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Old 06-26-2017, 05:37 PM   #1
hobbes3
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Sonoma Raceway crash - turn 4


youtu.be/9kqGVdZ-Lxo

I wrote most of the description in the video itself, but feel free to ask me any additional questions.

Any comment, criticism, and advice are welcomed!

My take is that I didn't lean my body off enough (and the bike was too leaned over) and I was still adding lean angle (ever so slightly) before I lost traction. I also chose a bad line; not the worse, but not good either. I don't think adding the bit of gas during the turn made the situation worse. Lastly it also didn't help that I was riding street tires. Maybe race tires would have saved me.

My friend said I lost the front, which looks right but I was giving steady gas and acceleration during the turn...

Last edited by hobbes3; 06-30-2017 at 01:02 PM..
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Old 06-26-2017, 05:45 PM   #2
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To me it looks like you were adding lean angle and throttle at the same time, most likely as a response from being passed shortly before. To prevent this in the future I would recommend to get the bike pointed before adding throttle, and never add throttle and lean angle at the same time.

You and the bike okay?
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Old 06-26-2017, 06:49 PM   #3
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Underloaded front tire, just like every other track day crash on the front. You were on the gas a country mile too soon.
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Old 06-26-2017, 08:40 PM   #4
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Originally Posted by thedub View Post
Underloaded front tire, just like every other track day crash on the front. You were on the gas a country mile too soon.
Oh that makes sense. It definitely looked like the front gave out and I thought it was overloaded, but I was also on the gas so that didn't make sense.

If the front was underloaded, then that means the rear was overloaded, but why didn't I slide the rear? I'm not saying I would rather high side, but I'm curious.

By the way, the bike needs plastic surgery (gonna get white fairings now), but all the internal parts are completely fine. Still rideable (after getting a new front pegs). I'm also completely fine; the crash didn't hurt at all. The road scraped a bit on the right thigh and left palm (since I was on my stomach).

So basically next time:
  • Pick a better line and point the bike
  • Don't get on the gas until I start taking off lean angle
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Old 06-27-2017, 12:35 AM   #5
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What everyone else said. It didn't help that it was also your out lap.
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Old 06-27-2017, 06:48 AM   #6
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Thins to remember...
You were on cold tires
Turn 4 is downhill
Turn 4 is off camber at the exit
Turn 4 is notorious for losing the front.
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Old 06-27-2017, 06:49 AM   #7
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Originally Posted by hobbes3 View Post
Oh that makes sense. It definitely looked like the front gave out and I thought it was overloaded, but I was also on the gas so that didn't make sense.

If the front was underloaded, then that means the rear was overloaded, but why didn't I slide the rear? I'm not saying I would rather high side, but I'm curious.
  • Pick a better line and point the bike
  • Don't get on the gas until I start taking off lean angle
The later of the two items in your list is why you crashed. You can run all sorts of lines if you really want to.

When folks talk about "loaded" in this context they are talking about how much of the weight of you and the bike are on one contact patch or the other. You can't be "overloaded" in this way... weight here isn't bad for grip no matter how much.

You can only ask a given amount of grip to "do" so much work. Think about a 20 lb kid vs a defensive lineman standing in the same model sneaker on the track. If they stand normally it's going to take much less force to pull the big person's sneaker hard enough to slide it. That is what you can think of as available grip. If that linemen leans heavily to the right leaving 10 lbs of weight on this left foot then you can slide his sneaker just as easily as the 20 lb kid's.

You got on the gas pretty hard and reduced the weight on your front tire to less than how hard you were asking it to turn. Make more sense?

Get on hands and feet and have someone push you backward and forward. It's illuminating to the concept. Motos are tougher than cars to figure as when we lean them over the weight on both ends and splitting between trying to simply hold the bike down and pushing sideways in a way that will eventually slide the tire. Don't think about that too much though... think about which end the weight is on and how much.

Dave
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Old 06-27-2017, 07:23 AM   #8
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weight transfer... under braking the weight transfers to the front as you ease off the brakes the bike settles to a more neutral position and as you apply the throttle the weight transfers backwards.

open throttle (weight transferred from neutral to the back unloading the front), leant over, downhill, off camber, out lap colder tires..... front washed out
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Old 06-27-2017, 07:49 AM   #9
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Quote:
Originally Posted by hobbes3 View Post
If the front was underloaded, then that means the rear was overloaded, but why didn't I slide the rear? I'm not saying I would rather high side, but I'm curious.

...
  • Pick a better line and point the bike
  • Don't get on the gas until I start taking off lean angle
nope. just because one tire is underloaded, that doesnt mean the other was overloaded. as a new rider, you are not generating any large loads in either tire. you didnt brake hard and u didnt gas it hard either. dont worry about overloading tires - they can take a lot more load than u think.

your throttle application was small... and thats part of the problem. it was just enough throttle to unload the front tire and reduce grip. but it wasnt enough throttle to extend the rear suspension and re-load the front. it also wasnt enough throttle to cause a wheelie, removing the front tire from the whole situation. had u gassed it harder, u probably wouldnt have tucked the front - but thats still not good riding technique, so dont do it
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Old 06-27-2017, 08:35 AM   #10
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Originally Posted by Maddevill View Post
Thins to remember...
You were on cold tires
Turn 4 is downhill
Turn 4 is off camber at the exit
Turn 4 is notorious for losing the front.
^^^^^^^^^^^^^
Above is spot on to me...

Also, the camber change is quite abrupt there (walk the track thru there someday.) You were wide, tires were cold, you were downhill, you just got passed... < all of that added to what the pavement did, & YOU did added up to a bail.

That line would have been ok, IF you had not been on cold tires & on the gas (sharper off camber section/fall-away), OR just going slower warming tires, & not added throttle in a BAD spot. (gassing it LATER would have been ok once past the very short pavement change & minimal grip.)

This should be easy to see. Learn the lesson: Turn 4 is just a place to "get-through" until you get traction again, so you can roll-on WFO tossing it into 5 entry, then flat out thru 5 searching for traction before entry into 6.

Yeah I know, everyone does it differently, but for me 1st outlap, I would have been touring for longer....warming tires. (edited for bluntness)

-d
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Last edited by EastBayDave; 06-27-2017 at 08:39 AM..
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Old 06-29-2017, 09:34 AM   #11
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Originally Posted by EastBayDave View Post
^^^^^^^^^^^^^
Above is spot on to me...

Also, the camber change is quite abrupt there (walk the track thru there someday.) You were wide, tires were cold, you were downhill, you just got passed... < all of that added to what the pavement did, & YOU did added up to a bail.

That line would have been ok, IF you had not been on cold tires & on the gas (sharper off camber section/fall-away), OR just going slower warming tires, & not added throttle in a BAD spot. (gassing it LATER would have been ok once past the very short pavement change & minimal grip.)

This should be easy to see. Learn the lesson: Turn 4 is just a place to "get-through" until you get traction again, so you can roll-on WFO tossing it into 5 entry, then flat out thru 5 searching for traction before entry into 6.

Yeah I know, everyone does it differently, but for me 1st outlap, I would have been touring for longer....warming tires. (edited for bluntness)

-d
Yup, thanks for all the advice from everyone else too. The cold tires make sense since it was the first lap after an hour lunch break too (on street tires so no tire warmers).

I'll be more careful and smarter next time!
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Old 06-29-2017, 09:50 AM   #12
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Originally Posted by Smash Allen View Post
To me it looks like you were adding lean angle and throttle at the same time, most likely as a response from being passed shortly before. To prevent this in the future I would recommend to get the bike pointed before adding throttle, and never add throttle and lean angle at the same time.

You and the bike okay?
I'm trying to parse this thread into a "what should OP try to do" take away, and I'm struggling. Smash Allen's comment is what resonated the most with me.

Clearly cold tires, outlap, sketchy turn - chill! Clearly if the front wheel gets under loaded it can tuck.

But the key question is what does one do, when approaching turn 4, and tricky turns like turn 4,
- set lean angle and line before applying throttle (don't add lean and throttle at same time)
- set speed for slowest part of turn (where the off camber is greatest, like you do in decrease radius turns). This of course requires you have learned the turn at slower speeds and gradually have worked up your speed.
- for turn 4 specifically, take a tighter line and hit the apex to keep to the section of track where it is less off camber.
- take at least the first if not the first two laps easy until you have put some heat into the tires

Does this sound right?

Thx (I'm learning too)

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Old 06-29-2017, 10:03 AM   #13
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Hobbes,

This crash wasn't due to a single error as far as I can see. Other people have mentioned some of the factors. I'll list the ones I think contributed and give you a little more information about some of them.
  1. Being the first lap, your tires were cool. By turn 4, you were making your third right turn.
  2. You're correct that you were on the throttle while adding lean angle.
  3. If you freeze the video right at the moment your front starts to slide, you will see a scratch on the pavement right where your bike is going to end up.

On point #1 above, the tires were not as sticky as they would be later in the session. Q3's aren't bad when cold, but like all other tires, they're a lot stickier when hot.

On #2, you'll often hear that it's a bad idea to roll on the gas while adding lean angle. We don't often talk about why. The relationship between throttle and lean angle change is important and if you could change one thing for a different outcome it would be when you began rolling on in relation to turning the bike.

Much more often than not, if people crash because of rolling on while steering, they lose the rear. Prior to switching to BMW S1000RR's, the Superbike School statistics showed that 45% of crashes we saw at the school were caused by spinning up the rear when the rider added throttle and lean angle at the same time.

Where it can be a problem at the front is in a bumpy corner. During cornering, the steering is part of the suspension. With the bike leaned over, the front wheel maintains best contact with the ground if it is able to wiggle back and forth to let the front wheel follow the bump contours. When we apply pressure to the bars, we are interfering with the front wheel's ability to track bumps. Off the throttle, there is enough weight on the front to force the wheel to follow the bumps to some extent. When on the gas, we take some of the weight away and the front end is more prone to skipping off the bumps. If we are pressing on the bars, we may cause the front to cock a little sideways at the top of a bump and begin to slide.

Also, note that it takes more bar force to steer the bike while on the gas than when you're off the gas. This not only makes the bike harder to point, it also worsens the problem I describe above. We would be more apt to upset the front over bumps because we are pressing harder on the bars.

The correct sequence for steering and rolling on is: Set the lean angle, make sure the bike is on line, then begin rolling on as soon as possible after that.

Note that while in the corner, rolling on the gas not only takes weight off the front, it also takes away some cornering load. Under acceleration, the bike wants to wheelie. When leaned over, that "wheelie" isn't vertical; it's both up and to the inside of the cornering arc. Had you completed the steering prior to rolling on the gas, you would likely have been fine rolling on the gas in that same location.

On point #3, the line you were on may not have been ideal, but it should have allowed you to get through the corner with acceptable throttle control. It is interesting to see that someone else had crashed in the same location very recently before you did. It may or may not indicate a problem with the surface in that spot. It could have been an especially bumpy part of the corner, or the previous crasher may have left something slippery on the track surface that wasn't evident.
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Old 06-30-2017, 09:38 AM   #14
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TZRider: excellent analysis and explanation! Thx!
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Old 06-30-2017, 09:42 AM   #15
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TZRider: excellent analysis and explanation! Thx!
agreed Much better than I can do. WTG!
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