help with shimano 8-sp rear sprocket

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blckwlfny1

New Member
I'm having a little trouble with using an internal gear hub on my bike.
I have a skyhawk with h/c head and a sbp **** kit
9t of the jackshaft
...To a 36t on the crank (larger will not clear the motor)
...A 24t on the inside pedal going to the rear sprocket
...A shimano 21t on the alfine 8-speed hub
The gear ratios work PERFECTLY for what I want. I don't have to use the pedals to move from a dead stop. And the gears are high enough so I don't WANT to go any faster (32 mph is fine)
The problem is NOT failure in the gears or freewheel of the hub. The problem is that the rear sprocket keeps breaking itself off of the 3 splines that hold it to the hub.
It will begin by popping free then catching a few times and then it will eventually spin freely. Does anyone have any suggestions on how to affix the splines more securely?
 
Alfine is an internally geared hub, Pilotgeek. It's a little higher-end than the Nexus.

OP: the sprocket is coming off even with the snap-ring attached?
 
Its not coming off, it is stripping the splines (the three half-moon tabs off of the rear sprocket and then spinning free
 
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See, internal hubs typically like 2:1 ratio or higher. Since you have a 24T drive, that would mean the driven hub gear should be 12 or lower. But you have a 21 driven. That is a lot of gear reduction and transferred torque. Smaller than 12T is prolly not possible. The only other way you can change that is to step up to a larger drive sprocket. Even if you had dual 36T on the front, you'd need an 18T or smaller on the wheel to get the 2:1 ratio.

Of course, maybe your driven sprocket is really cheap, soft steel. You could have someone laser-cut you a sprocket out of high-grade steel, like 304 stainless or better. Might be expensive, but it would be strong.
 
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