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They're effectively the same process occurring to different degree. A high side is what you get when you arrive at a point of unrecoverable inflection in such a

by hexaga 3y ago

They're effectively the same process occurring to different degree. A high side is what you get when you arrive at a point of unrecoverable inflection in such a wobble.

seanhunter 3y ago
Not sure that’s true. My understanding is the lowside happens when the tires lose traction while cornering so the bike skids along the road on its side with rider often beneath it (or hopefully behind it). The highside happens when the bike is cornering in a skid and the tires regain traction but he angle of the bike is insufficient for the speed and the radius of the corner[1]. This regaining of traction causes the bike to flip towards the outside of the corner, throwing the rider over the high side. A death wobble happens on any road (ie not just when cornering) and you hit a bump that the suspension can’t recover from which also causes a deflection in the steering. The action of the bike attempting to gyroscopically self-correct, coupled with the rebound of the suspension causes the bike to go into the wobble from side to side (if the bike has a steering or suspension flaw). You eventually get thrown off the bike either side. [1] Given the speed of the bike, the angle of lean and the radius of the corner I would think it is often the case in a high side that if the tyre had not regained traction that the bike would have skidded out and the rider would have had a low side crash instead.
irjustin 3y ago
> They're effectively the same process occurring to different degree. A high side is what you get when you arrive at a point of unrecoverable inflection in such a wobble. Simply not true? Lean a bike in a turn and jam on the brakes will give you a low side. No wobble. Loss of friction holding the bike up through the turn. Went from static to kenetic.
- hexaga 3y ago
  I don't disagree, but I also didn't mention low sides at all so I'm unsure of what you're trying to express here. My point is that a high side is what happens if you lose and regain rear traction, landing you in an unstable death wobble that immediately flings you out. It's possible to regain traction after losing it in a corner and not high side, you just get some wobble which you (more, the bike's suspension) can hopefully correct for. It's a matter of degree.
MarkMarine 3y ago
Nah. Incorrect. The wobble can happen when you’re 100% straight up and down. Highside needs a lot of yaw force to get the flick.
- hexaga 3y ago
  Well, yes. How 'high' the side is depends on many factors, but it's a gradient. A death wobble when going in a straight line happens to be relatively weak with regard to how much force the rider is ejected with should it fully destabilize / lose contact w/ the road in either direction, but you still get ejected in the same way. As you increase wheel misalignment with the direction of travel (and speed), more energy goes into the fling. As you increase lean angle (more lean means more time for the wobble to accelerate you) the fling gets more violent on one side and less violent on the other (the 'high' and 'low' sides). Hence, the observation that high sides are what happens when you enter a death wobble that is already past the point of stability.
  - MarkMarine 3y ago
    Do you have sources to prove this? I race motorcycles, I have a mechanical engineering degree and build race motorcycles, spent a lot of time researching motorcycle suspension dynamics to improve my systems and I think you’re basically making this up. We can chat about it more, but I’d like to see your sources so I can see what you’re basing this on.
    - hexaga 3y ago
      Prove what, specifically? I'm honestly unsure which part is a controversial enough claim as to require sources. It seems trivial to me that in both cases a perpendicular force applied at the road acts to fling you, and that said force comes from wheel misalignment with the direction of travel. Is that not the case?
      - MarkMarine 3y ago
        Prove that the dynamic instability that causes a speed wobble is the same thing that causes a high side. Here is an article on the physics of wobble: https://en.wikipedia.org/wiki/Speed_wobble https://en.wikipedia.org/wiki/Speed_wobble A high side happens when the rear tire breaks traction at lean, and is no longer able to hold the arc it’s trying to turn on. The forces in the tire, suspension, twist and deflection in the swingarm and the frame of the motorcycle rapidly unload, and the bike turns around the z axis if x and y are the flat plane of the road surface. Then catches traction, and that z axis rotation and gyroscopic forces becomes a violent flick to stand the bike up straight. These things are totally different.

by hexaga 3y ago

They're effectively the same process occurring to different degree. A high side is what you get when you arrive at a point of unrecoverable inflection in such a wobble.

seanhunter 3y ago

Not sure that’s true. My understanding is the lowside happens when the tires lose traction while cornering so the bike skids along the road on its side with rider often beneath it (or hopefully behind it). The highside happens when the bike is cornering in a skid and the tires regain traction but he angle of the bike is insufficient for the speed and the radius of the corner[1]. This regaining of traction causes the bike to flip towards the outside of the corner, throwing the rider over the high side. A death wobble happens on any road (ie not just when cornering) and you hit a bump that the suspension can’t recover from which also causes a deflection in the steering. The action of the bike attempting to gyroscopically self-correct, coupled with the rebound of the suspension causes the bike to go into the wobble from side to side (if the bike has a steering or suspension flaw). You eventually get thrown off the bike either side. [1] Given the speed of the bike, the angle of lean and the radius of the corner I would think it is often the case in a high side that if the tyre had not regained traction that the bike would have skidded out and the rider would have had a low side crash instead.

irjustin 3y ago

> They're effectively the same process occurring to different degree. A high side is what you get when you arrive at a point of unrecoverable inflection in such a wobble. Simply not true? Lean a bike in a turn and jam on the brakes will give you a low side. No wobble. Loss of friction holding the bike up through the turn. Went from static to kenetic.

hexaga 3y ago
I don't disagree, but I also didn't mention low sides at all so I'm unsure of what you're trying to express here. My point is that a high side is what happens if you lose and regain rear traction, landing you in an unstable death wobble that immediately flings you out. It's possible to regain traction after losing it in a corner and not high side, you just get some wobble which you (more, the bike's suspension) can hopefully correct for. It's a matter of degree.

MarkMarine 3y ago

Nah. Incorrect. The wobble can happen when you’re 100% straight up and down. Highside needs a lot of yaw force to get the flick.

hexaga 3y ago
Well, yes. How 'high' the side is depends on many factors, but it's a gradient. A death wobble when going in a straight line happens to be relatively weak with regard to how much force the rider is ejected with should it fully destabilize / lose contact w/ the road in either direction, but you still get ejected in the same way. As you increase wheel misalignment with the direction of travel (and speed), more energy goes into the fling. As you increase lean angle (more lean means more time for the wobble to accelerate you) the fling gets more violent on one side and less violent on the other (the 'high' and 'low' sides). Hence, the observation that high sides are what happens when you enter a death wobble that is already past the point of stability.
- MarkMarine 3y ago
  Do you have sources to prove this? I race motorcycles, I have a mechanical engineering degree and build race motorcycles, spent a lot of time researching motorcycle suspension dynamics to improve my systems and I think you’re basically making this up. We can chat about it more, but I’d like to see your sources so I can see what you’re basing this on.
  - hexaga 3y ago
    Prove what, specifically? I'm honestly unsure which part is a controversial enough claim as to require sources. It seems trivial to me that in both cases a perpendicular force applied at the road acts to fling you, and that said force comes from wheel misalignment with the direction of travel. Is that not the case?
    - MarkMarine 3y ago
      Prove that the dynamic instability that causes a speed wobble is the same thing that causes a high side. Here is an article on the physics of wobble: https://en.wikipedia.org/wiki/Speed_wobble https://en.wikipedia.org/wiki/Speed_wobble A high side happens when the rear tire breaks traction at lean, and is no longer able to hold the arc it’s trying to turn on. The forces in the tire, suspension, twist and deflection in the swingarm and the frame of the motorcycle rapidly unload, and the bike turns around the z axis if x and y are the flat plane of the road surface. Then catches traction, and that z axis rotation and gyroscopic forces becomes a violent flick to stand the bike up straight. These things are totally different.