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Old 08-13-2004, 05:31 AM   #1
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Default Re: R1 vs 911

That video showed the bike & 911 riding together on the Nurburgring...

No way the rider can hang it all out when he's got a 3500+ lb car on the track with him, as well as all the minivans, etc.. that they pass during the video.

There are various articles in car magazines from time to time poppping up to prove that someone's $100,000 penis attachment is faster than a bike. Usually there is some car guy riding the bike.

The most interesting one was Kevin Schwantz riding the Gixxer 1000 and Z06 back to back last year in Motorcyclist. Schwantz has raced pro in both car & motorcycling racing. He turned in a time close to the SCCA record in the Corvette... he was so much faster on the Gixxer that they said he would be lapping the corvette every 10 laps. He was actually going way faster through the corners on the bike too, not just on the straights.

Basically if the rider is very good no car is going to beat an expert racer on a track unless it is an open wheel race car. (1500lbs, 600-900hp, lots of downforce) Open wheel race cars (CART, IRL, F1, etc..) will demolish a Superbike or GP bike. There will never be a street car with that kind of performance, as the downforce will cause it to get about 5mpg. Who knows at what point the cars are faster.. but it is nowhere near a street car. Maybe a Le Mans Prototype class car is faster? Maybe a GTS?

Think of it this way.. the car has four big tires. But they aren't THAT much bigger than the bike tires. At full cornering the car is transferring most of it's weight onto the two outside tires.

But most of all the important thing is the car + driver weigh 8-10x as much as the bike and rider do. There is no way to get around physics. The only way for the car to corner better than the bike is by having massive downforce. Many high end cars have neutral aerodynamic forces, but very few have significant downforce due to the drag it creates.

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Old 08-13-2004, 05:47 AM   #2
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Default Re: R1 vs 911

Couldn't agree more here in the UK we have the Touring car championship which is supposed to emulate prodie cars. They run on the same tracks as the British Superbikes. For example at Knockhill in Scotland the top cars were lapping at best in the mid 54s while John Reynolds qualified in a 50.7, nuff said.
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Old 08-13-2004, 05:54 AM   #3
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Default Re: R1 vs 911

I have some background in physics, although it's wave physics, but most of the parameters brought up here are pretty basic...

First let's clear up a mis-conception about how friction works. Friction is a coefficient, which means when we have fixed mesaurement such as how many pounds of force are pressing two surfaces together, then we can use the coefficient of friction of the surfaces, which for most regular surfaces can readily be looked up in a table, to determine how much friction exists between the surfaces.

But something that does NOT effect that final measure is surface area.

See surface area is great for traction in a non-perfect world where at any given time parts of the road or tire might have slick spots, grease, or imperfections which will allow for momentary loss of contact with the road. More surface area means more reassurance that the friction you should have by mass of the vehicle and types of surfaces is maintained even over imperfections and temporary unfavorable circumstances. But more tires does NOT equal more friction.

Think of it this way. If you have a 600 Pound bike and four square inches of contact patch you have rubber pressing against ground at about 150 LBS / square inch, over four inches.

If you only had one square inch of contact patch that seems really bad, except that now that one square inch is pressed to the road at 600LBS / square inch. Which sliding over a surface, or rolling over a surface has the same total friction as the four square inches expressed as a coefficient.

The disadvantage is that if you go over a one square inch pothole, you can lose ANY friction you have for that instant, which in a tight turn could be enough to screw you.

Now I haven't seen the video either, so I don't know what happens, but If the Porsche which let's admit is a really well engineered car, beat the bike in the turns I would guess it has to do with where energy is absorbed when turning.

In a perfect world, one uses energy whenever they are accelerating. And acceleration is defined as change in velocity. Velocity inlcudes both a speed and a direction component, so acceleration can be changing either one of those measurements. So, if you are turning, and you aim to cover exactly the same amount of ground per second as when you were going straight, you need to put a little more energy into changing the direction of the car. Which is why you'll notice in a long enough sweeper, if you want to maintain the velocity you had entering the turn you have to give it just a tad more throttle.

Much of that energy is dissapated through friction on the tires. Tires only have a finite amount of friction. In a straightaway, you can use all of this friction to accelerate the car forward, in a turn some of that friction must be used to change the heading of the car. (Remember in a no gravity situation in space, something moving tends to stay moving forever in a straight line. But you need to apply force to change it's direction.) If you exceed the total amount of friction by turning to hard, or accelerating too hard through a turn, you break the wheels loose.

Now I don't think Bikes have inherently any more problems staying tacked to the road based on tire material, road surface (Obviously in this test it was the same) or even mass distribution. If I had to guess, I'd say it has to do with the mechanics of how a bike turns.

When you alter course from a straight line in a moving mass, you are fighting the inertia of the mass. This is most easily demonstrated in the illusion of centrifugal force. In reality, there is no force that says things moving in a circle want to move to the outside of the circle. It's just that an any given time, if the force "tethering" the object to the circular path were removed, the object would continue to move in a straight line.

In a bike you not only fight this by turning, you fight this by leaning the bike in. It takes energy to alter the heading of the bike, and additional tire friction is used to hold the bike in it's leaned over position when obvisouly, without that effort the top of the bike would stand up, and probably roll to the outside of the turn. (Assuming that standing it up didn't settled it back into a straight line immediately.) In the case the tires serve as the fulcrum of a lever, and when you push the bike over to one side what keeps the bike form rotating about it's Z axis is the friction of the tires on the road, which you are borrowing from to do that.

The car on the other hand has its axis in between the tires, and as you throw it into the turn, the body rolls to the outside of the turn actually counterbalancing some of the force the tires have to absorb to change the cars direction, and mitigating some of the "centrifugal" effect. Finally as it does so, while the tires on the inside lose some force to the ground, the tires on the outside gain some making for a zero-sum type proposition. But nither set of tires is used as the pivot point for that body motion on the Z axis and so nothing additional is subtracted form the friction they use to both keep the car moving forward, and to change it's velocity.

Anyway that's all just a guess.

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Old 08-13-2004, 06:48 AM   #6
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Default Re: Excellent, let see what sportbike_pilot says as well

I don't have a degree in physics, but I did stay at a Holiday Inn last night. Somebody please administer the euthanasia before it's too late. VWW
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Old 08-13-2004, 06:56 AM   #8
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my brain hurts. allow me to summarize:

cars suck.

bikes rock.

engineers ... can't live with 'em, can't live without 'em.

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Old 08-13-2004, 07:54 AM   #9
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Default Re: R1 vs 911

I thought it was pretty well known that a race car can corner faster than a bike. The car has four wheels and a lot more traction for its low center of gravity.

On the street, passenger cars have to corner through a narrow lane and they are built with soft suspension for comfort so the car rolls back and forth through corners, whereas a bike can take a very different line through a corner and leans into the corner so suspension can operate in a vertical plane. But, mostly I think bike riders ride better than car drivers drive.

Have you ever been up in the mountains and encountered a car flying through the corners? There are a few guys out there that can really corner hard.
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Old 08-13-2004, 08:51 AM   #10
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Default Re: R1 vs 911

i've run both cars and bikes on a track extensively. i'm a decent driver and an ok rider, though not a pro by any stretch. all in all i've run about 3,000 laps at portland in a variety of machinery (see www.dpcars.net for details and tons of video, if you care). i've generally been faster in cars. this is not because cars are faster, they are just easier and more comfortable to push the limits in. the skill of the operator matters a lot in both cases (i pass corvettes and 911s in my stock, street-tired mini all the time), but on a bike it's just much more so. while in cars i might be only a second off the pace that a top club racer could post in the same machine, on a bike i'm more like 6-8 seconds off. my best effort on the R1 i recently got is a 1:20 flat (hoping to get below that next track day), a decent amateur racer time on the same bike and tires would be in the 1:14 range.

bottom line is, unless you have experienced and skilled drivers/riders at the controls any such 'contests' are completely meaningless. earlier this year i rented a 1.6L golf and ran it on the nurburgring in germany. i was able to keep up with a 911-C4 and passed a bunch of bmws, porsches and a maserati in the process. that doesn't mean that a cheapo rentagolf is faster than those cars!
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