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Discussion Starter · #1 ·
I was thinking about going -1/+2 on the sprocket. I was wondering if anyone knew the average amount of mpg loss when riding on highways. If it's only a couple mpg difference for roughly 10% more torque, then i see it as worth it. but if it's more than that than i'm not sure the cost is worth the benefit. i'd like decent fuel economy seeing as how my bike is my daily driver. Thanks for all the help in advance guys.
 

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I was thinking about going -1/+2 on the sprocket. I was wondering if anyone knew the average amount of mpg loss when riding on highways. If it's only a couple mpg difference for roughly 10% more torque, then i see it as worth it. but if it's more than that than i'm not sure the cost is worth the benefit. i'd like decent fuel economy seeing as how my bike is my daily driver. Thanks for all the help in advance guys.

10% more torque?
The gearing doesn't give you more torque, it just gives you more rpm. Since the engine makes more power the higher it revs you get to use more power at the same road speeds.
If you want to know how it will effect your mileage just spend a week riding one gear lower than you normally do.
-1/+2 brings sixth gear a bit lower than your current fifth gear.
 

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Discussion Starter · #3 ·
this article explained it logically as torque so now i'm confused;

"We know that subtracting teeth in the front increases acceleration and decreases top speed and adding teeth in the rear does it even more. How much speed loss will you get if you go one down in front, and add two in the rear sprocket?

We will use my 2005 750 as an example, which has a stock gearing of 17F 43R.

Speed loss due to the front sprocket:

16/17 = .94, which is 94%. Your speed at any given RPM will be 94% of what it was before. So you will lose 6%.

Speed loss due to the rear sprocket:

43/45 = .96, which is 96%. So you will lose 4%. Note that because of the higher number of teeth, the effect of changing teeth is less than in the front. How did we know to divide the smaller number by the larger number? a) it's reversed because it's the rear sprocket and b), we already know the number has to be smaller.

Speed loss due to both:

.94 x .96 = .90, so at any given RPM, you will travel at 90% of your speed, or lose 10%.

Note that that I word it so that AT ANY GIVEN RPM you will lose 10% speed. It is not true that you will necessarily lose 10% of your top end speed - 600's and 750's are limited by power, not RPM. Particularly on a 600, you probably won't lose much at all.

Now, regarding acceleration, we cannot calculate that affect by simple math, since it is dependent on weight, tire rotational inertia, wind resistance and a few other factors. So, it isn't true that you accelerate 10% faster. It IS true that you have 10% greater torque available for acceleration."

i'm wondering what the rpm difference is when in 6th gear going say 80 mph.
 

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this article explained it logically as torque so now i'm confused;

"We know that subtracting teeth in the front increases acceleration and decreases top speed and adding teeth in the rear does it even more. How much speed loss will you get if you go one down in front, and add two in the rear sprocket?

We will use my 2005 750 as an example, which has a stock gearing of 17F 43R.

Speed loss due to the front sprocket:

16/17 = .94, which is 94%. Your speed at any given RPM will be 94% of what it was before. So you will lose 6%.

Speed loss due to the rear sprocket:

43/45 = .96, which is 96%. So you will lose 4%. Note that because of the higher number of teeth, the effect of changing teeth is less than in the front. How did we know to divide the smaller number by the larger number? a) it's reversed because it's the rear sprocket and b), we already know the number has to be smaller.

Speed loss due to both:

.94 x .96 = .90, so at any given RPM, you will travel at 90% of your speed, or lose 10%.

Note that that I word it so that AT ANY GIVEN RPM you will lose 10% speed. It is not true that you will necessarily lose 10% of your top end speed - 600's and 750's are limited by power, not RPM. Particularly on a 600, you probably won't lose much at all.

Now, regarding acceleration, we cannot calculate that affect by simple math, since it is dependent on weight, tire rotational inertia, wind resistance and a few other factors. So, it isn't true that you accelerate 10% faster. It IS true that you have 10% greater torque available for acceleration."

i'm wondering what the rpm difference is when in 6th gear going say 80 mph.

I think that is trying to confuse.
As I said before, dropping one front tooth simply lowers sixth gear down to where fifth gear is currently. The acceleration you currently have anywhere in fifth gear will simply be the same as you will have in sixth gear after lowering the gearing. The lower gears are further apart so the differences are greater. On the '06/'07 1000RR you would need to go down to -2/+6 to pull second gear down to equal stock first gear for example. For racing on tighter circuits this can be advantageous as it brings the upper gears closer together.

If that last question is yours, your rpm would be 7% higher than is now in the same gear at the same speed. If you're doing 80mph in fifth at 6000rpm now then you'd be doing 6400rpm with lower gearing - probably about the same as simply shifting down to fourth currently.
 

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go to this site the numbers are here and all the info you will need except fuel economy Gearing Commander: Motorcycle Speed, RPM, Chain & Sprockets Calculator

I can tell you though when i was messing with my gearing on my 96 900RR i went diwn one up two i hated it, yes it was quicker but on th highway you will always be looking for that next gear. I settled for 16-45 stock is 16-43 and the difference in mPG was like 2 MPG. fuel economy really depends on how you like to twist the throttle.
 

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Discussion Starter · #6 ·
Thank guys. Makes a lot more sense now. :)
 
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