Cog and hub thread mismatch?
 

I bought a new EAI 17t cog recently for my Kilo TT Stripper.

Dude at my LBS said the threads were a different format. Got a second opinion from another guy working there and we installed it anyway after me being all like "come on you can make it work" (could not return the cog).

Basically they said it was cool but had hesitations due to the threading not being exact for my hub.

Should I be worried? I mean it's on there tight (with a dura ace lockring) and I have no desire to change my cog as I love riding at 48/17. Same ratio I've been riding for almost a decade and have zero plans to change.

Anyway, I'm not going to die or anything right? Slight mismatch in threading but the jawn is on there, and tight. Should be OK right?

Dude at shop is full of ****.

It is on there now. So, I wouldn't worry about until you're ready to replace it.

See freewheel sizes.

Traditional Thread-on Freewheels

It sounds odd if the parts are "new". But, apparently with vintage bikes, Italian, US, British, and ISO freewheels are generally interchangeable, but some may be tighter than others.

FRENCH IS NOT.

It's NOT a freewheel. It's a fixed gear track cog. They are all English threaded 1.370"x24tpi. Like I said, the bike shop guy that said it was different from the hub threading is full of ****.

Correct. A fixed cog (not freewheel).

Here is the exact cog I bought (in 17t):

Euro Asia Imports Deluxe Steel Track Cog 1 8" Single Speed EAI Made in USA | eBay

Bike is a Kilo Stripper, stock wheel set.

Anyway, the thing is on there but was the bike store dude just full of ****? Literally he was all "this wont work" and then another dude working there was like sure it will and it's installed now.

Yeah, he most likely didn't know what he was talking about. What shop was this? I used to live in Philly.

After you left the shop, the guy who installed the cog called the guy who said you couldn't a dumbass.

I guarantee it.

Philadelphia Bikesmith at 19th and Spring Garden. My first time there. Used to go to this dude Jay in Fishtown, small one man shop at the time but he relocated downtown with a bunch of employees and it's not the same service, also further from my place and I've been meaning to check out Philadelphia Bikesmith anyway. Overall the place was cool and I'm sure I'll go back there for the occasional wheel truing or to pick up some tubes or whatever.

It was funny though. The first dude was all "yeah, this cog won't work, blah blah blah threading, blah blah blah" and then the next guy who looked at it (who had much more of an aura of a man who knows what he's doing) was like "no problem, it'll work". Haha.

Hmm, never been to that one. Sounds like the guy just made a rookie mistake, which can happen anywhere. I used to go to Bicycle Revolutions for a lot of stuff. The owner there is a good guy and pretty knowledgeable. I had a set of wheels built by him several years ago that I'm still riding.

Everything you need to know about threads....

Basic Thread Concepts - Park Tool