bearing size? - old K1 track monster 24

I’m trying to find out what size the bearings are on my old 24" track monster. I got this thing when it went on clearance sale early in 2011. Doesn’t even have brake mounts. Uses a seat tube spacer, 160mm cranks, had a street seat with it. Reinforced hub, other than that I don’t know anything else about it. Having trouble finding anywhere with information on this older model.

Here’s some old photos of what it looked like before I had my way with it (second set of pictures) The red trimmed seat on the 20" was originally on the track monster.

if the cranks are cotterless the bearing will be 40mm. If it is isis or splined the bearings will be 42mm - this is due to the fact that the isis axle is actually wider than the cotterless axle requiring thicker bearings.

The cranks look like they are isis but i cannot be sure

Oh yeah it’s isis. Thanks, I never realized the bearing size difference was from ISIS vs square

A little more information… this is an odd one.

The old koxx ISIS uses a shim and a 42x25x12mm bearing instead of the standard unicycle ISIS bearing which is 42x22x12mm.

These bearings are really rare and to be honest, crap. It is better to remove the shim (or cut it down) and replace the bearings with standard unicycle ISIS ones with a thin spacer behind it.


Well I’m planning on getting a new frame soon. Thats what the real point of this thread was. I’d have to get new bearings then when I get a new frame no?

It’s got the original POS frame that came with it, it has so many big dents in it.

I don’t quite understand the measurements on bearings. The larger number is the diameter of the ring, but which one is the thickness? And what is the other measurement?

You wont need to replace the bearings when you swap the frame. The outer diameter is still 42x12mm, its the inner diameter that is different.

What Roger is suggesting is that when the bearings die, to replace them with something more standard rather than looking for rare bits.

so 40 outer diameter, 22 would be inner diameter, and 12 would be thickness of the bearing?


On ISIS the outside is 42mm. The inside is 22mm and the width is 12mm

For reference. Cotterless are 40mm outside, 17mm inside and 12mm wide.


I think Kris Holm ISIS bearings are 40mm

Nope, 42. Unless you’re talking about the conversion bearing kit that allows you to use an ISIS hub in an old 40mm frame.

oop! jtrops, you are correct.

I was just referencing the number order :stuck_out_tongue:

Thanks for the helpful info roger!