By all counts, the disc brakes vs rim brakes debate should have been over by now. It’s far from it. People continue to rummage the web asking if they should buy a road bike with disc or rim brakes.
In this post, I’ll try to shed some light on the pros and cons of both systems to help you understand what this disc vs rim brakes fuss is all about.
The Birth of a Bicycle Disc Brake
Hayes developed the first bicycle disc brake system in 1996 and released it to the market in 1997. The invention took off and by the end of the century everyone wanted a disc brake on their bike.
Mountain bike that is.
The road cycling world, constrained by tradition and UCI regulations, remained cold to the idea. Shimano and others tried to introduce disc brakes to the market but they didn’t catch enough attention. The innovation died a quick death.
Plus, most people thought disc brake is a solution to a problem we don’t have on our hands in road cycling — we don’t ride in mud, we don’t clog our brakes with it. Rim brakes worked for decades, nothing to innovate here.
It took the advent of adventure cycling for the industry to realize, hey, these adventure bikes with disc brakes we sell like hot cakes, maybe we can offer road bikes with disc brakes, perhaps we can sell them too.
In fact, the thinking went, if people want them, we’ll sell more bikes. It’s going to be a new road bike category. Let’s do this.
Few years on and we’re still debating the disc brakes vs rim brakes question.
The Basic Difference Between Disc and Rim Brakes
It might be obvious but it needs to be said for clarity’s sake: what’s the difference between a disc brake and a rim brake?
How Disc Brake Works
- In a disc brake system, you have a brake caliper attached to a fork blade and a rotor to the wheel hub.
- When you squeeze a brake lever, the cable (in a mechanical disc brake) or the brake fluid (in a hydraulic disc brake) transmits the force to the brake pads.
- The brake pads push on the rotor to slow down or stop your bike.
How Rim Brake Works
- In a rim brake system, the front brake caliper bolts to the fork’s center at the top and the rear caliper to the brake bridge between two seat stays.
- When you squeeze a brake lever, the cable transmits the force to the brake pads the same way it does with disc brakes except the pads now push against the rim, not a rotor, to stop the bike.
Now let’s look at the pros and cons of each system to help you make an informed choice.
Rim Brakes: The Pros
- Cost: Although you can find expensive rim brakes and cheap disc brakes, rim brake is a cheaper proposition from engineering and manufacturing point of view — less parts, simpler design. Take two identical bikes and the disc version will always cost more.
- Weight: Rim brakes, as a system, weigh less. With two identical bikes side by side, a rim brake version will generally weigh less by a good pound (see disc brakes cons for more details).
- Maintenance: Set it and forget it — for months, not forever. Once a year or so, you’ll have to get new cables and brake pads. A good bike mechanic can do this job for you in half an hour if you can’t do it yourself (check YouTube if you want to learn, you’ll need some tools though).
- Reliability: This pro applies only to hydraulic disc vs rim brake angle but you need to know it (it’s important) — it’s possible for a brake cylinder to fail. The result — no brakes. With rim brakes, you can snap one cable (happens all the time) and still make it home safe and sound with one working brake.
- Aesthetics: A hot issue in the disc vs rim brakes debate. Me, bikes with disc brakes have too much meat on them.
Rim Brakes: The Cons
- Performance: No contest here, disc brakes 1, rim brakes 0. Zero doesn’t mean rim brakes fall short in their duty to stop your bike. They work fine (in the dry, see disc brakes pros) but how they work and how much control you have over braking — rim brakes lose.
- Tire clearance: Rim brakes limit the tire width you can fit to your wheel (a fat tire won’t fit between brake pads).
- Heat build up: Under heavy braking and given enough time, the heat generated by the brake pads may blow up your inner tube. A typical example is a long, steep decent where you have to work your brakes for longer to control the speed.
- Alignment: It’s possible for a brake pad to go out of alignment and start eating into the tire. If you don’t catch it on time, you’ll blow up your tire and may not be able to repair it on the road.
- Clogging: Mud or snow may clog your rim brake.
- Grabbing: A dent on a rim or debris and braking residue buildup in one spot will cause uneven braking that will grab the brake in that spot.
- Myth con: In the disc brakes vs rim brakes debates, disc brake advocates like to bring up this point: they say rim brakes wear out from braking. Over time, you need to either get new rims or new wheels. It’s true, rims do wear out (everything does). Question is, how long does it take for brake pads to thin the rims to a breaking point? The answer: tens of thousands of miles. A long time. Sand and wet debris speeds up the wear but the process is long enough for this to be a moot point as far as rim vs disc brakes debate goes.
Disc Brakes: The Pros
- Performance: This is the disc brakes’ Ace of Spades. They work in all weather conditions with a tiny loss of performance in the wet. In the rain, rim brakes don’t grab the rims hard enough until friction dries the rims and the pads for the brakes to start working properly.
- Slack: Hydraulic disc brakes don’t suffer from slack common to cable-actuated brakes (both rim and disc). Their performance doesn’t change over time while rim brakes’ performance deteriorates as cables stretch and housing gets clogged with dirt.
- Heat: Disc brakes generate plenty of heat but it stays on the rotor.
- Tire clearance: Ride any tire width you want as long as it fits your frame. Bike manufacturers take advantage of this and make frames to fit fat tires good enough for off-road cycling.
- Bike transformation: You can transform a road bike with disc brakes to an off-road beast if you swap your road wheels with narrow tires to a pair with fat ones.
- Auto adjust: Hydraulic brakes (not mechanic) self-adjust as the pads wear out.
- Out of true wheel: When you break a spoke and the wheel goes out of true, it won’t bang on your brake pads.
- Precision: Disc brakes give you a wide range of force you can apply to the braking — more control.
- Clogging: No such thing. Mud or snow, just ride.
- Braking residue: After a rainy ride, your bike won’t be covered in filthy residue you see on bikes with rim brakes.
Disc Brakes: The Cons
- Cost: Between 2 identical bikes, one with rim brakes and another one with disc, a bike with disc brakes will cost more. Like it or not, bikes with disc brakes cost more to manufacture.
- Cost of service: Disc brakes cost more to service over the life of a bike. Brake manufactures recommend bleeding your hydraulic brakes once a year and pads wear out faster than pads on rim brakes.
- Weight: A road bike with disc brakes will weigh more by about a pound (450 g) compared to an identical bike with rim brakes. It’s not the brakes that add weight — it’s the heavier wheels and more material on the frame and fork added to deal with forces disc brakes unleash to these parts of a bike.
- Brake steer: Because disc brake caliper sits behind a fork blade only on one side, you may experience a brake steer under heavy braking on a fork with weak rigidity.
- Safety: Because of the physics involved, heavy braking can pull your front wheel out of the fork. For this reason, if you want to buy a bike with disc brakes, make sure the fork on it is a closed fork.
- Rotors: Easy to bend. A bent rotor should go to a bin.
- Rubbing: Sometimes hard to stop a rotor rubbing against the caliper. Noisy and annoying.
- Howling: Disc brakes may howl for a bunch of different reasons: brake pads or rotor contamination, bent rotor, wrong setup or wet weather. Hydraulic disc brakes may also howl from a resonance created by frame’s vibration under heavy braking.
What Bike Should You Choose?
Reasons to choose a bike with disc brakes:
- It’s the only bike you own.
- You ride a lot in the rain and need reliable braking in wet conditions.
- You want to ride off-road without buying an off-road bike.
- You don’t care about extra weight.
- You don’t mind paying more for a bike with disc brakes vs rim brakes bike.
- You’re OK with spending more to service your disc brakes.
Reasons to choose a bike with rim brakes:
- You know how to handle braking in the wet with rim brakes.
- You want a lighter bike with rim brakes vs disc brakes bike.
- You don’t want to pay extra for the bike and disc brakes maintenance.
- You care about aesthetics and prefer the look of a bike with rim brakes.
- You plan to buy another bike to ride it off-road.
- You don’t want to fiddle with setting up disc brakes or pay someone to set it up for you.
- If you want to start racing, you won’t have a problem getting a spare wheel in a race for your bike with rim brakes if you puncture. A wheel for disc brakes — forget it. Okay, you might get lucky but by the time you swap the wheels, you’ll be down by at least a minute.