As would be 5.5, 6.5, 7.5 etc. be if you haven't run 1/12.

No one wants to walk before they TRY to run, but you will do yourself a GREAT dis-service to start out with what is, essentially, Mod racing.

If I was starting a 1/12 program I would create the class to use Tamiya Silver Can motors. They're a whopping $15 each and can be operated from a brushless/brushed controller. They also give a chance to LEARN TO DRIVE THE CAR. 1/12 cars are dramatically affected, and never in a good way, by hitting barriers. The Silver Can motors are about a lap slower over 8 minutes driven by similar caliber drivers but they don't "bind" the car up with torque so they are MUCH smoother/easier to drive.

Then as people are REALLY ready to move up (at least a season), having learned set-up, what affects what,, etc, break out the 13.5 motors that came with the aforementioned brushless/brushed esc and start running those. The neat thing is the roll-out isn't a whole lot different (60-ish mm for Silver Can, 63-4mm for the brushless...or so I'm told).

Then get REALLY nutty and try 10.5.

The above pre-supposes you are running on a "normal" club or hobbyshop track. If you're outdoors and have 100+ foot straight and 10' lane widths, etc, take each recommendation up one notch (begin with 13.5 and progress).