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Hello Travis,
Last month I had a customer bring in his bike for service after his hydraulic brakes completely failed on his gravel bike. Let’s call him Fred. Unfortunately, Fred’s bike had never been serviced at all since it was purchased from me in 2018. Also unfortunately, many folks, such as Fred, don’t bring their bikes in for service until something fails. Components wear out gradually and usually the rider never notices because their bike feels the same from ride to ride. Then, something fails (like Fred’s brakes – and he also needed much, much more work performed).
I always make a point of explaining to customers when they pick up their new bikes that are equipped with hydraulic disc brakes that the hydraulic fluid will need to be replaced, but many times it falls on deaf ears or gets forgotten. Most bikes purchased now have disc brakes, no matter the discipline (road, gravel, mountain, comfort, hybrid, commuter, etc.) and they need to be maintained regularly.
I’d like to explain some steps for you to take that will make your bike rides safer and more enjoyable.
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Bedding-In
When a bicycle is new or has had the disc brake pads and/or rotor replaced, there is an initial “bedding in” process that must be performed for the brake system to work optimally. Unlike rim brakes, which usually have some sort of rubber compound brake pads that squeeze either an aluminum or a carbon rim surface to stop, disc brakes use pads with more abrasive compounds (Metal, Ceramic, etc.) that squeeze against a stainless-steel rotor.
The disc brakes are way more powerful but need to be set up correctly – they need to be “bed in”. Bedding in disc brakes allows the brake pads and rotors to establish an optimal level of friction. During the bedding-in process, the brake pads are heated and gently worn into the rotor’s surface. This takes time to do, so unfortunately, many bike shops don’t do this when assembling new bikes, especially bikes that are priced lower and sell more than “fancy bikes”. Heck, even some of the stores that sell the upper-end bikes don’t do it. Also, if you’ve purchased your bike online and assembled it yourself, you NEED to make sure that the bedding-in process is performed.
So how is the bedding-in process performed? Rather than making this email longer than it already is by explaining the process, I’d rather share with you Park Tool’s video on how to do it properly. (click the link). You’ll want to perform this whenever you purchase or build a new bike, or whenever you install new pads and/or rotors. This is how JRABS has done it for years, on every new bike or as an extra service after new pad and/or rotor installation. It’s worked well and has performed the job, but it’s not consistent – there’s no way any human can pull the brake lever with the exact same amount of force every time as well as be going the same speed every time.
So, I’m changing the way I bed-in brakes. From here on out, for every brake bed-in procedure (for tire’s up to 3”), I will be using the Sinter Smart Bedding Machine (or you can purchase one for yourself by clicking the link). I’ve chosen this machine for a couple reasons: 1) consistency and quality 2) Weather: Rain, snow, sleet, cold, hot, sandstorm, or whatever – I can do it in the store without having to wait for the weather to be nice 3) Time – Each brake with this machine takes between 3 to 5 minutes vs. me going out in the parking lot for 20 minutes (remember, I’m a one-man show here).
Didn’t buy your bike or parts from me? No problem! If you assembled your bike or installed new pads and rotors yourself, I’d be happy to do this for you (for a fee, of course). Just let me know.
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Facing
Ok, so this should have probably been first. Why? Because it should be performed on most bikes before the disc brakes are installed.
So, what is “Facing”? Facing is making the mounting surfaces square to each other. Yeah, I know that that might not mean anything to you, but it does to bike nerds like me. Here we go….
Disc brake calipers are mounted the frame and fork by two bolts – all of them. There are different attachment types: flat (most gravel and road bikes, IS (International Standard – most front discs before flat mount arrived), and Post Mount (also before flat mount and is common on suspension forks).
No matter what the attachment types, they are attached by two bolts. Those two attachment points must be both perfectly parallel to each other – if they are not, then the brake caliper will be out of alignment which could: 1) make it impossible for the disc brake pads to not touch the rotor (when it’s not supposed to) 2) increase rotor wear by not clamping it evenly and square.
You’d be surprised at how much this service must be performed – all manufacturers, price levels, types of bikes, etc. I’ve had $15k bikes in my stand that were horrendous, and $500 bikes that were perfect. It’s a crapshoot.
I use a couple of different disc brake facing tools, depending on the configuration (which are plentiful). For bikes with quick-release axles, I use the Park DT-5.2 Disc Brake Mount Facing Set. For bikes with thru-axles I use the VAR Brake Mount Facing Tool, which is way better than the Park DT-5.2 but can’t be used with non-thru axles brake systems.
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Bleeding
This is the maintenance that must be performed on ALL hydraulic disc brakes. As stated earlier, I tell every customer who purchases a new bike from me and it has hydraulic disc brakes, those brakes will need servicing.
When you pull your brake lever, it pushes the hydraulic fluid through the hose and into the caliper. The caliper holds the brake pads, which are pushed into the rotor by ceramic pistons. When the brake pads are pushed into rotor, brake dust from the pads and any other debris is being sprayed onto the exposed ceramic pistons. When the brake lever is released, the pistons retract back into the caliper, bringing the dust and debris into the closed system. This is how the fluid gets contaminated and needs to be replaced (or bled). Heat is also a factor that can break down the fluid and warp the rotors.
So when should a bikes brakes be bled? There are many factors: Where the bike is ridden (mountains, rolling hills, flats, etc.), rider weight (heavier rider = more braking force applied), braking technique (if a rider only uses one brake it will wear out twice as fast, or if a rider brakes hard to stop rather than anticipating stops and “feathering” the brakes). A bike that’s ridden consistently in rolling hills should be maintained at least once per year. A bike that’s ridden on flat surfaces every once in awhile can go a few years. A downhill mountain bike racer can need them bled after a hard weekend.
Once you pull your brake lever and you feel sudden power loss, or significantly less power than the last time you rode – it’s time. I recommend also replacing the brake pads when the brakes are bled. They need to be removed to bleed the brakes anyways, so why not just do it then – they’re not that expensive.
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Rotors
Most rotors measure 1.8mm – 2mm thick when they are new. For most brands they’ll need to be replaced when the get to be 1.5mm thick. Usually, you’ll go through at least a few sets of pads before the rotors need replacing, unless they become warped, contaminated, or glazed. Glazing occurs when the brake pads or rotors develop a hard, shiny surface due to excessive heat buildup, often from repeated hard braking.
Your rotors should be sized to match the amount of force applied, which depends on rider weight and where the bike is ridden. Most braking force is applied through the front brake, so it is usually larger – Most road bikes come with a 160mm front rotor and either a 140mm or 160mm rear. Generally, a rider over 200lbs should have a 160mm rear rotor on a road bike as the 140mm one will overheat and wear out faster.
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E-bikes
E-bikes weigh more than standard bicycles, especially those that are used for utilitarian purposes. They also go faster, which sometimes requires harder braking. If you have an E-bike, expect all brake components to have roughly half the life expectancy of those installed on regular bikes, and expect them to need to be serviced more frequently.
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