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Discussion Starter #1
Today at the recycle center I saw a couple of thrown away 10 speed bicycles. One didn't look in too bad of shape so I threw it in the truck and brought it home. A couple of adjustments, LOTS of Liquid Wrench, and some air in the tires and I was out wheezing and gasping for air trying to keep up with Sprout1.
As I was going through the different gears, making notes on how to adjust the derailers I noticed that the smaller of the crank gears made it MUCH easier to pedal while on the largest gear in the rear. Although I had to pedal much faster to keep the same speed, it was easier to pedal than on the larger crank gear.
WTF does this have to do with motorcycles ? Well, currently I run 15/48 gearing in my SV and I'm kind of sick of it. If I needed new chain/sprockets, I would go back to around 45/46 or so. I know the larger sprocket gear makes life easier on the chain, so I went big on the rear sprocket. Besides, I like the look of the larger rear sprocket.
It occured to me that I could run a 16 tooth front sprocket (read: cheap) but what I want to know is:
Would a larger front/rear sprocket make life easier on THE ENGINE vs. a smaller front sprocket/big rear ?!
Screw chain life, it's a consumable anyway. What would make life easier on the ENGINE and tranny ? (ie: faster revs, less stress, more torque to the rear?, etc )
I can't figure it out. :-\
 

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Today at the recycle center I saw a couple of thrown away 10 speed bicycles. One didn't look in too bad of shape so I threw it in the truck and brought it home. A couple of adjustments, LOTS of Liquid Wrench, and some air in the tires and I was out wheezing and gasping for air trying to keep up with Sprout1.
As I was going through the different gears, making notes on how to adjust the derailers I noticed that the smaller of the crank gears made it MUCH easier to pedal while on the largest gear in the rear. Although I had to pedal much faster to keep the same speed, it was easier to pedal than on the larger crank gear.
WTF does this have to do with motorcycles ? Well, currently I run 15/48 gearing in my SV and I'm kind of sick of it. If I needed new chain/sprockets, I would go back to around 45/46 or so. I know the larger sprocket gear makes life easier on the chain, so I went big on the rear sprocket. Besides, I like the look of the larger rear sprocket.
It occured to me that I could run a 16 tooth front sprocket (read: cheap) but what I want to know is:
Would a larger front/rear sprocket make life easier on THE ENGINE vs. a smaller front sprocket/big rear ?!
Screw chain life, it's a consumable anyway. What would make life easier on the ENGINE and tranny ? (ie: faster revs, less stress, more torque to the rear?, etc )
I can't figure it out. :-\
small front, big rear... to an extent.
 

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You have a lot higher RPM's I think. I mean the engine would have to turn the front so many more times in order to maintain the same speed.

I actually cycle (ie ride a road bike) so think of it like this.

If I'm in my smallest chainring up front and my largest cassette ring in the back...

or

If I am in my largest chainring up front and for simplicities sake still the largest cassette ring in the back...

and

Pedaling at the same cadence...

What you do you think will happen?

I'll go considerbly slower with the first instance. In order to maintain the same speed in both instances I would need to increase cadence with the first instance, which would also stress the engine (ie me) more.

Make sense?
 

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Discussion Starter #5
Faster revs actually means MORE wear and tear on the engine.

Lower revs means longer life, as there is less rubbing of metal on metal.
Sorry, I should have clarified. To me, that is basic/basic knoweledge. What I am more interested in is what happens during acceleration.
What makes it easier on the engine/tranny to put down power during acceleration ?
 

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Sorry, I should have clarified. To me, that is basic/basic knoweledge. What I am more interested in is what happens during acceleration.
What makes it easier on the engine/tranny to put down power during acceleration ?
I would still say somewhere in the middle. Too small and you have to hit a lot of revs and too big and you are requiring a lot of either inertia and/or torque.

That being said I'm guessing and really can't remember much of college physics and have NO engine knowledge.
 

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From a non-technical but cycling-oriented viewpoint...something near stock is probably best.
smaller front/larger rear makes acceleration easy on the engine, but in a narrower powerband, just like on your new bi-cycle. You run out of revs sooner, and unless you want to live at 9K, you shift more, which is tranny wear.
Larger front, smaller rear makes the engine lazier and loafing is easy, right? But the engine tends to lug at lower speeds, which means more shifting, which is harder on the tranny...
You see where this is headed. Probably a tooth either way up front or in back and you'll notice some slight difference in acceleration, but nothing you do in that range is gonna be materially better or worse on the engine.
If you have lots of highway miles, add a tooth in the front for loafing. If more street/twisties, subtract a tooth in the front for more acceleration.

edit - saw your recent post. acceleration (torque to the rear) is increased with smaller front sprockets. I think that's where you were headed... :bacon:
 

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Making the bike accelerate quicker by having the larger rear sprocket will cause the bike to rev higher at higher speeds, so it'll be paid for in shorter valve life, shorter piston ring/cylinder wall life, and shorter bearing life (in the crank).

Having the engine rev lower at high speeds (smaller rear sprocket) will cause less wear and tear, but the bike will not accelerate as well.

"As well" is a relative term.

If you perform proper maintenance, having a larger rear sprocket (higher highway revs) will not significantly affect the life of the engine, given that you use sprockets that are available for this bike.

Now then, putting one on that is big enough to peg the engine at 8k rpm when on the highway WILL shorten the engine's life, but you'll accelerate from 0 to 60mph in about a second and a half...
 

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Sorry, I should have clarified. To me, that is basic/basic knoweledge. What I am more interested in is what happens during acceleration.
What makes it easier on the engine/tranny to put down power during acceleration ?
I am going to say that it doesn't make a lick of difference. Now if we were seeing engine failure mostly due to broken cranks or things of that nature (major engine failure) instead of things wearing out of spec, then what you're saying might be true. But the fact that the engine is wearing out due to mileage means that having higher gearing would make your overall average rpm lower, and increase engine life.
 

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Discussion Starter #10
Making the bike accelerate quicker by having the larger rear sprocket will cause the bike to rev higher at higher speeds, so it'll be paid for in shorter valve life, shorter piston ring/cylinder wall life, and shorter bearing life (in the crank).

Having the engine rev lower at high speeds (smaller rear sprocket) will cause less wear and tear, but the bike will not accelerate as well.

"As well" is a relative term.

If you perform proper maintenance, having a larger rear sprocket (higher highway revs) will not significantly affect the life of the engine, given that you use sprockets that are available for this bike.

Now then, putting one on that is big enough to peg the engine at 8k rpm when on the highway WILL shorten the engine's life, but you'll accelerate from 0 to 60mph in about a second and a half...
SOrry Bro, but again, this is basic knoweledge. I know all about that, which is why I went with a 48 tooth rear. Actually, I screwed up on that cuz when I ordered a new sprocket for my Gixxer wheel I thought I had a 48 on my SV wheel. I was supposed to order a 47. :rolleyes: )

WHat I want to know is what combo makes it easier for the engine/tranny to transmit the POWAH !!
 

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By powah you mean acceleration - that kick in the pants feeling?
Then you're probably on it now, 15/48, that's about 3.2:1 ratio. If you go back to a 45 in the rear, you'd want a 14 up front to go with. I don't think you can get smaller than that.
 

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SOrry Bro, but again, this is basic knoweledge. I know all about that, which is why I went with a 48 tooth rear. Actually, I screwed up on that cuz when I ordered a new sprocket for my Gixxer wheel I thought I had a 48 on my SV wheel. I was supposed to order a 47. :rolleyes: )

WHat I want to know is what combo makes it easier for the engine/tranny to transmit the POWAH !!

Ah. I misunderstood the question.

There is no combo that will do that. You'll pay one way or the other. More power always equals shorter life in some way or another.
 

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WHat I want to know is what combo makes it easier for the engine/tranny to transmit the POWAH !!
So, are you asking what gearing combo (if any) will improve engine to wheel efficiency? That is, (since rwhp is the same regardless of gearing) are you wondering if different sprocket combos result in different rear wheel horsepower measurements... and you're looking for the combo that maximizes rwhp?
 

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Discussion Starter #14
So, are you asking what gearing combo (if any) will improve engine to wheel efficiency? That is, (since rwhp is the same regardless of gearing) are you wondering if different sprocket combos result in different rear wheel horsepower measurements... and you're looking for the combo that maximizes rwhp?
YES, THIS !! Not that.
 

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Hmm, first of all, efficiency and rear wheel horsepower are one in the same. I know that HP isn't your goal; engine longevity is. Think of it this way though. If you had zero drive line losses, you would produce more HP going to the rear wheel at every RPM, allowing you to ride at a lower RPM to overcome wind resistance and friction.

Not totally sure where I'm going with this, but here's what I have to say about your original question.

First of all, you have to take into consideration that your cycle analogy involved your perception of what was more difficult.

But as for the sprocket thing, here's my theory. You're looking for the most efficient combo, right? I'd argue that a chain/sprocket combo that lasts the longest is the most efficient. It takes energy to destroy a chain and sprocket, right? And excessive heat is no good for the chain either. Well, if your chain goes to crap fast, that means a lot of energy was needed to do that. If your chain and sprockets stay in good shape, not much energy went into deforming them, meaning more energy would have been passed on to the rear wheel - where you want it.

It would be pretty tough to test that, as chain maintenance plays such a big part in how long stuff will last, but I have heard that going too small in front causes fast wear, because the teeth don't match up the best with the spacing in the chain as well.
 

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There are trade offs for both higher and lower gearing. The higher the gearing (low numerical reduction ratio, analogous to a larger front/smaller rear sprocket) reduces the RPM at any speed, but the specific loads on the engine are higher. So you turn fewer revs but at higher mechanical loads.

Conversely, the lower the gearing (high numerical reduction ratio, analogous to a smaller front/larger rear sprocket) increases the RPM at any speed, but the specific loads are lower. So you turn more revs but at lower mechanical loads.

Within the range of what most people use on SVs it won't make much difference in the life of the engine. The chain life is affected more by the number of teeth on the front sprocket, primarily, so going from, say, a 15 to a 14 will have some effect on chain life. Rear sprocket doesn't make as much difference because it will be a much larger radius.

What you're changing is the torque at the rear wheel. The rear wheel horsepower is the same as engine horsepower no matter what the gear ratio is (minus mechanical drag losses in the primary drive, final drive and transmission). The torque changes with overall reduction ratio. The higher the gearing (lower numerical reduction) the lower the rear wheel torque, the lower the acceleration rate. The lower the gearing (higher numerical reduction) the higher the rear wheel torque, the higher the acceleration rate.
 

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First of all, you have to take into consideration that your cycle analogy involved your perception of what was more difficult.
Just to be an @ss...

I'd argue that if we put a road bicycle on an indoor trainer, maintained the same cadence, and did the gearing examples as desribed, wattage numbers would support perception.

Now outside in the elements with variance in wind, surface, and grade everything can change. ;)
 
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