A high-side motorcycle crash is potentially devastating, and it can happen at lower speeds than you think. Consequently, it’s not a problem for road racers only.
You may not have thought about it but that comfy cruiser can body-slam you on the pavement every bit as readily as those quick-as-lightning MotoGP bikes you see in the online videos.
Thing is, a high-side can happen so fast, you don’t know it’s coming until you’re in the air, but then it’s too late. So, knowing the sequence of events that can lead to a high-side is important to strategies and riding techniques that can help you prevent the event.
In my many years in the saddle of a motorcycle, I’ve been fortunate to never have had experienced a high-side crash. But I do remember having done some of them back in my bicycle days as a kid and I imagine the dynamics are basically the same—although all my bicycle high-side get-offs were the result of deliberate actions in combination with poor technique.
They were low-grade events that went something like this: pedal like crazy to get some speed, then slam on the coaster brake and cut the bars in an effort to swing the bike 180° in a cool, leaned-over slide, pivoting on the inside foot.
Always practiced on gravel, I thought I had mastered it, but when I tried it on the blacktop, I discovered the hazard of the rear tire regaining traction, stopping the skid, and the remaining energy being transferred up causing the bike and me to high-side. Those early experiences were instructive and to this day have kept me from doing the same maneuver on a motorcycle.
The Internet is well-stocked with videos illustrating the high-side crash, particularly from motorcycle racing. There seem to be a couple of scenarios that most often result in the high-side:
- Trail braking too hard, losing rear-wheel traction on the entrance to a curve or up to the apex.
- Trail braking too hard to wheel-lock on a slick surface causing the back end to lose traction and fish-tail into a side-long skid.
- Down-shifting too aggressively entering a turn effectively locking the rear wheel—less of a threat on s bike with a slipper clutch—but a potential factor.
- Using so much front brake force in a corner that the rear tire loses traction or even lofts off the pavement entirely.
- Accelerating too hard on the exit from a turn, breaking rear-tire traction while still in a hard lean.
- Leaning far enough to ground a part of the bike such as the muffler, fairing, or other parts with enough force to momentarily loft the rear tire. This is apparently what causes the lurid high-side crash in the video of Yvon Duhamel.
What happens next may, in many instances, be a decisive factor in whether the above scenarios result in a high-side launch over the bike with the bike flipping as well or in a low-side slide.
In nearly every video of a high-side crash, careful stop-action observation of the crash shows the rider instinctively counter-steers in the direction of the skid.
This appears to allow the side-long slide to continue until, usually within a second or two, enough speed is lost causing the rear wheel to suddenly reacquires traction causing the weight of the bike and rider to instantly transfer into a catapult motion, causing the rider to be vaulted into the air, often coming down in front of or on top of the bike.
The mechanics of the high-side crash are easy to see in this classic video (by Dailymotion>FFM Bike 70) of one of my life-long racing heroes, Yvon Duhamel getting launched from the saddle of one of his very fast, but hard-to-handle factory Kawasaki road racing triples.
This is accentuated by the compression of the bike’s rear suspension when the forward momentum is stopped when the rear tire re-acquires traction and then the suspension de-compresses, transferring some energy upward. This adds to the lofting of the rider up and over the bike.
Now, it is true that this is exactly the technique used in flat track racing, but the key to the technique being successful in cornering there is the continued application of power to keep the rear tire spinning resulting in a (usually) controlled slide.
Comparing those observations to similar traction-loss situations where the rider does not counter-steer and the rider’s weight takes the bike down to the pavement, the result is usually a low-side slide that generally is less spectacular and appears to most often result in less destruction to rider and bike as long as other collisions don’t ensue.
This suggests that a potential counter-measure against the deadly high-side crash is to not counter-steer, bring the bike down on one side and opt for a potentially less dangerous low-side slide, since regaining control after any but the smallest degree of rear-wheel side-slip is very unlikely.
Of course, pulling this off as a deliberate counter-measure for most riders who don’t have the proprioceptive power and speed of The Flash is a very tall order.
So, that brings us to the most effective counter-measure: prevent the scenarios noted above that potentially can lead to a high-side in the first place:
- Keep the rear tire keyed into the road surface to prevent the rear-wheel side-slip that can lead to the high-side.
- Enter corners at a speed well within the limits of rear tire traction. The posted speed limit is a good indicator, but sand, gravel, liquids, tar joint road repairs, you-name-it may require substantially lower speeds. Enter blind corners with caution.
- Be smooth on the brake and throttle entering and exiting corners; downshift with care, even with a slipper clutch if the road surface looks questionable.
- In hot weather beware of large hot-tar road repairs that can get down-right greasy in high temps.
- Know your bike’s maximum lean angle—to that point where some part of the bike will hit the ground. Depending on your bike, it may be substantially different from one side to the other.
Most important—be safe out there, have fun, and keep the shiny side up!