Gearing for 200 MPH Milestone...

[lopycam]

You also need to have enough "power" to get you there.
There are things that you need to over come.

Nathan

[bigred875]

ya once you get past a certain point it takes tons of hp to gain even a couple more mph....

you gonna give it a go on the 7 in your t-shirt, shorts and ipod blasting?

[bigred875]

Originally posted by Mystery Squid
I know the whole HP deal, here's a brief logic trail:

Let's take my 7R for example , Kawi says, stock, my bike is good for 171mph (and let's assume a real 171mph for illustrative purposes), and has stock HP of roughly 121 (at the crank).

Given,

Versus attempting all sorts of modifications to yield more HP, how many more MPH's do you think you might get IF you replace the normal rear 46 tooth sprocket, with something ridiculous like a 20 tooth sprocket? (and let's also exclude the possibility that it might keep stalling in 1st)

well for one thing I would guess that 171 is speedo indicated, if so you are prolly looking at more like 160-165 real mph....so to see a real 200mph you will to change more then gearing...engine work...maybe even aerodynamics..etc....

just guessing but I beleive if you do change the gearing like you said you would be running into an HP/aerodynamic problem.....

Got NOS?

[slingblade]

Gearing huh?

I'd say 2 sets of full leathers, and some sick body armor



You'd need to overcome the drag, and friction of the road at those speeds. It takes a LOT more HP to from 180 to 190 than it does to get from 120 - 130. It starts going up exponentially.

[bigred875]

Originally posted by Mystery Squid
Concept here, CONCEPT!

How many more MPH's do you think you'd get by using a ridiculously smaller rear sprocket?

you'd prolly see something in the 180's..not much more then that..

[benVFR]

You might lose MPH by going to a ridiculously small sprocket.

There is an alternative to upgrading the bike to massive HP to get to 200mph.

Make a custom fairing for your 7R which looks something like this:



That is just a bicycle and it's probably good for close to 70mph on flat ground.

GP bikes were headed for shapes like this in the 50s or 60s and the fairings were banned because the bikes were hitting stupid fast speeds even though they made a tiny fraction of the power a current racebike makes.

ISTR the GP bikes in question with fairings like this were making in the neighborhood of 10-15hp and were going upwards of 130mph.

Ben

[bemused]

two words: frontal area.

[Honclfibr]

Drag increases with the square of velocity.

[RandyO]

I can go faster in 5th gear than I can in 6th

[Degsy]

I believe it takes more torque to rotate the rear wheel with a smaller rear sprocket, right? So, the answer is that you would probably get less speed out of it.

Do the math on the sprockets you already have stock and you will find that the bike probably could do 200mph plus if you were in a vacuum (I know the motor needs air so don't point that obvious one out).

Derek

[Paul_E_D]

You would surely go SLOWER with the 20 tooth rear sprocket.

You can get marginally higher top speed on some bikes by dropping a tooth or two, but the manufacturers gear many bikes a tad shorter than the motor can actually redline in 6th gear so they can advertise the theoretical "171MPH"

Many bike will actually go a few MPH faster if you ADD a tooth or two because the motor will then reach redline in Sixth Gear. I believe the 7R is one of these bikes.

[bbhzx10]

Why buy a sprocket, just get on the highway and twist! And once your over 160 make sure to keep your head down!
PS...GO BIG OR GO HOME!!

[Kham]

might be less mod to zx12 or busa. lose some weight or put me on it.

[dhuze]

this might help you out a bit although it is for an r6 i would thonk the gearing is approximate if you use the tooth calculator at the bottom




http://www.yzfr6.net/sprocket_speed.php

[SEVENSGT]

squid, you wanna hit the salt flats with me , we can try all kinds of crazy gearing on the hawk and the 7

[beet]

aint easy & no stock 7 can get close ..
Drag increases with the square of velocity
its not the front dirty rear that holds bikes

[Suf Daddy]

get a turbo 'Busa..............

I'd see what those speedfreak do with their gearing, then find a long downhill grade in Montana...................

Twist the wrist....... ECHO: Go big or Go HOME..........lol
-Suf Daddy

[URL=http://www.sportrider.com/bikes/146_0110_hayabusa/[/URL]

CLIP:
It's worth taking a look at both bikes' gearboxes at this point, and how the Hayabusa and ZX make their power differently. The Suzuki-producing a lot of torque over a wide rev band-has a widely spaced box, with first gear good for only 83 mph at redline, but sixth set to a wishful 207 mph. Because it revs just past its power peak in sixth gear at 190 mph (10,250 rpm), adding gearing drops revs off the downside of the horsepower curve, and the Hayabusa can't cope with the lowered rpm.

On the other hand, the Kawasaki-comparatively high revving and with a narrower powerband-has a closer-spaced gearbox with a taller first gear (85 mph) and a shorter sixth (201 mph). Because our modified bike carries its peak horsepower further (right to redline, in fact) it can pull as much gearing as the rev limiter will allow. Helping the ZX in this department is the 46-tooth rear sprocket; dropping a tooth changes gearing only 2.2 percent, whereas dropping a tooth from the Hayabusa's 40-tooth rear sprocket is a change of 2.5 percent.

[Suf Daddy]

Originally posted by bbhzx12
Why buy a sprocket, just get on the highway and twist! And once your over 160 make sure to keep your head down!
PS...GO BIG OR GO HOME!!

[SSearchVT]

An easy way to remove the drag concern is to try it on a dyno. Most portable or shop dyno's don't read this fast, so you will have to do some searching. This will let you know if the engine can turn enough RPM's.

[benVFR]

I'm tellin ya... build yourself a dustbin fairing!

Ben

[oreo_n2]

rather than dyno (that costs money) just do a burn out... keep it spinning through all the gears... and see whats indicated when you top out 6th.
No really, it will be perfectly accurate for speed!

[SSearchVT]

"rather than dyno (that costs money) just do a burn out... keep it spinning through all the gears... and see whats indicated when you top out 6th.
No really, it will be perfectly accurate for speed!"

And safe too......

[TLRMan]

Speedos lie!
So even doing a stationary burnout won't give you the true MPH..

BTW, you will need about 240 hp to get into the 200 mph range without flogging the motor to death......

[Tarmac]

Prolly already discussed but I got ADD & no patience, so about the 4th post down I shot to the end.

Aerodynamics will get you there far sooner than HP.

I've "heard" (never validated) that the highest paid engineers in Motorsports are aero-dynamacists (is that a word?), and I guess that makes sense seeing as though the advancemtn curve on internal combustion R&D is prolly flatter then aero R&D.

...but again, this is prolly old news by now..

[Kham]

SQUID, get a turbo busa just for the 200mph and posing and save the 7R the other stuff.