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Can someone please clear this up for me. A friend of mine went 3 up on his rear sprocket on his GSXR600 race bike. He seems to think that the change has changed the output of the bike.

Surely this change will only affect the revs at which the bike makes its peak HP but not change the actual output of the bike?
 

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Can someone please clear this up for me. A friend of mine went 3 up on his rear sprocket on his GSXR600 race bike. He seems to think that the change has changed the output of the bike.

Surely this change will only affect the revs at which the bike makes its peak HP but not change the actual output of the bike?
Yes, it will change the final output, ie. improve acceleration.

No, it wont change engine character, like the rpm bike makes it's max power.

-J-
 

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The larger you go in the rear, the quicker your acceleration, but your top speed will be lower.

The Smaller you go in the rear, the slower you will accelerate, but you will have a faster top speed.
 

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Mostly you do it so that you almost hit the rev limiter on the longest straight. That gives you the most options throughout that particular track. Sometimes it is done specifically for one turn that maybe between optimum RPMs. In one way he is right. It gives him top HP when he wants it if he set it up right.
 

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For him to go up 3 teeth in the rear, tells me that its a very tight track he is racing on. I would doubt that he even uses 6th gear. That big of a change, does allow him to use the most of the bikes power, that otherwise would go untapped on that track. Racing somewhere like Road America, you do just the opposite, because that track is long and extremely fast. Top speed is much more important there.
 

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He is actually realizing an increase in torque at the rear wheel not an increase in horsepower.
:plus1: confussion over power and torque by your friend. power is the same, but the change in gearing is providing more torque at the wheel, hence it is quicker off the line.
 

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The larger you go in the rear, the quicker your acceleration, but your top speed will be lower.

The Smaller you go in the rear, the slower you will accelerate, but you will have a faster top speed.
This might be the case, but if the original gearing was too tall, and the bike couldn't hit it's peak power rev range, then dropping the gearing (larger rear sprocket) would increase the revs and bring the motor into its peak power, therby increasing the top end. Of course there are limits. You might run out of revs beforeyou actually achive the top speed if you put too big a rear on. You need to select a gear so that you can't go any faster when your engine is making max power.
 

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look at it this way. the fewer the teeth, the faster the back wheel will spin. the more the teeth, the slower the back wheel will spin. so what does this mean? he will get more top speed but his acceleration will slow down. sso town or city riding won't be nice but his freeway cruising speed goes up. that's why he feels like he's got more HP. the engine hp remains the same. hope that helps.
 

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look at it this way. the fewer the teeth, the faster the back wheel will spin. the more the teeth, the slower the back wheel will spin. so what does this mean? he will get more top speed but his acceleration will slow down. sso town or city riding won't be nice but his freeway cruising speed goes up. that's why he feels like he's got more HP. the engine hp remains the same. hope that helps.
He put +3 on the back sprocket. So Flip it around and you are right.
 
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