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R Sole

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Everything posted by R Sole

  1. My understanding is that you can get washout in two ways on the front wheel on corner (assuming decent speed to start off with). The one is the situation above with overloading of the front wheel by sudden deceleration, and the other is almost the exact opposite - where you accelelrate hard out of the corner while still at a lean, and the resultant speed increases the outward force, and the weight coming off the front wheel reduced the capacity for traction. Is this correct?
  2. So the chopping of the throttle results in the riders weight moving forward onto the front wheel, This additional force downwards on the forks has a downwards component and an outwards component. The acceleration outwards causes the friction from the tire to be overcome, and it to lose grip. Makes sense I guess. Although an increased weight at the front wheel should also increas the friction from that wheel (as friction is proportional to force downwards)
  3. Keith - This may or may not be on the same topic, but you explain why "chopping" the throttle mid-turn causes the front end to break away? After all the same forces apply, but the speed is decreased, so the forces acting outwardly on the bike should decrease, not increase to them to cause them to overcome the friction of the front tyre? I came up with a few theories: 1) Perhaps the weight shift to the front of the bike causes the forks to dip, and the steering geometry to change, causing a quick change in turn in (i..e a suddenly decreasing turn radius) that increases the cenripetal forces due to the sudden changes in radius? To my mind then, this effect would not be seen in bicycles with no suspension? maybe a cyclist can confirm this? 2) Is it because the sudden deceleration causes the front tyre to start skidding, and the dynamic friction afforded by a slipping front tyre is a lot less than the rolling friction? Although this does not make sense as there si noreason the tyre would not just continure to roll?
  4. Aim for his back wheel and use it to slow you down progressively, and make sure that the cyclist fool also walked away with scars.
  5. I am still not quite sure why sudden deceleration in a corner cause teh wheel to break away though? Angular velocity changes, as does angular acceleration, but why does it make the traction break away? Is it because the change in trail cause the bike to turn in more suddenly, changing the radius of the turn too quickly and increasing the centripetal acceleration so quickly that the friction of the tire is overwhelemed? This makes sense, as it is only the front wheel that gives way. Also, you dont get that highsiding effect on bicycles (that do not have a suspension set up, with a changing trail).
  6. So am I correct in thinking that trail braking (gently so as not to cause sudden deceleration and hence breaking away of the front tyre) into a corner decreases the trail of a bike and helps it turn in, and then rolling on slowly and constantly (again no suddent acceleration/deceleration) to move the suspension to a balanced configuration between front and back wheels settles/stabilisies and optimises the suspension during cornering? And getting your wight far over allows for the bike to stay as far upright as possible to enable its suspension to be used in the right directions for maximum traction. I am an engineer, and I love getting technical about these things, because it makes more sense if I can see teh applied mathematics of it. I see the cornering forces as the balanceing of moments (or torque) on the rider and bike (when looking at teh bike from the front) about the wheel traction points (where tire meets road). One monet is the combined inward component of teh weight weight of the bike and rider and countersteering gyroscopic force acting inwardly. The other moment is the centripetal acceleration acting outwardly on the mass of bike and rider at the centre of gravity of bike and rider. So increasing speed in the corner increases the pentripetal force and hence moment acting outwardly, and needs to be balanced by increased lean angle and/or lower body height. Assuming body height is as low as you can get it anyway, then lean angle must increase (for additional weight component acting inwardly), or the countersteering gyroscopic force must increase by using more countersteering. Does anyone need a force diagram?
  7. And being inexperienced, you probably could have got through that corner if you had just stayed smooth and not turned to the Survival Reactons (SR's) and chopped/braked and stood up. I reckon its better to stay smooth and KNOW that you were too fast for the corner than run off (at least off a public road) into God knows what obstacles and die wondering...
  8. Whenever I get that tighteneing in my gut, I find it helps to concentrate on realxing my inside arm,and focus on getting my weight far over and low (to keep teh bike as upright as possible). Relaxing that arm (the one I countersteer with) also makes my turning input easier and smoother, and the bike makes it around no problem. I am quite inexperienced, but what I am noticing more and more is that the physical limits of trning are so bloody high that most problems are caused by the riders mental attitude rather than their bikes capabilities.
  9. I like to "show intent". If I am riding a particular way, I maintain that way, without changing or being to unpredictable. I also try and ride like the cars expect bikes to. They expect bikes to be faster than them and slightly more agressive in riding style. So I ride about 10km/h faster, and overtake aggressively. IfI wishy washed behind tehm, slowing down and speeding up, the get anxious and may do stupid things to try and get you to do what they expect you to do, like slowing down, or pulling over a bit where there is no space to etc. I ride with intent (from A to B like you say) and try and telegraph this intent by looking where I want to go to change lanes. I also kep physics in mind. I ride a VTR 1000 firestorm, so I KNOW I can accelerate faster than pretty much any car, but I know that most cars can brake harder than me. I accelerate into gaps, knowing that at a particular moment things are like X, and it is not physically possible for them to change to Y if I have done things correctly. Then I can just focus on unexpected events.
  10. I grew up in South Africa and I wrote off a mates bike (DT 125) at 18 on a dirt road when I got on it and thought turning was weight shifting like a bicycle, but harder. I could not understand why anyone would ride things that they could not control an I could not understand why/how small GP type guys could fling bikes through chicanes the way they did. When I was 28, I started riding a mates bike CBR250RR and finally figured out countersteering (I never learnt anything about it until after). I could have avoided my 2 accidents. Now I am a preacher of c/s. I rode my cousins bike a bit when I was 32 - a BMW R80GS. I have since moved countries to NZ, and bought a VTR 1000 Firestorm (Night Hawk? in the US) 6 months ago and commute to work on it everyday. I have not yet attended a track day, but voraciously gobble up everything I can find about riding technique. I have plans for a track bike and hope to attend the CSBK at Auckland's new Hampton Downs raceway soon.
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