If this week’s Tech Talk title caught your attention, it was supposed to. But I didn’t really make it up – I pretty much stole it. I paraphrased the title of the online Outside magazine article that ran recently, Why You Should Throw Your Rim Brakes in the Trash.
The author basically says that discs on road bikes are so much better than rim brakes that you… well, you already know what he wants you to do with your rim brakes.
Rim brakes are disc brakes, too
The problem with this point of view is that it ignores the basic fact that rim brakes are essentially disc brakes. Instead of the separate discs (called “rotors”) attached to the hubs with disc brakes, rim brakes rely on much, much larger discs, the rims.
This much larger disc found on all road bikes with rim braking actually has a huge mechanical advantage over even the finest disc brakes. The first bicycle engineers way back in the 1870s already understood this.
The earliest bikes were directly driven by pedals attached to the front hub. Braking was done by holding back on the pedals the same way fixies without brakes are stopped today. It was and is a form of hub braking a little like disc braking.
But after only a few years of foot braking, the limitations were obvious and mechanical braking arrived. These first brakes weren’t very good yet because they rubbed on the tire, and only one tire. But they were attached to the top of the wheel, showing that engineers were taking advantage of the leverage principle.
Let’s fast forward to 2017 and hear from Santana Tandems, a company that has done a lot of brake analysis. When you’re designing the fastest descending bikesin the world and responsible for the safety of two riders per bike (or more), maximum speed control is all-important.
3 times the leverage
Quoting Santana, “On a 700c road bike rim brakes apply power at a leverage point that’s over three times more effective than that of an 8-inch disc. While rim brakes may seem crude or old-fashioned, a 300% difference in leverage (and braking power) can’t be ignored.”
That’s not to say that disc brakes aren’t powerful enough for single road bikes. Just that rim brakes offer even more power. Santana points out, for example, that a rear disc on a tandem cannot cause the rear wheel to skid. Yet rim brakes can easily do it.
So you might ask why some roadies love their new disc brake bike and swear that they brake so much better than their former rim brake bike. It’s entirely possible that’s the case. However, it’s probably because the rim brake system on the old bike is of lesser quality, old, worn out or damaged.
Disc brakes add weight
The other issue with disc brakes is that they make road bikes heavier. Yes, maybe it’s not enough additional weight to matter to some riders. But it’s undeniable that they’re heavier. And more weight means more energy is required to ride the bike.
One reason disc brakes are heftier is that they’re composed of more parts, mainly the rotors. Which also require a mounting place on the hubs, making them heavier, too. Plus, the cables/hoses are longer and for hydraulic discs there need to be fluid reservoirs.
The other thing that adds grams is beefing up the frame at the front and rear so it can withstand braking forces at the hubs. Note that rim brakes are attached at two of the strongest parts on the frame (seat stays and fork).
And even though cool mountain bike technology like thru axles are making their way onto disc brake road bikes to add the strength needed for the braking forces, these changes add even more weight.
Rim brakes, disc brakes, it’s all good
All of this is not to say that there’s anything wrong with disc brakes on road bikes. They work great, especially in wet weather. They also keep working even if the rims get damaged. And disc brakes don’t drag on and wear rims like rim brakes do.
But if the bike industry were to lose its marbles and follow Outside magazine’s recommendation and nix rim brakes for good, it would come at a cost in stopping power and pedaling efficiency. Which is a high cost if you’re looking for maximum road bike performance. Instead let’s just keep improving rim and disc brakes and let riders choose which they prefer.
For further reading on the pros and cons of disc brakes, the best article I’ve seen recently is by Jan Heine on his wonderful blog Off The Beaten Path.
Jim Langley is RBR’s Technical Editor. He has been a pro mechanic and cycling writer for more than 40 years. He’s the author of Your Home Bicycle Workshop in the RBR eBookstore. Check out his “cycling aficionado” website at http://www.jimlangley.net, his Q&A blog and updates at Twitter. Jim’s streak of consecutive cycling days has reached more than 8,000. Click to read Jim’s full bio.
Eric Irwin says
Really sad to see such a one-sided article about brakes on this site. I didn’t read the Outside magazine piece, but I’m sure it is just as one-sided the other way. Ok, so you tried to save it by giving disc brakes credit for their advantages (or some of them) in the final paragraph. After spending the entire rest of the article bad mouthing them, that final couple of sentences hardly makes up for it.
I rode rim brakes for decades. Saying that disc brakes only work better than worn out rim brakes is comical. Nothing about any of my rim brakes was ever really worn out. Other than pads and really old rims, there is much to be “worn out” to begin with. There are lots of comparison videos out there showing how both style of brakes perform side by side. It isn’t until the conditions get nasty that disc brakes really shine over rim brakes.
There is a weight penalty currently, not very much but to gram weenies that is all that matters. I’m sure that will get better with time. Most road bike disc brakes are just MTB brakes that have been slightly reworked to fit on a road bike. That is changing rapidly though.
I like the disc brakes on my Cross bike that I use for commuting. The are ready for any conditions from cold/snow/ice to a downhill on the hottest of days to a downpour of rain with all the sandy grit on the roads. I don’t have to think about how they will perform, I never have to replace or adjust another cable, I don’t have to recenter the calipers after changing a tire, etc.
Should rim brakes be thrown away? No. Should most people carefully consider both rim and disc brakes when purchasing a new bike? Definitely!
John Marsh says
Just to be clear, Jim’s piece was intended more as a “reply” or reaction to that Outside piece — which (obviously) was entirely one-sided.
I think most of us have a broad enough perspective to understand the utility of both types of brakes for different types of bikes and riding. They surely both have their places — which is why you SHOULD NOT trash your rim brakes.
I would suggest reading Jan Heine’s article, as well. He offers a broad-based perspective, to be sure. I think you might find his take very interesting.
Bike Fitness Coaching says
Everyone, all good points. I like Eric’s summary – “Should rim brakes be thrown away? No. Should most people carefully consider both rim and disc brakes when purchasing a new bike? Definitely! ”
My take on it is that when the weather gets to the point of disc brakes exceeding the performance of rim brakes, believe me, most people are not on their bikes!
Greg Titus says
It’s really the kind of cycling you do. If my climate had a lot of rain (Pacific NW), I’d for sure consider disc brakes. In drier climates discs would not be compelling. If I road single track, I’d use a mountain bike. If I’m on paved 2-lane roads, I’d use a road bike. The right tool for the job is just common sense. Evangelical enthusiasm for one-size-fits-all seems silly.
Layne Simpson says
I have been riding mountain bikes with disc brakes for about 10 years. A big advantage is a much lighter touch required on the brake lever. Anyone who has ridden a road bike with rim brakes on a very long and very steep descent knows how tired the hands can become on the brake levers. Another advantage to disc brakes is they are virtually unaffected by wet weather.
Larry K says
I vividly recall visiting my LBS years ago where a prominent pro customer was switching out brake pads on a new set of campy dual pivot brakes. He was looking for something with less friction because he said the new brakes had poor modulation and he was skidding where he didn’t want to. There may be a place for disks but for most of us consumers, good rim brakes with fresh pads is good enough–particularly if using aluminum rims and clinchers (overheated rims can soften glue with tubulars on long downhills and carbon rims don’t dissipate heat as well).
I actually question Santana’s claim that disc brakes cannot make the rear wheel skid on a tandem. What brake system did they use? What size of rotor? What about going on a long descent?
Dave H says
I ride a number of different bikes (road, CX and mountain), and after years of riding both rim and disc brakes, I can unequivocally state that disc brakes are by far superior. While disc brakes may add some weight, the advantages of the disc brakes far out-weight that issue (no pun intended). I have blown tires off rims on long steep descents due to rims overheating from braking. I have nearly crashed due to the inability of rim brakes to work in wet and sloppy conditions (particularly with carbon wheels). I have worn out rims due to sidewall wear. And I have experienced incredible forearm cramps from trying to apply enough pressure to my rim brakes. These issues are not due to the quality of my components (all my bikes have high end components), rather it is due to the fundamental inadequacy of the design. The force produced by calipers in disc brake systems exceeds that of rim brake calipers, particularly if the disc brakes in question are hydraulic. Also, because the discs are up close to the hub, they are less suscept to fouling than rims that may be within an inch of the pavement.
That said, I own a number of rim brake bikes (both my road bikes and my single speed) and I will continue to ride all of them. The purists and traditionalists may always shun the disc, but it is the wave of the future; as time passes they will get lighter and even more efficient. I can definitely say, the next time I am in the market for a road bike, the requirement for disc brakes will be near the top of the list!
It is mostly true. Two factors in play that are not obvious: The cable length is much longer than a single bike, so you get some cable stretch and housing compression and run out of lever; There is more weight on the back wheel of a tandem. I have not experienced it, but I suspect some of the new hydraulic brakes could lock the rear wheel.
John Schubert says
I think many riders would enjoy their rim brakes more if they used sandpaper or a file to buff the brake pads every few hundred miles. Use a plastic scouring pad on the rim surface too.
There, that narrows the performance gap.
I don’t think there’s a right or a wrong here. Pay your money and take your choice. (I’m sticking with the sunk costs of the rim brake bikes I already own, even though a week on a disc brake equipped CoMotion tandem has shown me that the discs are very good.) Economy and ease of maintenance matter to me. And good rim brakes have more stopping power than a bicyclist can use; the only issue is the ease with which the operator modulates brake pressure at maximum braking efforts.
My buddy Jim didn’t mention one point: if you’re comparing a hydraulic disc to a cable-actuated rim brake, the performance gap will widen. Hydraulics don’t have the friction that is common to all cable systems. (The hydraulic brake pioneer Bill Mathauser used to show this at trade shows, with dial indicators measuring the “squeeze” at the brake pads. With hydraulic brakes, you can modulate the squeeze far better than with cable brakes.)
Mike Feinstein says
My Campy rim brakes are great BUT my mountain discs are fabulous and I would put discs on a new bike purchase in a second!!
Santana tandems is way off the mark. I cannot believe they would endorse rim brakes – when everyone knows – and has for decades that rim brakes on the rear of a tandem will heat the rim and can cause blowouts. Even in the early 90’s I had an Ibis Tandem with a drag disc for this very issue. Now we ride a Cannondale with big discs ( not even hydro’s ) and I can lock them up without an issue and have done drifts to a stop with the back wheel locked up.
I have a Cannondale tandem – I lock the back disc all the time. they as simply mistaken.
My current touring bicycle has mechanical disc brakes. I have done many extended self supported tours using both a bike with rim brakes and a bike with disc brakes riding too many mountain passes to remember with at least 50 pounds of luggage on my bike. For touring purposes, disc brakes offer too many advantages over rim brakes. As mentioned by others, the brake type you select is dictated by how you use your bike. If you ride a lightweight racing bike on only sunny days, disc brakes are probably overkill. If you are touring with a loaded bike weighing 75-100 pounds, including your gear, or riding in the rain a lot, disc brakes should be your choice.
Larry Best says
I recently bought a new bike that has disc brakes. I wouldn’t have opted for them, but if I wanted that particular bike that’s what I was getting. I’m in a 350 member bike club & a lot of riders don’t have disc brakes. On virtually every club ride a couple of riders ask me how I like the discs. My answer is meh, they’re OK. It’s flat where I live so I can’t compare them when riding on mountains, but if I didn’t have them I don’t think I’d miss them. I will admit they’re great in the rain though.