rear sprocket wobble.

E

Eric2.0

New Member
Just finishing my first MB build on a Cranbrook and no matter how much a measure, true, tighten ect ect...I cannot get that rear rag joint gear to go around straight and true. It has the slightest wobble that we don't think will bother, but I don't want to chance that chain being thrown off.

The more I get into this the more I see the potential of getting really hurt, so I'm trying my best to make this thing safe safe safe as possible.

I spent countless hours getting that drivetrain perfect as possible, but that slight wobble has me worried.

Is it going to throw a chain if I leave it be? The tension on the chain is perfect, I fashioned some nifty drop-out stops so the wheel doesn't move forward and the chain doesn't make hardly any noise and appears really straight.

This is my dad's bike, but we decided I'll be the test pilot.duh. Due to me being 36 and he 67. I do not want to see him go down on the road with this thing.
 
How much wobble are we looking at here? And, is it a lateral (side to side) wobble or an off center (up and down) thing?
We typically suggest that the rear sprocket run as true as possible. This reduces the possibility of the chain being derailed. I've seen sprockets with as much as 1/8th" side to side wobble that ran fine.
It could be that what you're seeing is not a result of your installation but of a warped/bent sprocket. Wobbles can also be produced by the rubber parts of the rag joint not being consistant in thickness. You might want to check these things before trying to run with an untrue rear sprocket. Good luck. Let us know what you find.
Tom
 
It's a side-to-side wobble. Not a ton, but enough to make me think that a possibility for the chain to fly off exist. I got it perfect centered though and it doesn't move up and down at all.

Another thing is that cheap Cranbrook wheel...it obviously wobbles a bit. It looks like both wobbles are separate though....I could be wrong.

I may get a better quality wheel and try that .
 
One other thing to look for, does the center hole of your sprocket fit over the bearing without the rubber? You may have to make the center hole bigger, I have successful using a 1.5' round grinding stone on a 10,000rpm die grinder,keep going around and around, don't stop in any one place. just a thought

Mac
 
Mac said:
One other thing to look for, does the center hole of your sprocket fit over the bearing without the rubber?

Mac
Click to expand...

Yepp I grounded out the hole and that fits perfectly. I used a stone on a Dremel tool and went around and around a million times lol. I made sure it was big enough of a hole to not rub the bearing dust cover at all.
 
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