First high side BW CCW Grapevine

[viva_brasil]

I don't have video footage unfortunately. I clipped the curb on the inside left of grapevine (running CCW) front end slid and caught on the asphalt.

When the tire got back on the asphalt - I believe that's when the steering went to full lock (i likely was "almost down" over the curb and the shallower bike angle coming onto the asphalt caused the steering to whip to full lock). The tire briefly skid, wiggled the whole bike and hooked up (all within about ~6 inches of travel across the asphalt). After hooking on the asphalt it launched the bike upwards, the bike traveled through the air for about 8 feet and landed again close to the outside edge of the track on the right side of the tire, slammed down on the right side of the bike, and slid on its side through the dirt. I was booted off the bike at some point during the flight. I felt like I was doing a somersault and my instinct was to tuck my head in.

I landed on the back of my head and part of my shoulder, my techair airbag went off in flight the only thing I "felt" was my neck stretching and my left leg / shin hit something (probably the handlebar) - it was stinging even through the huge chunk of armor. My left shift peg was completely bent / twisted downwards, I believe I bent it with my foot during the initial "snap" that launched the bike.

We were able to piece it back together based on the small front tire skid marks left on the track, what I remember, and what a rider behind me saw. The "flight time" felt like slow motion, it was actually very peaceful.

Luckily I just strained my neck slightly, I got back on my other bike and rode the rest of the day with a new helmet. After lots of icing (and pain) on the drive home I had almost full mobility the next day (I was expecting a completely stiff neck for several days...). I'm now a true believer in icing injuries, had no idea it could have such a big impact on recovery.

So stay off the curbs at all costs at high lean (at least for buttonwillow!).

Anyone have a similar experience? Is there something I could have done?

 

[afm199]

Is there something I could have done?

Get your eyes up a bit and look where you want to go.

 

[scotinexcile]

Did you make any throttle adjustments once you felt the slide start?

 

[viva_brasil]

Did you make any throttle adjustments once you felt the slide start?

Given the line I had been running that day, I would have just started getting on 5-10% throttle. I hit the curb more towards the early part of the apex / corner. I turned in a bit too early that lap and was cutting through the curb section to stay on my line towards my track out point after the apex that I was aiming for.

My intention with a slide during a corner / turn is to make no adjustments or changes, just keep the bike as stable as possible and stay loose.

I had clipped the curb a few times the day before when it was wet (much less lean angle), the front end would sliiiide and then eventually grip again. Slow enough that I could observe myself not making any adjustments to brake / throttle / or bars and just waiting for the tire to come back. I once tried to steer out of a front slide and it caused the rear to slide immediately after the front came back and I got into a mini tank slapper. Since then I don't try to correct a front slide but just let it come back smoothly.

I do remember when the front slid on the curb before the high side, I was 'waiting' for it to come back. But when it hit the asphalt again, it was very violent and the chassis never settled.

 

[stangmx13]

sounds like one of your biggest mistakes was clipping the curb previously and repeating that error. dont practice bad lines. fix them right away so they dont become habit.

 

[viva_brasil]

sounds like one of your biggest mistakes was clipping the curb previously and repeating that error. dont practice bad lines. fix them right away so they dont become habit.

Grapevine I hadn't clipped before, the day before we were running CW and I clipped 2nd cotton corner once and bus stop once. It was my first time running this track so was trying out different markers trying to carry more roll speed.

I just mentioned the other curb clips from the previous day because it was wet and slow and I was able to observe my reaction to the front end sliding (in response to the other question).

But point taken - when a line doesn't work, don't repeat it.

 

[Holeshot]

I agree with Robert, but would add: stay off the paint/ curbs when it's wet. Go where the rubber is if you can...you're a car guy, you get that part.

How many times are you pushing the front or having the rear step out in a particular lap?

 

[viva_brasil]

I agree with Robert, but would add: stay off the paint/ curbs when it's wet. Go where the rubber is if you can...you're a car guy, you get that part.

How many times are you pushing the front or having the rear step out in a particular lap?

Not very often at all, I'm usually very neat with the front... I've only pushed the front on cold tires or when it was wet.

I've also worked on being smooth with the rear, getting on the throttle - the 5-10% - immediately off the brakes and smooth roll on out of the corner.

On the EBR I have more rear end feedback and can feel when I'm leaving a black mark behind me and can more confidently rotate the rear with throttle. That bike's TC is pretty bad, so I ride with it off. The linear v-twin torque curve also makes it easier to control.

There are a couple high speed turns where the rear end slides even at neutral throttle. I believe it's because of a slight change in track camber combined with the high speed / angle. Specifically turn 7 Thunderhill and the end of Riverside at Buttonwillow.

 

[Holeshot]

You're sure the rear end is losing enough grip to slide in those two turns (CW @ BW)? I've had the front push through T7 TH, but not the rear...hence has me wondering what's different in what we're doing.

 

[viva_brasil]

You're sure the rear end is losing enough grip to slide in those two turns (CW @ BW)? I've had the front push through T7 TH, but not the rear...hence has me wondering what's different in what we're doing.

Yea definitely rear slide, not front. It's very smooth. Maybe combination of body position and different level of maintenance throttle. I think I was possibly adding a bit of throttle - more like 25% instead of 10% in the area where it would slide.

Also geometry: the bikes are not set up for high speed rear end stability (not by design). The EBR is very much on its nose and front spring rate is too soft (compensating with maxed compression and heavier oil, planning to fix soon), and the R1 wheelbase is max short because of bigger sprocket and not adding links to the chain. With geometry adjustments, the front would likely push first before the rear at high speeds... arguably safer / better

 

[Holeshot]

I think we're talking about the same T7. Given it's essentially a kink and there's a brief moment when relaxing the throttle, but you're on the throttle hard since coming off of T6, any loss of rear wheel traction is going to load the front, but also give up drive grip.

Weird tho, IMO. I don't think that's a place I'm spinning the rear on either bike, nor am I seeing other people spin up there. Out of T8, yeah, but through T7..can't recall seeing that. I'll have to think more on that. Then again, we're running the softer rubber mostly so, YMMV. I don't want to lose the rear into/ out of T7. That's a scary fast section...

 

[viva_brasil]

Here's one on YT, this is exactly where I've felt it - between T7 and T8. I believe the track goes negative camber a bit there.

https://www.youtube.com/watch?v=0Ms7um_qS04

Similarly on riverside it's towards the end before picking up and flipping to the left before going up to Phil hill. It goes slightly negative camber there as well.

 

[stangmx13]

Fast corners usually require far more than 10% throttle on exit to actually load the rear and accelerate. I’m not logging TPS on my R6 so I can only approximate. 3rd gear corners feel like they need at least 20%. 4th gear, prob 40%. 5th gear corners seem to need tons, maybe >75% on my R6.

 

[viva_brasil]

True but my point is the slide is not on exit, it's approaching exit on T7 - second half of the corner, so not purely exit acceleration induced.

My %'ages were off a bit, I'm probably closer to 30-40% throttle through there and rolling on, but there's some off camber track section that invites the rear to slide out a bit. Similar to T5 sensation actually if you're off line, though T5 is gnarlier.

Riverside may well have been an exit acceleration slide...

 

[stangmx13]

my percentages were just to highlight that u may or may not be at neutral throttle in fast corners and could be unloading the rear tire. if u are using 30-40% in that section, u are likely neutral.

uve got some serious setup issues if the rear is trying to step out at or near neutral throttle. running a shorter swingarm actually increases rear weight bias, so its not that. and max comp damping might be the worst way to compensate for soft fork springs.

 

[viva_brasil]

Roger on setup issues, will be fixed soon. Incrementally better than stock settings but working my way up from stock setup.

I would say it stepped out while rolling on throttle on the second half of T7 but at a throttle input that it usually holds fine in other situations. More than neutral / maintenance throttle. It appears others have similar experience, caused primarily by the slight off camber section there. The shorter swingarm, steeper steering angle reduces rear end stability on corner exit from my experience. More black strips. I can picture the physics in my head but don't have the theory to translate into words

 

[stangmx13]

IMO, screw working up from stock settings. Pay a good tuner for their in-range setup and run it. It’s gonna take years of self-tuning to get anywhere close to that. All that time you should be working on your riding on a properly setup bike - not working on riding around bike issues and confusing yourself with setup problems.

Stability is not the same thing as grip. You can have one without the other, both, or neither ��

 

[viva_brasil]

The bike was set up by a suspension tuner with the current settings, we just kept adding compression and a bit of preload and the front end got better.

I don't usually even think about setup, I just rode the R1 and it made me realize that there's room for improvement on the EBR. But both bikes are very stable and give feedback in different ways.

The rear end slides I wouldn't say are a stability issue - the bike was very stable. As it is in other sections of the track where I can expect / predict the slide. I just wasn't expecting the slide in that section on the EBR, and the almost identical slide through a piece of Riverside on the R1. And I believe it is a slight off camber piece of the track there that lowered the throttle % threshold for a slide.

 

[stangmx13]

The bike was set up by a suspension tuner with the current settings, we just kept adding compression and a bit of preload and the front end got better.

thats not the setup I mean. a trackside setup on out-of-range components isnt even halfway to producing a bike that will get around a racetrack like it should. there are 15+ major parameters that go into a good setup, most of which arent (or cant be) adjusted by a trackside tuner. so u havent even scratched the surface yet.

a real setup is where u drop your suspension off a race tuner's shop for new springs, damping curves, and maybe some other custom work. all the parameters are set and u are told where to mount the forks. then u spend some more time at the track with the same tuner to optimize it further for your riding.

 

[viva_brasil]

Oh wow, yea that's something I'll aspire to - I'd like to start racing AFM hoping to do a NRS this year, and then I can justify going deeper down that rabbit hole.

But usually I just set it and forget it... Riding different bikes is what has helped me understand what suits my riding and where one set up has advantages over another. And now I'm going deeper on the EBR's setup.

appreciate the feedback and discussion! thank you