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faffi

What happen here?

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Hotfoot    50

Would "adding throttle and lean angle on cold tires" be too simple an answer? :)

You can hear him rolling the throttle on as he is swerving back and forth and the at the point where he is leaned over the most you can hear the tire spin up. Maybe he hit a slick spot but most likely the combination of lean and increasing throttle just exceeded the available traction for the tire - which was most likely cold, since he was just starting his session.

The rear tire then slides out sideways, the rider lets off the throttle (you can hear it), the rear tire regains traction and whips back the other way, and then you can see the rider start getting pitched forward, and my suspicion is that he ends up putting pressure on the bars so that they can't move freely thereby eliminating any chance of the bike straightening back out. You can see the front end trying to correct at first but by the time he actually falls it seems like he is leaning heavily onto that right-hand bar.

So, couple of questions back at the group:

1) What is a rider typically trying to do when they are swerving the bike back and forth like that, and does it work?

2) What should a rider do (or better yet NOT do) with the throttle when the rear tire starts to slide, and why?

  

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faffi    12

Spot on according to the explanation given by the magazine. Despite being an experienced racer, he did not take into account the fresh tyres - probably because he had gotten away with similar actions before.

Since I know the answer to your first question since it was given in the article, I will let others have a go.

Question number two; I would say either maintain throttle or gently roll off a bit, depending on how quick and big the slide was, and ride it out - power will (unless you have applied tons of throttle) taper off and allowing the tyre to regain traction smoothly and under control. Personally, I chop the throttle in panic every time :D By shear luck I have managed to not be tossed off yet. When the front goes, or both tyres slide, I notice I tense up but somehow I manage not to do anything with the throttle. This is not due to me being excellent or staying calm, it's just something that has stuck in my reflexes since I was a kid and used to bicycle a lot in snow and on ice. Later, I have also ridden motorcycles through 3 full winters. This has teached me to be generally smooth without ever thinking about what I did.

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JohnCBoukis    2

I waited for someone else to jump in, but I will answer it. The rider is steering back and forth in a vain attempt to warm up the tires. To answer Hotfoot's question about effectiveness, here is an older post which contains cool references to studies:

Note the comments on the effectiveness of the sun. The sun heats primarily via infrared light. This electromagnetic spectrum can penetrate deep inside of objects which convection (heating air and circulating it) or conduction (direct contact) will not do. Unfamiliar with the current technology, my research shows that some tire warmers now take advantage of IR.

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Hotfoot    50

Wow, John, look at that thread from way back in 2004, how did you find that? :) But yes it is very good info. And yes, I was asking about why the rider was weaving back and forth. You do see this pretty often at track days, riders weaving back and forth in an attempt to warm their tires - but it doesn't work. It can be dangerous, too - not just because a rider could crash doing it (that would be embarrassing!) but also because if you are unaware of another rider about to pass you and make a sudden swerve like the you could run into them.

Good answer, faffi, on question 2. There are some training tools at CSS to help learn to control the Survival Reaction of wanting to chop the throttle when the rear tire starts to spin.

The S1000rr bikes we use also have traction control. So here's another question for the group - do you think traction control would have prevented the crash on the video?

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Jaybird180    31
2 hours ago, Hotfoot said:

Wow, John, look at that thread from way back in 2004, how did you find that? :) But yes it is very good info. And yes, I was asking about why the rider was weaving back and forth. You do see this pretty often at track days, riders weaving back and forth in an attempt to warm their tires - but it doesn't work. It can be dangerous, too - not just because a rider could crash doing it (that would be embarrassing!) but also because if you are unaware of another rider about to pass you and make a sudden swerve like the you could run into them.

Good answer, faffi, on question 2. There are some training tools at CSS to help learn to control the Survival Reaction of wanting to chop the throttle when the rear tire starts to spin.

The S1000rr bikes we use also have traction control. So here's another question for the group - do you think traction control would have prevented the crash on the video?

The 2017 CBR1000RR is Honda's first go at a Ride By Wire system and includes traction control.

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faffi    12

The article stated it was to warm the tyres, and also that it does not work. Due to the cold tyres, throttle application together with leaning, the traction control - adjusting the throttle position only - could not react quickly enough to save it. The article suggest a car-type system applying the rear brake could perhaps have saved the rider.

For warming up the tyres, the article suggested alternating between acceleration and braking. This will flex the carcass and as a result of internal friction the tyre will warm up quickly, and not just the surface, but the whole tyre.

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Hotfoot    50
2 hours ago, faffi said:

For warming up the tyres, the article suggested alternating between acceleration and braking. This will flex the carcass and as a result of internal friction the tyre will warm up quickly, and not just the surface, but the whole tyre.

This is what the school recommends as well, and it works.

Yep, traction control cannot necessarily save you from adding throttle and lean angle at the same time - it's too much changing too quickly, there is not enough time for the traction control to react AND there is no time for tire feedback to warn the rider, which is why we always warn riders not to add throttle AND lean simultaneously. Just as an interesting note, I suspect the BMW S1000rr's rain mode could have prevented the crash, as it limits how much throttle the rider can apply based on lean angle, and I think it would not have allowed to rider to apply as much throttle as he did at the lean angle he was using.

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