How To Adjust Disc Brakes On a Bicycle: Why Your Disc Brakes Are Failing

Written By: Jonathan
Fact Checked By: Caroline Dezendorf
Reviewed By: Matt Tanner

Now-a-days disc brakes have become the standard braking system on modern bicycles due to their powerful stopping power, reliability in wet or slushy conditions, and significantly less maintenance when compared to older rim brakes.

So, whether you have a mountain bicycle, road bicycle or hybrid bicycle, chances are it uses either mechanical or hydraulic disc brakes.

Also, according to market analysis by Future Market Insights, disc brakes actually now account for over 65% of new bicycle brake systems worldwide, and this really shows just how reliable and widely adopted they have become.

But no matter how good your brakes are, they need to be properly adjusted to work safely and efficiently.

If you have poorly adjusted disc brakes, this can cause annoying rubbing noises, inconsistent braking, or even cause them to stop dangerously when you need them to.

This is where this guide on how to adjust disc brakes on a bicycle comes in really handy, as you know how to inspect, align, adjust and tune your disc brakes, you can ride your bicycle with confidence, ease and most importantly, safely.

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Tools

Tool/Material	Purpose
Allen wrenches (usually 5mm or 6mm)	This is a great tool to use for loosening and tightening bolts.
Bike stand (optional)	Yes, it is indeed optional but it gives you easier access to the wheels and brakes.
Isopropyl alcohol & cloth	You can use this for cleaning rotors.
Rubber gloves (optional)	This is also optional, but it really helps to keep your hands clean from brake fluid.
Rotor truing tool (if needed)	Rotor truing equipment is actually designed to gently bend the rotor back into its shape without damaging it.

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Let’s Understand Disc Brake Types

There are two main types of disc brakes available on bicycles: mechanical disc brakes and hydraulic disc brakes.

1. Mechanical Disc Brakes (Cable-Actuated)

Indeed, mechanical disc brakes come with a standard steel cable that is similar to the cable used in traditional rim brakes: that’s how it pulls the brake caliper and applies pressure to the rotor.

Also, these brakes are very easy to install, and simple to adjust and are also very cost-effective, which is why they are a popular choice for beginner cyclists or those who want a budget-friendly disc brake bicycle.

Yes, they do not really depend on the fluid system, that is the basic reason why they are also easy to maintain at home and do not require any special kind of equipment.

However, over time the cables on these mechanical disc brakes can stretch or rust: this can subsequently reduce braking performance, unless you adjust them regularly.

2. Hydraulic Disc Brakes (Fluid-Actuated)

And on the other hand: Hydraulic disc brakes actually use a sealed system filled with brake fluid which is usually mineral oil or DOT fluid to transmit the force from the brake lever to the caliper.

Also, this setup allows for really stronger, more consistent braking power and that is why they are so efficient on wet, muddy or sloped conditions and that is why they are so popular.

Also, this is the main reason why hydraulic brakes are commonly found in high-end mountain bikes and road bicycles.

Not only that, but the brake pads can also be adjusted manually as they wear out, which essentially means there will be less need to tune them as frequently.

But hydraulic systems are actually more complex and you need special types of equipment to maintain them and the process of maintaining them is called bleeding which is literally removing air bubbles from the fluid lines, and if you don’t do this process correctly, it can directly affect the brake performance.

3. Key Difference Between the Mechanical Disc Brakes Vs Hydraulic Disc Brakes

Feature	Mechanical Disc Brakes	Hydraulic Disc Brakes
Activation	It actually pulls a cable.	To activate it: This ideally pushes fluid through the brake hose.
Maintenance	Yes, it is easy to maintain and requires only basic tools.	It is actually more complex, which is why it requires specialized tools for its maintenance.
Braking Power	Braking power is good.	It has much stronger and more consistent braking power making it a more popular and safer choice.
Common On	You often see these on entry-level bicycles.	It comes with mid-range to high-end bicycles, which are also expensive options.
Adjustment Frequency	You actually have to adjust them manually and you will have to do this more often.	Hydraulic disc brakes are self-adjusting, which is why you have to adjust them less often.

So, this is the first step because you actually need to first understand what type of braking system your bicycle has so that you can make adjustments for that system only.

Mechanical systems are generally more beginner-friendly and hydraulic systems actually offer better performance but also require more care.

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How to Diagnose the Problem in the Disc Brakes

Let’s first understand the warning signs of what device is not working properly so we know what type of adjustment we need to make to your disc brakes.

Disc brakes are designed to provide really powerful, smooth and consistent stopping power: but that’s true of any part of your bicycle as they can wear out or become misaligned over time, this is why you need to learn to recognize the early signs of trouble so you can easily avoid major problems and keep your bicycle safe.

So, here are the most common problems that indicate that your disc brakes actually need adjustment.

1. Brake Rubbing Against the Rotor

If you hear a slight scratching or pulling noise while cycling, even if you’re not pressing the brake lever at all, this usually means that the brake pad is actually rubbing against the rotor.

And this could be because the caliper isn’t centered properly, causing the rotor to be slightly bent or even the pad clearance is too tight.

While it might seem like a harmless sound, the constant rubbing can actually wear out your brake pads faster and is actually responsible for significantly reducing the efficiency of your bicycle.

2. Weak Braking Power

So, when you actually press the brake lever and it feels soft, sticky or you feel that the bicycle is not slowing down effectively, it is a sign that your brakes actually need adjustment.

Additionally, for mechanical disc brakes, the cause could be cable stretching, which also reduces tension.

And for hydraulic brakes the reason could be that the brake line is filled with air and hence the system needs to be bled.

It is obvious that poor braking is very dangerous, and it becomes even more concerning in traffic and when driving at high speeds.

3. Uneven or Pulsing Braking

If your bicycle stops really unevenly or you feel a pulsating sensation through the brake lever, the cause could be a warped rotor, uneven pad wear, or dirt and debris between the rotor and pads.

Therefore, this can really make braking unpredictable and even very dangerous at higher speeds or on technical roads.

4. Squealing or Squeaking Noises

If you hear a rattling noise when you apply the brakes it often means that the rotors or pads are dirty or possibly contaminated with grease, bicycle oil or sweat, and these are one of the most common complaints in the braking system.

Also, in some cases, the cause could also be glazed pads, which basically happens when the pads get overheated and become hard, which is actually responsible for reducing their grip.

So, you can clean the braking surface with isopropyl alcohol, as that might help, but if you notice that the squeaking sound is persistent, then the pads might need to be replaced or even the rotor sanded.

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How to Adjust Mechanical Disc Brakes

In fact mechanical disc brakes are found on most entry-level and mid-range bicycles.

Plus, they are relatively simple to adjust and you can do them at home with the help of some basic tools.

As these brakes use a steel cable that pulls the caliper arms and puts pressure on the rotor and even some small changes and adjustments you make to the cable tension or caliper alignment can really make a big difference in how smoothly and safely your brakes perform.

Centering the Caliper

This is actually the most common cause of disc brake rub, as the caliper is misaligned, as the caliper is the part that actually holds your brake pads and it needs to be perfectly centered around the rotor so that it can avoid contact when the brake lever is not pulled.

So, here’s how to actually center the caliper:

1. Loosen the Caliper Mounting Bolts

Using a 5mm or 6mm Allen wrench, slightly loosen the two bolts that actually hold the caliper to the bicycle frame.

Also, you don’t actually need to remove them, you just have to loosen them enough so that the caliper can actually move from side to side.

2. Squeeze the Brake Lever Firmly

So, while you loosen the bolts, you now need to hold down the brake lever, as this will actually force the caliper to center on the rotor since both brake pads will be applying pressure equally from each side.

3. Tighten the Bolts While Holding the Lever

Now, you need to tighten the caliper mounting bolts evenly and firmly, without releasing the lever.

And once you have actually done that, you need to release the brake lever and spin the wheel, thus now your rotor should spin freely without any kind of rubbing problem.

So, this is actually a method that works pretty well because most modern mechanical disc brakes are actually designed to self-align when pressure is applied to them while tightening.

How to Adjust the Disc Brake Pads

So, now you’ve centered the caliper, you may still need to tune how close the brake pad should be to the rotor, because this is where the pad adjustment and cable tension really come into play:

1. Use the Barrel Adjuster (Cable Tension):

On most brake levers or calipers you’ll need a barrel adjuster, which is essentially a small dial that you can easily turn by hand.

So, when you turn it anti-clockwise it increases the tension of the cable, which basically means that it moves the brake pad closer to the rotor, thus speeding up the response.

And if you turn it clockwise it reduces the tension as it moves the pad back.

You should always make small adjustments and then test the brake lever after each turn, so that you can easily know the best adjusted setting without damaging it.

2. Adjust the Pad Position (If Caliper Has Pad Screws)

Yes, some mechanical disc brake calipers actually have a small dial or screw on the inside pad that actually allows you to move it closer or farther away from the rotor such as in the Avid or Tektro.

So this little dial or screw really helps eliminate uneven pad wear and brake rub, and you should turn the screw slowly when checking rotor clearance.

And you also want to make sure the pads aren’t so tight that they cause drag on the rotor when you’re not braking.

Note: If you do these adjustments together it will surely help you restore full braking performance and then it will eliminate the annoying problems like squeaking, pulling or weak stopping problems in mechanical disc brakes this also makes a huge difference in the quality and safety of your bicycle ride.

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How to Adjust Hydraulic Disc Brakes

Hydraulic disc brakes offer virtually strong, smooth and highly responsive stopping power that really makes them the top choice for modern mountain bikes, gravel bikes and performance road bikes.

So, instead of using a steel cable as we’ve seen in mechanical systems, hydraulic brakes actually use pressurized brake fluid, which is either mineral oil or DOT fluid, to transfer the force from the brake lever to the caliper.

Yes, it is also true that they are self adjusting but hydraulic systems also need tuning, yes they need tuning much less frequently but if there are problems like rubbing, weak braking or pad wear then they also need your attention.

How to Align the Caliper of Hydraulic Disc Brakes

Even if you have a hydraulic system, misalignment of the brake calipers is actually one of the most common reasons why brakes rub or cause them to stop unevenly, and you can fix it easily by following these steps:

1. Loosen the Caliper Mounting Bolts

First, you’ll need to use a 5mm or 6mm Allen key, then gently loosen the two bolts that actually attach the caliper to the frame or fork, as this actually allows the caliper to float freely on the rotor as well.

2. Squeeze and Holt the Brake Lever

Once the bolts are loose, you will now need to press the brake lever firmly.

As the hydraulic system will automatically center the caliper, both pads will apply equal pressure to the rotor from each side.

3. Tighten the Bolts While Holding the Lever

Now, you have to hold the lever down and then you have to tighten both the caliper bolts evenly and securely, and once you have done that, simply release the brake lever and spin the wheel so that you can check that the rotor is spinning freely without rubbing.

4. Check Rotor Clearance

Now, you need to look at the caliper from the top or side to make sure there is equal space between the rotor and both pads.

And if you still notice that they are still rubbing then the rotor might be slightly warped, so in that case you will need to correct it.

In fact, this method works completely safely and reliably, as the hydraulic system provides consistent pad pressure during alignment, which also helps to center the caliper automatically.

How to Inspect Hydraulic Brake Pads

Therefore, over time hydraulic brake pads also wear out and lose braking efficiency.

That’s why you should perform regular inspections which are important to ensure safe performance, and specially for riders who frequently ride in wet, muddy or sloped conditions.

1. Remove and Visually Inspect the Pads

Now, to properly inspect your pads, you have to first remove the wheel and then take the pads out of the caliper with the help of a flat tool or your fingers, just check your brake brand or the exact steps for removal as well. Also, check the thickness of the braking material.

2. Check the Minimum Thickness

Yes, this is very important as most manufacturers actually recommend that disc brake pads should be replaced when the friction material is 1mm thick or less.

And if the metal backing is damaged or shows some uneven wear, then it’s the ideal time to replace it immediately.

3. Check for Glazing or Contamination

In fact, if you notice that the pads look shiny or feel too hard, it might be glazed over caused by overheating, and this leads to less grip and squealing noises.

And if the pads have become contaminated with oil, brake fluid or dirt then cleaning or replacement is actually necessary.

Therefore, changing pads on time actually ensures both safety and braking stability, and it also becomes very important specially at high speeds or emergency stops.

Moreover, when you align the calipers and also ensure that the brake pad wear should not cross that 1 mm mark, it remains a really responsive, quiet and powerful hydraulic disc brake.

Although hydraulic systems actually require less maintenance than any mechanical system they still benefit from any regular checks and basic adjustments are enough to keep your ride smooth and safe from all the problems of squeaking or unwanted sounds.

Furthermore, thermal studies show that during heavy braking with power up to 400W, the disc temperature can actually rise to 500 K, which significantly affects the pad friction characteristics and which increases the risk of fade during prolonged use.[¹]

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How to Fix Disc Brake Rotor Rub

This is also a common problem and is actually a big problem for cyclists, and in the case of disc brake systems, it is a very frustrating problem.

And that’s exactly what happens when the rotor, which is the thin metal disc that’s attached to your wheel’s hub, strikes one or both of the brake pads as the wheel turns, even when you’re not pulling the brake lever.

Because rotor rubbing can cause a really frustrating noise, which also reduces efficiency and leads to premature pad wear if you don’t fix it in time.

1. Spin the Wheel and Identify the Rub

First of all, you need to lift your bicycle up so that you can rotate the affected wheel easily, and you can even use a bicycle stand or turn your bicycle upside down for this purpose.

Just turn the wheel slowly and then look very carefully at the brake caliper area as there may be a scratching sound or you may hear or even feel a slight vibration in the rotor.

In addition, you will also need to pay attention to where exactly the rotor is rubbing, and this will let you know which part is actually slightly out of alignment.

2. Gently Bend the Rotor Using a Truing Tool

Now, if you’ve noticed that the rotor is slightly warped or bent, you’ll need to realign it with the help of a rotor truing tool: a simple, flat tool specifically designed to straighten brake rotors without damaging them.

Now, you need to gently insert the tool into the part of the rotor that is rubbing and then apply light and careful pressure in the opposite direction of the bend.

Also, keep in mind that you should always make small adjustments, as minor errors don’t take much time to fix.

Additionally, you should avoid using pliers or your hands as this could worsen the problem or even leave grease on the braking surface.

3. Re-Check the Alignment

After correcting the bend on the rotor, you now need to spin the wheel again and check if the rubbing is gone.

And sometimes it takes some tweaking to even get the rotor to spin perfectly straight, so just look from above or through the caliper window so you can easily make sure there’s equal space on both sides of the rotor and that it’s not actually touching any pads while it’s spinning.

IMPORTANT: Brake rotors are actually made of stainless steel and can warp slightly from heat, bumps or improper storage. And even brand new rotors may have a slight bend from the factor, this is why it is completely normal for the rotor to be slightly warped and something you can easily fix at home. But, if you find that the rotor is severely bent, cracked, or worn thin altogether, the best solution is to replace it for safety’s sake.

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How to Clean the Disc Brake System

You really must keep your bicycle’s disc brake system clean and this is literally the most important but overlooked step, as it maintains strong, safe and squeal-free braking.

Because over time, brake rotors and pads actually collect dirt, dust, road grime, chain lubricant or even skin oils from your fingers, and while these contaminants may not be visible, they can actually severely degrade braking performance and they can also cause high-pitched squeals and even dull or damage brake pads.

This is why regular cleaning is required, which prevents any brake damage and squeaking and keeps your brakes quiet, strong and reliable even in wet, muddy or dusty conditions.

1. Wipe Rotors and Pads

To safely properly clean braking surfaces, you must use 70% or higher isopropyl alcohol with a clean, lint-free cloth.

So, just gently wipe the rotors which are metal discs and if possible just remove the brake pads and then clean them as well.

Plus, isopropyl alcohol evaporates quickly, so it leaves virtually no residue and doesn’t harm the braking surface either.

And you should never use any kind of soap, degreaser or water as it can leave a slippery film which is responsible for virtually reducing the braking effectiveness.

2. Avoid Touching Rotors with Bare Hands

In fact, your fingers also naturally produce oils, which can contaminate the rotor surface, and even if your hands appear perfectly clean, they may still contain oil.

That’s why you may want to wear rubber gloves when handling rotors or brake pads, or at least hold them by the edges.

3. Keep Oils and Grease Away from Brake Parts

When you actually lubricate your bicycle chain or drivetrain, you need to be very careful that the oil or grease does not get into the brake system.

As lubricants can easily stain the rotor or pads or spill while riding, you need to be extra careful, specially when you’re using a spray lubricant.

And to prevent this, you should cover the brake rotor with a clean cloth when applying lubricant to the chain, and therefore always wipe off any excess lubricant after application.

IMPORTANT: You can easily clean your brake system after riding in the rain, snow or on off-road trails, and just a quick cleaning can remove mud, dust or moisture that can cause rust or noise. So, basically regular maintenance actually improves the performance and it also increases the lifespan of your pads and rotors which is very beneficial in the long run in terms of saving money.

Read More:

How To Install Gear Shifter On Bike

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Conclusion On How To Adjust Disc Brakes On a Bicycle

When you adjust disc brakes correctly it actually provides more powerful, consistent and very reliable stopping performance in all types of riding conditions.

If you want to extend the life of your pads and rotors, you need to get them checked at regular intervals as this also prevents that annoying squeaking or rubbing sound.

Do you still have unanswered questions in your mind then ask them in the comment section.

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Frequently Asked Questions

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References:

[1] Feier, I., Way, J., & Redfield, R. (2020). Bicycle Disc Brake Thermal Performance.
https://www.researchgate.net/publication/342204829_Bicycle_Disc_Brake_Thermal_Performance_Combining_Dynamometer_Tests_Bicycle_Experiments_and_Modeling