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Old 08-16-2004, 08:26 AM   #51
Andonyx
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Default Re: Porsche Vs. Donkey

Well, if it makes anyone feel any better in Lisbon at least we can say the Cycle would beat the crap out of the Porsche, a donkey cart already did:



http://story.news.yahoo.com/news?tmp...t_040816161430



<blockquote>

LISBON (AFP) - A donkey cart beat a Porsche in a race held in a northern Portuguese city over the weekend to see which mode of transportation could best handle car congestion.</blockquote>
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Old 08-16-2004, 11:27 AM   #52
jkofsky
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Default Re: R1 vs 911

On the subject of Friction vs. Surface Area, experimentally, do you have better adhesion to the road on a steel plate or the steel grids they sometimes have on bridges? On flat concrete or rain-grooved?



I think that in the real world, it's fairly obvious that under some circumstances, friction is not a perfect coefficient.
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Old 08-17-2004, 05:49 PM   #53
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Default Re: R1 vs 911

OK, one more Electrical Engineer with too many physics classes to remember chiming in.



As others have mentioned, one reason a tire with a larger contact patch can sustain a higher lateral acceleration force is that it can conform to more irregularities. Asphalt is not remotely smooth, but lots of rounded surfaces. The more of those you can grip the more force you can exert. Concrete could theoretically be better, but it gets nicely polished very quickly. The grippiest stuff is what they put on racetracks. That doesn't have little round pebbles in it, but sharper bits, which brings us to my next point.



Tires don't work through pure friction. They actually work through abrasion as well (you've seen the scrapes at the edges of the tread on your car tires, or the beady little worms at the edges of race tires). Think of the road as sandpaper. Asphalt or polished concrete is like old, worn out sandpaper, where the grippy racetrack surface is brand new. There are tracks with great grip that just destroy tires because they're so abrasive.



On to lean angle helping or harming grip: nope. F=ma (OK, that's for a straight line, but the concept is still valid). For a given mass travelling in a constant radius at a constant velocity, there is a constant force (felt as centripetal or centrifugical acceleration) to maintain the path of travel (it takes a force/acceleration to turn). It makes no difference if that force is being applied by 1 wheel or 100, or if the car is heeled over to the outside or the bike leaned over to the insided.



Summary: even your Geo Metro with 13" tires has more contact patch than your GSX211M1. It just has really hard tires for high mileage and long wear, plus a lot worse land/sea ratio than any motorcyle tire I've ever seen.



Trivia question: why do F1 cars run grooved tires? To reduce the contact patch to reduce corner speeds without putting spindly, narrow, stupid looking tires on them. Same principle applies here.
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Old 08-17-2004, 06:11 PM   #54
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Default Re: R1 vs 911

Not likely. Most any sports car with performance tires (even the really high performance street car tires are less sticky than performance motorcycle tires, but they make up for it in contact patch) can achieve a higher lateral acceleration than a bike. A stock Vette can pull over 1G on the skidpad, and at that speed downforce is not a signficant factor. Really big honking tires with a suspension to maximize the contact area do it.



Where a bike can make time is in acceleration. Even F1 cars can't match the power/weight ratio of a modern race rep bike, and certainly not a Superbike or MotoGP bike. That said, it's a heck of a lot easier to get the power to the ground in the car, so the bike may not even be able to make much advantage of this.



Then the bike will lose time again in braking. The high center of gravity and weight transfer combined with the tiny contact patch of the front tire severely limits braking acceleration on a bike. The car doesn't transfer weight so dramatically (ever seen a car on level ground stand itself on its nose?) and has a dramatically larger contact patch (2 big ones up front, 2 lesser in back).



Unfortunately I can't find the Kevin Schwantz Bike vs Car article on the Car and Driver website, but this is what I recall from reading that article way back when, and it's logically consistent with physics.



I think a lot depends on the type of track, too, and the car had better at least be sort of competitive in power/weight ratio or it will never make up for the straight-line advantage of the bike.
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Old 08-17-2004, 06:27 PM   #55
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Default Re: Lap Times at Daytona

Let's see here. 999R power/weight ratio, say 150/450 with Eboz, so about 3lb/hp. And that's on qualifiers for a couple of laps. Not a clue about Tony Stewart's car pwr/wt, but since you give us details on the Barber car, that's about 9lb/hp with Mr. Andretti aboard. The other cars you're talking about aren't even in the same class. I sense an apples to oranges comparison on an HP track like Daytona.



Do the cars even run the same track? The bikes don't run the full oval like NASCAR, but I don't know about your other car series.



One more minor detail: your Camaro's speedometer doesn't significantly change with lateral acceleration. The bike, however, runs a substantially smaller diameter on the tire when leaned over, so even if it's not overly optimistic in a straight line (a big assumption), it most certainly is in a turn. Until you measure your corner speed with a radar gun you've got no useful comparison.
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Old 02-23-2007, 09:52 PM   #56
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Default Re: R1 vs 911

Telemetry from September/ October 2005 R&T speed: The average 200ft "skipad" g-force on a ZX-10 with a pro onboard and Ohlins suspension with DOT R compound tires is 1.04g's. For a completely stock 636 the same rider managed 1.01g's. On the same turn on the same day, a profesionally driven Skyline with Hoosier autocross slicks and many chassis mods managed 1.11g's for one lap before the tires "greased." A stock C-5 corvette with Hoosier slicks pulled .96g's. This was taken from a turn that was similar to a skidpad on a racetrack.



For various reasons, both bikes were significantly faster than both cars.



In March 1990 Hot Rod did a comparo where the FZR1000 managed .75g's and the Corvette ZR1 pulled .93 on an actual skidpad, but the bike was still faster on both big and little Willow tracks. The bike used stock Pirelli tires, the car used shaved Goodyear Gatorbacks and went through several sets trying to beat the bike.



I double checked the figures and dates, etc so you can verify the info.



I know of several other comparisons, but these are the only two I have seen with skidpad figures on pavement.

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