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CoffeeFirst

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CoffeeFirst last won the day on June 28

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About CoffeeFirst

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    Cornering Apprentice

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    Male
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    Atlanta
  • Interests
    Track, road and off-road riding. Photography and videography. Physical fitness. Travel. Skiing. Time with family.

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  • Have you attended a California Superbike School school?
    Yes. Consider me an L4 devotee.

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  1. Couldn't get the above video to play so here is a link to it on YouTube: Rea 1 Lap 6 Places Magny-Cours 2018 There is also a brief WSBK video of Rea bolting from 8th to 1st in five corners at the TT Assen circuit last April. His move from 8th to 3rd by the first corner is very impressive. This Assen video allows you to see him in context of the pack. What strikes me about his riding are three things: he is incredibly smooth, precise and takes racing lines that do an excellent job of setting up his passes. Here is the link: Rea 8th to 1st Dutch Round I searched for video footage of the 1977 AMA Grand National Championship round at Sears Point where Kenny Robert's famously went from last to first in four laps. I could not find it, but I did find a wonderful video of the 1979 Silverstone round showing highlights of Robert's battle with Barry Sheene. As you would imagine the video quality is poor given the era but the racing is marvelous nonetheless. It is six minutes in length. Enjoy. 1979 Silverstone - Kenny Roberts versus Barry Sheene As to Jaybird 180's questions … "Is this possible with consumer level tires?" Consumer tires is a broad term. There are lots of track tires the average consumer can purchase include race slicks. But if by "consumer level" you mean typical street tires then no, not compared to track focused tires. "Is there some type of electronic gadgetry at play here?" Absolutely. WSBK and MotoGP bikes use sensors, software and ECUs to the fullest advantage possible. But great riding and winning still comes down to the skills of the racer. "Or maybe I can get on the gas harder on corner exits?" Speaking for myself - almost always! Dave
  2. The first video with Hickman - incredible! He must have the same, very rare, amygdala / frontal cortex neurology as Alex Honnold (the El Capitan free-solo climber) to ride so fearless. What scares the bejeezus out of 99.99% of us doesn't even move the needle for these folks. Fascinating stuff.
  3. I have to believe a solid lock-on with both knees into the tank when braking hard helps (1) keep your arms as relaxed as possible, (2) keep your butt from sliding into the tank, and (3) has you in good position to quickly execute a knee-to-knee / hip-flick motion. Not sure how one could quickly execute a hip-flick when the leg needed to push on the inside of the tank when coming into a corner is dangling off the side. But, Moto GP and WSB riders are on a whole different level of body and bike control, I know, so the pros have to out weight the cons for them. To the point above about it keeping the back end from coming around, if does often look like a stabilizing action by these pro riders as the rear of their bikes dance about. It seems like the more you see bikes sliding around the more you see legs out. For mere mortals I wonder if it would be considered a SR? I guess that depends on how intentional the action is or isn't. Only a matter of time.
  4. Yes, I see it now. It is a very slight roll off for sure. It is so slight I had to watch the rpm needle to pick it up. Very impressive throttle control! Thanks Keith.
  5. Very nice! Completely agree about 2-strokes being a ton of fun - road an early 70's Hodaka Super Rat (remember those?) as a kid.
  6. Here is Will's lap from 2014 … https://www.youtube.com/watch?v=TFjm8cJ-z9g Here is what I think I see, but check me on this. Will has a nice roll-on out of T2. Then rolls completely off the throttle and trail brakes pretty hard before he gets to the T3 turn point. It looks like he carries his trail brake past the turn point but ends it well before the first apex. It also looks like he is back on the throttle before the first apex as well and holds it essentially steady (just a very slight increase in rpms) through the middle of the turn and second apex. He then rolls on as he exits.
  7. I'm curious Cobie, what is your off-road / dirt motorcycle?
  8. Took a quick look at video footage from L4 training and CODE Race last fall. I roll on, have a slight roll off, then roll on again. Ditto on this comment by Hotfoot.
  9. If Eddie had to back out, wouldn't he have rolled off the throttle tightening up his line in relation to the corner versus running wide? On the other hand, I guess if he had to get on the front brake as part of backing off that could have caused him to come up and wide.
  10. Suggest watching it on YouTube here ... https://www.youtube.com/watch?v=omk5sHY2xwI&feature=emb_err_watch_on_yt To see the accident jump to 17:00 time marker. 17:45 shows it in slow motion. To pull apart what happened I think there are three things we could try to understand: (1) What was each rider's racing line coming into the corner and trajectory at point of impact? (2) Given their individual racing lines where was each rider's actual apex point for turn 1? (3) What was the relative speed and motorcycle attitude (i.e, accelerating vs decelerating / braking, going into more or less lean angle, etc.) for each? From what I see Kevin Schwantz is further to the left side of the track coming into the Turn 1 (right hander) and on a wider, faster, more open racing line than Eddie Lawson, who was carrying more initial speed to grab the inside line at the corner's entrance. Given the camera angle it is hard to see exactly where each rider's actual apex point was - they may very well have been charging for the same apex - but it looks to me like Eddie's apex point was a little earlier in the corner then Kevin's. Schwantz does carry more speed through the corner and is leaned over longer than Eddie, coming across Lawson's front tire with an apparent trajectory to cut off the inside line in the middle & late sections of the corner. After he hits his apex Lawson seems to stand his bike up as Schwantz comes across his front, but I don't think I would characterize it as a pre-accident panic pick up. In fact, when you try to go frame by frame it looks like Lawson's pick up may really be because they had touched (Kevin's rear wheel to Eddie's front), which would cause a reaction like Eddie's from all of us. I think my conclusion is Kevin came across too tight and clipped Lawson's front end in his effort to close off the inside line. However Lawson's intended trajectory may have been to move further to the left on exit given he was in the process of bringing the bike up, so not exactly helping matters. Not sure how this was ultimately evaluated by MotoGP officials but would guess it was just chalked up as a racing incident.
  11. yakaru, I'm not sure it is as much a question of friction being applied in more places (unless more 'keying' is happening) as it is the extent to which the contact patch 'coefficient of friction', at that particular moment in time (so factoring in the portion of the contact patch that has been disrupted) has not reached the point of 'slip'. In some of the articles I've read the point of slip is expressed algebraically and can be calculated (theoretically) if all the other variables in the equation are known. Dave
  12. Thanks, Dylan. I've read about these dynamics in various articles but have never seen them summarized in such a succinct manner. Very helpful indeed. I would add I think 'keying' may also be a dynamic property (in addition to static) given the extent to which keying is constantly changing as tire energy dissipation, surface and interior heat, abrasion / shearing stress, and load change. For those who may be interested in the engineering details, one of the websites I found helpful is multiscaleconsulting.com. In their publications section are various papers on rubber friction and contact mechanics. A warning - their papers are filled with lengthy algebraic formulas supporting their analysis. I try to just focus on their key points and not get lost in all the math. I think the next evolution of this for me will be to learn how to read a tire so I understand what is happening to it and my traction/friction equation. Dave
  13. I've been trying to develop a better understanding of traction over the last couple of months as well. As such I've read a number of articles and technical papers about friction, and specifically, friction as it applies to the interaction between rubber and hard/asphalt surfaces. As I understand it, there are four types of friction: static, sliding, rolling and liquid. I may be wrong but I think the Amontons-Coulombs three laws of friction do apply to tires/rubber as it relates to "static" friction - tires may not be rigid but they are solids. However as soon as you move to sliding and rolling friction (which are the only applications we really care about) the three laws need to be modified for rubber specific properties and what happens between rubber tires and asphalt friction as heat and tire deformation change. Attached below are a couple of articles that help explain rubber-hard surface dynamics that cause rubber related friction to act differently. After reading these articles (and several others) I am now thinking about the "coefficient of friction" between tire rubber and asphalt, at any given moment in time, as being determined by the following ... For road surface … its material, texture, condition (including extent of surface oils/moisture present), temperature, gradient/camber. For tires … their material, construction, condition (also including extent of oils present), energy dissipation and resulting temperature (a hugely significant factor), stiffness, extent of flex/deformation and how well the rubber fills asphalt surface gaps and creates microasperity contact points (so yes, contact patch size matters), and finally tire pressure (which has direct impact on extent and rate of tire temperature changes and flex/deformation). Pressure or load between the tires and road surface … from both vehicle weight and riding forces (ergo cornering forces) The list may be missing a few things, but I think it hits the major elements. And since cornering force has such high impact, I think about the extent of "cornering force" being driven by a number of factors as well, including ... Weight Vehicle balance (shifting of weight, pitch and angle) Kinetic energy (speed) Corner radius and extent / rate of radius change (e.g. closing versus opening radius corner) Centrifugal force (directional inertia) Centripetal force (force acting on a moving body at an angle to the direction of motion, tending to make the body follow a curved path) Rolling resistance (from braking and accelerating forces) I'm still learning on all this (traction / friction) so feel free to correct me where I am off base. Dave Guidance-Rubber-Friction.pdf Rubber_Friction_and_Tire_Dynamics_A_Comparison_of_Theory_with_Experimental_Data.pdf
  14. Hi Roberts, Thanks for the insights. Very helpful feedback on center of gravity, velocity/comprehension dynamics, tire wear challenges, and the ability to lock in body position and focus with fewer physical action distractions. As CSS has taught us all, the less of our $10 of attention we spend on distractions the more we can focus on what matters (wide vision, throttle control, RPs, POT, hitting the apex, elevating our speed, etc., etc.). And the notion of a "constant sweet spot" is a pretty compelling idea. Thanks again. Dave
  15. Good for you! You'll greatly enjoy it. The CSS team and their training are outstanding. And as someone who started track riding in his late fifties, it is "never too late to teach an old dog new tricks" as they say. Dave
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