Rotor Choices : G3 Modified Rotor Tuning Made Easy – HOBBYWING Guru Support Center

By Matt – HOBBYWING

Ever thought to yourself, rotors in modified? Why do we tune with them, or why does your buddy use a 12.1 rotor, versus the stock 12.5 rotor?

This is the article for you ;)

Let’s break it down and make rotor selection easy—whether you're dialing in for off-road or on-road, low grip or high bite.

Stock Rotor (Comes in 8.5 – 6.0 motors)

Part #: 30820020

Size: 12.5mm OD x 24.1mm Length
This is your baseline rotor
Shorter magnet = weaker magnetic field = less torque and softer brakes
All the popular mod tuning rotors share this same 24.1mm length

It’s smooth, controllable, and works great for most medium to high grip tracks.

Option Rotor #1 (Comes in 5.5 – 3.5 motors)

Part #: 30820017 – 12.3mm OD

Slightly smaller diameter = less punch, more RPM
Smoother throttle and braking feel
Helps reduce wheel spin on low grip
Good for high-speed/high-bite tracks to avoid brake lock-up

This is a great all-around tuning rotor when you need to tone down the bottom end.

Option Rotor #2

Part #: 30820019 – 12.1mm OD

Even less magnet = even more RPM
Least amount of torque and brake force
High amp draw = watch battery temps and fade
Mostly used in 1/12 scale with 3.5T motors for max speed

Use this when you want all the RPM and none of the punch.

BONUS ROTORS – Titanium Shaft Series

These are for racers looking for smoother feel, better efficiency, and longer run time—especially in classes like 1/12 where you’re driving hard for 8 minutes.

Titanium Rotor #1

Part #: 30820402 – 12.3mm OD (Ti Shaft)

Smoothest driving rotor in the lineup
Lower amp draw than standard 12.3 or 12.1 steel
More runtime with similar top speed
Perfect for long runs with high turbo/boost

If you're looking for controllability and efficiency, this is the go-to rotor.

Titanium Rotor #2

Part #: 30820401 – 12.5mm OD (Ti Shaft)

More efficient version of the stock 12.5
Good top end, but slightly more punch than the 12.3 Ti
Great for drivers stepping into mod, but want to keep some bottom end

This one’s for when you want smooth, but still want that drive out of the corner.

Matt’s Take

If you're moving up from spec and want something easy to drive, the 12.3 Ti is hard to beat.
If you’re already mod-savvy and want to squeeze more RPM or fine-tune feel, the 12.1 or 12.3 steel rotors give you flexibility.
Need runtime without fade? Titanium is the way