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-1/+2 vs +5

  #1  
Old 12-30-2009, 02:11 PM
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Default -1/+2 vs +5

which is better? im thinking they are about the same as gear ratios go, but i heard, or read somewhere that going down one in the front kinda offset the rise in your rpms-i have no idea if thats true or not. so my question is are they the same or would the -1 in the front be better. i like the way the bigger sprockets look so i would want to go with the +5 if they are the same but i dont wanna over rev my bike all the time. also what size(length) chain for a +5 would i need?
 
  #2  
Old 12-30-2009, 07:02 PM
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Please correct me if I am wrong as I have absolutely no first hand experience but coming from an engineering standpoint, I would rather reduce 1 in the front then go up in the rear. As you make the rear bigger, the centrifugal force is greater pushing out, and can do a couple things. One it can actually try to force/push the chain towards the outside (which may wear the sprocket easier) and it also creates a larger rotating mass which would make it harder to accelerate/decelerate.

The chain would need to be lengthened, I would imagine.

That's all the input I have, now none of this may actually be noticeable, so i'll wait for others to chime in .
 
  #3  
Old 12-30-2009, 07:40 PM
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hmm... i have -1/+2 and i like it alot. i only notice my rpms are sorta high on the highway. 65 mph, i think im at 6000 rpm so not too bad...
 
  #4  
Old 12-30-2009, 10:22 PM
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I use a handy online utility called Gear Commander to see what effect changing gearing would have on my speed at various rpm and things. Just plug in your model bike at the top of the screen from their database and experiment away.
 
  #5  
Old 12-30-2009, 11:56 PM
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the gearing is going to be basically the same

most people go with -1/+2 bc they don't want to either replace their chain or cut it and add links

never talked to anybody running a +5 with a stock front sprocket....it's usually used in conjunction with -1 or 2 on the front for stunt riding
 
  #6  
Old 12-31-2009, 01:05 AM
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Originally Posted by GDM YO View Post
Please correct me if I am wrong as I have absolutely no first hand experience but coming from an engineering standpoint, I would rather reduce 1 in the front then go up in the rear. As you make the rear bigger, the centrifugal force is greater pushing out, and can do a couple things. One it can actually try to force/push the chain towards the outside (which may wear the sprocket easier) and it also creates a larger rotating mass which would make it harder to accelerate/decelerate.

The chain would need to be lengthened, I would imagine.

That's all the input I have, now none of this may actually be noticeable, so i'll wait for others to chime in .
From a physics stand point, isn't the force directed toward the center of the sprocket regardless of size?
 
  #7  
Old 12-31-2009, 10:58 AM
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Originally Posted by Fallen3 View Post
From a physics stand point, isn't the force directed toward the center of the sprocket regardless of size?
I think you are mistaking centripetal force, to centrifugal force.

If the chain was on the inside of the sprocket, the chain would experience a centripetal force
 
  #8  
Old 12-31-2009, 11:07 AM
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Originally Posted by GDM YO View Post
I think you are mistaking centripetal force, to centrifugal force.

If the chain was on the inside of the sprocket, the chain would experience a centripetal force
But there is no force called centrifugal force. The chain being wherever still gives it centripetal force. Any body rotating has centripetal force.

I don't really want to seem haughty or anything, I'm just trying to understand. If the back sprocket increases in size, the same principles apply, only you'd need a bigger chain. Wouldn't that be the only difference?
 

Last edited by Fallen3; 12-31-2009 at 11:10 AM.
  #9  
Old 12-31-2009, 11:19 AM
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Originally Posted by Fallen3 View Post
But there is no force called centrifugal force. The chain being wherever still gives it centripetal force. Any body rotating has centripetal force.

I don't really want to seem haughty or anything, I'm just trying to understand. If the back sprocket increases in size, the same principles apply, only you'd need a bigger chain. Wouldn't that be the only difference?
The centrifugal force of the chain is being pushed towards the outside. look up a centrifugal clutch, same idea.

Having the sprocket larger also creates a larger moment / torque when rotating, as it is farther away from the center, so that is why I said it could make it harder to accelerate / decelerate.

Again none of this is probably noticeable, just something to consider.
 
  #10  
Old 12-31-2009, 12:36 PM
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Sheesh...you guys are making my brain hurt. The larger sprocket creates a greater recipricating mass as does steel compared to aluminum. BUT it is SO minute NONE of us will EVER notice the difference. Oh back to the subject at hand... I have a stock size front sprocket (16 teeth) and a 50 tooth rear sprocket with a 525 width, only because I found great deals on the sprockets.
 

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