Disc Brakes 101

Disc brakes are very common nowadays, as an avid cyclist or want to be mechanic you should know about working on them, adjusting and replacing pads.

How often do you need to change them?

A common mis conception is that disc pads last an incredible mount of time. They don’t. I change my pad’s twice a year with ~4000miles of riding (~2000 on one set of pads). If you ride a lot in the city with a heavy or loaded bike expect to change the pads more frequently

Changing Pads

This can vary model to model, but here are the basics.

Tools you will need. – Plastic tyre lever, (Pedros is great) 2.5mm allen wrench. Clean rags, Isopropanol alcohol (~$3 32oz). A 5mm, 6mm or T25 wrench to adjust calliper bolts, and of course new brake pads.

1. Remove the wheel
2. At the brake caliiper, Remove the pin that secures the pads, there maybe a safety clip on the end of the pin that needs removing first. Many pins nowadays use a 2.5mm allen wrench, some older style will use a cotter pin that needs removing with pliers.
3. Remove old pads and clean inside the caliper and the surrounding area. Use the alcohol.
4. Use the plastic tyre lever to angle and push the pistons back into the caliper so that the pistons are flush and tucked away, allowing you to install new pads easy. Plastic is important as it wont damage the pistons.
5. Clean inside again if needed
6. Install new pads, Take care not to touch the surface with your fingers. This will ruin the pads. If in doubt use some clean rubber gloves. Make sure to install the spring that came with the new pads.
7. Install the pin and the safety clip
8. Switching to the wheel. Use a clean rag and the alcohol, use liberal amounts of alcohol to clean the disc rotor, both sides. Don’t touch the clean rotor with bare fingers / hands
9. Switching back to the bike, ensure there is a nice wide gap between the new pads you installed, then put the wheel back on the bike.
10. Check the centering of the rotor in the caliper. Use one eye and look straight at the caliper and judge if the rotor is sat in the center of the gap. In most cases if you have just replaced pads, the rotor will be centered. If it isn’t centered see “centering rotor” below.
11. Ensure the wheel is in correctly and slowly squeeze the brakes, do this several times.
12. New pads require breaking in to become most grippy. Follow in the breaking in instructions that came with your new pads. Normally this is riding at a slower speed, apply brakes gently but firm almost to a stop but not quite. Do this five times. This ensures your pads will operate most efficiently.

Pro Tip. If you have pistons that won’t push in easily / easy-ish… put the old pads back in the caliper, then use a large screwdriver on the inside of the old pads to twist and apply larger force or leverage to spread the pads apart, pushing the pistons back into the caliper.

Super Pro Tip – only attempt this if you are very comfortable with your skills. When the pads are out of the caliper, advance the pistons using the brake lever taking care that you don’t over advance them so they fall out. This allows access to clean deeper on the exposed sides of the pistons making future operation smoother and more consistent. Only clean with alcohol, and a cotton bud / q-tip is the bomb for this. Never put oil or degreaser in here.

Centering the Rotor

Why? – centering will create a more even braking experience and also remove any rubbing noise if that is occurring.
First make sure yoour wheel(s) are tight and correctly mounted in the frame. The basic premise is the rotor is fixed in location but the caliper position is adjustable on the frame attachment. Normally fixed by two 6mm bolts or T25 bolts. Loosen the bolts and adjust the location of the caliper so that the rotor runs in the center of the caliper gap. I will adjust this by eye, but there are tools you can purchase that assist you with setup.
There is also another way you can try, I have 50/50 luck with this. Loosen caliper bolts slightly so the caliper can move a little, squeeze brake lever (theory is caliper will move and center on rotor) then tighten the caliper to frame bolts.

Note: if you do any of these procedures always double check the bolts are tight before riding. – working disc brakes are important

Disc Rotors

The part attached to your wheel wears down also. In general pads wear out much quicker than rotors, but if you ride a lot then you should check your rotors every year or so, or even take a look when changing pads. If it looks thin and sharp it probably needs changing. Otherwise get your local bike shop to check. Manufacturers of the disc rotor say if it measures less than 1.5mm thick on the active braking surface then it’s worn and needs to change. To measure you will need special measuring calipers that most people don’t have, unless you are an engineer or mechanic. That’s why I say go to a bike shop. New rotors range from $20 to $80.

p.s. GALFER pads ….

I’m checking out these lesser know, but well experienced brand from Spain. Large in the moto world, Galfer offer high quality at a normal price point. GALFER. So far with 80miles on them I have good things to say, but let’s wait for a little while to see how they settle in.

p.p.s. Finding the right pads

Matching and choosing by shape is the best way to approach this. Here is a great link that lets you identify pads and look at the shape and features. Cross referencing with other guides and pads in hand can give you extra confidence you got the right ones.

https://jagwire.com/products/brake-pads/disc-brake-pads

Good Luck ….Comments, issues, problems. Comment below, I check the messages 🙂

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