does anyone know when going smaller stops being efficient? such as, -2 in the front and -3 in the back for a total of +3 in the back, but with less rotational mass?
any con's to a smaller front sprocket?
in regards for racing im getting its a good idea to go smaller fronts, instead of larger rears, obviously for weight reasons and braking but also stability on turn ins because of that reduced rotational mass on the rear sprocket.

 

I like my stock gearing for now but will change it down the road as well.

 

Worrying about rotational mass is kind of pointless unless you're racing competitively. You'll never see the benefits on the street. Consequently, doing less in the rear will partially/wholly negate going less in the front (depending how many teeth you drop on each side), so that's kind of silly.

-1 in the front is about the same as -3 or -3.5 in the rear. So if you want just a little bit of change without drastically affecting your RPMs or mileage, go +1 or +2 in the rear by itself. -1 in the front is then a little bit more drastic, then -1 +1, -1 +2, etc.

Keep in mind that for racing, they need to find a sweet spot between low end torque and high end speed. You won't find really crazy gear ratios on race bikes.

Also remember that depending on what type of gear ratio you select, and what you had before, you may need a different number of links in your chain.

And it's always a good rule of thumb to replace your chain and sprockets together as a set.

 

-1 in the front is about the same as +2 or +3 in the rear. And if you go two small in the front it's not good on the chain. I run -1f and +3r with a 520 chain and it accelerates like an SOB and keeps up with GSXR750's up to about 90. It's on an f4 though. It sucks on the highway but I only ride that bike around town. I will probably go with that setup again.

And as far as that 15/45 setup that is only about a +1r over factory if stock was 16/46.

 

Going smaller on the front puts alot more stress on the sprocket teeth and isen't recommended past -1. As for rotational weight, racers don't care, it isen't enough to make any difference. They do care about how gearing can affect swingarm movment and will use it to their advantage. Of course thats ama+ level tuning, I doubt ricky racer at your local track takes that kind of stuff into consideration.