High side question

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Gunslinger · Sun Aug 31, 2008 8:46 pm

I see alot of videos on the net where the back of a bike will snap suddenly and throw someone high side. What causes this type of accident, and what's the best way to avoid it? See a nice demonstration here: http://www.youtube.com/watch?v=mKsV6a278gE

Seems like most of the time the rider is either coming out of or entering a curve.

Shorts · #2 Unread post by **Shorts** » Sun Aug 31, 2008 11:33 pm

When the rearend steps out sideways from loss of traction then quickly regains traction while out of track with the front. It can happen just like in the vid you posted in a loss of traction on acceleration. Or, it can happen if you lock up the rear brake and the rear end slips out sideways...to which you release the rear brake and it regains traction and tosses you over.

Lion_Lady · #3 Unread post by **Lion_Lady** » Mon Sep 01, 2008 8:29 am

In a nutshell: A high side happens when your rear wheel loses traction on clean, dry pavement (usually from too much rear brake), then suddenly regains traction (usually when the rider incorrectly releases the rear brake pedal, in response to the slide).

It can also happen if you just "let go" of the clutch lever when downshifting to slow down.

P

Grey Thumper · Mon Sep 01, 2008 3:12 pm

Hope you find this useful; pretty comprehensive article on highsides . . .

http://www.msgroup.org/Tip.aspx?Num=001&Set=001-031

"To begin with, a highside starts when you use so much rear brake pressure that you lock your rear wheel. If you are in a curve, (or if you have also applied your front brake while going in a straight line, or if there is substantial road camber, or severely unbalanced loading of the motorcycle), this starts the rear end sliding/skewing away from the direction the bike had been moving because traction is diminished on the rear tire (it has become 'sliding friction' - about 80% of what it was just prior to the skid) and that tire has begun to MOVE FASTER (in the direction of bike movement) than the front tire (centrifugal force, among others, is having its way.) The automatic, and correct, driver response to this situation is to turn the front wheel in the direction of the slide. [Actually, the front wheel will turn in the direction of the slide by itself - your job is merely to let it.]

Let me be clear about that - I do not mean that the front-end ACTUALLY is steered or turns toward the slide but that it will APPEAR to be doing so. Without steering input the front-end will continue to point in the direction of bike travel while the rear-end slides to the side which makes it look like the front-end is being steered in that direction - and your job is NOT TO FIGHT these dynamics."

bandit600 · #5 Unread post by **bandit600** » Tue Sep 02, 2008 5:12 am

Although it's less common than brake induced rear traction loss, accelerating too hard out of a turn before the bike is far enough upright and has a decent contact patch can cause this as well. In that case the high side would happen when the rider gets scared by the slide and abruptly cuts off the power and the rear tire grabs again.

You'll see that more often in MotoGP races than on the road but you could probably do it pretty easily with some inexperience, lack of judgement and a way too powerful liter bike...

flynrider · #6 Unread post by **flynrider** » Tue Sep 02, 2008 1:29 pm

bandit600 wrote:Although it's less common than brake induced rear traction loss, accelerating too hard out of a turn before the bike is far enough upright and has a decent contact patch can cause this as well. In that case the high side would happen when the rider gets scared by the slide and abruptly cuts off the power and the rear tire grabs again.

Correct. Rather than associating the problem with bad braking procedures (which is just one cause), perhaps a more general statement is in order.

Anytime you lose traction and the front and rear wheel are no longer pointing in the same direction, you have a very good chance of a high side when traction is regained.

Locking the rear wheel and over accelerating out of a turn have been cited as causes, but as long as you keep in mind that it can happen whenever traction is lost for any reason, you'll be on guard. For instance, a traction loss because of wet or sandy road conditions can also result in a high side.

HYPERR · #7 Unread post by **HYPERR** » Tue Sep 02, 2008 1:49 pm

Ruben Xaus says "what's a high side?"

Gunslinger · Tue Sep 02, 2008 6:23 pm

flynrider wrote:
bandit600 wrote:Although it's less common than brake induced rear traction loss, accelerating too hard out of a turn before the bike is far enough upright and has a decent contact patch can cause this as well. In that case the high side would happen when the rider gets scared by the slide and abruptly cuts off the power and the rear tire grabs again.
Correct. Rather than associating the problem with bad braking procedures (which is just one cause), perhaps a more general statement is in order.

Anytime you lose traction and the front and rear wheel are no longer pointing in the same direction, you have a very good chance of a high side when traction is regained.

Locking the rear wheel and over accelerating out of a turn have been cited as causes, but as long as you keep in mind that it can happen whenever traction is lost for any reason, you'll be on guard. For instance, a traction loss because of wet or sandy road conditions can also result in a high side.

I appreciate all the responses. The MSF teaches us to stay on the rear brake if it locks up. I say easier said than done. I think the first instinct when the bike starts sliding is to let off the brake and hope like hell it straightens itself out. If I wasn't such a chicken I'd like to practice that sometime on a closed course. When I see professional road racers going high side it makes me wonder what chance do I have as an amateur street rider to avoid this type of 'get-off'. I suppose I just need to stay vigilant and try to be aware of my limits of traction as best I can.

HYPERR · #9 Unread post by **HYPERR** » Tue Sep 02, 2008 11:19 pm

Gunslinger wrote:
flynrider wrote:
bandit600 wrote:Although it's less common than brake induced rear traction loss, accelerating too hard out of a turn before the bike is far enough upright and has a decent contact patch can cause this as well. In that case the high side would happen when the rider gets scared by the slide and abruptly cuts off the power and the rear tire grabs again.
Correct. Rather than associating the problem with bad braking procedures (which is just one cause), perhaps a more general statement is in order.

Anytime you lose traction and the front and rear wheel are no longer pointing in the same direction, you have a very good chance of a high side when traction is regained.

Locking the rear wheel and over accelerating out of a turn have been cited as causes, but as long as you keep in mind that it can happen whenever traction is lost for any reason, you'll be on guard. For instance, a traction loss because of wet or sandy road conditions can also result in a high side.
I appreciate all the responses. The MSF teaches us to stay on the rear brake if it locks up. I say easier said than done. I think the first instinct when the bike starts sliding is to let off the brake and hope like hell it straightens itself out. If I wasn't such a chicken I'd like to practice that sometime on a closed course. When I see professional road racers going high side it makes me wonder what chance do I have as an amateur street rider to avoid this type of 'get-off'. I suppose I just need to stay vigilant and try to be aware of my limits of traction as best I can.

Unless one has total feel for the rear brake, it is almost 100% guaranteed that you will lock it up in a panic situation. Keith Code has always stated that rear brake has caused more crashes on and off the track than anything else. If you have not totally mastered the rear on your bike, I would just learn to use the front in emergency stops. Only when you have learnt the limit of your rear, should you be using both in emergency stops.

When you lock up the front brake, you lose all control. However, unlike locking up the rear, you have a split second window of opportunity to release the brake, "unlock" it and then apply the brake again.

motokid · #10 Unread post by **motokid** » Wed Sep 03, 2008 2:19 am

Gunslinger wrote:...If I wasn't such a chicken I'd like to practice that sometime on a closed course. When I see professional road racers going high side it makes me wonder what chance do I have as an amateur street rider to avoid this type of 'get-off'. I suppose I just need to stay vigilant and try to be aware of my limits of traction as best I can.

Practicing the emergency breaking should be a part of routine. It doesn't have to be at high speed - important thing is to achieve a feeling for the deceleration and the point of lost traction. It is the same regardless of the initial speed. There are lots of places on the internet that describe safe and effective way to do it.

K