KDXRIDER.NET

Hi guys. Just wondering if anyone has any input about the power boost you might get from having smaller sprockets. As far as the gearing ratio goes, I know that a 12/44 is equal to a 13/47. But by going to the smaller set-up, you reduce the amount of weight the engine has to turn, due to the smaller sprockets and shorter chain. From what I've read in some posts, reducing the amount of turning weight can have a significant effect on power. Any thoughts?

If I remember my physics prof correctly, even though they have the same ratio, you still have effectively increased torque/decreased top speed with the smaller sprockets. Horsepower remains the same (the engine itself is unchanged). Since most estimates put properly lubricated chain drive systems around the 98% mark in efficiency, and you really are shaving off only ounces in regards to the smaller sprocket mass and the couple of chain links you might lose, likely all you'll see is a bike that accelerates quicker to a lower top speed really the only way you're going to see a "power boost" is to work the engine over (head mods, carb mods, exhaust mods). Gearing changes don't affect power, only torque and speed. Now if we want to talk flywheel weights, then that is exactly what happens...a Steahly weight increases the rotational mass of the crank, effectively decreasing horsepower and mellowing out that ride so the girlfriend/wife/limp wristed can hang on longer

http://www.gearingcommander.com/ is a handy site for experimenting with gearing changes. 13/47 top speed at 8600 rpm 70.6mph, 12/44 @ 8600rpm=69.6mph

Of course an 8/60 would make wheelies a breeze!

12/44 = a 3.67/1 ratio while a 13/47 = a 3.62/1 ratio. 12/44 is a slightly lower ratio.

You're always better off using larger sprockets if chain and sprocket life are of any concern.

If you are happy with the power delivery and speed of the bike now then leave it alone.If your just trying to loose a little weight then take a good dump before you ride. If you find that you hardly ever get into 6th gear and want more pull from the bottom then go ahead and gear it down to like a 13/49 or so. If you are always getting into 6th and don't need the low end pull and want more speed try a 14/47 or 14/45.

rbates9 wrote:If your just trying to loose a little weight then take a good dump before you ride.

lololol

And ride longer, bike gets lighter the longer you ride!

Thanks guys for your input. I asked the question mainly because I'm curious. I like the stock gearing of 13/47. I tried 12/47 for a little while last year, but didn't like it very much - too much shifting. By the end of this season I'll have to buy new sprockets and chain. Hence, the question. Just wanted to know if there was any significant advantage to having a drive train that is a little less heavy. I'm guessing you could drop a pound or two by going from a 13 to a 12 on front and from a 47 steel to a 44 aluminum on back, and going from an o-ring chain that is longer to a regular chain that is shorter. Again, just curious to know if anyone tried it and found any advantage.

I've tried a bunch of gearing combos over the years, but for what I usually ride the stock just works best. If I'm feeling up to it and have time I'd throw on a smaller rear when I was heading over to the desert side of the state, but usually I'm just too lazy!

IMHO, gearing changes are best for slowing the bike for more low end pull or making it faster for high speed terrain. Any minute difference in rotating mass I think would be too small to feel or notice on a bike. Anything that could possibly be gained from the reduced weight of the shorter chain and lighter sprocket would be lost quickly at the first sign of wet ground that builds up on the tire.

And P.S. If you go with a non O ring chain and aluminum sprocket then plan on a much quicker replacement interval.