So how/why do you "lose traction" in a (downhill?) curve?
09-02-11, 06:15 AM
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Basic high school physics. If you look in auto magazines at tests, you'll see lateral acceleration results - the g force required to break traction. For some econo boxes, it's 0.75. For high end sports cars, it's greater than 1.0
09-02-11, 06:29 AM
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The simplest way to look at it imo is this:
Acceleration + Deceleration (Braking) + Cornering </= 100% (Friction)
Acceleration, braking, and cornering force coefficients must be less than or equal to the coefficient of friction present (road + tires). If the combined forces of acceleration, deceleration, and cornering exceed the friction coefficient, you "lose traction."
In physics terms, this means that you go from static friction to kinetic friction. The coefficient of kinetic friction is generally significantly less than the coefficient of static friction for the same surface (road + tires) and in order to go back to static friction (traction) you must lower the forces present below the friction threshold (from kinetic to static).
Acceleration + Deceleration (Braking) + Cornering </= 100% (Friction)
Acceleration, braking, and cornering force coefficients must be less than or equal to the coefficient of friction present (road + tires). If the combined forces of acceleration, deceleration, and cornering exceed the friction coefficient, you "lose traction."
In physics terms, this means that you go from static friction to kinetic friction. The coefficient of kinetic friction is generally significantly less than the coefficient of static friction for the same surface (road + tires) and in order to go back to static friction (traction) you must lower the forces present below the friction threshold (from kinetic to static).
09-02-11, 07:30 AM
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09-02-11, 08:05 AM
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Not to rain on your parade, but I would bet I would easily go around a corner at double the advisory speed on my m/c. In fact if I am riding on roads that I don't know very well, I use double the advisory speed as a good guide to what I can SAFELY go through the corner at.
To the OP, if you have never lost traction on a m/c without the aid of gravel/oil/water then you have not been riding hard enough! It does happen, but you have to be pushing pretty hard. It is much easier to reach this limit on a road bike (bicycle) due to the much smaller contact patch as a previous poster said.
JMR
To the OP, if you have never lost traction on a m/c without the aid of gravel/oil/water then you have not been riding hard enough! It does happen, but you have to be pushing pretty hard. It is much easier to reach this limit on a road bike (bicycle) due to the much smaller contact patch as a previous poster said.
JMR
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09-02-11, 08:51 AM
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As a former motorcycle racer yes you can just loose traction in a turn. It's easy. I've done it at Barber and Road Atlanta. I have the scars and metal plates to prove it. It's not hard to understand.
Keith Code put it simply that you have 100 points of traction available (as a simplification of course.) Going forward in s straight line you can use all 100 to increase speed. Use all of them up and you do a burnout.
In corners you have to use a large percent of those points to counter the g forces of the turn. Add a little request for forward traction and exceed the limit and you spin your rear wheel. If you're lucky you keep spinning and don't get high sided to the moon.
Brake too hard in a turn and the front wheel uses some of that traction to decelerate as well as corner. Exceed the limit and the front end tucks. Lowside.
Go in too hot to a turn and you'll tuck the front end as well.
And if you still have chicken strips you are not getting close to the edge of your MCs performance.
Keith Code put it simply that you have 100 points of traction available (as a simplification of course.) Going forward in s straight line you can use all 100 to increase speed. Use all of them up and you do a burnout.
In corners you have to use a large percent of those points to counter the g forces of the turn. Add a little request for forward traction and exceed the limit and you spin your rear wheel. If you're lucky you keep spinning and don't get high sided to the moon.
Brake too hard in a turn and the front wheel uses some of that traction to decelerate as well as corner. Exceed the limit and the front end tucks. Lowside.
Go in too hot to a turn and you'll tuck the front end as well.
And if you still have chicken strips you are not getting close to the edge of your MCs performance.
09-02-11, 08:52 AM
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09-02-11, 09:02 AM
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Before this becomes another boring safety preaching thread, I will say that if tires lose enough inflation you can lose traction even on the slightest of turns at the slowest of speeds. I had a slow leak in my front tire and I went to take a 90* turn and couldn't figure out why I was sliding out of the turn. Nearly crashed. True story.
09-02-11, 09:13 AM
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In regards to sand and gravel.... when I descend there are two speeds-
1 I just climbed the hill and know the condition of the corners and if there us any loose gravel lying around. Set for LUDICROUS speed.
2 I'm descending and unknown hill and don't know the condition of the corners.
Set for BIG FAT CHICKEN speed.
1 I just climbed the hill and know the condition of the corners and if there us any loose gravel lying around. Set for LUDICROUS speed.
2 I'm descending and unknown hill and don't know the condition of the corners.
Set for BIG FAT CHICKEN speed.
09-02-11, 08:43 PM
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09-04-11, 07:06 PM
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Just remember- confidence is the feeling you have before you fully understand the situation
09-05-11, 09:03 PM
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Not to rain on your parade, but I would bet I would easily go around a corner at double the advisory speed on my m/c. In fact if I am riding on roads that I don't know very well, I use double the advisory speed as a good guide to what I can SAFELY go through the corner at.
To the OP, if you have never lost traction on a m/c without the aid of gravel/oil/water then you have not been riding hard enough! It does happen, but you have to be pushing pretty hard. It is much easier to reach this limit on a road bike (bicycle) due to the much smaller contact patch as a previous poster said.
JMR
To the OP, if you have never lost traction on a m/c without the aid of gravel/oil/water then you have not been riding hard enough! It does happen, but you have to be pushing pretty hard. It is much easier to reach this limit on a road bike (bicycle) due to the much smaller contact patch as a previous poster said.
JMR
09-05-11, 09:25 PM
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09-06-11, 08:48 AM
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Simple demonstration. Take your bike outside, tilt it to one side (toward you), and put all your weight on it and keep leaning further and further. At some point the tire will slide and will likely be further than you thought. That's pretty much static, with zero momentum and cold tires. Things change with movement, varying road surfaces and warm tires. Cheers
