What May Have Caused This Crash?

[czeebBusa]

I would be very interested in hearing from the experts on this forum as to the possible reasons for this crash.

 

https://www.youtube.com/watch?v=2S4pOG9n_n8&feature=em-uploademail

[FieryRobot]

In a quick view, it *looks* like acceleration while leaning.

[czeebBusa]

Does it look like he did a mid turn correction? It appears he pushed a second time on the inside handlebar.

[FieryRobot]

Maybe. Which is why it would have been not so good to add lean while OTT.

[rchase]

What I would really want to know is what mode the bike was in and what were the ambient conditions. I would also love to see the data from the bike.

 

All of that would be rather moot though as it looks like the front tire lost grip which is something the onboard systems can't do anything about. If you watch the tach he did not "roll out" but he stayed static on the throttle so there may have been some weight shift to the front end overloading the tire and causing it to loose grip. If you listen as the bike drops to the ground the typical "rev up" is missing and the bike did not yaw at all when it dropped. It likely was not the back tire that was the issue.

 

The turn did not help the rider either. Down hill and off camber. He could have entered way too hot so that no matter what he did the front end would have let loose.

[Dylan Code]

I was there. He added throttle and lean at the end. I pointed it out to Adam when we saw the video in the pits and he agreed.

[Hotfoot]

Best way ever to preface a crash evaluation: "I was there."

Thanks, Dylan, for letting us know what happened to the rider in the video.

[rchase]

Not much better understanding than being able to talk to the rider afterwards.

 

So. I'm curious. How does the physics behind an adding throttle and lean crash work? I had always assumed these style crashes were caused by the rear loosing traction but it appears in the video that the front was the culprit.

[Dylan Code]

Not much better understanding than being able to talk to the rider afterwards.

 

So. I'm curious. How does the physics behind an adding throttle and lean crash work? I had always assumed these style crashes were caused by the rear loosing traction but it appears in the video that the front was the culprit.

I'm very careful when answering in terms of physics because I'm not formally trained in physics and even if I was, a full explanation of the physics involved would be very long and quite technical. With that being said, we can take a big step back and say the majority of the single vehicle, loss-of-traction-in-a-corner crashes we have witnessed have been due to an increase of both throttle and lean angle simultaneously. This has been spoken about many times on this and other forums.

 

One way of looking at it would be saying that leaning the bike over creates a turning arc, and the more you lean the bike over, the tighter the arc for a given speed and body position. Now if someone was in the process of leaning a bike we could say he was tightening his arc.

 

Now throttle enters the scene: the throttle has a stabilizing effect on the bike and when applied smoothly evenly and constantly causes the bike hold a line. A lot of throttle would increase speed and widen the arc but not necessarily change lean angle much or at all. In other words good throttle control gets the bike to stay put on its line.

 

Now if someone is applying throttle (saying to the bike "stay put on your line") and then leans the bike over further during that throttle application, essentially the bike is being asked to do two things in conflict with each other: 1) hold line and 2) tighten the line. The tire(s) give out when the forces are strong enough, meaning fast for the conditions.

 

Whether it is the front or rear that gives out first would have so many variables connected to it that I could not begin to guess. "Weight on contact patch in a corner" does not all by itself guarantee traction or lack of traction. Downforce does but motorcycles only have gravity and a very negligible about of downforce. Cars at speed however do have downforce and it can be extreme in the case of an F1 car or similar winged-body vehicle. With an F1 car, grip increases with speed, but a motorcycle does not seem to gain or lose traction in relation to speed in a corner. It usually seems to hover around the max of 1g in a flat (not banked) turn.

[rchase]

Dylan,

 

Thanks for taking the time to answer that difficult question. For me the "adding lean angle" crashes have always been the most mysterious. I understand a bit better now. Essentially by adding lean you are abusing the limits of your contact patch. That's good enough for me. Front or rear being the loss of grip the results are much the same.

 

These types of crashes make me realize that some of the technique in the school's books really can protect you if you use them. Making one steering input per turn not only makes for a better line. It can keep you from crashing too.

[tmckeen]

I believe they way it was described to me at one of my CSS briefings was basically, Tire's are like Union workers, they do one thing incredibly well, but when you ask them to do multiple things at once, they go on strike

[czeebBusa]

Great info. I'll be at Streets of Willows this Saturday doing Level 1.

[tmckeen]

I'll be there, waving flags at naughty people

[Spaghetti]

Dylan great explanation. Also if you're in need to increase speed while leaning further (that is before the apex), it means rolling speed was too low.

[wishy thinky]

Ah! Found it. Sort of.

 

Tire's are like Union workers, they do one thing incredibly well, but when you ask them to do multiple things at once, they go on strike

Now if someone is applying throttle (saying to the bike "stay put on your line") and then leans the bike over further during that throttle application, essentially the bike is being asked to do two things in conflict with each other: 1) hold line and 2) tighten the line. The tire(s) give out when the forces are strong enough, meaning fast for the conditions.

 

Whether it is the front or rear that gives out first would have so many variables connected to it that I could not begin to guess.

I have been spending some time looking for the answer to the throttle/lean question (which tire gives? is there warning? is adding throttle and holding throttle equally bad? what are the limits of the rule?). Maybe the search for answers made me super conscious of it and caused a brain freeze today. Knowing this rule--but not understanding how traction is lossed--locked me up. I was approaching a right turn probably going 10 to 15 mph, needing to turn onto a road where traffic is going 50+mph. Need to lean, can't accelerate, what to do, just not sure. Other skills broke down too from the brain freeze. Made this turn so many times before just fine but can't hardly ride today, but think I understand better now.

[Willsportbike]

I was there. He added throttle and lean at the end. I pointed it out to Adam when we saw the video in the pits and he agreed.

 

Dylan hit the nail right on the head. You could even hear the rider cranking the throttle at full lean.