I need to replace the cracked ratchet ring on my Novatec hub so I want to know how to do it?
Novatec hubs use 2 types of ratchet rings as far as their installation is concerned. It can be either threaded type or press-in type. Picture below shows them both and it’s obvious that threaded type is in the right-hand side of the picture.
Now you should check which type of ring you have and let Novatec EU staff know this information, especially if you want to buy a new one from them. When asking for new rings (or any other spare parts) I strongly recommend to always specify the hub model name so that they know exactly how many teeth your ratchet ring has thus they can offer you the correct one.
Speaking of teeth, there are following available ratchets ring used in Novatec hubs:
- 24 teeth: used in old hubs
- 27 teeth: used in recent hubs
- 33 teeth: used in new hub model D462SB and D162SB
- 42 teeth: used in Novatec MTB wheels (hub XD642SB or XDH42SB) and Synergy Cantilever system (hub D542SB or DH42SB)
- 60 teeth: used in high-end Factor wheels (XD602SB)
A tool needed for threaded type of ratchet ring looks like this:
Please note there’s not any tool available for press-in type of ratchet ring in the market yet. Novatec is working on such tool so it should be available soon.
Until then, you’ll need to improvise and push it in there with some pressing tool/machine (jaw vice maybe) or have it done by your local bike workshop.
Number of teeth determine also Angle of Engagement. For 27 teeth you can calculate the angle like this: 360 degrees divided by teeth count.
360 / 27 = 13.33 degrees
Similar analogy you'll use for any other number of teeth on the ratchet ring (24T, 33T etc.).
Number of teeth actually indicates also Point of Enagagement parameter so for 33teeth there are 33 POI (provided all pawls engage simultaneously).
If cassette body has 6pawls which engage first 3 of them than another 3, so not all 6 at the same time, POI doubles and angle of enagagement goes to half. Math looks like this for 27teeth:
360 / 27 / 2 = 6.67 degrees
In Documents section below you can check a drawing of 24T and 27T for your information.
There's also a pdf file showing how to dissasemble and assemble threaded ratchet ring.