No. I have a cog board of Regina cogs for the fully-threaded freewheels, and not a single new cog shows any sign of being dished. The dishing has something to do with the fact that the cog is offset to one side of its very narrow hub, and that the hub screws tightly against the next sprocket in. The tighter the cog gets, the more pronounced the dish. The largest two cogs are both termed "position 3" and they are exactly the same, but installed in opposite directions, with the offset portion of the hub meeting and providing the spacing between them. (I've always figured that this requirement of being able to run the cog in either direction is the reason why they used the poor-shifting but symmetrical notched tooth profile.) The second cog seats against a shoulder, and this keeps it from dishing. Of course, the biggest cog usually receives the most torque, if you ride steep hills at all, as it's all you've got, no matter the slope. Any other gear can be shifted out of to a lower ratio.
This dishing phenomenon is easily replicable. Just take any of these freewheels with a 24t or larger cog, remove the last cog (good luck), and thread it back on, tightening it as tight as you can get with a chain whip. When you come to, after hitting yourself in the face with a flying chain whip, you will see that a dish has appeared bending the cog toward the spokes. Either that, or you need another bowl of Wheaties. I have NEVER seen one dish the other direction, and I don't expect to. Usually, the dish is very slight, or nonexistent on a cog less than 21t, but I have one freewheel that has a severely dished 19t top cog. All I can figure is that it must have belonged to that mountain goat, Chuck Schmidt.
Steve Barner, Bolton, Vermont
> Date: Thu, 21 Aug 2003 11:01:19 EDT
> From: BobHoveyGa@aol.com
> To: classicrendezvous@bikelist.org
> Subject: [CR]Re: Dished cogs
> Also, didn't someone mention in an earlier message that the dish on those
new
> large cogs was in the opposite direction (towards the spokes) that they
would
> be dished from pedalling forces (i.e., towards the centerline)
>
> Bob Hovey
> Columbus, GA