are NOT thrown off the footpegs.

The rear tire DOES NOT break loose in a speed weave. The front tire loses
grip. The rear tire overwhelms the front tire with its excess traction.

To recover from a violent speed weave, roll off the throttle and lean forward
to weight the front tire contact patch.

Voluntarily taking your feet off the pegs helps the situation by lowering the
combined
motorcycle/rider center of mass.

The disadvantage in taking your left foot off the foot peg is that you could
run over your foot or get it caught in the drive chain. Doug Polen lost his
toes when he ran over his foot.

Once the rider's feet are knocked off the pegs during a *speed weave* or
"wahoo", the best bet is to let the motorcycle go.

In one video, a rider tried twice to set a land speed record on a dry lake
bed, not realizing how little traction the top layer of dust offered.

He was going 175 mph, trying to exceed 200 mph.

When his Kawasaki lost a little *front wheel traction* the motorcyle chassis
did what came naturally, it tried to fall over to one side.

Then the trailing front tire contact patch levered the chassis upright, but
*it kept going the OTHER way*, and the motorcycle started falling over that
way.

Then the trailing front tire contact patch levered the motorcycle back up,
only to fall off to the first side.

The rider's feet were knocked off the pegs by the violent oscillation known
to engineers as a "speed weave".

The rider finally had to let go and the Kawasaki stabilized itself and ran
for a mile at 175 mph.

Then the rider rebuilt the Kawasaki, tried again and was thrown off for the
second time.

--
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