"calculated" speed

The number is not important to me
I have just gotten asked enough that I became curious
I think the old Cycle World road tests used to list calculated top speed (if the bike could reach redline with stock gearing) and then actual top speed based on test results
For those who gave links or provided formulas I would ask for a real world example using numbers from your bike
Yes, I'm a dummy looking for fill in the blank

 

Then you should really get a GPS laptimer. Honestly you can find good used ones (even some brand new ones) for pretty cheap these days. They are a great tool and will work anywhere and you don't have to rely on a beacon setup trackside. Mine is wired right to the battery and doesn't even need a charge, just hit the power button and out to the track.

None of this calculated this or that, not to mentioned not every bike is going to be exactly the same. If you really want to know how fast YOU are going

 

Calculated speed won't take wheel slip into effect either.

 

The 848 did 171 in Friday morning qualifying, with a tow and tailwind coming into the tri oval. During the race we had headwinds and the best I saw on the gps was 164.. FWIW.

 

That would be a pretty insignificant factor at top speed on an air cooled Ducati.
Panagale, maybe. Not spinning it up much on top end.
And to repeat, I am just curious as to the formula to calculate it.

 

Gino, didn't you have a built air cooled in an 848 chassis a while back? Pretty sure it was you I corresponded with about possibly buying it. Any clue as to top end on that bike at Daytona?

 

Psh. That's not what the SV guys say.

 

Remember, if you're trying to judge based on wheelspeed that tire circumference isn't constant. It's going to change if you have any lean angle at all relative to the surface, which is likely on the banking.

 

Velocity = (rpm * tire circumference) / combined gear ratios

For my 06 GSXR 750 the numbers would be:

15000 rpm * 60 = 900000 rph
Tire circumference is ~77.9" / 12" / 5280' = ~0.001229 miles
Primary gear ratio = 1.761
6th gear = 1.208
Final gear ratio for 16/45 gearing = 2.8125

(rpm was converted to rph and the tire circumference converted to miles or else you'll get inches/min.)

So top speed in top gear at redline is...

v = (900000 * 0.001229) / (1.761 * 1.208 * 2.8125) = 184.8 mph

Which is bullshit because I've totally seen an indicated 205!

 

By the math in a vacuum that works. We have this thing called an atmosphere on planet earth.

You are missing the frontal area of the bike so you can apply a factor for wind resistance. I guess in a draft that number would change as well.

 

Venom, as long as you used the actual attained RPM, the frontal area and wind resistance would already be accounted for, wouldn't it?

 

This.

Venom, wind resistance may limit your rpm, but if the crank is turning the wheel will too since everything is connected mechanically.

 

not even "accounted for", drag is irrelevant due to the mechanics.

 

That's working under the assumption that with the selected gearing that mechanics can overcome the resistance and make it all the way to redline.

But yes I eluded that by the pure math that works correctly. I could gear a 60HP bike for 205 miles an hour by the math but it will never reach that number...even down hill.

 

I see where you're coming from and you're correct. I doubt my bike can make redline in 6th. I was just throwing numbers out there. He'll actually need to know what he's revving at.

 

Well, it can. The trick is finding the right combination on the track you are on to put you near or at redline at the end of the longest straight away. That number changes track to track, draft vs no draft and with additional HP.

Somewhere like Tally is easy for most anything to reach the top speed. Daytona is a different matter, Certainly for the smaller displacement machines.

 

Yes, I still have the bike!

Let me look in my lap timer, I may have it.....stand by.....

 

EDIT: I don't have GPS data from the last time I rode it there. It was one of the fastest LW bikes though. Mark Evry has a video on YouTube of me driving right by him on the banking, a pack of about 10 of us were all together and I came out on top of the battle to finish like 7th or something. Shane Turpin was way out front on the Pierobon.

I think the highest top speed I ever saw was about 151 on the GPS. Going from memory now.

Don't forget with the RPM calculations that in the Tri-oval, you lean over and the RPM goes way up as you go onto the smaller diameter of the edge of the tire. Most dynos have a top speed function that just shows what the speed is at redline in top gear.... but if you knew that, and you knew your peak RPM at a given track, assuming you were not leaned over, you could figure it out that way.....

 

I try not to lean over
I might fall down
But coming off the west banking on the way to the chicane I am pretty straight up and down
And not spinning the tires
And hitting redline before braking
So most of these variables mentioned are not a factor
Wind resistance is factored out as RPM is what is achieved for the calculation
Down wind? More RPM upwind less

 

Point is I hit redline
Don't look down there much but saw the red light flashing
Apparently no mechanical rev limiter leaving me the personal luxury of turning my lump into shrapnel
Gear for Bonneville if you want though I suppose intelligent gearing means top gear redline at the fastest point on the track
Though not always
Sometimes better to give that up for gearing advantage elsewhere on the track