# Brakes CEMOTO D-series bikes use **hydraulic disc brakes** (dual-disc on the 72V models); eBikes use hydraulic or mechanical disc brakes depending on model. This page covers brake symptoms, adjustment and the brake error code. --- ## Related error codes | Code | Meaning | | --- | --- | | **E02** | Brake Error | Full definition: [Display & Error Codes](https://help.cemotoride.com/link/332). --- ## How CEMOTO brakes work The brake system is both **hydraulic** and **electrical**: - **Hydraulic:** the lever pushes fluid to the caliper, which squeezes the pads onto the disc. - **Electrical:** the lever also actuates a sensor that **cuts motor power** when braking. This second function matters for diagnosis: a brake sensor stuck in the "applied" position will prevent the bike from driving at all, even though the hydraulics are fine. --- ## Symptom: E02 Brake Error **Check in this order:** 1. **Brake lever sensor / switch.** Confirm the lever returns fully under its own spring pressure. A lever that binds will hold the sensor on. 2. **Lever connector.** Unplug, inspect for corrosion or bent pins, and reseat. 3. **Wiring.** Check the harness from the lever to the controller for chafing, especially around the steering head. 4. **Both levers.** The error may originate from either the front or the rear lever. 5. **Adjustment.** Confirm the brake is adjusted to appropriate tension so that it can respond in time without dragging. --- ## Symptom: brakes feel spongy or the lever reaches the bar Spongy lever feel is characteristic of **air in the hydraulic system** or a **fluid leak**. 1. **Check for leaks** at the caliper, the hose fittings and the master cylinder. 2. **Check fluid level** in the master cylinder reservoir. 3. **Bleed the system** to remove air. Hydraulic brake bleeding requires the correct fluid and a bleed kit; if you have not done it before, a bike shop can complete it quickly. 4. **Check pad wear.** Very worn pads require excessive lever travel and feel spongy even with a correctly bled system. > **Do not ride with a brake fault.** If the brake cannot stop the wheel reliably, stop riding and repair or replace the system. Brake failure is the most consequential fault a bike can have. --- ## Symptom: brakes drag or the wheel does not spin freely 1. **Caliper alignment.** Loosen the caliper mounting bolts, apply the brake to center the caliper on the disc, then retighten. The disc must sit centrally between the two pads. 2. **Bent disc.** Check the rotor for runout. A distorted disc can be straightened or replaced. 3. **Piston not retracting.** A dirty or corroded caliper piston will not return. Clean the pistons and, if needed, service the caliper. 4. **Lever preload.** A lever that cannot fully release holds residual pressure. Check the lever and the sensor. 5. **Contaminated pads.** Oil or fluid on the pads causes noise and poor performance. Replace contaminated pads — they cannot be cleaned reliably. > **Range impact:** a dragging brake is a constant energy drain. If range has dropped suddenly, check the brakes early. --- ## Symptom: brake noise | Sound | Likely cause | Action | | --- | --- | --- | | **Squeal** | Contaminated or glazed pads; damp conditions | Clean or replace pads; bed them in | | **Grinding / metal-on-metal** | Pads worn through to the backing plate | Replace pads immediately and inspect the disc | | **Scrape once per wheel revolution** | Slight disc runout or a marginally out-of-true rotor | Check rotor trueness and caliper alignment | | **Constant rub** | Caliper misalignment or a piston not retracting | Realign the caliper and service the pistons | New pads need a **bedding-in** period — a series of moderate stops from moderate speed — before they deliver full performance. --- ## Symptom: brake lever is hard to pull or feels stiff - **Cable-actuated brakes (some eBikes):** a dry, kinked or corroded cable. Lubricate or replace the cable. - **Hydraulic:** a blocked hose or a seized caliper piston. Service the caliper and inspect the hose. --- ## Routine brake maintenance | Interval | Action | | --- | --- | | **Before every ride** | Check lever feel, pad thickness and that the lever cuts motor power | | **After every ride (off-road)** | Inspect pads for grit and glazing; clean the caliper area of mud | | **Weekly / frequently** | Check pad wear and rotor condition; confirm no drag | | **As needed** | Adjust cable tension; bleed hydraulic systems; replace pads | | **Per owner manual** | Adjust brakes frequently and change brake pads in time | | **After wheel removal** | Re-center the caliper and re-verify disc alignment | --- ## Brake components and warranty Brake pads, rotors, brake handles, brake cables and covers are **wear-and-tear components and are excluded from warranty**. Replacements are available at cost — see [Spare Parts & Compatibility](https://help.cemotoride.com/link/382). Note the difference between: - **Consumables** — pads, rotors, cables: not covered. - **Manufacturing defects** in the brake assembly: covered under the 12-month electrical/mechanical component warranty, subject to exclusions. See [Warranty](https://help.cemotoride.com/link/391). --- ## Brake installation Hydraulic disc brake systems and brake pads for the D-series are available as replacement parts. A step-by-step video is available: *How to Install the Front Disc Brake on a CEMOTO Electric Dirt Bike*. See [Technical Guides](https://help.cemotoride.com/link/336). > **Critical during assembly:** when installing the front caliper, pull the transport plug only after seating the pads — squeezing the lever with the pads removed will over-extend the pistons. --- ## Related pages - [Display & Error Codes](https://help.cemotoride.com/link/332) - [Drive & Transmission](https://help.cemotoride.com/link/331) - [Maintenance Schedule](https://help.cemotoride.com/link/323) - [Spare Parts & Compatibility](https://help.cemotoride.com/link/382)