Ninja 250 lowside on track

[intortus]

This past weekend I had my first on-track crash in the dry. Fortunately I had cameras rolling when I went down (turn 16, Auto Club, Jan 7 2012):

[youtube]bXxoHAY6y8w[/youtube]

The main thing I noticed is in the rear-facing footage, where I see a skid mark starting just after a crack/seam in the pavement. I'm guessing that's from my front tire. The other thing I noticed, from slowing it down, is that I started getting on the gas right before I lowsided.

My current theory is that the crack upset my frontend, and getting on the gas made it worse. I didn't feel the front sliding or correct it, so down I went.

I believe there were also some contributing factors. I hadn't had lunch yet -- in fact I'd meant to before this session started -- so I was mentally and physically well below 100%. Yet I chose to push hard in just my fourth session ever on this track. I was also letting myself get frustrated at a couple of slower trackday riders, for no good reason. I was a bit off line, riding mentally behind the bike, and probably got on the throttle too aggressively to try to compensate for my bad line.

When I got back out there a couple hours later, I noticed while riding through that corner that I was putting a lot of weight on the handlebars. If I'd been doing that when I crashed, maybe that contributed an awful lot as well?

 

[just physics]

Looks like you were on the gas and leaning hard as you went over that seam on the track

 

[Lazerus]

That seam looks like a step "up" as you cross it. Is it?

Maybe a steeper angle of approach that allows you to finish your steering input before the seam (I have to do that in several places at buttonwillow). Looks like a line you could manage in warmer weather though.

 

[intortus]

That seam looks like a step "up" as you cross it. Is it?

Maybe a steeper angle of approach that allows you to finish your steering input before the seam (I have to do that in several places at buttonwillow). Looks like a line you could manage in warmer weather though.

Hmm, I'm not sure. I didn't even properly realize there were cracks there until I reviewed the video later. I always feel like I'm slower than other riders to notice and identify features of the pavement.

You may be right about a steeper angle of approach being better, though. My initial thought when I went down was about how bad my line was through there. Normally I would hit that crack at a steeper angle, and it didn't give me any more problems the rest of the weekend.

 

[tzrider]

I'm hearing something a little different. The rider is off the gas for a long time in that turn. He cracks the gas open for an instant, then closes it again before hitting the seam. Near the seam, he loses the front, then we hear the engine note rise again.

I think he lost the front because he was off the gas and there was too much weight on the front tire. The brief instant that he opened the gas prior to falling wasn't long enough for weight to transfer to the rear.

OP, thanks for including the slo-mo segment, as it makes it easier to identify the sequence.

 

[dammyneckhurts]

Adding throttle and adding lean angle at the same time is not a good thing.

I am not on a 250 so my lines are a bit different, but it looks to me like you need to get the bike slowed and turned a bit more in turn 13. In the video you are running just a bit wide out of 13 and this results in you running a bit too straight or "shallow" into turn 16.

Then in turn 16 your brain is saying "Add gas-go fast" but the problem is because of the shallow entry, that you dont have the bike turned enough yet.

Enter 16 just a bit wider, get the bike turned and pointed towards the exit of the corner a bit more, make sure you start to reduce the lean angle a bit before you add a fist full of gas.

Even the 28-30 horsepower of a 250 can be too much if you are still adding lean angle.

 

[tzrider]

Adding throttle and adding lean angle at the same time is not a good thing.

This doesn't really fit with what happened, that I can see. In the first place, his lean angle is set when he first cracks the gas. Secondly, he lost the front. The concern about adding throttle and lean angle at the same time is rear traction.

 

[intortus]

This doesn't really fit with what happened, that I can see. In the first place, his lean angle is set when he first cracks the gas. Secondly, he lost the front. The concern about adding throttle and lean angle at the same time is rear traction.

Hmm, actually, I do agree that getting on the gas contributed. It's a lot more difficult for the suspension to compensate for bumps (or abrupt weight transfer) when the bike is leaned over. 30hp may not seem like much, but you can still feel major changes in throttle on these bikes. I think hitting the crack or getting on the gas alone would not have resulted in a crash, but the combination at the same time (plus a few other factors on my part) let the front lose grip.

Also, what dammyneckhurts said about my line matches my experience at the time. All those corners link together, and when I crashed in turn 16 I was still struggling to compensate for a bad line out of 13. So, another reason to always focus on hitting apexes before trying to push for more speed.

 

[tzrider]

Hmm, actually, I do agree that getting on the gas contributed. It's a lot more difficult for the suspension to compensate for bumps (or abrupt weight transfer) when the bike is leaned over.

How do those two statements relate?

Also, what dammyneckhurts said about my line matches my experience at the time. All those corners link together, and when I crashed in turn 16 I was still struggling to compensate for a bad line out of 13. So, another reason to always focus on hitting apexes before trying to push for more speed.

You may have hit upon something important there. Can you say more about "struggling?" What were you doing?

 

[dammyneckhurts]

Good thinking about hitting the apexs before pushing for speed, and I have one thing to add.

In this context regarding the apex I assume you are refering to the curb on the inside of the corner and setting your line so you are "tight to the apex".

Another critical point is that at the apex, you need to make sure your bike is pointed the right direction. If your bike is pointed the right direction you can reduce lean angle and add throttle.

I only say this because its possible to enter a corner on slightly different lines that will all result in the bike being at almost the same apex...but the bike woud be pointed in slightly different directions. If you dont have the bike turned enough when you arrive at the apex you cant add throttle, you have to wait till the bike finishes the corner a bit more.

 

[intortus]

How do those two statements relate?

I'm used to the front suspension keeping the front tire sticking, regardless of what I do. But in this case I asked for too much: stiff arms, leaning on the bars, with the bike at full lean, running over a seam while opening up the throttle. Fix one or two of those things and I think, in that particular situation, I would've stayed up.

You may have hit upon something important there. Can you say more about "struggling?" What were you doing?

Well, this gets at how I got into the suspension-compromising situation I described above. My mental state was slightly arrogant and frustrated, and I was also just learning the track. I'd just spent half the session battling some B-group riders with weird lines, and was working on my final getaway. I'd also skipped lunch. So all sorts of bad physical and mental habits creeped in.

Coming out of 13 wide (which I did quite a few times, having not yet understood how it links into 14-16) forces you to have to lean the bike more to make turn 15 (the right-hand kink before 16). This means you have to do much more countersteering to flip the bike back over for turn 16. It's fun, but it also means that at the time of the crash I was working twice as hard as I should just to steer the bike, while also desperately wanting to pin it ASAP to get up to speed for the front straight (if you line up turn 16 right, then it's just full throttle from there until turn 3 on a 250).

So I think I should modify my track-learning strategy. I should eliminate the struggling before trying to fly. If I had worked out turns 13-16 at a softer pace, then when I did start to push I'd have better lines and a smoother, more relaxed form.

 

[intortus]

In this context regarding the apex I assume you are refering to the curb on the inside of the corner and setting your line so you are "tight to the apex".

Another critical point is that at the apex, you need to make sure your bike is pointed the right direction. If your bike is pointed the right direction you can reduce lean angle and add throttle.

You're right. The day I crashed I was talking to a teammate about lines, and I was trying to explain the same concept. An apex isn't just a spatial location, it also includes the orientation and velocity of the bike (and, I would argue, also the distribution of weight or state of the suspension).

I did have experience at "hitting" that apex with the wrong orientation earlier that morning (and consequently jumping over that plastic curb on the outside). So many warning signs I missed that day.

 

[tzrider]

I'm used to the front suspension keeping the front tire sticking, regardless of what I do. But in this case I asked for too much: stiff arms, leaning on the bars, with the bike at full lean, running over a seam while opening up the throttle. Fix one or two of those things and I think, in that particular situation, I would've stayed up.

You're right, to a point, but staying off the gas isn't the answer. The reason I asked how you would relate your statements about suspension compliance and throttle is that being on the throttle will make both ends of your suspension more compliant. When you're off the gas, both ends sag to somewhere in the bottom third of travel. When you're on the gas (and weight has transferred to the rear) the suspension is usually somewhere in the middle third, where it is better able to track bumps.

When you lose the front instead of the rear, you have too much pressure on the front. The additional info you provided about still applying force to the bars helps. It's a contributing factor.

The line you were on did influence all of these things. It forced you to wait on the gas and it required you to keep pressure on the bars longer than you want. Had you been on the gas sooner and relaxed on the bars, I doubt you would have slid.

 

[stangmx13]

im having a difficult time wrapping my head around this one.

i agree that the front let go from being overloaded. however, ive never seen this exact situation b4. for example, if u trail-brake too hard into a corner and blow it... no one expects the front tire to let go when u finally stop braking. but that is exactly wat seems to have happened here. thoughts?

 

[tzrider]

He may be right that the seam triggered the initial slide. At the same pace but light on the bars and on the gas, I doubt he would have had a slide.

 

[KazMan]

My observation was that you were off throttle and trying to make an apex to the curb but were late. Thus the weight was on the front end while you were trying to force more direction to the curb and then you hit the seam which bounced the front end and put you down.
Logan, we need to put a zip tie or an oring on one of your front forks so we can start tracking travel and more importantly begin doing suspension tuning. Your speeds are good enough now that you will have to work on suspension to get more out of the bike.
I know you have been targeting lap times and that's great, but I am a firm believer in disecting the track and then going after speed, but in reality, there is a corrolation between the both. But by disecting, you also get to learn where line b, line c, etc are so you have those in your arsenal when someone is clogging up your a line.
Also, a couple more sessions with Rich at the Mystery School, you will begin to develope a feel for when a front or rear is at limit and perhaps be able to pull yourself out of that by putting the bike on your knee and lifting the bike back up and/or stand the bike up to get your contact patch/downward force of gravity back under you. Although with your riding style the latter is a bit more difficult because of where your riding weight is.
But in the end, you did damn good that weekend and it was fun to watch!

 

[OldMadBrit]

im having a difficult time wrapping my head around this one.

i agree that the front let go from being overloaded. however, ive never seen this exact situation b4. for example, if u trail-brake too hard into a corner and blow it... no one expects the front tire to let go when u finally stop braking. but that is exactly wat seems to have happened here. thoughts?

If the rebound damping is insufficient, the couldnt the front tire unload suddenly when you get off the front brake? I suspect that this is what contributed to my lowside at Thunder Hill - I was trail braking into T14 and went down as I came off the brakes.

 

[scotinexcile]

If the rebound damping is insufficient, the couldnt the front tire unload suddenly when you get off the front brake? I suspect that this is what contributed to my lowside at Thunder Hill - I was trail braking into T14 and went down as I came off the brakes.

One of the MAJOR lessons I learned from Ken Hill was the "speed" you release the brakes is just as important as the "speed" you get the brakes. To learn more you would have to attend one of his private days or the YSR school. There is also some good info on fastersafer.com

 

[khill]

I watched the video 2x...he added throttle while adding lean angle. If you add throttle, where does the weight go? Is the contact patch bigger or smaller on the front tire?

Plus, he was off his apex, his trajectory was incorrect and his turn in rate seemed pretty abrupt.....my .02...

Ken

 

[KazMan]

huh, good catch, I was attributing that pulling the throttle as the bike was leaving from underneath him, or the classic spin-up you hear with a low side