Jantaras

Hello,

lets say the seller doesn't know and has no chains nearby to check and can't measure thickness. Is it possible to tell if the cog is for 1/8 or 3/32 chain just from the image? Is there a difference in teeth shape or something?
For example this, there is 18 stamped, does this mean 1/8? Were old Dura-aces or Campagnolos usually 1/8 or 3/32? Do they have distinct markings?

Bianchigirll 

Is it a Uniglide cog or a fixed gear/ track / Pista cog? Is it really 18 or a blurry 16? Check some of the reference sites and see if Dura Ace ever came in 3/32 fixed cog sizes. It always possible it's a typo and should be 16 for the teeth.

Jantaras

It is a fix, at least stated in ad. 16 teeth. Now I think it can be a blurry 16... So, old fixed type cogs were usually 1/8?

Reynolds 531 

Yes. I'm quite sure it's a 1/8 track cog.

79pmooney

That cog could be either. Dura Ace came about in the '70s. I started my fix gear journey then on 3/32nds chains and sprockets.

Ask the seller if he has calipers and could he measure. Post it here (and quote me). I'll run back and measure mine. (I have both.)

'02 nrs

looks very similar to this 1/8 track cog on feebay;

https://www.ebay.com/itm/Shimano-Dur...-/302239888748

Jantaras

Ok, thanks for your input. The seller said that chainwhip fits it so it should be 3/32. I said that I want to buy it. If I get it I will get back here to confirm

79pmooney

But - I've held in my hands the same cog in both 1/8" and 3/32". Identical except for the thickness. And the OP's photo being end on, you cannot even guess that. Now your cog is stamped "MP". OP's is "LF" Are those the thickness?

OP, the Dura Ace cogs are nice but not remotely rare or exotic. If the seller doesn't know what he's selling and isn't willing to find out, pass this up and go elsewhere. If you widen your search, consider also looking for Eurasian Imports cogs. Just as good and preferred by many (including me). Made in USA despite the name.

Also, you could just assume the cog is 1/8". If it is not, it will work just fine on an otherwise all 1/8" drivetrain. I'm surprised that hasn't been said already on this thread. I don't. I stick to 1/8" everywhere on the theory that 1/8" is the hardest to throw off the cog or chainring, therefore the setup that allows the most chain slack. A real advantage if you ride rough roads; not smooth velodromes, use road cranksets with their often greater eccentricity and/or do quick on-the-road wheel flips in gassed state at the tops of hard climbs.

(The reason we no longer ride 1/8" chains is exactly because they are too hard to throw off. The derailleur system is really just one that throws chains off and organizes the landing.)

Jantaras

Thanks for information! I bought it, should be 3/32. I need a cog for fixie that I will sell. My other fixie also has 16t 3/32. Also, both chains are already shortened for 16t cog, so 3/32 cog is the simpliest solution.
in Europe I had very little success finding 16t 3/32 cogs. From USA there would be higher shipping cost and customs...

79pmooney

Sorry, I didn't notice the Finland. So Europe is much more 1/8" friendly? I'd like that. Now with internet, a bit more money in my pockets and the 1990s/00s boom here in fix gears, everything is easy to get but for my first 20 years of fix gear, I had none of that. The two different widths meant half the choices in tooth number, available condition, etc. because there was simply so little to be had unless you lived near a velodrome. (I would have a much easier time of it if I was running in cycling circles but I was per-occupied on other fronts in my life and only at times knew folk with knowledge of where unusual bike stuff could be found.)

Edit: if you ever are at a place of starting a fix gear from bare bones, consider 1/8". One of the pluses is that common 1/8" chain has pressed in pins that protrude a real amount. The wonderful plus if that is that you can drive those pins out and back in multiple times without danger of chain breakage. Also true of the early 3/32" chains and some to this day. I have seen perhaps one modern 1/8" chain with little protrusion but there are lots with plenty. Ordering 1/8" sight unseen is 99.5% likely to be a chain with those easy to drive links. A simple chain riveter is all you need. And if you make a mistake and cut it short, no big deal. My favorite is the Izumi chain from Japan. Moderate price, $25 US, very reliable. Popular on the velodrome for those not wanting to spend big bucks, both because they work well and their competitors don't fear them breaking and taking them out.

Jantaras

It also could be that the demand for 3/32 is bigger than supply. I am more familiar with geared bikes than fixes, but it feels that a couple of years ago (or, at least, before Covid) there was no problem finding these. Now, in most online shops here, these are out of stock. I definately feel that parts availability is worse than before, for example, lots of "out of stock and we do not know if it will be available soon" items in big German online stores that before had all that you could possibly want.
Again, thanks for information about 1/8 chains

Jantaras

So, I the cog arrived and I can confirm it is 3/32. Thank you all for help!

Reynolds 531 

Is it too late to edit my post?

base2 

I know it is too late. But for what it's worth: Dura-Ace track components, for a short time experimented with 10mm pitch instead of the usual 1/2 inch all other bicycle chains in the world use. If the chain fits weird, you have a rare historical artifact. I only mention the unlikely possibility because it seems the seller doesn't know what he is selling thus you don't know what you are buying.

The number in question looks like a 10 to my eye.

79pmooney

So: if I can manage to remember, I'll hunt up what Dura Ace cogs I've got and see if the "LF"/1/8" and "MP"1/8" holds true.

I also saw and noticed a little thing that bugs me. The lettering is stamped very close to the threads. Completely hidden by the lockring. I have to count the teeth anytime it is on a wheel. EAI (Eurasian Imports) cogs have the lettering further out and visible on 16 tooth and above.

Trakhak

Of course, if the pictured Dura-Ace sprocket turns out to be 3/32", the OP can still use a 1/8" chain with it, thereby enjoying all the benefits of that size. The only downsides, such as they are, would be the slightly looser fit (theoretically, but of no importance practically) and maybe a bit of noise. (And maybe triggering a few old track bike guys like me.)

Trakhak

Shimano called the system "Pitch 10." IIRC, There are a few photos floating around out there that show a catalog page, or maybe a service bulletin, featuring Pitch 10 derailleurs, hubs, freewheel, crankset, etc. They apparently never made it into production.

base2 

I've seen them. I held a whole complete drivetrain in my hand. (New chain, a small selection of cogs and a few chainrings) After many fruitless months of trying to sell it at the Co-Op, I donated it to the museum case of a neighboring bike shop I/We were/are on good terms with. It's still in their case, prominently displayed.

I have no idea it's value. I just know I couldn't sell it.

P!N20

A 10 Pitch cog would have the old Dura-Ace logo

ign1te

What you need is a picture of the cog from above to estimate the thickness of the teeth.

clubman 

LF = June 1987

Reynolds 531 

and possibly an NJS logo? I don't know, and too rare to have ever seen one. Not sure 10mm ever got NJS approved.

P!N20

Nah, that was the kicker - it didn't gain NJS certification so was banished to history's spare parts box.

merziac

No NJS = DOA.