Cornering crashes high/side

[popandmod]

Teammate of mine went down in a race the other day. Folks who were nearby said it looked like a "high/side" slide out.
From what I can tell from the web (mostly motoGP) the causes of this seems to have something to do with lean angle and contact patch.
Can anyone share some science and wisdom on this senerio? What causes this, how to avoid it?
Thanks

[David Tollefson]

In motorcycling, it happens when the rear loses traction, slides, then regains traction (usually because the rider let off the throttle). I doubt this is what happened on the bike. But a plausible scenario is catching a pedal, hopping the rear wheel, and then high-siding when it regains the road. How to avoid it? Don't lean the bike so hard (lean the body), don't pedal through the corner (unless you're standing and can rock the bike outward with the inside pedal stroke), or slow down...

[nrs5000]

I high side crashed a road bike once in a gravelly corner. I think I was leaned over, started to slide, overreacted, and ended up on the high side. But it happened very fast and I could be wrong about this.

[david]

adding to what david said, there are two common motorcycle crashes, other than collisions.

one is the low side. that's where the rider simply loses traction and the bike goes down on the side that is leaned over into the corner - the "low" side.
this can happen when either or both the front and rear tires lose traction.
usually results in rider and bike sliding across the road/track/grass until they come to a stop.
can get nasty when bike and/or rider catch on something while sliding and start tumbling.

the other is the high side. this is the more dreaded type of crash because of the way the bike behaves during the crash - and it's impact on the rider.
as david said, this usually begins with a rider losing traction at the rear, either by laying down too much power or simply losing adhesion.
problem occurs when adhesion is suddenly re-established.
the rear tire grips the surface and this immediate re-establishment of adhesion snaps the bike back into an upright position.
the violence of this action often pitches the rider up and over the "high" side of the bike.
usually, both rider and bike tumble and the results are nasty.

i suppose this is possible on a bicycle, because it's not the re-introduction of power that causes a high side on a motorcycle, simply the re-establishment of adhesion.
i've never experienced it on a bicycle.

[maggierose]

Since I have high-sided a racing motorcycle (more than once)...

As stated earlier, a low side usually involves loosing traction on the front wheel and sliding off the "low" side.

Conversely, a rider gets "flicked" to the high-side when a rear tire first spins (loss of traction) and suddenly re-gains traction. The missing component, in this discussion, is suspension. When power is applied to rear wheel, weight is transferred to the rear wheel and the rear suspension is compressed. Rear tires loose grip because the rear shock can not efficiently deal with the load put on it. If the rear tire re-grips, the rear suspension unloads and launches a rider up over the high-side of the motorbike.

So, without suspension or a motor, high-siding like a motorcycle is not feasible on a bicycle (even if the rider landed on the "high" side to due clipping a pedal and or some other random act of physics).

[cp43]

Can you high side by locking the rear wheel with the rear brake, skidding it, then releasing the brake, and allowing the rear tire to regain traction, all while leaned over in a corner? That scenario gives you the required loss and regaining of traction that results in a high side crash.

I've only ever low side crashed on my bike, and (not yet, hope it stays that way) crashed my motorcycle, so I'm not speaking from any experience here.

Chris

[jscottyk]

Since I have high-sided a racing motorcycle (more than once)...

As stated earlier, a low side usually involves loosing traction on the front wheel and sliding off the "low" side.

Conversely, a rider gets "flicked" to the high-side when a rear tire first spins (loss of traction) and suddenly re-gains traction. The missing component, in this discussion, is suspension. When power is applied to rear wheel, weight is transferred to the rear wheel and the rear suspension is compressed. Rear tires loose grip because the rear shock can not efficiently deal with the load put on it. If the rear tire re-grips, the rear suspension unloads and launches a rider up over the high-side of the motorbike.

So, without suspension or a motor, high-siding like a motorcycle is not feasible on a bicycle (even if the rider landed on the "high" side to due clipping a pedal and or some other random act of physics).

Nails it. I'm going to say it's impossible do to on a bicycle but it is damn near impossible. Somebody might go down with what is technically a low-side crash but then fall over the other side of the bike but this is not a high-side crash.

That said, I have seen friend high-side himself off a Z50 minibike (and snap his collar bone) while flat-track racing!

[Nathanrtaylor]

I agree with everything said about motorcycle vs bicycle dynamics and high siding except for this:

How to avoid it? Don't lean the bike so hard (lean the body)

That's motorcycle dynamics, not bicycles. Road bike tires don't have the adhesion required to really take advantage of putting the body mass deeper into the turn than the bike. In fact, you actually maximize traction on a bicycle by doing the opposite. Lean the bike more (inside pedal up, of course) and keep body weight more centered over the bike so if there is any loss of traction you aren't adding your body mass to the forces that want to widen the turn. Body mass is more downward and only the centripetal forces go outward.

This is especially true on loose surfaces encountered on mountain bikes, but it applies on the road due to the smaller contact patch. A road rider hanging off the inside like a MotoGP racer will not recover from even a momentary loss of traction.

[Nathanrtaylor]

Also, I've "high-sided" the heck out of a mountain bike by clipping a pedal, but that's not what anyone ever means by the term.

It is also, as has been said, probably what happened in the OP's description.

[jscottyk]

Lean the bike more (inside pedal up, of course) and keep body weight more centered over the bike so if there is any loss of traction you aren't adding your body mass to the forces that want to widen the turn. Body mass is more downward and only the centripetal forces go outward.

One more little tip for this technique is concentrating putting all weight on the outside (down) pedal. This is basically the same technique used in riding motorcycles in the loose stuff; both MX and flat-track.

[David Tollefson]

I agree with everything said about motorcycle vs bicycle dynamics and high siding except for this:



That's motorcycle dynamics, not bicycles. Road bike tires don't have the adhesion required to really take advantage of putting the body mass deeper into the turn than the bike. In fact, you actually maximize traction on a bicycle by doing the opposite. Lean the bike more (inside pedal up, of course) and keep body weight more centered over the bike so if there is any loss of traction you aren't adding your body mass to the forces that want to widen the turn. Body mass is more downward and only the centripetal forces go outward.

This is especially true on loose surfaces encountered on mountain bikes, but it applies on the road due to the smaller contact patch. A road rider hanging off the inside like a MotoGP racer will not recover from even a momentary loss of traction.

Not leaning so far was referring to clipping the pedal on the pavement.

[david]

Since I have high-sided a racing motorcycle (more than once)...

As stated earlier, a low side usually involves loosing traction on the front wheel and sliding off the "low" side.

Conversely, a rider gets "flicked" to the high-side when a rear tire first spins (loss of traction) and suddenly re-gains traction. The missing component, in this discussion, is suspension. When power is applied to rear wheel, weight is transferred to the rear wheel and the rear suspension is compressed. Rear tires loose grip because the rear shock can not efficiently deal with the load put on it. If the rear tire re-grips, the rear suspension unloads and launches a rider up over the high-side of the motorbike.

So, without suspension or a motor, high-siding like a motorcycle is not feasible on a bicycle (even if the rider landed on the "high" side to due clipping a pedal and or some other random act of physics).

i wonder about that.
not the point about the suspension acting as a spring and adding to the force of the rider getting pitched.
but isn't the key factor here the sudden re-establishment of traction that causes an object that's sliding to suddenly NOT slide?
i've always pictured it as if the sliding wheel is sliding at an angle different from the direction in which the wheel is pointed.
when traction is suddenly re-established, the tire stops sliding and the wheel immediately starts rolling in the direction it's pointed.
the sudden forward movement stands the bike up with urgency and the rider gets pitched.
sure, the sudden unweighting of the suspension contributes to the drama. but i didn't think it was the primary cause.
so, in theory, couldn't this happen on an un-suspended bike - or motorcycle?

i think it's far less likely on a bicycle given the lower speeds and the smaller contact patch of the tire.

i wonder if another way a "high side" might appear to happen on a bicycle if if a sliding read tire hit an obstacle of some sort - a seam in the road, etc. - and the sudden halting of forward motion at the tire caused the bike and rider to pitch forward over the pivot point created by the tire and the obstruction. like a pole vault.

[David Tollefson]

Can you high side by locking the rear wheel with the rear brake, skidding it, then releasing the brake, and allowing the rear tire to regain traction...

Seems to me some one did that in one of the Tour descents (right in front of He-who-must-not-be-named) and ended up with a broken pelvis...

[Nathanrtaylor]

Nails it. I'm going to say it's impossible do to on a bicycle but it is damn near impossible. Somebody might go down with what is technically a low-side crash but then fall over the other side of the bike but this is not a high-side crash.

That said, I have seen friend high-side himself off a Z50 minibike (and snap his collar bone) while flat-track racing!

I think it would be impossible too. The critical high side component is the weight of the bike. Even a Z50 minibike weighs around 170 lbs. A sportbike weighs more than twice that. That much mass going from leaned over to upright really quickly generates a lot of force, which is why riders get tossed. The "high side" force if a bike skidded and then regained traction mid skid might be enough to bruise your leg, but isn't likely enough to toss you even if you could replicate everything else about a high side.

[jscottyk]

...I'm NOT going to say it's impossible do to on a bicycle but it is damn near impossible. Somebody might go down with what is technically a low-side crash but then fall over the other side of the bike but this is not a high-side crash.

Correcting my post.

[Nathanrtaylor]

Not leaning so far was referring to clipping the pedal on the pavement.

Noted. Same Page.

[jitahs]

In the wet I leaned more than the bike, not motoGP elbow down shenanigans tho. Whatever works.


*Riding thesaurus alert*

A "slide out" is a low side.
A high side is a violent catapulting of the rider through the time/space continuum, usually resulting in the orbit of stars around your grey matter.

Never shall the twain meet.


I've also discovered when crashing on a trail, you can get the whole endo/high/low/tank slapper Vitamix-set-on-high buffet in one go. Ah yeah, the days before GoPro.

[jscottyk]

Seems to me some one did that in one of the Tour descents (right in front of He-who-must-not-be-named) and ended up with a broken pelvis...

I don't think that was a high-side but rather a tubular rolling off due the high heat. Regardless, broken pelvis happened.

[jitahs]

I don't think that was a high-side but rather a tubular rolling off due the high heat. Regardless, broken pelvis happened.

Hey can you high-side a 911?

[jscottyk]

Hey can you high-side a 911?

If any car could do it, it would be an air-cooled 911. Probably a turbo!