Squeaky brakes and skipping gears: causes and fixes

They are two of the most common complaints at any workshop: “my brakes squeal” and “my gears keep skipping”. Both have well known causes, and some can be fixed at home in ten minutes. Others cannot, and it helps to tell them apart before you start turning screws.

First: what brakes do you have

Look at the wheel before anything else.

• Rim brakes: two rubber pads that squeeze the edge of the wheel. Common on city bikes, many hybrids and older road bikes. The usual types are V-brakes and caliper brakes.
• Disc brakes: a metal disc (rotor) bolted to the wheel hub, and a caliper that squeezes it with two pads. They can be mechanical (cable operated) or hydraulic (a hose filled with fluid).

The causes of noise are different for each.

Rim brakes that squeal

Dirty or wet rims. The most common cause. Dust, grease or road water make the pad vibrate against the rim. Wipe the braking surface of the rim with a cloth and isopropyl alcohol, and clean the pads.

Worn or glazed pads. Over time the rubber hardens and goes shiny. If you can barely see the grooves on the pad, replace it. If there is still rubber left but it is shiny, a light pass with fine sandpaper may be enough.

Embedded grit. A rough, sandpaper sound usually means sand or bits of metal stuck in the rubber. Take the wheel out or look closely and pick them out with a sharp tool. Left there, they score the rim.

Poor alignment. The pad should hit only the rim, never the tyre, and sit flat against it. Many mechanics give it a slight “toe in”: the front of the pad touches first. That reduces squeal. It is a fiddly adjustment, but doable at home with some patience.

Disc brakes that squeal

Contaminated pads or rotor. The number one cause. A bit of chain lube, grease from your fingers or overspray from a cleaning product on the rotor is enough. The symptom: a loud squeal and much weaker braking.

• Clean the rotor with isopropyl alcohol and a clean cloth. No oily degreasers, no lubricants.
• If the brake still does not bite, the pads are probably soaked. The reliable fix is new pads.
• To avoid it happening again: never use spray lube near the rear wheel, and cover the rotor when you clean the bike with products.

New pads not bedded in. New rotors or pads need a series of progressive stops to bed in. Find a spot with no traffic, build up some speed and brake hard without locking the wheel, several times.

Misaligned caliper. If the rotor rubs one pad as the wheel turns (a “tsss, tsss” every rotation), the caliper may be off centre. Loosen its bolts, squeeze the brake lever and tighten the bolts again while holding the lever. If the rotor itself is bent, the rub comes and goes each turn: that is one for the workshop.

Worn pads. A metallic scraping sound is a bad sign: usually the pad’s metal backing on the rotor. Stop riding like that. Replace the pads and have the rotor checked.

In the rain. Disc brakes often make noise when wet. If it goes away once they dry, it is not a fault.

If the brake does not stop well

Beyond the noise, pay attention to the lever:

• Cable brakes (rim or mechanical disc): if the lever comes almost to the bar, the cable has stretched or the pads are worn. The barrel adjuster on the lever lets you take up some slack.
• Hydraulic brakes: if the lever feels spongy or the bite point moves, there may be air in the system. Bleeding is a workshop job, with the right fluid for each brand.

Skipping gears: the usual causes

“Skipping” can mean several things: the chain jumping to another sprocket when you push hard, not shifting up or down properly, or a constant clicking. In order of likelihood:

1. Stretched or slack cable. The most common cause, especially on new bikes: cables bed in during the first months. If shifts to bigger sprockets are slow or some gears are noisy, the cable has lost tension.

2. Indexing out of adjustment. Indexing is what makes each click of the shifter put the chain right on a sprocket. When it is off, the chain sits between two sprockets and you hear it or it skips.

3. Worn chain. A stretched chain no longer meshes properly with the teeth and skips under load, especially on climbs or when pulling away.

4. Worn cassette or sprockets. If you replace a very worn chain and the new one skips on the sprockets you use most, the cassette teeth are worn too. Chain and cassette wear together.

5. Bent derailleur hanger. The hanger is the small part that attaches the rear derailleur to the frame. It bends easily if the bike falls on its right side or gets pushed around in a bike rack. Typical signs: the derailleur looks crooked when you view it from behind, or the gears went bad right after a fall.

What you can try at home

Adjust cable tension with the barrel adjuster. On the rear derailleur or the shifter there is a small knurled barrel where the cable goes in.

1. Shift into the smallest sprocket.
2. Shift one gear towards a bigger sprocket. If the chain does not climb or hesitates, turn the barrel a quarter turn anticlockwise (adds tension).
3. If it overshoots or is noisy heading towards the big sprockets, turn it clockwise.
4. Repeat a quarter turn at a time, testing every gear.

Do this with the wheel turning, with the bike on a stand or someone holding it. And only the barrel adjuster: the limit screws (H and L) set how far the derailleur can travel, and changing them without knowing what you are doing can put the chain into the spokes.

Measure the chain. A chain wear checker tells you in seconds whether it needs replacing.

Clean and lube. A very dirty drivetrain also shifts badly. Clean the chain, wipe off excess lube and try again.

When to take it to a workshop

• The barrel adjuster does not fix it after a few turns.
• The derailleur hanger looks bent. Straightening it properly needs a dedicated tool, and if it is badly damaged it has to be replaced.
• The chain is worn, and maybe the cassette too.
• Hydraulic brakes that feel spongy or leak fluid.
• A bent rotor, or contaminated pads that do not recover.
• Metallic noise when braking.

With brakes, do not take chances: if you are not sure you have got it right, have a mechanic look at it.

In short

A squeal from a dirty rim or a gear that needs a quarter turn of the barrel adjuster are home fixes. A bent hanger, hydraulic brakes with air in them or a worn drivetrain are workshop jobs, and they are rarely big ones if you catch them early. On madridbikes.com you tell us what the bike is doing (when it squeals, which gears skip), in English or Spanish, and we assign a workshop in your area, in any of Madrid’s 21 districts. For other common problems, see bike repair in Madrid in English.