These days, disc brakes are almost universal on mountain bikes, and quite common even on the lightest-weight road bikes. They’re gone from a bit of a luxury to a fairly standard part.
But when anything gets that popular, it’s hard to tell fads from actual improvements.
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Here’s whether disc brakes are actually better on bikes?
Disc brakes are better than rim brakes in terms of sheer stopping power and predictability in wet or dirty conditions. Disc brakes also make it easier to remove and insert wheels. However, they’re harder to service, more expensive, and slightly heavier. Rim brakes remain popular because of their better modulation (feel), simplicity, and lower cost. Both types perform well when properly adjusted, but demanding terrain or weather may tilt the balance toward disc brakes. It is possible to convert a bike from rim to disc brakes, but it’s generally not worth the cost or effort.
In brief, the answer for you depends heavily on the terrain and weather you’re riding in.
But for most urban riders, their benefits are a bit exaggerated.
We’ll briefly look at how disc and rim brakes are designed, then get into some pros and cons to help make the right choice a little clearer.
How disc & rim brakes work
Both rim and disc brakes work by squeezing some sort of disc.
For a rim brake, the “disc” is actually the wheel itself. Because it’s so far from the point of rotation (the hub), it doesn’t take much clamping force to slow you down.
If you needed to stop a spinning merry-go-round, you’d try to do it from the edge, not from near the center, right? Much easier! That’s the same physics principle at work with rim brakes.
With proper adjustment, this works terrifically well. It was the standard design for many decades until motorcycle disc brake technology made its way into the bicycle market.
With a disc brake, the “disc” is called a rotor. It attaches directly to the hub, which means all the braking force is applied to one side of the hub and consequently one side of the frame.
That requires special reinforcement of the frame and fork. It may also require building the wheel a little asymmetrically to compensate for the width of the rotor mount. (As we’ll see below, this is why converting a rim-brake bike to disc brakes isn’t straightforward or generally worthwhile!)
Anyway, because the rotor is so much smaller in diameter, the brake needs to be extremely strong. Like in our merry-go-round example, you would need a whole lot more strength and traction/grip to stop it from near the center.
This extremely high clamping force builds up a lot of heat. Disc brake rotors have holes in them primarily to help dissipate heat, and also to help shed water and debris.
Hydraulic vs. mechanical disc brakes
Almost all rim brakes are mechanical (a.k.a. “cable-actuated”), meaning they’re tightened and released via a cable that runs up to the brake lever. (Hydraulic rim brakes do exist, but they’re extremely uncommon, especially in North America. They’re essentially the worst of both worlds, in my opinion!)
But disc brakes can be either mechanical or hydraulic. Mechanical ones are simpler and cheaper, but they can’t always produce as much force. They also require more frequent adjustment that many riders find irritatingly finicky.
Inexpensive mechanical disc brakes are just plain terrible. Even though they’re predictable when wet, they may have far less power than decent rim brakes.
Hydraulic ones, or at least good hydraulic ones, produce much more power that most mechanical options. They also self-adjust (to some extent) so that the pads keep themselves just the right distance from the rotor at all times. They’re not totally set-it-and-forget-it, but they’re relatively hands-off once properly adjusted.
Types of rim brakes
There are about four common types of rim brakes on the market today.
V-brakes (more formally called linear pull) are the norm for anything with wider tires: fitness/hybrid bikes, older mountain bikes (before disc brakes took over), and some cyclocross bikes. They are the most powerful kind, and sometimes come in a “mini-v” version for road and cyclocross bikes that require a little less power.
In fact, good v-brakes can be just as powerful as some disc brakes. They can clamp down very hard, and because the rim is effectively a “disc” itself, that adds up to tremendous braking power.
Cantilever brakes also fit wide tires nicely, even if not quite as wide as v-brakes. They’ve long been popular on cyclocross and touring bikes, and were also common on mountain bikes before v-brakes came around. They sometimes lack in power, especially compared to v-brakes, but can provide terrific modulation and feel.
Dual-pivot and center-pull brakes have been standard on road bikes for decades. They can perform and feel terrifically, with more power than you might expect. They encircle the tire, so they require longer arms to accommodate bigger tires. Longer arms may feel flexible and “mushy,” and perhaps less powerful, which means dual-pivot and center-pull brakes are best for bikes with relatively narrow tires.
That’s not quite the full spectrum of brake designs, but it covers everything you’re like to own or find. There have been others over the years, but they’re too rare to bother covering here.
Roller brakes: another option for urban cycling
Some bikes, like bike-share models and classic Dutch designs, need to withstand year-round outdoor storage with essentially no maintenance.
One key part is the use of roller brakes. They’re a type of drum brake, meaning fully sealed away inside the front and rear hubs, and totally protected from weather.
Mechanically, they’re like the coaster brakes on beach cruisers and kids’ bikes, but with more power and better modulation. Weather doesn’t affect their performance at all, and maintenance seldom involves more than a squirt of grease.
Older models were on the weak side, but newer versions like the Shimano IM80 perform remarkably well. They feel a lot like good mechanical disc brakes, in my experience.
On the downside, roller brakes are a bit costly and heavy, but it doesn’t matter much on a fully-equipped city bike. The only real issue is that deeper maintenance is quite an undertaking. They often go years without being touched, but finally opening them up will be a complex and perhaps expensive job.
These are disappointingly hard to find on bikes made for the North American market. Fortunately, it’s not too hard to find European imports like WorkCycles from the Netherlands or Pilen from Sweden. If you ride at a relaxed pace, and want to minimize maintenance, then you’d do well to find a bike with roller brakes.
We won’t compare them below, however, since they’re just not a common option for most readers.
4 major advantages of disc brakes
Disc brakes wouldn’t be so popular if they didn’t bring something seriously valuable to the table.
It turns out they have several unique advantages, which we’ll dive into here. Keep in mind that everything assumes they’re of decent quality and have been set up appropriately.
1. More braking power
Assuming we’re talking about hydraulic or good mechanical disc brakes, you’ll get significantly more stopping power. In some cases, we’re talking enough power to stop a heavy rider bombing down a mountainside with just one finger on the lever.
Now, this site focuses more on city and transportation cycling, so suffice to say that’s plenty of braking power for your commute or grocery run.
(Bad mechanical disc brakes on cheap bikes are another matter, and I’d categorically avoid them. You’ll know them when you try them…)
2. Consistency in grimy conditions
The other major benefit of disc brakes is that rain and mud barely affect them. Between their tremendous clamping force and the holes in the rotors, conditions just don’t matter that much.
If you ride in significant mud or snow, then that’s a good reason to opt for disc brakes.
But if rain is the harshest condition you regularly face, then you may not need disc brakes after all. (And as a year-round commuter in the Pacific Northwest, I’ve learned a thing or two about riding in the rain!)
When rim-brake pads drag on the wheels for a couple of revolutions, they push most of the water away, and start to feel surprisingly “dry” again. If you make a habit of dragging the brakes very lightly as you roll around town, then your braking doesn’t have to suffer when you need it. And it’s always a good idea to ride conservatively and avoid hard stops in the rain anyway.
One minor drawback is that rim brakes wear down rims more quickly when they’re wet and gritty. In perpetually wet places like my native Seattle, that’s a reasonable argument for disc brakes if you’re a very high-mileage rider. But unless you crank out many thousands of miles per year–much more than the average commuter–it’s not likely to be a regular problem.
3. More tire and wheel choices
If you’ve ever thought of switching to a much wider tire or swapping your 700c wheels for 650b, then disc brakes make it easy.
They’re not a position to interfere with a wide tire, and a smaller or larger wheel diameter is unrelated to the disc caliper’s position.
But for everyday cyclists who just want to get to work and the grocery store and their kid’s dentist appointment, tire and wheel choices aren’t much of a concern. If you’re more on the sport or touring side of cycling, then it’s great to have that flexibility, but the practical benefits are limited.
4. Painless wheel removal/reinstallation
One minor nuisance with rim brakes is that you have to release the calipers in order to remove or reinstall the wheel.
Hopefully, that’s such a rare occurrence that it doesn’t even matter. But if you also need to haul your bike inside a vehicle, or on certain roof racks that require wheel removal, then disc brakes are one less thing to fiddle with.
Just remember that hydraulic disc brakes should always have spacers (like these) inserted whenever the wheels are out. Otherwise, one accidental squeeze of the lever will jam the pistons firmly together. (That’s the downside of self-adjusting calipers!)
4 ways disc brakes fall short
1. Less subtle modulation
Generally speaking, rim brakes have better modulation than disc brakes. That means it’s easier to control power very subtly, as opposed to a more binary, “on/off” feel.
As we’ve covered, the extremely strong clamping force of disc brakes does help them perform well in terms of sheer power. But it also makes it harder to apply them in a gradual, delicate way. They tend to lack the more subtle and gradual feel of well-adjusted rim brakes.
This might be the single biggest reason many cyclists still prefer rim brakes. That’s especially true in city and road riding, where sheer power isn’t as relevant in the first place.
2. More mechanical complexity
Frankly, it’s rare that disc brakes fail these days. It was another story back in the late 90s, but it’s not a common occurrence today.
Short of a tree branch ripping a brake line out, it’s just not something most riders in non-extreme conditions need to worry about.
But when it is time to tune or repair a brake, you’re in for a bigger ordeal with disc brakes than with tried-and-true rim brake designs. The latter might be a 5-minute tweak at home with common tools. The former can involve a trip to the bike shop for a full fluid replacement (“bleeding”).
Again, any modern brake is likely to serve you without issues as long as it’s set up properly in the first place. But as a practical urban cyclist, I like to avoid things I can’t readily fix. For me, disc brakes fall on the wrong side of that line.
3. Changing mounting standards
In my couple decades of cycling, I’ve seen at least four or five disc brakes standards come and go.
Rotor sizes also change.
Together, this means dozens of possible configurations with little guarantee of future availability.
(To be fair, most haven’t truly gone away, but gradually fade away as manufacturers shift to newer standards.)
But during this same period, I’ve seen precisely zero mainstream changes in rim brake standards. They just work, and always will!
4. Slightly higher price and weight
Price and weight come last because they’re rather trivial in the big picture.
Weight hardly matters when your bike is set up with fenders and racks and lights. Still, it’s only fair to point out that disc brakes will add at least a few ounces above and beyond rim brakes.
The cost difference isn’t a game-changer, either. That said, a good v-brake like the Shimano Deore (available here) costs around $20, but a solid cable disc brake like the Avid BB7 (available here) is upwards of $70 as of writing. Those prices are per wheel, and hydraulic discs cost more, of course.
Can I upgrade my bike to disc brakes? Should I?
If you’re still thinking disc brakes make sense for your riding, then you might wonder if it’s really necessary to replace the entire bike.
It is in fact possible to upgrade most bikes to disc brakes, but I don’t recommend it. To understand why, let’s look at what that upgrade would involve.
Disc brakes require two special things:
- Disc-specific hubs
- A caliper mount on the frame and fork
That’s in addition to the actual brake set, of course.
Regarding hubs, it’s possible to have your current wheels rebuilt with disc hubs. That’s rather expensive, though, so it’s usually a better deal to sell the current wheelset and buy a new disc-specific one.
As for mounting calipers, that’s easy to do in the front by installing a new, disc-compatible fork. Aftermarket ones like the Surly Disc Trucker fork are readily available if your bike has a 1 1/8th” threadless steerer, which looks like this:
If in doubt, check with any bike shop first!
Note that vintage bikes and most traditionally-designed modern bikes have a 1″ threaded steerer and quill stem. It’s extremely hard to find disc brake forks for these, and may even require a one-off design from a custom frame builder. (The reason is that buyers of more traditional modern bikes usually prefer rim brakes–myself included–so there’s just no market for this sort of “upgrade.”)
For the rear brake, you can still find conversion kits like this one from Chaser Tech. There used to be several on the market, but fewer companies make them anymore since disc brakes are so common and inexpensive.
If you’re mechanically inclined, then here’s a great walk-through of the installation process:
You may be able to find cheaper options like a simple bracket, but I wouldn’t use one personally. As mentioned above, disc brakes focus nearly all of the braking force onto one side of the frame. When a frame isn’t reinforced for that stress, there’s a higher chance of flexing and/or cracking than I’m comfortable with. The costlier kit above will disperse the force better (although it’s still not ideal).
Clearly, upgrading a bike to disc brakes isn’t a simple task.
A new fork ($150), rear mounting kit ($50), decent disc brakes ($150) and cheap or secondhand wheels ($100) brings the total to about $450. And that’s with just entry- to mid-level parts and completely DIY labor! Random cables and housing and hardware might add a further $10-$30.
Seeing as new road, mountain, and city bikes with disc brakes all start around $500 or less, I’d strongly recommend going that route. Another consideration is that your bike may have even less resale value after disc brake conversion. No matter how well it works, it’s an unconventional set-up that few (if any) used-bike buyers will want.
Conclusion: when disc brakes are & aren’t better
The focus of this site is urban riding first and foremost. Disc brakes certainly don’t hurt in that setting, but they’re rarely necessary.
Mountain biking on steep terrain and/or in muddy conditions is an ideal scenario for disc brakes. That’s largely what created demand for them in the first place.
They’re also valuable on heavily-loaded cargo bikes, which can build up a ton (literally!) of momentum. Tandem bikes also use them in the rear, at least.
If your riding is practical and relaxed, then well-adjusted rim brakes should suffice.
It’s my experience that wet weather alone doesn’t necessitate disc brakes, either. “Feathering” your brakes as you ride–that is, very gently dragging them for a few seconds–will shed water and help them perform surprisingly well even in the rain.
But if your riding really does demand disc brakes, or you’d just feel more confident with them, then it’s best to buy a new bike. Upgrades are certainly possible, but will cost hundreds in parts and quite a bit of labor, too. Unless your current bike is somehow irreplaceable, then you’re better off buying a different bike altogether.