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Discussion Starter #1
what are the real top speeds for racing bikes? This guy was telling me yesterday that he put 12,500 RPM 6th gear on his Gixxer 1000 and that when he is at 6,000rpm he is at 100 mph, implying that at 12K rpm he should be at around 200 mph. :hmm :hmm :hmm


I was confused, because i had the impression that MotoGP and SBK were around 200 mph as well, so how can a slightly modded Gixxer achieve this?


Another thing that came in mind was that I read about those guys going to boneville and breaking records and they all topping around 210mph...


Whats going on here?
 

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The spedo might have read 200mph but at that speed its probably close to 10-20% optimistic (factory error + wheelspin) I'd guess.

A guy from the DC sportbikes group ran 208 on a nearly stock ZX12 (I think) at speed week not long ago. A gsxr1000 isn't a lot slower. IIRC Mag tests showed top speed in stock form to be low-mid 170's.
 

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Discussion Starter #3
A guy from the DC sportbikes group ran 208 on a nearly stock ZX12 (I think) at speed week not long ago.
I thought that bike was heavily modified... it didnt even had breaks on it.


But still, that is 208mph on a lightweight ZX12 IIRC.

How can it be so hard to access real top speed numbers for bikes?
 

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Over here it's easy. 300kph isn't possible, the speedo newer shows more than 299kph :laugh
The RPM vs speed calculation is wrong, though. That would mean a internal and final drive of 1.

Greetings
Rufer
 

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Discussion Starter #5
The RPM vs speed calculation is wrong, though. That would mean a internal and final drive of 1.

:confused :confused :confused


His reasoning does adds up. On any gear you running, the speed is directly related to the RPM. If you double it, u should double the speed. I am not sure what you were trying to say.
 

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Maybe youre right :idea

Greetings
Rufer
 

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when he is at 6,000rpm he is at 100 mph, implying that at 12K rpm he should be at around 200 mph.
my TLR is going along at 100mph at 6000rpm according too my speedo.

debs' raptor for comparison is at 7000rpm for 100mph.
 

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I thought that bike was heavily modified... it didnt even had breaks on it.


But still, that is 208mph on a lightweight ZX12 IIRC.

How can it be so hard to access real top speed numbers for bikes?
It had front brakes, mirrors and a few other parts removed. Also had NOS, exhaust, fuel remaped and the basic stuff, but no internal motor work or forced induction. IIRC he broke 200 without the nos but only just, then with it got to 208.

Anyway, top speed numbers aren't that hard to find - MCN does a top speed run on all the bikes they test. Their performance index (pdf on their website) lists the top speeds of all the bikes they have recently tested. Pretty much all the liter bikes are low 170's for actual top speed.

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:confused :confused :confused


His reasoning does adds up. On any gear you running, the speed is directly related to the RPM. If you double it, u should double the speed. I am not sure what you were trying to say.
im sure this isnt entirely correct. at higher speeds drag plays a bigger role.

i would put money down that a bike at 100mph running at 5000rpm, is NOT doing double the rpm at 200mph.

id love to elaborate but its late :)
 

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Unless I really am missing something BBorgs is correct I do belive. Assuming no tire slip and no clutch slip, speed will increase linearly with respect to RPM. This is not to say it will increase linearly with HP, quite the contrary you have that pesky V^2 when calculating wind resistance. So double your rpm and you double your speed, but that will likely require much more than double the power.

If you think about it, for a given gear and assuming no clutch slip, rear wheel rpm is simply a linear factor of engine rpm and bike speed, assuming no wheel slip is a linear factor of wheel rpm....

From what I've read at very high speeds, wheel slip can account for as much as 10% of overall speed, not sure of the accuracy of this though:O

Also note that stock spedo's and tachs are generally optimistic, this combined with some tire slip at high speeds can mean that indicated speed is much higher than actual speed.

So I would have to say that if a bike did a true 100mph at 5k rpm then it would be doing 200mph at 10k rpm not accounting for wheel slip. That is not to say that it would actually be able to pull to 10k rpm, but if it could, it would be doing 200mph at 10k rpm

have fun
 

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Just dug this up from an article :

At higher speeds aerodynamic forces become important, increasing as the square of the airspeed. A flat plate of one square foot area and perpendicular to the relative wind will produce drag force of zero at zero miles per hour, 33 pounds at 100 mph, 133 pounds at 200 mph and 299 pounds at 300 mph. The corresponding horsepower required to overcome the aerodynamic drag is zero, 9 hp at 100 mph, 71 hp at 200 mph, and 239 hp at 300 mph. A drag racer may have drag equivalent to a flat plate 12 feet in area and acting several feet above the ground, requiring 2,868 hp to overcome the aerodynamic drag at 300 mph.

So I doubt that a standard GSXR would get anywhere near 200mph. It would require very different aerodynamics and a hatfull more HP. Theres a load of money to be paid to get even a Busa up to a real 200mph+

:hail TLR's
 

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I'm not arguing that, aerodynamic resistance increases at the square of speed more or less.

The point was that the relationship between rpm and mph is linear:)

Its not all that hard to get a busa or ZX14 to 200 though. The guy who just broke the speed record went a legit 208 on a ZX12 that wasn't all that modded out.
 

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.........

From what I've read at very high speeds, wheel slip can account for as much as 10% of overall speed, not sure of the accuracy of this though:O .............
In the old 500cc days when they raced at Hokenheim the bikes wouldn't go any faster because they were wheel spinning in 6th.

Out here an AU spec Superbike (CBR1000) with data logging had the rear wheel doing 30km/h (~18mph) more than the bike on th front straight due to wheel spin. Not doing 200mph either.

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Even if the engine was doing a genuine 12500rpm in 6th on OEM gearing, there would be wheel spin. Only a GPS would tell you.

OEM tacho's are as optimistic as speedo's (Yamaha went overboard with the R6 though :laugh)

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No clutch slippage, no wheel spin, no tyre growth at speed and speed vs. rpm is linear.

Y= mX+c
(m = (Y1 - Y)/(X1-X))
C can = 0
:laugh
 

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Discussion Starter #16
I'm not arguing that, aerodynamic resistance increases at the square of speed more or less.

The point was that the relationship between rpm and mph is linear:)


Exactly. Wind Drag DOES increase with the square of the speed. Well known physics law.


It i should be also well known that for any gear, the RPM is directly related to the speed.


In doubt? Try it out. Drive your car and double RPM and see the speed doubling. Or get the gear calculation XLS for the TL (or anyother bike) and see how the speed is related to the RPM.



Later
 

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as a guide as to how far out your speedo can be i ran my 12 on a dyno and got an indicated 216mph which was an actual 203mph.. doubt i would see an indicated 200 on the road although i have been up pretty close to an indicated 190.. :devious
 

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well, i did 201.463 and had it checked by a friend who is a lt with the highway patrol. mod'ed motor, had to lower susp. and i will never do it again.
 
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