Rich robinson wrote:
"... Even on the NOS Mod. 99 crank I purchased the 50T ring is sharp while the 45T ring is rounded. Is there a reason for this? If the sharp teeth were not uniform I would guess they were worn down from use and not NOS. Does the tooth profile indicate vintage?... "
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Good question Rich,
Sharp chainrings; Yes, I've noticed the exact same thing. I have a number of NOS, unused, never fitted to a crank chainrings for 49D cranks... some are very sharply pointed and others have more tapered, champhered, points which are actually milled with wider shoulders between the drops.
If my painfully vivid memories of the many cuts and gouges in my legs, long ago, still serves me, I believe the sharper circular-saw-blade chainrings were somewhat earlier.
I initially had thought this design modification was due to the "safety" issue, ... but perhaps they were just being cut a bit more fully to extend their useful life expectancy before the inevitable chainwear "hooking" occurred.
Really, the only thing I can offer to back up my presumption of the relative dating issue with is the fact that I have a couple sharp-point "inner" rings which were bored 7mm for the smaller hex-head chainring bolts. Some of the pointy, and All of the rounded "outer" rings - of the same size - are bored for the later 10mm allen wrench type chainring bolts.
But, I'm just inferring this chronology with no way of really knowing when they may have actually stopped producing rings intended for those smaller, earlier style, chainring bolts.
Bob Hanson, Albuquerque, New Mexico, USA