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Old October 19th, 2017, 05:13 AM   #28
tgold
ninjette.org sage
 
Name: Timm
Location: West Seneca, NY
Join Date: Oct 2015

Motorcycle(s): 2006 1050 Speed Triple, 2010 250 Ninja racebike, YZF320RR? Racebike

Posts: 556
MOTM - Nov '15
Quote:
Originally Posted by JacRyann View Post
Sure, if they're both 520 sprockets. The 428 sprocket is thicker than stock 520 to match wider chain rollers.

I'm using this RS8R steel sprocket on my street-bike:


It's about 1/2 the weight of the factory steel sprocket:


Similar in weight to a more solid alloy sprocket:
Of course I'm referring to sprockets for the same sized chain.
Clearly the steel sprocket that you show has been more optimized for weight reduction than either the stock sprocket or the aluminum one, so the weights aren't reflective of what is possible with a good design in aluminum.

One thing that you cant get away from with a steel sprocket: The mass concentrated at the perimeter where the teeth are is going to be higher than than for aluminum. That means the moment of inertia (MOI) is going to be higher and a high moment of inertia affects acceleration. Think of swinging a baseball on the end of a rope in a circle. The longer the rope, the higher the MOI and the harder it is to swing the baseball around.

Still the steel sprocket that you show looks like a fairly good design and certainly you should get more life out of it than an aluminum one, but it's a compromise that is your choice to make It's going to cost more for the well-designed part and have a higher MOI. I often find the aluminum sprockets I want for less than $30.00 on ebay which is likely less than half the cost of the steel one. I'm willing to sacrifice the time it takes to swap out the to a new aluminum sprocket when it wears out faster. (not that often on a 250 Ninja)

IMO hard anodizing doesn't do much, it is very thin and it's effectiveness is also dependent on the strength of the base metal it is applied to. And all aluminum is not created equal. If you really want a good aluminum sprocket, then get one made out of 7075 aluminum instead of the more typical 6061 stuff. 7075 is significantly stronger, allowing further possible weight reduction with careful design.

We're not likely to shear teeth with 250 and 300 Ninjas, but on one of my other bikes I have seen what seems to be quicker wear on Vortex sprockets than other brands.
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