Dura ace/ EAI difference?
 

I have a 15t dura ace cog, 16t EAI cog, and 18t phil wood cog here in front of me.

I have only ridden the EAI and Phil and am impressed but hereis the question....

Is there a distinguishable difference between the dura ace and EAI cog. In race situations mainly. I am about to get a 14t and cant tell what the extra 10 bucks is going for on the EAI. Finish is different but they both feel solid. granted i havnt ridden the DA yet.

chime in...

The heat treating that EAI cogs go through CAN make them brittle. I've heard of two different EAI cogs snapping off teeth under high-torque situations. Never heard of it with DA.

I mostly ride DA cogs and love 'em.

I love DA. I don't think it's worth the extra ten for the EAI cogs plus not to sound like a NJS *****, but DA are certified, so it can't be all that bad right?

good news....

i really like DA cogs but i went with EAI cog this time because i wanted a 17 tooth to add the bonus amount of skid spots. if DA increased their teeth availabilities i would be sold forever.

DA come in 17t.
I've got one on order right now.

Although I am having no luck finding one anywhere online.
I think my LBS might have ordered me something that doesn't exist.
Crap.

You will have the first.

maybe they changed something but i'm thinking your lbs just goofed.

Damnit.
I guess I'm gonna go EAI.

There's always the Phil...

I know...I know...
I guess after dropping $$$ on 75s and a Phil Wood BB, an extra $20 wont be a big deal.

Phil donated a 17t cog as swag for the Poker Ride in January. I spent a day rolling it through my knuckles...man, that's a lotta cog, super nice.

14t, 15t, 16t are all $39 but 17t-22t are $46?
Lame.

I like both EAI and DA.
The biggest difference?
Put them both on a table with the teeth sorta touching each other.
Notice the different heights of the teeth from the table top.
They have slightly different flange dimensions. in terms of standoff from the hub.
I have heard/read that one should pick one cog manufacturer or the other, and not mix them on the hub, because their threads differ slightly from each other and switching back and forth shortens the life of the hub's threads.
On my Bianchi Pista, with the stock Sugino RD crank, the EAI cog, with the flange against the hub, gives me the best chainline.

The thread issue that you are talking about is mixing between ISO, British and Italian threading. If you stick with one threading, even between brands, you should be fine...