Heat is what stops you turning your controller up. Fix the heat and the motor you already own can handle far more power. This guide covers how riders safely run more power through a direct drive hub motor, what else on the bike has to keep up, and exactly which motors HubSink fits.
To be clear, HubSink does not make power. Your controller and battery do. HubSink lets your motor handle much more of that power without overheating. If you want the background on why motors overheat, start with why ebike hub motors overheat and how to stop it.
Why heat is the limit on hub motor power
Power through the motor turns into torque and speed, but part of it always turns into heat in the copper windings, and that heat rises with the square of the current. Double the phase amps and you make about four times the heat. A typical hub motor sheds heat poorly, so it cooks long before the magnets or copper reach their real mechanical limits. The result is a motor that hits thermal cutoff, or gets cooked, on the first long climb after a controller upgrade.
Cool the motor properly and that ceiling moves up. That is how an 8kW MXUS, a 7500W fat bike, an Adaptto controller at 120 amps and 20kW race prototypes have all been run on HubSink in the real world (HubSink official thread), and why HubSink has been tested on bikes from 1kW up to 22,000W, including an 18kW hill climb through a 3000W class hub motor.
The two part cooling upgrade for more power
- Statorade ferrofluid inside the motor moves heat from the windings to the shell. Shop Statorade
- HubSink fins on the outside move heat from the shell into the air. Grin Technologies' wind tunnel testing of a Cromotor found HubSinks improved shell to air cooling by 50 to 60%, and added up to 20% more total cooling on top of Statorade (Grin results). Shop HubSink V2
HubSink only works properly with a cooling fluid inside the motor, so fit them together.
How to run more power, step by step
- Fit a temperature sensor and log a baseline. Ride your normal hard route before changing anything and note the motor temperature at the top of the climb. A Cycle Analyst can show motor temperature live and roll back power for you. This also gives you the evidence you need for the HubSink guarantee.
- Fit Statorade and HubSink. Follow the installation guide, use the full tube of thermal paste across all the pieces, and ride hard once so the paste seats.
- Raise power in steps. Turn up your controller's phase current and battery current in small increments, and ride the same route after each step. Watch motor temperature, not just how the bike feels.
- Set thermal protection. Use your controller or Cycle Analyst temperature rollback so the motor is protected if you push past what it can shed on a hot day.
- Stop when temperatures hit your limit. The common builder rule of thumb is to keep the hottest part of the motor under about 93C, with 60C comfortable for continuous riding (Endless Sphere). Whatever power gets you to that temperature on your hardest climb is your new power limit.
What else has to keep up with more power
A cooler motor is only one part of a high power build. Before turning up the power, check:
- Battery and wiring: the pack must deliver the current without sagging, and wiring and connectors must be rated for it.
- Controller: its current limits, cooling and settings must suit the motor.
- Torque arms and dropouts: more torque puts far more load on the axle and frame. Use proper torque arms.
- Brakes and tyres: you will be going faster and accelerating harder.
- Local laws: power limits for public roads and paths vary, and high power builds are generally for private land or places where they are legal.
Which hub motors does HubSink fit?
HubSink V2 is made for direct drive hub motors. On the HubSink V2 product page, choose the option that matches your motor:
- QS205: the QS205 in V1, V2 and V3 form. See the QS205 hub motor cooling page.
- MXUS: MXUS 3000W class motors including the XF40 and 3K Turbo. See the MXUS hub motor cooling page.
- Leaf motor: Leaf direct drive hubs.
- Crystalyte 35XX series: the H series hubs.
- Crystalyte 54XX series: the larger Crystalyte hubs.
- 9C and 9C clones: the popular 9C hub and the many motors copied from it.
- Cromotor: the motor Grin used for the wind tunnel testing above.
- Generic 222 to 238mm (8.7 inch) outside diameter: for other direct drive hubs in that size range. Measure the outside diameter of your shell and choose this option if your motor isn't listed.
- Crystalyte TC Crown: a larger shell, with its own option.
- QS273: a beta version with its own option, shaped to the larger shell. The pieces need a little forming with a rubber mallet to give full contact all the way round. There is also a QS273 kit with Statorade.
Not suitable: geared hub motors and mid drives, which are built differently, and motors with shells outside these sizes. Grin also list the Grin All Axle motor as incompatible with their HubSink set. If you are not sure, contact us with your motor model before ordering.
What riders say
These are reports from riders in the HubSink official thread on Endless Sphere:
- Quokka, Adaptto at 120 amps: motor around 30C cooler on the same hills while going faster, over 80km of dirt and trail in mid 30s heat.
- Jesse Haubner, MXUS at 8kW: no longer needs to stop and cool down on hills that used to thermal limit him.
- Hugh Pomeroy, 7500W fat bike: motor not warm at all after a full speed mountain climb.
- rberger, Crystalyte 3540 on a PhaseRunner controller with Statorade and HubSinks, carrying panniers at about 150kg total: hill peak motor temperature dropped from around 110C to under 80C (thread).
- Tats, HS3540, 1800W, about 125kg total, 37C ambient, hilly route with no pedalling: peak motor temperature stayed around 87 to 88C (thread).
- ridethelightning, QS205: reported the HubSinks "worked a treat", with motor temperature falling quickly whenever he eased off or stopped (thread).
- RollerBoy, a commuter, said the HubSinks were very well made and fixed his motor's cooling problems with Statorade after about nine months of use (thread).
- ebike11, QS273: found the QS273 HubSinks very effective on a high power hub motor, needing only a little massaging for full contact and one tube of Statorade (thread).
- Andy Braidford installed his in 10 minutes and reported better heat shedding, and Dr Bass said they work well and plans to test them in summer heat (thread).
Tip from the thread: if your motor has open brake rotor screw holes, make sure they are sealed. One rider found Statorade had leaked out of an uncovered hole and had to top it up.
Common questions
How much more power can I run with HubSink?
It depends on your motor, controller and riding, but most customers turn their controllers up to more than double the power they could run before, and we guarantee it. The rule is to raise power in steps while watching motor temperature.
Will HubSink alone make my bike faster?
No. HubSink does not add power. Speed and torque come from your controller settings, voltage and battery. HubSink keeps the motor cool enough to use them.
Do I need Statorade as well?
Yes. HubSink is designed to work with ferrofluid inside the motor, and the two together give the biggest temperature drop.
Can I run more power through a QS205?
Yes, the QS205 is one of the most popular high power hub motors, and many riders run it well above its rated power with Statorade and HubSink fitted. See the QS205 cooling page.
Can I run more power through an MXUS?
Yes. Riders have run MXUS motors at 8kW and more on hills that used to force a stop. See the MXUS cooling page.
Cool the motor, then turn it up
Fit Statorade inside and HubSink outside, and your motor can handle double the power or stop overheating at the power you run now, or your money back within 30 days. Shipped worldwide from Australia.