At least 4 questions

Here's a quick question for anybody that has either dropped their bike
at speed, or run over something significant on the highway, like a
block of wood. I realise this might be a bit traumatic if I'm asking
anyone to re-live a previous accident, in which case I'm sorry about
that.

Last night I was doing 100kph in a straight line (http://goo.gl/7eqmR)
when I noticed a block of wood about 40cm x 10cm x 5cm (high) at an
angle in the middle of my lane. I swerved to the right and missed it
by a few cm. Now I'm thinking about what would have happened if I
hadn't swerved enough, and the left hand side of the front wheel had
hit the block at an angle.

I think:
a) if the front wheel went over the block I'd be looking at fully
compressing the front shocks and, after passing over the block, the
front wheel would be off the ground for a few metres.
b) if the angle between the wheel and the block was sharp enough, the
wheel might not have gone over it, instead the wheel would turn away
from the block (to the right), the bike would try to go straight on
due to its momentum, lean over?, my body would carry on in a straight
line, finally the bike would lurch to the left and I would be thrown
off.

Looking at Google images there's a lot of variation on what happens to
the motorcycle. Some bikes have survived with little damage and
others have flipped at the same sort of speed. What is the minimum
speed for a highsider?

Are all alloys designed to shatter on impact or only some of them?
eg. Alloys in the R15/FZ series are designed this way. If so, what
does it take to do it? Would hitting a kerb stone at 100kph be
enough?

I have no idea how far I would have slid. Ideas? Assuming all the
kit, if I _only_ hit the flat freeway surface (not posts or other
cars), would I just get a few bruises?

I'm looking for any insights from other members of this forum who have
either dropped a bike at speed or ridden over something similar.

 

5 cm high?

<bump> and carry on.

Maybe a skittish bike would shake it's head.

In the "right kit" hitting the road and sliding at 100 kph (assuming you
don't collide with a fixed object) should have about the same effect as
hitting the road and sliding at 5 kph. Something between an
uncomfortable bump and broken bones and concussion, depending how you fall.

I had no idea alloy wheels were "designed to shatter". I can't see why
you'd do that as a deliberate design aim. I'd have thought it was more
an unfortunate effect in some of them.

Moike

 

I hit something similar to this on my 1993 GSX750F and the impact (after
the forks bottomed out) was actually strong enough to break a small bone
in my right hand.

The front wheel ended up with a bad flat spot and some stress fractures
near the impact point but I was able to ride the bike (slowly) home.

I wouldn't automatically assume the wheel would fracture and as for
falling over that's more a combination of angle of impact, bike weight
and rider skill combined with luck.

G-S

 

Thanks everybody.

 

I think you're possibly overestimating what may happen in some respects,
and underestimating in others. You're ignoring the fact that the block
of wood is not fixed to the road, so it may react to the bike depending
on how the bike reacts with it. I think you're overestimating the
affect on the suspension. I doubt a 5cm bump would fully compress the
suspension. I think the result of the wheel and the block contacting
would vary greately depending on your reaction, ie if you braked, you'd
be loading up the front suspension at the point of impact and therefore
the bike would react completely differently to if you hit it with the
throttle on.

If you've have every been taught anything about countersteering, you'll
know that the faster you go, the more difficult it is to turn the front
wheel, so I doubt a small obstacle like a movable block of wood would
turn the wheel that far, and if it did, that wouldn't necessarily cause
the effect that you suspect. It might initiate a tankslapper, but if
you know anything about the way a motorcycle behaves, without any
external inputs, it will most likely return to normal operation. That
is, if you get into a tankslapper, and you don't do anything which
causes the effect to transfer to the rear wheel (ie you just need to
relax your grip) and the bike will probably correct itself and stay
upright. The first hit when i youtubed for "tankslapper" was this link
which demonstrates quite nicely how survivable a tankslapper is, if the
bike is upright, travelling in a straight line and you just enjoy the
ride and don't make it worse.


Hitting the block is probably no different to hitting a similarly sized
pothole in the road. I suspect that as long as you did not grab the
brakes and cause the front wheel to lock and the suspension to compress
you'd probably poop your pants a little and 5 seconds later you'd have
forgotten about it.

Nev..