Originally Posted by HillRider

You need a 4-tab disc to install on a 36 spoke wheel and there is no good way to adapt a 3-tab disc. And, yes plastic discs do get brittle and crack after a while so either buy spares or look for a metal disc that won't break but will probably rattle and drive you nuts.

As mentioned above, proper adjustment of the low limit screw should make the disc unnecessary.