Adjust mechanical disc brakes by centering the caliper and setting cable tension so the pads bite without dragging, and adjust hydraulic brakes by aligning the caliper and bleeding the system if the lever feels soft; replace the pads when the friction material wears to about 1mm. These are the two adjustment routines every e-bike owner needs, and both take under an hour with basic tools.

Procedure applies to TST models with hydraulic and mechanical disc brakes.

What Is the Difference Between Mechanical and Hydraulic Brakes?

Symptom	Likely cause	Fix
Squeal	Contaminated pads	Clean the rotor, sand the pads
Spongy lever	Air in the system	Bleed hydraulic brakes
Dragging pads	Misaligned caliper	Center with the lever squeezed
Grinding	Worn pads	Replace the pads immediately

Mechanical disc brakes pull the pads with a cable, which means adjustments are cable-tension and caliper-position jobs. Hydraulic brakes push the pads with fluid, which means the system needs a bleed when air enters and the adjustment is mostly caliper alignment and pad inspection. TST's heavier models (R7, Carrier) use hydraulic discs, while some folding and budget models use mechanical discs.

Know which type you have before buying tools: a cable barrel adjuster and Allen keys handle mechanical brakes, while a bleed kit and fluid are needed for hydraulic service.

Tools You Need for E-Bike Brake Adjustment

Before buying any tool, confirm the brake type on the official page for your exact model, because buying a bleed kit for a mechanical brake bike is money wasted, and the same is true of buying cable cutters for a hydraulic system.

For mechanical brakes you need Allen keys (usually 4-5mm), a 5mm hex for the caliper bolts, and possibly a cable cutter if replacing cable. For hydraulic brakes you need Allen keys, a bleed kit matching the fluid type (mineral oil or DOT), and clean rags. A torque wrench is worth having for the caliper bolts, because brakes must not loosen under vibration.

Check the brake type on the official page before buying parts, and confirm the fluid type for any hydraulic system, because mixing mineral oil and DOT fluid ruins the system.

How Do You Center a Mechanical Disc Brake Caliper?

With the wheel installed, loosen the two caliper mounting bolts slightly so the caliper can move, squeeze the brake lever firmly, and retighten the bolts while holding the lever. This centers the caliper over the rotor, eliminating most rubbing. Spin the wheel to check, and repeat if the rotor still drags on one side.

If the caliper is centered but still rubs, the rotor may be bent; check by spinning the wheel and watching the rotor for wobble. A slightly bent rotor can be straightened with a rotor tool, but a badly bent one should be replaced.

How Do You Set Cable Tension on Mechanical Brakes?

Set cable tension so the brake engages firmly about a third of the way through the lever travel. Loosen the cable clamp bolt at the caliper, pull the cable snug, and tighten the bolt; then use the barrel adjuster at the lever or caliper to fine-tune. The pads should not drag when the lever is released, and the lever should not reach the bar under full squeeze.

If the lever pulls to the bar, tighten the cable a turn at the barrel adjuster. If the pads drag, loosen it. Small adjustments at the barrel, not big ones at the clamp, are the correct technique.

How Do You Adjust a Hydraulic Brake Caliper?

For hydraulic brakes, loosen the caliper bolts slightly, squeeze the lever to center the caliper, and retighten. If the lever feels spongy or pulls far before engaging, the system needs a bleed to remove air from the fluid. A bleed requires the matching kit and fluid, and the procedure is: attach the bleed cup, open the bleed port, pump the lever to push air out, close the port, and top up the fluid.

If you have never bled a hydraulic brake, watch the manufacturer's video and work slowly, because introducing more air makes the problem worse. When in doubt, a bike shop bleed costs less than a ruined system.

When to Replace the Brake Pads on an E-Bike

Buy the replacement pads before you need them: brake pads are the most predictable consumable on an e-bike, and having a set on the shelf turns a weekend job into a 20-minute swap instead of a week of riding on worn brakes. Check the pad thickness with the wheel off at the same time you check the tires, and note the model number from the caliper so the replacement matches. TST sells the brake assemblies and components directly, so matching the exact pad for the R7 or Carrier hydraulic calipers is straightforward.

Replace the pads when the friction material wears down to about 1mm, when the lever pulls noticeably farther, or when braking becomes noisy and metal-on-metal grinding appears. Grinding means the pads are gone and the rotor is at risk, so replace immediately. On heavy e-bikes like the R7 or Carrier, pads wear faster because of the weight, so inspect them monthly.

Check the pad wear through the caliper window or by removing the wheel, and replace both pads in the caliper as a pair. TST sells brake assemblies and components directly, so matching parts is straightforward.

Fixing Brake Squeal Without Replacing Parts

The contamination routine fixes most squeal in under 15 minutes: remove the wheel, clean the rotor with isopropyl alcohol, lightly sand both sides of the pads on a flat surface, and reinstall with clean hands. If the squeal returns within a week, the pads have absorbed oil and should be replaced, because no amount of cleaning fully removes oil from porous brake material. Also check the rotor for a blue or glazed surface, which signals heat damage from repeated hard braking, and replace it if the surface looks scorched.

Most brake squeal is contamination, not wear: oil, chain lube, or road grime on the pads or rotor. Clean the rotor with isopropyl alcohol and a clean rag, sand the pad surface lightly with fine grit if contaminated, and re-center the caliper. If the squeal persists, the pads may be glazed and should be replaced.

Do not sand or clean pads with solvents that leave residue, and never ride with a contaminant that reduces braking, because the brake is the one component where "it probably still works" is not a plan.

Safety Checks After Any Brake Adjustment

Make the brake check part of the pre-ride routine rather than a one-time event: before every ride, squeeze both levers once to confirm firm pressure, and every month, inspect the pads and calipers for wear, contamination, and loose bolts. On hydraulic brakes, check the fluid level through the sight window and watch for leaks at the caliper and lever, because a slow leak turns a good brake into a soft one without warning. Brakes are the one system where routine inspection pays for itself in avoided crashes.

After adjusting, perform the standing brake test: with the bike stationary, squeeze both levers and confirm the bike cannot be pushed forward. Then ride slowly and test both brakes from a walking pace and from riding speed, checking for smooth, straight stops without pulling to one side or pulsing.

Recheck the caliper bolts after the first ride, because vibration can settle them, and include the brake check in your weekly pre-ride routine alongside tire pressure.

Conclusion: Centering, Tension, and Pad Health Are the Routine

Adjusting e-bike brakes comes down to three routines: center the caliper, set the cable tension or bleed the hydraulic system, and replace the pads at about 1mm of material. Do these checks monthly and the brakes stay predictable, which is the most important reliability feature on any e-bike.

Brake Service Checklist

Identify mechanical versus hydraulic before buying tools.
Center the caliper with the lever squeezed, then torque the bolts.
Set cable tension so the lever engages a third of the way.
Bleed hydraulic brakes when the lever feels spongy.
Replace pads at 1mm and after any metal-on-metal grinding.
Test both brakes from speed after every adjustment.

See the TST rear hydraulic brake assembly page for replacement parts, and browse the universal accessories for service tools.

FAQs

Why do my e-bike brakes squeal?

Usually contamination or glazing: clean the rotor with alcohol, sand the pads lightly, and re-center the caliper.

How do I know if my brake pads need replacing?

Replace them at about 1mm of friction material, when the lever travels farther, or at the first sign of grinding.

Can I bleed hydraulic brakes myself?

Yes, with the matching bleed kit and fluid, but work slowly and follow the manufacturer's video; a botched bleed introduces more air.

Why do e-bike brakes wear faster than bike brakes?

E-bikes are heavier and faster, so the brakes convert more kinetic energy to heat; inspect pads monthly on heavy models.

How Do You Adjust E-Bike Brakes?