I am flying YYZ>EWR>SIN in J class.
YYZ has US pre-clearance and I land at terminal A. I land 08:05 on AC.
The SIN leg is 9:45AM at Terminal B on SIN, I believe.

How tight will this be and what is my best option to not re-clear security? I read about the airside bus, is that an option on star alliance carriers? Any express options for J class?