Bleed or adjust your e-bike brakes: what is needed?
OnTheRoad4 min reading time
Bad braking has three possible causes and three different solutions: adjustment (free of charge, self-do), new brake pads (wearing, fast on an e-bike) or bleeding (air in the hydraulic pipe, specialist work). Check below which of the three your bike needs before you book or buy anything.
Recognize the symptom
Hendel feels spongy and almost comes to the wheel
Check: Squeeze the brake at standstill: does the lever gently spring along and do you need to extend it far for braking?
Diagnosis: This is air (or moisture) in the hydraulic pipe. Adjusting then does not help, the brake must be bled and the liquid refreshed. Typical for hydraulic disc brakes, including Cowboy C4 and Cruiser.
Hendel feels normal, but the bike slows down
Check: Look (with flashlight) between brake caliper and disc: is there at least 1.5 mm brake pad left on both sides?
Diagnosis: Thin, shiny or unevenly worn blocks are replaced on: E-bikes wear blocks faster than regular bikes by weight and speed, replacing once or twice a year is normal for daily use.
Beeping or sanding when braking
Check: Does it always beep, or only in wet weather? Does it also sand if you don't brake?
Diagnosis: Wet beeping is normal. Always beeping indicates contaminated or vitrified blocks; sanding without brakes on a leaning disc or claw. Cleaning or aligning usually solves it, oil or chain spray at the disc is the mortal sin.
The brake drags or the wheel runs heavily
Check: Lift up the wheel and turn it around: is it stuck after a few revolutions or do you hear constant contact?
Diagnosis: The brake caliper is crooked or a piston is not coming back. You can carefully try to center the claw again (unscrew two bolts, squeeze the brake, tighten the piston); a hanging piston is mechanic work.
What you do well yourself, and where you stop
Mechanical (cable) brake adjustment
Is there a cartel wheel or gear screw at the lever or brake caliper? Turn it out a quarter stroke at a time until the brake hits earlier. Squeeze after every quarter stroke for a moment; the wheel must keep running freely.
Check brake pads visually
Less than 1.5 mm of material, shiny surface or uneven wear left/right = to replacement. Do you doubt, then take a picture and compare in two weeks, quickly thinning blocks do not wait.
Center brake caliper
Unscrew the two attachment bolts of the claw half a stroke, squeeze the brake firmly (the claw centers itself around the disc) and tighten the bolts as you keep squeezing. Then check freely.
Hydraulic brake bleeding: when to stop and get help
Bleeding requires the correct fluid (mineral oil or DOT; using the wrong one damages the brake), a bleed kit with adapters for the brake brand, and experience filling the system without introducing air. This is particularly important for SunRace brakes on the Cowboy C4/Cruiser. Having it done professionally is a sensible choice.
Frequently asked questions
How do I adjust the brakes of my electric bike?
For a cable brake, turn the barrel adjuster at the lever or caliper out a quarter turn at a time until the brake engages earlier. Check that the wheel still spins freely. There is little to adjust on a hydraulic brake: a spongy lever means air in the line and calls for bleeding, not adjustment of a screw.
How do you bleed bicycle brakes?
Use a bleed kit that fits your brake brand. Flush the brake through the lever and caliper with fresh mineral oil or DOT fluid until all the air is removed. This requires care: the wrong fluid or poor filling can leave the brake worse than before. For most e-bike owners, professional servicing is the sensible option.
Can I bleed my e-bike brakes myself?
Technically, yes: with the right kit (€25–50), the correct fluid for your brake brand and an unhurried afternoon. But mistakes with brakes are immediately dangerous. Checking adjustment and pad wear is suitable for DIY. Have bleeding done professionally, especially on SunRace brakes (Cowboy C4/Cruiser).
How much does brake bleeding cost?
At OnTheRoad at home in Amsterdam: €30.00 per side on top of the service visit of €45.00, both brakes €105,00 total, incl. travel, fresh liquid and VAT.
How much does replacement of brake pads cost on an e-bike?
€24,00 per side on top of the service visit of €45,00; both sides €93,00 total at the door. We have the appropriate blocks for Cowboy, Tenways and common 28-inch brands standard with us.
When should I have my brakes bled?
As soon as the lever feels spongy or extends further than before, and in any case every one or two years as maintenance: brake fluid absorbs moisture and thus loses braking force, especially at long runs or emergency stops.
Ready to book?
Cowboy C4 or Cruiser with SunRace brakes? Read our dedicated Cowboy C4 brake bleeding page, or the Tenways brake bleeding guide. All prices are listed in the cost guide. The mechanic comes to your home, usually within 1–2 days.