Adjusting and Servicing Your Brakes (Rim & Disc)

Tools Needed: For rim brakes: an Allen wrench (usually 5mm) or screwdriver (for caliper centering or pad holders), and possibly a small adjustable wrench for older calipers. For disc brakes: hex/Allen wrenches (often 5mm or 6mm for caliper bolts), and Torx wrench (T25, if adjusting rotor bolts). A clean rag and isopropyl alcohol are handy for cleaning braking surfaces. It also helps to have a partner or bike stand to hold the bike while you spin wheels and test brake function.

Step-by-Step Guide (Disc Brakes):

1. Inspect Brake Pads and Rotor: Lift the bike wheel off the ground and spin it. If you hear rubbing, determine if the rotor is rubbing the brake pads. Check pad thickness – replace pads if they are worn too thin (disc pads have ~3-4mm of material when new, and should be replaced before the backing plate is exposed). If contaminated (glazed or oily), pads might need cleaning or replacement. Also ensure the wheel is correctly seated in the dropout; an improperly seated wheel can cause brake rub or misalignment​.

2. Align the Caliper: A common cause of disc brake rub is a slightly misaligned caliper. To realign: Loosen the two caliper mounting bolts that attach the brake caliper to the frame/fork (usually 5mm hex) just enough that the caliper can move side-to-side​. Squeeze the brake lever firmly (this centers the caliper on the rotor), and while holding the lever, re-tighten the caliper bolts evenly. Release the lever and spin the wheel – the rotor should no longer rub, or rub much less. You may need to repeat and nudge the caliper by hand slightly before tightening if one side still rubs. It can take a couple tries to get it perfect, but it’s usually straightforward and fixes most rubbing issues.

3. Adjust Cable Tension (Mechanical Discs): If you have cable-operated disc brakes (common on entry-level gravel bikes), check the brake lever feel. If the lever pulls too close to the handlebar or feels soft before engaging, you need to tighten the cable. Follow the cable down to the caliper and find the cable pinch bolt. Loosen it with an Allen key, pull a bit more cable through (so the pads sit a tad closer to the rotor), and re-tighten the bolt​. Don’t overdo it – you want a little gap so the rotor doesn’t rub when not braking. You can fine-tune using the barrel adjuster (often on the brake lever or caliper): turning it out (counter-clockwise) adds tension, moving pads closer; turning in releases tension. Aim for a lever feel that is firm by halfway through its travel.

4. Inner Pad Adjustment (Mechanical Discs): Many mechanical disc calipers are one-sided (one pad moves, the other is fixed). You should adjust the fixed pad as well: look for an adjuster dial or hex on the inner side of the caliper (facing the wheel spokes). Turn it clockwise to move the inner pad closer to the rotor, until it’s very close but not touching. This reduces lever travel and improves power, as both pads will grip the rotor sooner.

5. Centering Rim Brakes (if applicable): If you have rim brakes (side-pull calipers or V-brakes), adjustment is slightly different. First, ensure the wheel is true (no big wobbles) and properly seated. Check pad alignment: the brake pads should contact the rim squarely, not hit the tire or miss the rim. Loosen the pad bolt and reposition if needed​. Next, squeeze the brake and see if both sides hit evenly. If one pad hits first or the brake is off-center, adjust the centering screw (small screw on the caliper) or, for side-pulls, loosen the mounting bolt slightly, center the caliper by hand, then retighten​. Finally, set the cable tension: there should be about 1-2mm pad-to-rim gap on each side when brakes are released​. Use the barrel adjuster at the lever or caliper to get the right tension; or reclamp the cable if it’s very slack. Rim brakes may also benefit from “toeing in” the pads (having the front edge of each pad hit the rim slightly before the rear edge) to reduce squeal – you can achieve this by placing a business card under the rear half of the pad when tightening it.

6. Test Braking Performance: Spin the wheels – they should spin freely with no rubbing sounds. Squeeze the brake levers hard: they should feel firm, not touch the handlebar, and both wheels should lock or slow strongly. If the rear brake feels weak but the front is fine, or vice versa, you may need to readjust tension or pads. For hydraulic discs, if the lever feels spongy or pulls to the bar, the system might have air and could require a bleed (an advanced task beyond basic tools – in that case, have a shop service it). But normally, alignment and pad adjustments solve most issues.

Common Mistakes: Getting oil or grease on the brake pads or rotors. For example, when lubing your chain, be very careful or cover the rotor – even a drop of oil can cause loud squealing and loss of power. If contamination happens, clean rotors with isopropyl alcohol and consider sanding or replacing pads. Another mistake is over-tightening the brake cable such that the pads drag on the rotor/rim continuously – this causes fast wear and hot rotors. Always leave a slight gap for free movement​. For rim brakes, be sure the pads contact the rim flat and fully; if they catch the tire or hang off the rim, it’s dangerous (the pad could rub the tire or dive under the rim). Not checking pad wear is also common – worn-out pads won’t stop well; replace them before they’re gone. Finally, forgetting to re-engage a disconnected brake (many rim brakes have a quick-release to open for wheel removal) – after fixing a flat or adjusting, make sure the brake is closed and functional before riding off.

Quick Tips: Clean your braking surfaces regularly – wipe rims with alcohol to remove black gunk, and wipe rotors with alcohol to remove any glaze or dirt. If you hear a slight rub on a disc brake and can’t fix it perfectly on the road, a temporary trick is to slightly loosen the caliper bolts and retighten after a ride when you have more time – often it’ll recentralize. Carry a spare set of pads on long trips; they’re small and easy to swap if needed. If a rotor is bent (wobbling), you can true it gently by bending it with an adjustable wrench or dedicated rotor truing tool – tweak at the spot it deviates, a little at a time. For rim brakes, if you experience squealing, try toe-in adjustment as mentioned, and make sure the rim’s surface is clean (no oil). Remember, well-adjusted brakes are crucial for safety: after any brake work, do a slow parking lot test to ensure you can stop quickly and reliably.