Bleeding the Brakes on a 2015 Honda Grom: A Rider’s Step-by-Step Guide
Shop parts for a 2015 Honda Grom Motorcycle.
The 2015 Honda Grom uses hydraulic disc brakes at both ends — a single front caliper fed by the lever-mounted master cylinder, and a rear caliper fed by a pedal-driven master cylinder. There is no ABS and no linked brake system on this model year, which is good news for the home mechanic: each circuit is independent, straightforward, and fully serviceable in a garage with basic hand tools. That means you can bleed the front and rear separately, at your own pace, without worrying about a pump or proportioning valve that needs a dealer tool to cycle.
What follows is a complete walkthrough for refreshing the fluid and purging air from both circuits on your Grom. Take your time, keep the reservoir from running dry, and the job is well within reach of a rider who is comfortable with a wrench.
When Your Grom’s Brakes Need Bleeding
The most obvious signal is feel. If the front lever comes back closer to the grip than it used to, or feels spongy rather than solid, air has likely found its way into the system. The same goes for the rear pedal — a pedal that feels soft or travels further before biting is telling you something. A lever that slowly sinks toward the grip while you hold steady pressure is another classic symptom.
Visual clues matter too. Pop the reservoir cap and look at the fluid: fresh brake fluid is clear and nearly colorless to light amber. Dark, cloudy, or murky fluid has absorbed contaminants and moisture and should be replaced. Brake fluid is hygroscopic, meaning it pulls moisture out of the air over time, and that moisture lowers the fluid’s boiling point. Under hard or repeated braking, fluid that boils creates vapor, and vapor compresses — which is exactly the fade and soft-lever feeling you want to avoid. Many riders simply refresh the fluid on a regular interval as preventive maintenance, symptoms or not.
You should also bleed after any work that opened the hydraulic system: replacing a brake line, servicing or replacing a caliper, or rebuilding the master cylinder. Any of those jobs introduces air that has to come out before the brakes are trustworthy again.
Tools and Supplies to Gather First
- Fresh brake fluid of the type marked on your Grom’s master cylinder reservoir cap, from a sealed container — once a container is opened, it starts absorbing moisture, so use fresh stock
- A box-end wrench that fits the bleeder valve on each caliper
- Clear tubing that fits snugly over the bleeder nipple
- A small catch bottle for the old fluid
- Rags or shop towels, plus a syringe or turkey baster for pulling old fluid out of the reservoir
- The correct driver for the reservoir cap screws
- Optional: a one-way check-valve bleeder or a vacuum bleeder, both of which make a one-person job much easier
Brake fluid attacks paint and many plastics on contact, so treat it like a chemical spill every time. Wipe up any drip immediately and rinse the area with water if fluid reaches a painted or plastic surface.
Setting Up the Bike Safely
Get the Grom securely upright on a stand so it cannot tip while you are working. For the front circuit, turn the handlebars until the reservoir on the lever perch sits level — an off-angle reservoir lets fluid spill out the moment you open it. Drape rags over the surrounding plastics, the instrument cluster, and any painted bodywork below the reservoir. Lay a rag under each caliper as well, since old fluid will drip from the bleeder.
Work through one circuit at a time. Doing the front completely before starting the rear keeps you from mixing up tools, tubing, and fluid levels.
The Bleeding Procedure, Step by Step
- Remove the reservoir cap and diaphragm. Use the syringe or baster to draw most of the old fluid out of the reservoir, but stop before the level drops near the bottom port — never let the reservoir run dry, or you will pull air straight into the system.
- Refill the reservoir with fresh fluid from your sealed container, leaving the level at or slightly below the full mark for now.
- Push the clear tubing onto the bleeder valve and route the other end into the catch bottle, with the bottle positioned so the tube’s end stays submerged in fluid if possible.
- Squeeze the front lever (or press the rear pedal) firmly and hold it. With the lever held, open the bleeder about a quarter turn with the box-end wrench. Fluid and air will push out through the tube.
- Close the bleeder before you release the lever or pedal. Releasing with the bleeder open draws air back in through the valve — this is the single most common mistake in the whole job.
- Repeat the squeeze-hold-open-close-release cycle, topping off the reservoir every few cycles so it never runs low. Watch the tubing: you will see bubbles at first, then fewer, then none.
- Continue until the fluid coming through the tube is clean and fresh-looking and completely free of bubbles. On the Grom each circuit has a single caliper, so there is no second caliper to work through — but if you ever work on a bike with two front calipers, bleed them one at a time, starting with the caliper farthest from the master cylinder.
- Repeat the entire process on the rear circuit using the pedal, with the rear reservoir level and the same squeeze-hold-open-close-release rhythm.
Finishing the Job Correctly
With clean, bubble-free fluid confirmed at both ends, close each bleeder snugly with the box-end wrench. Snug is the goal — firm enough to seal, not so tight that you risk damaging the valve or the caliper threads. Top the reservoir to the correct level marking, reinstall the diaphragm and cap, and wipe down every surface that saw fluid. Then inspect the bleeder valves and the banjo fittings at the master cylinders and calipers for any sign of weeping or seepage.
Testing Before You Ride
Before the Grom goes anywhere, check the feel. The front lever and rear pedal should each feel firm and consistent, and neither should slowly sink while you hold steady pressure. Spin each wheel by hand to confirm the brakes are not dragging. Then, in a safe, low-speed area, test the brakes gently before riding normally. If anything feels soft or inconsistent, stop and investigate rather than riding it out.
Troubleshooting and When to Visit a Shop
If the lever will not firm up after several full bleeding passes, or it only firms up temporarily after pumping, air is still getting in somewhere — often past a worn master cylinder seal or a loose fitting. Persistent bubbles at the bleeder, or fluid weeping from the master cylinder or caliper, also point to a component that needs attention beyond a simple bleed. Because the 2015 Grom has no ABS unit to trap air, a stubborn circuit usually means a hardware problem rather than a procedure problem, and that is the point to hand it to a professional. Brakes are not the system to guess at; if you are not confident in the result, have a shop verify the work before you ride.
Related Shopping Categories
Shop Brake Fluid for a 2015 Honda Grom Motorcycle.
Shop Brake Lines for a 2015 Honda Grom Motorcycle.
Shop Brake Pads for a 2015 Honda Grom Motorcycle.
Shop Stands for a 2015 Honda Grom Motorcycle.
Shop Brake Tools for a 2015 Honda Grom Motorcycle.
Disclaimer: This guide is provided for general informational purposes only and is not intended to replace your motorcycle's official owner's manual. Always refer to your manufacturer's documentation for model-specific instructions, torque specifications, safety procedures, and maintenance requirements. If you are unsure or inexperienced, consider seeking assistance from a qualified mechanic or technician.
