I knew disc brakes on road bicycles was a tech topic on your minds because I received a number of emails about them, which prompted me to write about them in the first place.
And now, after providing an overview of how they work and some basic pros and cons, for the past two weeks in Part 1 and Part 2 of this series, you submitted some excellent feedback from your experiences with them that I can share. Thank you!
Below are the best comments and emails that came in, with a few additional thoughts from me beneath. As always, keep the conversation going by posting on our Community Comments page.
Frequent correspondent Bob Eltroth wrote “I wouldn't be too quick to dismiss well set-up cable-actuated disc brakes, Jim. For touring on the road, they have an advantage that they're easier to fix on the road a couple of hundred miles from a bike shop. They're also easier to pack if the bike has S&S couplers (frame-splitters). Have you seen any quick release hydraulic line couplers? It’s easy to find cable splitters.
“I have hydraulic disc brakes on mountain and cargo bikes, but our coupled touring tandem has cable discs, although we sometimes change out the rear wheel for a rim brake and Arai drag brake for loaded touring with major hills.
“Unfortunately, it's common to see mismatched cable levers and calipers on road bikes with cable-actuated discs. We happen to have mountain calipers, but Cane Creek makes levers with the proper pull for them. Of course, we also happen to use bar-end shifters for touring so we aren’t dealing with shifting braking and can use whatever brake levers we need.
“And, to add to your cons list, Jim, one disadvantage of disc brakes for loaded touring is trying to find rear racks that accommodate them. Some have the skewer run through them, causing difficulties changing flats on the rear wheel.”
Road and mountain biker Steve Fenn pointed out, “Regarding overheating: Yep, no more rims getting hot and wearing out to the point of cracking. But disc brake rotors get hot. On a 26-inch-wheel mountain bike I thought mechanical disc brakes were great! Especially after moving from rim brakes and doing 5-mile, or longer, downhills. No issues.
“But on a 29er MTB, on those same 15-24% downhills, with the stock 160mm diameter rotors, the rotors were turning blue and screaming and squealing. I replaced the rotors and pads and experienced the same thing. I upgraded to Shimano XT ICE disc brakes with 160mm rotors and the same thing happened. Finally, I ended up installing 180mm rotors front and rear. Now, the heating isn’t a problem and I pretty much have one-finger super strong braking action.
“So, knowing my experiences on a 29er, which is close to a road bike’s 700c wheels, l wonder if 160mm rotors will handle the 20-24% paved descents I ride? It might be necessary to go to 180mm. I'm squeezing pretty darn hard on my rim brakes for now.
“Also, maybe a larger disc rotor is all it would take to make a set of mechanical-disc brakes with smaller diameter rotors stop much more powerfully?”
Tips: Speaking of hot rotors, Steve, it’s worth pointing out that excessive heat during braking can warp the rotors and mean having to straighten them. So you don’t want to ride the brakes to that extent if you can help it. Also, if you stopped after a long downhill and had to remove your wheel to put your bike on your car, etc., it’s a good idea to remember not to touch a hot rotor.
Longtime tourist and frame-builder Mark Perkins offered his perspective, which goes back a ways.
Mark says, “Before the new generation of disc brakes came on the market, back in '92, I designed and built a front and rear drum-brake-equipped bike for loaded touring and even off-road use. It was a good choice at the time, especially for someone who wants to avoid rain or mud compromising their brakes.
“I used Sturmey-Archer drum-brake hubs, which were sealed-bearing hubs that worked really well for what they are, but not as good as today's disc brakes. (FYI: The brake shoes in those now 22-year-old drum brakes still don't need to be replaced, and should be good for at least another 22 years!)
“My main point is that although most articles I've read about the new road bike disc brakes mention their use on road bikes meant for single-day rides, the advantage these brakes should have on a touring bike should be even greater. This should be a natural use for these brakes.
“I do realize that a huge percentage of bicycle tourists use mountain bikes or hybrid bikes, some of which already come with disc brakes. But I don't tour on a fat-tire bike, and want to use these disc brakes on 700 x 32c wheels on a nice touring bike for excellent braking when I’m traveling with all my gear.”
Tip: I lost the person’s name who offered this tip (sorry), but loaded touring usually results in more flat tires. And that’s another reason for disc brakes, which make wheel removal and installation quicker and easier, since there are no brake pads to have to fit the tire through.
A reader with the username SportVelo feels the way I do about discs on performance road bikes. He commented, “Thanks for the clear, concise write-up on disc brakes for road bikes, Jim. I couldn't agree more with your personal conclusion: that for road riding and racing this technology is overkill. Disc brakes make sense on motor vehicles (both 4 and 2 wheels (speed, suspension, and weight)), plus mountain bikes, and cross bikes for the possible extreme conditions.
“I'm certain the ultimate performance of hydraulic discs can be better than cable-actuated calipers, but measured against the added complexity, different loading forces and weight, it just doesn't add up for me. If and when this becomes the de facto standard (service, and parts repair availability), I'll be a very late or non-adaptor.”
A roadie who goes by jerryh3052 offered a good warning for some of us who might soon have bikes with disc brakes and bikes with standard ones. He writes, “I have 2 road bikes, an older Giant Cadex with standard brakes, and a 2-year-old Marin Lombard with mechanical-disc brakes. I am quite satisfied with the Marin but find the biggest challenge is for the first 5 minutes or so when having changed bikes I need to remember the correct amount of pressure to apply to stop the bike or risk being surprised by the power.
“Also, I have not had to have the disc brakes adjusted between tune-ups and am always having to adjust the standard sidepull brakes. For that reason alone, I would much rather have the mechanical-disc brakes than standards. Hopefully, I’ll get to try the hydraulic brakes to experience the difference from mechanicals.”
Lastly, here’s an idea from reader Russ Starke, who wrote, “With most of the braking power of vehicles coming from the front, why not put a disc on the front and leave the rear brake traditional? More bikes could be updated with just a new fork, instead of new frame/fork, and it would be less expensive, too.”
Cool idea, Russ. Thanks! And thanks to everyone else, too.
Jim Langley has been a pro mechanic and cycling writer for 38 years. He's the author of Your Home Bicycle Workshop in the RBR eBookstore. Check 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 7,370.