Rag joint and sprocket... does the center hole have to fit ???

A

abefroman

New Member
I've built two Genesis Astra bikes and the rear sprocket center hole fit perfectly over the hub/dust cover on the bike. I'm now doing a Genesis Onyx with coaster brake and the sprocket center hole does not fit on the hub. Can I just eyeball it when putting the rag joint together and just super-tighten it and hope that it stays centered ??? or will it slip ?

cheers
 
if the dust cap doesn't have clearance under the sprocket, the wheel won't turn at all

people that remove the dust cap usually blow out those bearings in less than a month

if you have no other tool to do it, use a half-round file to open out the hole in the sprocket about 1/8 inch till the dust cap clears well

in spare time, I work on these to always have some on the shelf for guys that want to mount on coaster wheels - I charge them $8 exchange for their standard sprocket
 
crassius said:
if the dust cap doesn't have clearance under the sprocket, the wheel won't turn at all

people that remove the dust cap usually blow out those bearings in less than a month

if you have no other tool to do it, use a half-round file to open out the hole in the sprocket about 1/8 inch till the dust cap clears well

in spare time, I work on these to always have some on the shelf for guys that want to mount on coaster wheels - I charge them $8 exchange for their standard sprocket
Click to expand...


^^^^ Yep. I used a Dremel on mine.

Good luck with your project!
 
Use a dremel.

But for the record, I removed the dust cap on mine and I've got 375 mi of service on that bearing. I blew up the stock bearing because I cooked the grease at 75 miles. Put a new bearing in and grease the rearend and I'm good. Just cleaned and regreased the rear and everything is spiffy.
 
Abe, are you saying that the hole in sprocket is larger than where it fits to the hub?

If not (and the sprkt hole is too small), then heed the advice above.

If so, then I think people have either found a spacer that fits the "gap" or they do as you mentioned: i.e. "just eyeball it when putting the rag joint together".

And, IIRC, certain freewheel spacers might actually work in this case.
 
FMB42 - thanks for the reply. I'm pretty sure I could get the sprocket and rag joint on pretty much centered by "eyballing it". My main concern is that if I tighten the living H$LL out of it, will the rag joint slip and become out of round ?

cheers
 
abefroman said:
FMB42 - thanks for the reply. I'm pretty sure I could get the sprocket and rag joint on pretty much centered by "eyballing it". My main concern is that if I tighten the living H$LL out of it, will the rag joint slip and become out of round ?

cheers
Click to expand...

As long as it's properly tightened, it should be fine. You can always re-center it if needed later on.
I've built several ONEX coaster hub bikes for customers and all are doing fine (so far) with just normal maintenance.
It's always a good idea to completely re-grease ALL bearings in any big box store-bought bike build.
Opening the hole to allow the dust cover to clear is the best way to go. Tossing the dust cover means more wear or more maintenance.
 
The main point that no one has mentioned is that the center hole has little bearing on how the sprocket is centered on the hub. The center hole can be oval shaped or square; it doesn't matter. The important thing is the outer circumference, or the sprocket teeth must be concentric with the hub for proper chain performance.

Some will suggest shimming or measuring the distance from the hud or dust cover to the inner edge of the sprocket hole. That isn't important. What you're, or should be, concerned with is if the outer circumference runs true so there is not chain tension issues that come with a sprocket that isn't concentric (centered) on the rear hub.

Open up the sprocket hole so it clears the dust cover then concentrate on getting the teeth to run true. That can be done with a pointer attached to the frame and spinning the rear wheel and adjusting the sprocket so it runs as close to perfect as you can get it measured from the outer circumference or the outer edges of the sprocket teeth.

Tom
 
you can mill out the center hole almost as big as the bolt pattern for the rag joint if you want to lighten it, but no it can not be smaller than your hub if it is, cut it bigger so it fits around your hub and dust seal and coaster arm if need be .
 
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