I accepted a challenge on twitter, from an accident investigator ...
Oh dear ... was her response, apt that.
I shot my mouth off about bike stopping distances. It came from a 35m skid mark that a bike left before impacting a sedan, it was fatal. So i'm thinking about what kind of speed must one be doing to leave a 35m skidmark? I wouldn't be able to do a 10 metre skidmark on purpose? I added, in my haste, that a bike could stop within 10m, from around 80km/h, without needing to skid.
To initiate a locked back tyre at speed is a dangerous move on a bike, the overall handling dynamic of the bike changes instantly.
The momentum generated by a spinning wheel and tyre increases the faster it turns, and creates mass, a force which helps balance the bike and keep it upright. The moment that the back brake freezes that momentum disappears, and the back of the bike becomes lighter than the front. The motionless tyre has no traction with the road surface, it is neither steering nor slowing, merely skidding along aimlessly, and trying to speed ahead of the slower front wheel.
The harder the front brakes are being applied the more the back of the bike tries to overtake the front. If the back brake is released at this point, the bike performs what is called a "highside", where the back of the bike kicks up so hard the rider is thrown over the handlebars. Do not release the back brakes if you lock them up. So perhaps now you will understand why i don't see myself leaving 10m skidmarks for fun.
Stan Bezuidenhout @StanfromIBF
@davigilant @KenRoselt You say "a 35m skid says it all..." What "all" does it say, to you? Remember: 25m (for a car) is 60kph on a DRY ROAD.
vigilant @davigilant
@StanfromIBF @KenRoselt It says he locked the back wheel, suggests not enough training. 60kmh - 0 is less than 10m on a bike, dry road.
Stan Bezuidenhout @StanfromIBF
@davigilant @KenRoselt 10m at 60Km/h (back wheel locked)? Says who? And ABS? Cadence/Bias braking? Large/small bike? Mass? Injuries?
Stan Bezuidenhout @StanfromIBF
@davigilant @KenRoselt I challenge your claim. Let's do a test. I think you're wrong about 10m at 80Km/h. Remember - this is what I do. :-P
I see what he did there now, clever :D
No matter ... i have the biker fairy with me on this one. I will happily admit i know nothing about the subject, and i'll be happy to be wrong, nothing wrong with being wrong. Because it's not about me being right, at all, in any way. It's about twitter taking people and making things happen ... it's about a conversation taking place, a conversation so deadly serious it stuns us all into silence ... it is WAY overdue for not only laws to be obeyed (the law is an ass) but for us to interact with each other more intelligently, starting with the roads.
South Africa in all it's brutality is a very dynamic place to be, and part of that dynamism is where people must start looking after themselves, in spite of goverment, in spite of crime. This has been a conversation 19 years in the making, the road safety component being a one sided disinformation campaign by government up to this point. The next step is for us to come together and debate intelligently about our commmon problem, and the first part of that is information.
I ride a 2005 Yamaha FZ6 and we'll be testing 20 40 60 80 100 120 140 160, if conditions allow. I hope to have other riders there, to be part of what is only a conversation, but one of the most important conversations of out time.
PS:
I did some numbers:
80km/h = 22m/s
10m = 0.55s
80 - 0 in half a second is impossible, but the slower you move the longer that second stretches.
... rubber band man ...
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