Back before fixed-gear bikes became trendy, this was the only readily-available fixed/free hub in its price range (we generally sold them for under $20.) Back when there was nothing better avaialble anywhere near the price, these were a pretty good deal.

Now that much better quality hubs are available for not much more money, the old Sovos looks pretty poor by comparison.

The earlier Sovos fixed/free hubs were designed around existing cups and cones, and there was a clearance issue when they wanted to machine down the outer threads for a lock ring.

If they had machined it down to standard lockring size, the aluminum where the lockring threads go would get too thin, due to the large diameter of the pressed-in steel bearing cup. There were two possible ways for Sovos to deal with this:

• They could use an oversized, non-standard lockring thread with their existing cups/cones.
• They could tool up to make undersized cups and cones, permitting them to use standard sized lockrings.

Earlier batches of Sovos hubs used the first approach, with a non-standard lockring. Unfortunately, the lockring threads are so close to the diameter of the sprocket threads, that they would often interfere with the installation of a sprocket when new. It was unusually difficult to get a sprocket threaded onto these hubs without cross threading it.

I found the best way was to clamp the sprocket horizontally in a vise, then screw the wheel onto the sprocket. That way, if it started to thread on crooked, the axle would visibly start to wander in circles as you turned the wheel.

After several years, Sovos gave up on this approach, bit the bullet and manufactured new cup and cones for a smaller diameter. These later Sovos hubs used standard English/ISO lockrings.

Unfortunately, if you have one of the older model hubs, and need a new lockring, you're out of luck...the non-standard lockrings have not been made for several years, and as far as I know they were never actually available as a replacement part. If you're not sure which type of hub you have, it is generally obvious by looking at the cone dust caps...the older model (oddball lockring) hubs had identical cones and dustcaps on both sides.

The later (standard lockring) models used obviously different cones and dustcaps on the fixed and freewheel sides. I don't have one handy to check, but my recollection is that the cone on the fixed gear side used a 13 mm cone wrench, rather than the 15 mm size used for the other cones.