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Discussion Starter #1
I mainly use my monster 696 for commuting. While some of you might see this as heresy, my bike spends 95% of its time bringing me to and from work, so yes, I do have concerns about mileage.

I think it would be a little easier in stop and go traffic to switch to a smaller front sprocket, but has anyone done this and noted their mileage before and after the change? Right now I just make 50 mpg.
 

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Of course it will lower mileage, but I doubt if it would be enough to offset the ease of a 14t in stop and go traffic.
 

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According to gearing commander

http://www.gearingcommander.com/

Stock gearing is 15/45, Changing to a 14/45 increases RPM's at 65 from 4,553 to 4,878,
so the increase is only 325 RPM.

So, if you are getting nearly 50mpg, (4553/4878)*50= 46.67, so maybe a decrease of 3-3.5 mpg.

Certainly worth the change in drivability.
 

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There are two primary reasons why higher RPM for a given speed reduces fuel efficiency.

1. More combustion cycles per unit time means that not as much air/fuel is needed per power stroke to maintain your speed, which means that the throttle is held more fully closed, which in turn results in greater drag as the engine attempts to draw air past the throttle plate. This is a more minor effect and can be countered by the engine's efficiency (torque) curve.

2. Higher piston speeds means more physical drag which, IIRC, goes up with the square of the speed.
 

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There are two primary reasons why higher RPM for a given speed reduces fuel efficiency.

1. More combustion cycles per unit time means that not as much air/fuel is needed per power stroke to maintain your speed, which means that the throttle is held more fully closed, which in turn results in greater drag as the engine attempts to draw air past the throttle plate. This is a more minor effect and can be countered by the engine's efficiency (torque) curve.

2. Higher piston speeds means more physical drag which, IIRC, goes up with the square of the speed.
Well, yes, but the offset is that if you are crusing and a static speed, say 65mph, and you are essentially using more fuel due to an increase in rpm's, and you need to increase your speed, if at the point you wish to increase speed, you are at a higher rpm, and are into your torque curve, you would need less throttle opening to achieve your acceleration than if you were at a lower rpm, so a given increase in speed would require a smaller throttle opening and use less fuel for acceleration.

So all in all, it is probably a trade off to some extent. No one cruises at a constant speed while commuting, it is always up and down, so if by changing gearing you can get to a higher gear quickly, you will tend to save fuel.

I know that before my gearing change, I would not go to 6th until > 65mph, otherwise I would be downshifting frequently to make a pass, after the gearing change, I move into 6th earlier, and don't find the need to downshift.

I tend to think that this ultimately saves gas.

Time will tell, I just did the switch, and filled up the bike, I keep mileage records, and will have to fill up again today or tomorrow, so will see what happens.

Having said this, it is my experience that I don't always fill the tank to the exact same spot every time, so there is some slight variance in my tank by tank mpg.

For example, my last tank was 48, last 30 days was 45.9, last 6 months was 48.3, and overall was 49.2.

I always tend to think an average over some lenth of time is more telling that 1 tankful.
 

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Discussion Starter #6
Great! Let me know (if you don't mind) what your numbers look like. I wouldn't be surprised if the mileage drops, but I'm curious if it's a 1mpg drop or 10mpg.

I could see the mileage dropping, but in morning rush hour traffic I can seldom get past 65mph on the highway. Unless I constantly want to downshift when the speed drops to 60mph, I often end up staying in 5th gear. If 6th gear was just a tad lower, maybe I could stay in 6th.
 

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I still get over 50mpg on my 696 with the 14t installed.

Don't worry about it. Makes around town driveability allot better.
 
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