Big bike riders....explain this to me

This post is about a video I just watched…so I know it maybe should go in the media thread, BUT the media thread doesn’t have much discussion and I’m not sure if plasma, kwak, skylark…etc…even go in that thread. So this thread is for a discussion not viewing pleasure.

That said, I just saw this video where a guy loses control of his bike for no apparent reason. Was wondering if someone could explain what happens to him for me. The video is not gory…and I’m sure the guy lives…so I’d say it’s safe for work.

Looks like he fish tailed momentarily, then panicked and froze, thus being unable to regain control in order to avoid the wall. It’s rather like people who panick and mistakenly mash the gas pedal instead of the brake in cars. Perhaps also a jammed throttle?

Obviously he passed some scooter punks, slammed on his brakes to scare them a bit, then divine justice happened to him. :smiling_imp:

seems pretty straight forward… after the gentle cruising style shots in what was probably a nice high cruising gear, you can see him grab the clutch, dropping a gear as you can see by the RPM dial climbing as he releases the clutch (obviously lower gear = more pull = quicker accel…) he then goes for the “give it beans” ride away shot but is clearly a little ham fisted on the throttle and a little too close to what is usually the dusty more slippery outside verge of the road… spins up the rear momentarily while slightly leaned over… rear grips again, when it does the rear suspension does a mini kicker flicking him to the right and setting up a mini tank slapper… instead of applying gentle rear brake to put more weight through the front and hopefully settle the mini sapper and then hanging on, looking through the corner and steering for all he’s worth he gets his foot off the bike, tries to brake hard with the front, making further turning impossible and target fixates into the wall… bang…

being able to reflex react correctly is an acquired skill that requires jedi like clarity of thought in an emergency…

Well then, that proves it isn’t only me that does it. :stuck_out_tongue:

My two cents:

Given I don’t ride a motorcycle but when I was racing cars there was a certain amount of “drag” used when manoeuvering around other vehicles.
It seems to me that because the other vehicle videoing this guy down the street was obviously larger and therefor caused much more wind resistance. Also causing a “pocket” or "draft"around the morotrcycle. The rider didn’t have to use much gas or energy to throttle his bike but when the car sped forward that pocket of “draft” was gonezo. He gave the gas a squirt and it was alittle too much. This commonly happens in Nascar where the slightest touch or bump causes huge accidents.

A rear wheel wobble could be caused by overacceleration and probably compounded by the factors plasmatron posted.

For me it’s a classic case of focusing on your fears. Look at the guys helmet in the last couple of seconds, he was looking straight at the wall/barrier and naturally, that’s where he went.

“Focus on where you want to go, not on your fears.” was my mantra in my bike riding days. It’s not BS either. Try it, practie it and live it while you drive. I learned about it from someone who took race car driving lessons and it has served me well (mostly).

If the rider had turned his helmet and looked at the road, I believe he wouldn’t have hit the barrier.

The guys was learning. Notice how he takes his foot off the left peg as he tries to turn but he can’t lean the bike and he can’t stop it on time either. It was one of the the first curves he’s ever had to negotiate on a big bike I bet. He slammed on both breaks too sharply then he got so scared that his reaction time went by. He had plenty of time to stop on a dime or turn easily if he had proper reflexes. That guy just couldn’t drive a bike yet.


I agree. :uhhuh:

I figure I’d have stayed relaxed and accelerated a little. I then checked the google answers and found conflicting advice. Mine agrees with the one I listed below but you could choose anything to agree with you.

Turning + Accelerating + Front end lifted & set back down = Tankslapper

Prevent tankslappers. Don’t accelerate too hard with the bike leaned over if you are cresting a hill or there is a bump or object in the road (center reflector, etc.) in your path. This scenario has all the elements needed for a tankslapper, so watch for them and act accordingly.

Allow tankslapper oscillations to die out naturally by relaxing your arms. Trying to muscle the bike will increase the oscillations till you crash.

Negate tankslappers by accelerating. Lightening the front end or even wheelying will take pressure off the front end and allow the oscillations to die out.

Check your front brakes after a tankslapper. Pump them up again if necessary.

Invest in a steering damper, especially if your type of bike is more prone to tankslappers than other bikes (aggressive frame geometry, powerful engine, etc.). [/quote]

See the bold. It says to lighten the front end. Some web advice says to get your weight over the front end. That makes no sense to me. The front end is where the trouble is.

He may well have hit a spot of oil. But he should not have braked so hard on the ftront brakes and this reduces the cornering ability of the bike. His bike twitched twice and he got stage fright.

He was also damned lucky not to go over the wall instead of being thrown back onto the road.

He certainly didn’t have much lean angle and the accident was avoidable.

I hope he had full insurance coverage because a head on into the wall would have certainly stuffed the frame. Unfortunately you can’t get insurance against ineptitude.

If you can’t do learn to something well, learn to enjoy doing it poorly.

[quote=“Ironman”]I figure I’d have stayed relaxed and accelerated a little. I then checked the google answers and found conflicting advice. Mine agrees with the one I listed below but you could choose anything to agree with you.

See the bold. It says to lighten the front end. Some web advice says to get your weight over the front end. That makes no sense to me. The front end is where the trouble is.[/quote]

accelerating hard enough to lift/lighten the front when you’re rapidly approaching a wall with a 90degree left turn as that guy was is the kind of game plan that will keep you out of the hospital, but that’s because you’ll be in the morgue…

in fairness what that guy had was a weave or a mini tank slapper…
on a straight road lifting the front it is a “possible” although semi-suicidal save for a tank slapper for a few obvious reasons… firstly and most importantly the handle bars (in even a mild proper tank slapper) are slamming back and forth against the locks several times per second… any imput or force throught the bars will only complicate / worsen the oscilation… crucially, the necessary throttle and clutch control to accelerate sharply enough to raise/lighten the front would be almost impossible… check this well known tank slapper video to see what i mean… also as you accelerate enough to start raising the front, the reduced centering forces (see below) would decrease resistance to the oscilation, and cause the slapper to get worse up until the point that the front wheel lifts off the ground at which stage you’d be out of the frying pan… BUT…assuming you could do it, what you’d be doing apart from raising the front, is accelerating violently in a random direction since the bike is shaking it’s head furiously and oscilating all over the road, and as the front comes up the rear will become your single pivot point you’ll then be accelerating hard, in a random direction, in a crossed up semi wheelie which is another way to say “world of pain”…

in practice the front getting too light, and deliberately engineered “flighty” or “flickable” geometry is what causes most tank slappers… as the front gets lighter the natural effects of phsyics and frame geometry which keeps the wheel centered are reduced… this natural centering force acting on the front wheel is a result of the trail (see diagram) and it’s this force that keeps the front wheel on course… as you lighten the front the centering effect of the trail is reduced, if something causes the front to get kicked out of alignment, like a rock, pot-hole, poor surface, crossed up wheelie landing, etc. it may set up an oscilation that the centering effects of the trail and rake cannot overcome (see above video)… what you want to do is leave the front well enough alone, minimising additional unhelpful steering input, holding the bars with the lightest grip possible short of letting go completely, whilst applying light rear brake which brings more weight onto the front, increasing the effect of the trail and naturally dragging the front wheel into alignment, reducing the tank slapper to a controllable level…

so it’s not getting your weight over the front, it’s getting weight through the bike/frame onto the front wheel that counts…

well that’s the theory/physics of it anyway… in practice what you usually do is fall off… :wink: :help:

When you put chopper forks on you increase the rake. Do choppers tank slap?

When you apply brakes the rake is decreased because the forks compress, this does not sound like a good thing.

correct, choppers/cruisers have a very shallow rake angle and as a result are slower steering, more stable and almost impossible to tank slap… sportsbikes have a very steep rake angle, are quicker steering and tend to be less stable…

yes, rake is marginally decreased, which is one of the reasons why a small amount of fork dive on the brakes is a good thing since it aids corner entry steering, and (completely OT) why BMW’s early diveless telelever front suspension was a bit of a flop… however when a tank slapper is already in progress, the priority is to reduce oscilation by increasing the centering effect of trail and technically the safest, most direct way to do this is to move rider weight off the bars, bring more weight through the front with light rear brake, which encourages the natural tendancy of the bike’s front wheel geomtery to sort itself out…

in all this tankslapper talk its important to remember that the physics of motorcycle geometry are fiendishly complicated in normal riding and when you have a uncontrolled chaotic oscilations like a tank slapper it pretty much comes done to a random sudden death showdown between you and Isaac Newton and the old bugger almost always wins… :s

I’m ready to get shot down. Don’t feel full of holes just yet. I’d have applied gentle accelerator prior to reading this. Still seems like bad news to have the front end get more responsive (reduced rake) and add weight to the front end by braking.

I’ll have to try it and report back.