Bleeding the Brakes on a 2018 Honda Grom
Shop parts for a 2018 Honda Grom Motorcycle.
What the 2018 Grom's Brake System Looks Like
Before you touch a wrench, it helps to know exactly what you're dealing with. The 2018 Grom runs hydraulic disc brakes at both ends. Up front, a single caliper is fed by a master cylinder built into the lever perch on the right handlebar. Out back, a second caliper is fed by a master cylinder down at the pedal. Both are sealed hydraulic circuits, and both can be bled in a home garage with ordinary hand tools.
Two details are worth confirming on your own bike. First, some 2018 Groms left the showroom with ABS and some did not — look for the ABS ring at the wheel and the modulator plumbing near the frame if you aren't sure. Second, the Grom does not use a linked or combined braking system, so the front lever operates only the front brake and the pedal operates only the rear. That means you bleed the two circuits independently, one at a time, and a problem in one won't hide in the other.
When a Bleed Is Actually Due
Brake fluid is hygroscopic, meaning it pulls moisture out of the air over time. That moisture lowers the fluid's boiling point, and a boiling fluid creates vapor in the lines — which is exactly what a spongy lever feels like under hard use. So even a Grom that stops fine can benefit from a fluid refresh on a regular interval.
Bleed right away if the lever or pedal feels soft or mushy, if the lever now travels closer to the grip than it used to, if the fluid in either reservoir looks dark or cloudy, or if you've just had the system open for any reason: new lines, caliper service, master cylinder work, or a reservoir that ran dry. Any of those events invites air into the circuit, and air has to come out before the brakes are trustworthy again.
Tools and Supplies to Gather
- Fresh brake fluid of the type printed on your master cylinder reservoir cap, from a sealed container — once a bottle is opened, it starts absorbing moisture, so don't use the half-empty bottle from last season
- A box-end wrench that fits the bleeder valve snugly; a box-end grips better than an open-end and is less likely to round the hex
- A length of clear tubing that fits tightly 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
A one-way check-valve bleeder or a vacuum bleeder makes this a much easier solo job, since you won't need a helper to work the lever while you open and close the valve.
Setting Up Without Damaging Anything
Get the Grom solidly upright on a stand so it can't tip while you're leaning over it. For the front circuit, turn the handlebars until the reservoir on the lever perch sits level — a tilted reservoir will spill. Drape rags over the tank area, the plastics, the instrument cluster, and anything painted below the reservoir, because brake fluid attacks paint and plastic on contact. If a drop lands anyway, wipe it up immediately and rinse the area with water rather than waiting until you're done.
Bleeding the Front Brake
- Remove the reservoir cap and diaphragm, then use the syringe or baster to draw most of the old fluid out. Leave a little in the bottom so you don't push air into the line.
- Refill with fresh fluid from your sealed container, leaving the reservoir comfortably full.
- Slide the clear tubing over the front caliper bleeder and route the other end into the catch bottle, with the bottle positioned so the tubing runs upward away from the bleeder.
- Squeeze the front lever slowly and hold it against the grip.
- Open the bleeder about a quarter turn. Fluid and air will push out through the tube.
- Close the bleeder before you release the lever. Releasing with the valve open pulls air back in through the bleeder.
- Release the lever, then repeat the squeeze–hold–open–close–release cycle. Check the reservoir every few cycles and top it off so it never runs low enough to draw air.
- Keep going until the fluid coming through the tube is clean and free of bubbles, then finish with the lever held and the bleeder closed.
If your Grom has two front calipers, bleed them one at a time and finish the one farthest from the master cylinder first.
Bleeding the Rear Brake
- Open the rear reservoir at the pedal master cylinder and pull most of the old fluid out, then top it with fresh.
- Fit the tubing to the rear caliper bleeder and run it to the catch bottle.
- Press and hold the pedal, crack the bleeder a quarter turn, then close it before releasing the pedal.
- Repeat, watching the reservoir level, until the fluid runs clean and bubble-free.
Finishing Up and Checking Your Work
Tighten each bleeder snugly — firm enough to seal, never so tight that you risk damaging the caliper threads. Fill each reservoir to the level marking, reinstall the diaphragm and cap, and wipe down every surface you touched. Then look closely at the bleeder fittings and the banjo bolts at the calipers and master cylinders for any weeping or dampness.
Testing Before You Ride
Both the lever and the pedal should feel firm and consistent, and neither should slowly sink while you hold steady pressure. Spin each wheel by hand to confirm the brakes aren't dragging. Then, in a safe open area, test the brakes at low speed before riding normally.
If a lever won't firm up after several rounds, if it only firms up after pumping, if bubbles keep appearing, or if you see fluid at the master cylinder or caliper, stop and diagnose rather than ride. And if your Grom is ABS-equipped and the reservoir ran dry or the ABS unit or its lines were disturbed, air may be trapped in the modulator where a home bleed can't reach it — that job belongs at a shop with the proper diagnostic equipment.
Related Shopping Categories
Shop Brake Fluid for a 2018 Honda Grom Motorcycle.
Shop Brake Lines for a 2018 Honda Grom Motorcycle.
Shop Brake Pads for a 2018 Honda Grom Motorcycle.
Shop Stands for a 2018 Honda Grom Motorcycle.
Shop Brake Tools for a 2018 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.
