In the middle of restoring/converting an old Pinarello to SS...

I took off the 5-speed freewheel (needed a two-pronged tool), and had the 15t ACS in hand...

The diameter of the threaded part of the hub is bigger than that of the freewheel. WTF? I thought they all had the same diameter. And the same as that of track cogs as well. So, I took another couple junky old 27" wheels, and am going to the LBS to have the freewheels pulled off (4-hole and splined, respectively) to see if either of those sizes will work.

Is that hub a freak (it was made in W. Germany), or is the freewheel? I'd hate to have to end up buying a new hub for a junker conversion.

Update: I had another wheel's freewheel removed, and compared it to the first. Same size. I went to the more local LBS and got a 16t freewheel. That one fits. So, apparently 15t freewheels need specially sized hubs.

BTW, thanks for the deafening silence.

Did you get a metric threaded freewheel by mistake? The AC888 15t has english threads, but I don't think the ACS 15t comes in english. 16t freewheels used to be the smallest you could get because of obvious engineering reasons. I think the AC888 15t is now the smallest without switching to a metric flip/flop.

Small freewheels are pretty much relegated to BMX racing.

It wasn't the threading, but the diameter of the threaded part. I tried another 15t freewheel on the hub, and it was also far too small.

If the reason that 16t were the smallest was engineering reasons, then it makes sense that they would decrease the size of the hub to get even smaller (15t) freewheels.

I should have known better though, when they had to look hard to find a 15t. Me and my picky ratios...

15 tooth and smaller are usually for BMX hubs. Most BMX hubs come with a smaller side and a larger side for standard freewheels. You can fins a 15 tooth FW for standard hubs from ac racing (I think) and it is removed with a BB tool.

I sort of had the reverse problem. Over a year ago, when contemplating fixed gear for the first time, I thought I would need fixed/free hub. The only one flip-flop available in my neck of woods was high end BMX one.

When I finally got it from the seller, I realized that

1) there is no thread for lockring on either side of the hub
2) the threads on the left and right are left and right, respectively.
3) both threads are metric, and smaller size than regular ones.

Later, I have learnt that it would be costy to find a cog for that threading and that freewheels (14T) are very expensive.

I guess your cog fits my hub.

ACS freewheel will only work with certain hubs...mostly flip flops. Most Haro bmxs have flip flops hubs with an...ACS freewheel. Go out and buy yourself a cheap Dicta or something and it will work fine.

Yeah, I went to the more local (but run by idiots) LBS and asked them if I could try out a freewheel before I bought it. They did, and I ended up buying a shimano 16t. I also brought along the 1 pc crank I'm using on this project, and found a sweet 44t BMX chainwheel for it. With any luck, the frame should get painted this weekend, and I'll have the rest of next week to put together the most craptastic singlespeed ever.

Oh yeah, I'm returning that 15t freewheel today. Maybe they'll let me exchange it for a pile of lubes?