gearing it MORE?

Ken what's ypur purpose??? Remember for top speed, the peak of you're power curve needs to be the saem as your drag limted speed. At what RPM are you reaching drag limited speed at right now??? At what RPM is your peak horse power? How much does the power curve drop off from peak HP to redline???

Waht is the range of your powerband? For example peak my bike makes 96HP, at redline it makes 90HP, the other point that it makes 90 HP is 10,000 RPM. Therefore my powerband is 10k-14k. For max acceleration though I shiftr at 13k, and my gearign it tight enough that the RPM's only drop 2k, so then I have more than 94HP all the time.

This is all easier to explain visually with a power chart.

Remeber peak HP means nothing. It's that average HP throghout that powerband that is important.

In mathematics, you would use calculus to calculate that area under the power curve throughout your powerband.

I can figure out the optimum gearing for top speed, if you give me the folowing information:

1) a copy of you power curve from a dyno run
2) you rear wheel circumfrence, (measure this by marking a point on the pavement and rollign the bike forward and makign a seond mark)
3) your primary reduction, gear ratios (in your owners manual) and final reduction
4) the spockets you have on now.

I'll then assume about 2% wheelspin, and run those numbers into a excel spreadsheet I have.

Your bike makes what 140HP, and so does the Gixer 1000 and it does 168 mph, so your target should to have you RPM's in 6th gear at peak power, equal 168mph.

Now ot get max accelration, you need to figure out how to get maximum average power output all the way from the speed that equals you launch RPM in 1st to top speed.


I how I explained this well enough. Just give me all the info I asked for and I'll give you some objective recommendations.

cherry ill need some time on that...but heres something?

when i did the gearing and put the new chain...i also put on a new 190/70 M1 on and dialed it in.

well 2 tires later..and this one is ALMOST bald.


maybe the less diamiter...is taking away 3 mpr?

as far as hpr...its 145.3

i dont have that chart,,,left it at jims.

but my hpr curve doesnt drop off untill 12,750 rpms
it hits peak at 10,500 if i remember right. fucking thing is like a ladder with a slight leveling off from 11,000 hovering at 144.00

i am trying to atleast get that 3mpr to make it 170mpr top end...i LOVE the acceleration of it...it would scare or hurt most guys unleashing it like a raped ape without knowing how to handle it...thats why..i am not SUPER keen to gearing it lower.

is it just that the tire is bald and thats why i am losing the 3mpr.

i know all this for just 3mpr is anal but then again so am i:evil

Well, since you mentioned being anal, wouldn't the tire circumference increase with speed. I suspect that this would probably be enough to cancel out wheel slip in the equations.

Also, if you're looking for maximum acceleration, wouldn't you also need to consider the torque curve?

Anyway, then how would you gear the following two Busas?

1. "Stock" Busa, nearly linear sloped power curve where the slope levels off to a shallower angle around 8500 RPM but power contnues to increase until redline. The torque curve increases sharply to 80 ft.lbs. @ 4000 RPM, increases more gradually to 90 ft.lbs. @ 7500 RPM, the gradually decreases to 78 ft.lbs. @ 10500 RPM.

2. "Modified" Busa with power increasing nearly linearly to 9800 RPM producing ~200 HP @ 7500 to ~240 HP @ 9800. I don't have the torque curve on this one but typical is fairly flat with approx. 120 ft.lbs. above 4500 RPM.

Both bikes are top-speed limited to 186 (well sort of) and rider gonads limited to around 150.

Primary reduction 1.596 (83/52)
Final Reduction 2.352 (40/17)
1st 2.615 (34/13)
2nd 1.937 (31/16)
3rd 1.526 (29/19)
4th 1.285 (27/21)
5th 1.136 (25/22)
6th 1.043 (24/23)

Heck this may make a good refresher problem for Physics 101. Maybe I'll do a little spreadsheeting of my own!

Should I include the dynamic tension of my shoulder sockets?:twofinger

cherrypicker said:

I hear this a lot. I sat and thought about it and the best answer I have is this. At lower speeds when drag in a not a factor, yes it oes matter. But at those lower speeds, anything more than 40-50ft-lbs will typically lift the front end anyway, so there's no real advantage.

When top speed is concerned, power is everything.

Torque is only important because it determines the shape of the power curve. TO get more power out of a bike (on bikes that make peak power over 5250RPM), you never need to increase the peak torque value, you only need to prevent the torque curve from falling off.

Click to expand...

I need to give this a little more thought myself, but it seems as I think about it torque is essentially the force for angular acceleration, or put more simply how quickly the power can change from one static point on the power curve to another.

So, if torque is constant the power curve becomes a straight line and the amount of torque available determines the slope of the line. When the torque begins to decrease, the power curve may still be increasing but the slope of the line decreases. So given time you will eventually reach the point where horsepower and drag cancel each other (top speed) but the rate of acceleration decreases.

Makes sense, so now I need to think about how this applies to gearing in the real world. Ultimately you are trading top speed for acceleration, but it's slightly more complicated than that, depending on why you're speed limited.

Interesting conversation and great refresher course in physics!:thumbsup

This also seems to explain why I'm more comfortable on the turns between 4000-5000 RPM. This is where the torque curve flattens out but is still rising up to around 7500 RPM. Therefore this is the range where the engine is able to more quickly change its power output for maximum acceleration, making the power delivery more aggressive.

Interesting...perhaps what I really need is yet more throttle control to execute at higher RPMs. The throttle is simply more responsive in the higher RPM range.

Heck sometimes it already feels like I'm barely turning my wrist!

BusaDave said:

Makes sense, so now I need to think about how this applies to gearing in the real world. Ultimately you are trading top speed for acceleration, but it's slightly more complicated than that, depending on why you're speed limited.

Interesting conversation and great refresher course in physics!:thumbsup

This also seems to explain why I'm more comfortable on the turns between 4000-5000 RPM. This is where the torque curve flattens out but is still rising up to around 7500 RPM. Therefore this is the range where the engine is able to more quickly change its power output for maximum acceleration, making the power delivery more aggressive.

Interesting...perhaps what I really need is yet more throttle control to execute at higher RPMs. The throttle is simply more responsive in the higher RPM range.

Heck sometimes it already feels like I'm barely turning my wrist!

Click to expand...

Dave, you barely are turning your wrist:twofinger That's the problem. In a turnit's best to take it at higher RPM. The power delivery is smoother since the pistons are firing more often. Kind of like higher refresh rate on a computer or soemthing.

The one scenerio I can use to describe how torque and power relate ot vehicle performance. I use d to race bicycles. The human body is a interesting engine. IT's very similar ot a DC motor. IT makes max torque stalled (0 RPM), and the tirque curve drops off at a rate dependent on muscle stamina, corrodination, and various biochemical factors.

I guess that when I was in shape, my peak torque output to the rear wheel was around 60 ft-lbs at 0 RPM using a 180mm crankarm measured at 90 and 270 degrees from TDC (when the pedals are horizontal). My torque output steadily fell off up to my redline - around 150RPM with that crankarm where I was probably making only around 10 ft lbs. My peak power output was probably around 1HP at 120RPM.

My quickest acceleration was always in my powerband, 80RPM-120RPM.

How about this. What is required ot move the bike??? The exothermic reaction between oxygen and gasoline. Therefore, the bike that accelerates the fastest, is the one that can release the most energy. Torque is only a measurement of how powerful the reaction is at a given moment. Power is in fact the rate of fuel combustion. Simply put, burn more fuel and you will accelerate faster.