Three kinds of brake end up on trailers in the 3,500 to 8,000 lb class: electric drum brakes, surge-actuated hydraulic brakes, and electric-over-hydraulic (EOH) disc brakes, which is what every DeeMaxx conversion is. Opinions about which one "stops better" are easy to find. This guide sticks to what is documented: how each system makes braking force, what DeeMaxx has published about its own brakes, and what each system asks of the tow vehicle. The kits are in the DeeMaxx range.
How the three systems make braking force
Electric drum
The brake controller in the tow vehicle sends current to an electromagnet inside each drum. The magnet drags on the spinning drum face, levers the shoes out against the drum, and return springs pull them back when the current stops. The adjuster, magnet and springs all live inside the drum. These are the brakes most RVs and utility trailers ship with; our electric brake conversion guide covers what a drum setup needs and trailer brakes weak or grabbing covers what goes wrong with it.
Surge hydraulic
A surge coupler holds a master cylinder. When the tow vehicle slows, the trailer pushes forward on the coupler and that movement drives the master cylinder piston, sending fluid to drum wheel cylinders or disc calipers. DeeMaxx's own primer puts it this way: "the surge of you stopping actuates the piston in the master cylinder." Nothing electrical is needed, and no brake controller is involved: the trailer brakes only once it is already pushing on the tow vehicle.
Electric-over-hydraulic disc
An EOH actuator mounted on the trailer takes the same electric signal a drum brake would get and uses a motor-driven pump to build hydraulic pressure. In DeeMaxx's words, "the electric signal ramps up the motor and builds pressure." The pressure moves the caliper pistons, the pads clamp the rotor, and the brake controller in the cab still sets how hard the trailer brakes. DeeMaxx's disc actuators are rated at 1,600 psi (the EOHA1000 drum model at 1,000 psi), with 15.7 fl oz of fluid in the EOHA1600 and 28.7 fl oz in the EOHA1600XL for three or more axles. See DeeMaxx EOH actuators explained.
What DeeMaxx has published
- Dynamometer test to SAE J2681. DeeMaxx publishes a NUCAP R&D Center report on the friction behavior of its D289 brake, the 3-6K caliper and pad, on a 10.90" vented DeeMaxx rotor with a single 2.25" piston, run to SAE J2681 in September 2010 and signed off "test completed satisfactorily". DeeMaxx states on its site that it is the "only brake manufacturer to satisfactorily pass the SAE J2681"; that is DeeMaxx's claim, which we have not checked against other makers.
- Salt spray to ASTM B-117. A MAXX-coated cast steel caliper passed 1,008 hours at 5% salt with no corrosion noted on the coated areas (Aero Labs, 2010). Details in DeeMaxx MAXX vs stainless for saltwater boat trailers.
- Caliper bench tests. In August 2026 Link Engineering's Dearborn Technical Center bench-tested DeeMaxx's 3-6K and 7-8K single-piston floating calipers for fluid displacement and roll-back; DeeMaxx publishes both reports.
- Warranty. 7 years on galvanized, MAXX, zinc-coated and stainless parts and 3 years on actuators, against defects in materials and workmanship, with exclusions for wear, corrosion and improper installation. DeeMaxx says its warranty claim rate on major components is 0.1%.
What DeeMaxx does not publish is a stopping-distance comparison against drum brakes or against other disc brands, and we have not run one. The design points below are DeeMaxx's own, from its "How brakes work" page, plus etrailer's listing of the kits.
Design differences that are documented
| Electric drum | Surge (disc or drum) | DeeMaxx EOH disc | |
|---|---|---|---|
| Where the force is made | Magnet and shoes inside the drum | Master cylinder in the coupler, driven by the trailer pushing on the tow vehicle | 1,600 psi actuator on the trailer, driven by the brake controller signal |
| Brake controller in the cab | Yes | No | Yes, and it must support EOH brakes |
| Heat | Enclosed drum | Depends on the wheel brake | Vented rotor with radial cooling passages, in the airflow; etrailer notes drainage holes on the 13-1/8" rotors |
| Adjustment as the lining wears | Manual or self-adjusting shoes | Depends on the wheel brake | Floating caliper retracts only enough for pad clearance, so it self-adjusts |
| Parking brake | Separate mechanical brake, if fitted | Varies | Optional MECH/HY calipers with a lever: one-axle kits at 3.5K and 6K, caliper alone for 7-8K |
| Wet launching | Magnet, springs and adjuster sit in the drum | Depends on the wheel brake | Exposed rotor; MAXX or stainless finishes; salt-spray-tested coating |
| Power | Controller output | None | 12 V on a 30 A minimum circuit, 18-24 A at full pressure (etrailer's spec for the Alpha 1600) |
Two of DeeMaxx's points deserve a line each. On heat: the rotor has to absorb the trailer's kinetic energy as heat, and "exposed as they are to cooling airflow, this is one area where discs are superior to drums." On adjustment: a disc caliper only retracts the piston far enough to clear the rotor, so it compensates for pad wear on its own, which is also why disc systems need a larger fluid reservoir than drum systems.
What an EOH disc conversion asks of the tow vehicle
- A brake controller that supports EOH brakes. DeeMaxx's actuator warranty excludes failures caused by not selecting the EOH controller type or not fitting a proper controller for EOH brakes, which "may cause a short in the power relay system".
- A 12 V feed able to run the actuator: etrailer lists a 30 A minimum circuit and 18-24 A draw at full pressure, with four wires (black 12 V, blue brake controller, yellow breakaway, white ground). Our brake controller troubleshooting guide covers the tow-vehicle side.
- A breakaway battery and switch on the trailer. The EOHA1600P&P kit includes a 10 Ah breakaway battery with LED indicator and a breakaway switch kit; with the standard EOHA1600 you supply them. Our breakaway kit guide covers the rules.
What the conversion costs you in weight
A single-wheel DeeMaxx kit weighs 32 lb boxed at 3.5K, 38 lb at 6K and 58 to 63 lb at 7K and 8K, and a tandem master kit runs from 157 lb (3.5K) to 282 lb (8K, 5/8" studs) including the actuator and lines. That replaces the drum, backing plate and magnet assembly at each wheel, so the net change is smaller than the boxed figure; DeeMaxx does not publish a net comparison.
Comparing DeeMaxx with another disc brand
If you are weighing DeeMaxx against another hydraulic disc kit, compare the published items rather than the marketing: the coating test and its hours (ASTM B-117, 1,008 hours for MAXX), the brake test standard (SAE J2681), the actuator's maximum pressure (1,600 psi) and fluid capacity, whether a mechanical parking brake caliper exists, the pad reference you will be buying for years (D289 for 3-6K, D215 for 7-8K), the rotor minimum thickness (0.815" on DeeMaxx's 10.2" to 12" rotors, 0.957" on its 13.1" integral rotor/hubs), the finishes offered, and the warranty term and exclusions. We carry DeeMaxx only, so we do not quote other makers' figures here.
Frequently asked questions
Can I keep my existing brake controller?
Only if it supports electric-over-hydraulic brakes; check its manual for an EOH or hydraulic setting. DeeMaxx's warranty makes the controller selection the installer's responsibility.
Do I lose cab control with disc brakes?
No. The actuator responds to the controller's output, so the cab controller still sets how hard the trailer brakes, which is the difference between EOH and surge.
Can I convert one axle of a tandem trailer?
DeeMaxx sells one-axle kits, but its master kits and line kits are built to convert every axle on the trailer, and it does not document running a hydraulic disc axle alongside an electric drum axle, so plan on converting every axle.
Which DeeMaxx kit converts my trailer?
Start with which DeeMaxx kit fits your axle or the Kit Finder; the first-week procedure is in bedding in, bleeding and maintenance.
Every DeeMaxx part ships from our warehouse in Upland, California, and the kits ship free to the lower 48. Found it cheaper? Under our Lowest Price Guarantee we'll beat it.
Sources: deemaxx.com "How brakes work", warranty pages and published test reports; etrailer's DeeMaxx kit pages; our own listings. No stopping-distance figures are claimed because none are published.