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cggorman
02-12-2016, 12:22 PM
I just got my new PBI aluminum rear sprocket and dropped it onto the hub. The counterbore in the sprocket is maybe .005" oversize so it allows a bit of radial runout. Is there a spec or recommendation on max radial runout of rear pulleys/sprockets? If so, how to measure accurately? I'm probably overthinking this, but figured now is the time to sort it out if it's gonna be an issue.

DustyDave
02-12-2016, 12:55 PM
I just got my new PBI aluminum rear sprocket and dropped it onto the hub. The counterbore in the sprocket is maybe .005" oversize so it allows a bit of radial runout. Is there a spec or recommendation on max radial runout of rear pulleys/sprockets? If so, how to measure accurately? I'm probably overthinking this, but figured now is the time to sort it out if it's gonna be an issue.

Shim it with 3 chunks of feeler gauge, loctite and torque. Not as good as one that fits but it will work.
Dusty

cggorman
02-12-2016, 1:06 PM
That's pretty much what I was thinking. Think brass shim stock would be OK? I have lots of that.

cggorman
02-12-2016, 1:08 PM
Considering the spec on the rim runout is like .025, I figure a couple thousandths at the sprocket isn't a showstopper, but now is the time to address it.

DustyDave
02-12-2016, 2:34 PM
That's pretty much what I was thinking. Think brass shim stock would be OK? I have lots of that.

Sure a shim all the way around would be better. Just figured that most people would have an old feeler gauge around.
Dusty

cggorman
02-12-2016, 6:53 PM
I measured the sprocket. The counter bore is 2.215" with my calipers. I don't have a diameter gage that small, but I'll give PBI the benefit of the doubt and say it's dead on their advertised 2.214". My hub must be slightly undersized. It's in a bucket of solvent buried under other shit at the moment or I'd fish it out andeasure it. In the morning.

bohica2xo
02-12-2016, 11:22 PM
Clean both parts well, and check the clearance with a feeler gauge.

Chances are your calipers are the biggest issue.

boomboomthump
02-13-2016, 10:12 AM
Not trying to be rude but you're overthinking this one. This is a sloppy, chain drive setup. The .0025" tolerances you're asking about are half that of critical motor internals.

Put the sprocket on and tighten it evenly in a criss-cross pattern to proper torque specs.

cggorman
02-13-2016, 10:24 AM
I tend to over think most things. Just part of my nature. That's why I ask questions of those more experienced. I appreciate the sanity check.

DustyDave
02-13-2016, 11:43 AM
Since it is an aluminum sprocket I would like to see it tight on the register bore. Not supported only by the bolts.
Dusty