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Old 07-13-2009, 10:44 PM   #21
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This same thing holds true for accelerating and braking as well.... little guys rule at the racetrack.
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Old 07-13-2009, 11:00 PM   #22
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What has been left out of the analysis is that the coefficient of friction of the tires on the track surface is the same for both bikes and the increase in rider weight for the heavier rider when multiplied by the coefficient of friction will give a resulting increase in the amount of static friction of the tire on the track. This means that all other things being equal the heavier rider should be able to corner at pretty much the same speed as the lighter rider because the heavier rider has more gravitational force pushing the tire down into the track creating more static friction to overcome the additional cornering force.

The deficit in performance between lighter and heavier riders comes primarily in the engine's inability to accelerate the greater mass of the heavier rider as quickly as it can accelerate the mass of the lighter rider.
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Old 07-14-2009, 06:55 AM   #23
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CDILL,
Slow in = fast out! Try that!!!!
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Old 07-14-2009, 07:29 AM   #24
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Quote:
Originally Posted by lorin70 View Post
What has been left out of the analysis is that the coefficient of friction of the tires on the track surface is the same for both bikes and the increase in rider weight for the heavier rider when multiplied by the coefficient of friction will give a resulting increase in the amount of static friction of the tire on the track. This means that all other things being equal the heavier rider should be able to corner at pretty much the same speed as the lighter rider because the heavier rider has more gravitational force pushing the tire down into the track creating more static friction to overcome the additional cornering force.

The deficit in performance between lighter and heavier riders comes primarily in the engine's inability to accelerate the greater mass of the heavier rider as quickly as it can accelerate the mass of the lighter rider.
Oh really?
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Old 07-14-2009, 08:14 AM   #25
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Quote:
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CDILL,
Slow in = fast out! Try that!!!!
Not sure how well that works when you're trying to run up front. But I don't know.
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Old 07-14-2009, 08:25 AM   #26
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Call Colin Edwards. He should know this fairly well..
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Old 07-14-2009, 08:38 AM   #27
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Call Colin Edwards. He should know this fairly well..
He's pretty tall. But is he heavy? Like over 200#?
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Old 07-14-2009, 08:38 AM   #28
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To calculate the static friction it is necessary to use the following formula:

SF=CSF*W where SF=Static Friction, CSF=Coefficient of Static Friction, and W=Weight

A street tire may have a CSF of .9 and a sticky race tire may be as high as 1.1 or more so if we can keep it simple and use 1.0 for the CSF. Static friction is the friction available before the two surfaces begin to slide across each other. Once the surfaces begin to have significant slippage across each other the friction will be dynamic or kinetic and the coefficient of friction will be less than the static coefficient.

To continue the example of the two all-up weights where the lighter rider is 560 lbs then he will generate a static friction as follows:

1x560=560 worth of static friction

The heavier rider at 660 lbs will be as follows:

1x660=660 worth of static friction

If we then calculate the difference in available static friction:

(660-560)/660= .1515 or a 15.15% increase in static friction for the heavier rider that will offset the 15.15% increase in cornering force.

This effect can be easily experienced using a cardboard box and some books. Take an empty box and place it on the floor and push it across the floor. It will slide easily across the floor. Now fill it with books and try to push it across the floor again. It is more difficult to push. The coefficient of friction between the box and the floor has not changed but the weight pushing down on the box has.

This is why Formula 1 cars are able to corner with 4.5 Gs of cornering force. The down force generated by the aero loading from the wings, under tray, and diffuser create a huge amount of virtual 'weight' on the car which pushes the tires into the track with greater force thus creating more static friction.

Whether the 'weight' is real or virtual the effect on static friction is the same.

If anyone finds flaws in my analysis please elaborate.
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Old 07-14-2009, 08:47 AM   #29
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There is entirely too much scientific data being used in this thread. Keep this shat up and we might look like we know what the we're talking about.

Carry on...
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Old 07-14-2009, 08:52 AM   #30
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What if you have a heavy rider that doesn't get (lean) off the bike at all?
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Old 07-14-2009, 09:02 AM   #31
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Quote:
Originally Posted by lorin70 View Post
To calculate the static friction it is necessary to use the following formula:

SF=CSF*W where SF=Static Friction, CSF=Coefficient of Static Friction, and W=Weight

A street tire may have a CSF of .9 and a sticky race tire may be as high as 1.1 or more so if we can keep it simple and use 1.0 for the CSF. Static friction is the friction available before the two surfaces begin to slide across each other. Once the surfaces begin to have significant slippage across each other the friction will be dynamic or kinetic and the coefficient of friction will be less than the static coefficient.

To continue the example of the two all-up weights where the lighter rider is 560 lbs then he will generate a static friction as follows:

1x560=560 worth of static friction

The heavier rider at 660 lbs will be as follows:

1x660=660 worth of static friction

If we then calculate the difference in available static friction:

(660-560)/660= .1515 or a 15.15% increase in static friction for the heavier rider that will offset the 15.15% increase in cornering force.

This effect can be easily experienced using a cardboard box and some books. Take an empty box and place it on the floor and push it across the floor. It will slide easily across the floor. Now fill it with books and try to push it across the floor again. It is more difficult to push. The coefficient of friction between the box and the floor has not changed but the weight pushing down on the box has.

This is why Formula 1 cars are able to corner with 4.5 Gs of cornering force. The down force generated by the aero loading from the wings, under tray, and diffuser create a huge amount of virtual 'weight' on the car which pushes the tires into the track with greater force thus creating more static friction.

Whether the 'weight' is real or virtual the effect on static friction is the same.

If anyone finds flaws in my analysis please elaborate.
The flaw in your analysis is that the incremental force of friction due to the additional 100 lbs of the rider, pales in comparison to the incremental cornering force the weight brings on as speed increases, recall the v^2 in the equation. Unlike formula one, there is no incremental down force as cornering speed increases on a sport bike to offset this.
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Old 07-14-2009, 09:04 AM   #32
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not to good at the physics myself (more of a bio guy). anyways i really appreciate and find all the science of riding/trackriding super interesting. and to contribute (somewhat), i'm a little dude, weighing in at 135. everyone from instructors to other riders tells me to hang off the bike, both cheeks of the seat. saw some pics of me were it looks like i'm gonna fall off. once i got the position down, i felt like my bike was easier to turn and was easier to carry a bit more speed (im still slow). so to summarize, little dude = hang off the bike!

slightly offtopic. how would a lighter rider fair on a smaller bike on the track, say on a 250?
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Old 07-14-2009, 09:16 AM   #33
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Quote:
Originally Posted by maxgs View Post
The flaw in your analysis is that the incremental force of friction due to the additional 100 lbs of the rider, pales in comparison to the incremental cornering force the weight brings on as speed increases, recall the v^2 in the equation. Unlike formula one, there is no incremental down force as cornering speed increases on a sport bike to offset this.
But in this example aren't we keeping the velocity as a constant? Let's assume that both riders are going through the corner at the same velocity (which was the original question), so the V squared portion of the calculation is the same for both riders, correct? If that is the case then the only variable in the equation is the total weight which is different by 15.15 percent. Wouldn't the increase in cornering force at the same velocity be equally offset by the increase in static friction due to the increased weight of one rider?
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Old 07-14-2009, 09:20 AM   #34
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Originally Posted by cdill35 View Post
asking another serious question on MH.

Hypothetically speaking...

Let's say 2 bikes are set up identically. Same suspension, tires, etc. Tuned for each riders weight and riding style, exactly.

Can a taller heavier guy carry the same lean angle and corner speed as a smaller light guy? Or would a heavier guy hanging off require more of a contact patch before the tire gave?
The original question is whether a lighter rider can carry more speed through a turn than a heavier rider. The answer is that, yes, a lighter rider can carry more speed.
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Old 07-14-2009, 09:22 AM   #35
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Quote:
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Not sure how well that works when you're trying to run up front. But I don't know.
Think of it like this for the 10 feet or so you give up on the entry you can make up times on the exit. That is if you have maxed out your lean angle/grip/traction/suspension etc etc for your bike with your weight. If you gain anything on the entry and it blows your line or your losing grip on the exit your really not helping much. I may be slower than you but just think about it. Now that 10 feet you gave up to someone on the entry but your able to get on the gas sooner and harder, don't you think it will be magnitude by the race to the next corner? You gave up a few MPH on the entry but gained 10 plus on the exit. Build your lines from the exit not the entry. Ok I will stop giving advice but next year remember that slow guy who tried to offer advice and was shunned!
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Old 07-14-2009, 09:41 AM   #36
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Just run a RC car in a circle as fast as possible and then ask yourself if you could do the same thing on your bike.
The answer would be no.
Smaller/Lighter = Faster
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Old 07-14-2009, 10:00 AM   #37
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Good motivation to drop a few pounds.
At least thats the only thing motivating me.
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Old 07-14-2009, 10:22 AM   #38
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Quote:
Originally Posted by DEAN LADEN View Post
Think of it like this for the 10 feet or so you give up on the entry you can make up times on the exit. That is if you have maxed out your lean angle/grip/traction/suspension etc etc for your bike with your weight. If you gain anything on the entry and it blows your line or your losing grip on the exit your really not helping much. I may be slower than you but just think about it. Now that 10 feet you gave up to someone on the entry but your able to get on the gas sooner and harder, don't you think it will be magnitude by the race to the next corner? You gave up a few MPH on the entry but gained 10 plus on the exit. Build your lines from the exit not the entry. Ok I will stop giving advice but next year remember that slow guy who tried to offer advice and was shunned!
I agree that is you are in so fast that you blow the line = no bueno.

But..you should go in as fast as you can without blowing your line.

Which is actually what brought this thread up. I need to lean the bike more to carry more speed and stay on the line. I look at the leanangles in the pics of howard, wagnon, kelsey.. even gonzo and feel like I can't carry those angles...so I slow down because that speed couple with less lean angle makes me run wide at corner exit. Then I have to roll off a bit.
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Old 07-14-2009, 10:23 AM   #39
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Quote:
Originally Posted by maxgs View Post
The basic equation for cornering force is

Force = (mass * velocity^2) / radius of curvature

So, all things being equal, a lighter bike & rider will go around a corner at great speed than a heavier counterpart.
I'm down with that.
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Old 07-14-2009, 10:36 AM   #40
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Quote:
Originally Posted by cdill35 View Post
I agree that is you are in so fast that you blow the line = no bueno.

But..you should go in as fast as you can without blowing your line.

Which is actually what brought this thread up. I need to lean the bike more to carry more speed and stay on the line. I look at the leanangles in the pics of howard, wagnon, kelsey.. even gonzo and feel like I can't carry those angles...so I slow down because that speed couple with less lean angle makes me run wide at corner exit. Then I have to roll off a bit.
You are correct my friend. There are guys who are as big as you who carry that lean angle. Riding is as much mental as it is phsyical. trust me I am speaking my mind because they say if you want to learn something try teaching it. So here I am I need more lean angle and its not because of my size.
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