Sprockets and gearing

[Randy]

I have a general question about gearing and sprockets. Is there a database or some rule of thumb that defines how much gaining or losing teeth on a sprocket will affect maximum speed or low end acceleration?

I handload pistol and rifle rounds, when experimenting with new loads, you VERY gradually increase or decrease the amount of powder in each cartridge. Applying this logic to motorcycles seems logical, but very costly.

Just as a side note, I am more interested in getting as many miles per gallon out of bike, I am not really the racing type.

[Telesque]

If you can find the x% gained/lost per size of gear (which shouldn't be hard, I'll try to find it and edit it in later) then you could probably figure it all yourself..

If you're interesting in getting better MPG, dropping a tooth or two (in the rear/whichever sprocket is larger) will lower your RPMs at any given speed and will drop your acceleration a bit as well.

The problem with sprocket changes is that it will affect how every gear on your bike works- as opposed to setting up a specific fifth, or fourth, gear for cruising. It is, however, a lot easier/cheaper, I believe.

[poppygene]

If gas mileage is what you're after, I'd suggest going one tooth larger on the front sprocket. That's about as far as I'd go though. I've made sprocket changes on several bikes through the years and I've found that anything more than that causes you to lose too much torque at take-off, IMHO. This is especially true if you ride in hilly or mountainous country, or ride two-up.
Why go up on the front, and why not down on the rear? Larger diameter sprockets make chains last longer.

[Telesque]

If gas mileage is what you're after, I'd suggest going one tooth larger on the front sprocket. That's about as far as I'd go though. I've made sprocket changes on several bikes through the years and I've found that anything more than that causes you to lose too much torque at take-off, IMHO. This is especially true if you ride in hilly or mountainous country, or ride two-up.
Why go up on the front, and why not down on the rear? Larger diameter sprockets make chains last longer.

It's also important to note that when you add one tooth to a smaller gear (i.e. front) the single gear will have a larger effect than adding a single tooth to the larger gear.

For example: 15 front, 44 rear.

One tooth in the rear only accounts for around ~2% of the size of the gear (which in turn translates to speed/acceleration), while one tooth on the front is ~7%- A considerable difference.

[barmy_carmy]

Dave had a 43 cog sprocket on his 1997 FZX 750 this gave us more acceleration when pulling away but we lost quite a bit on top speed, So we had the sprocket changed to a 39cog sprocket, we didnt lose much when pulling away ie we can do 0 -90mph in a few seconds in 2nd gear, And what can I say about top speed but Wah Hey The top speed we have gone is 130mph but there is still more to spare.

[karlyn]

yes.. that definitely affects the maximum speed and acceleration.
better make sure you maintain your sprocket's temperature once in a while.

[Randy]

I apoligize for my ignorance, but what does it mean to maintain my sprockets temperature?