Road Bike Disc Brakes versus Rim Brakes

Introduction

There has been considerable debate concerning disc brakes versus rim brakes ever since disc brakes were introduced on road bikes. The professional peloton was initially hesitant to adopt disc brakes over safety and weight concerns, but now all the pro teams ride bikes fitted with disc brakes. Let’s find out what the real advantages and disadvantages are based on my own experience. You may or may not agree with points raised in this discussion and my opinion, but that is perfectly fine as you need to use equipment that best suits your requirements and budget!

Braking Performance

For me, I found the feel of the 105 hydraulic disc brake levers a bit too soft with less initial bite. Whilst you could brake with less effort, I had to pull the lever more to get the same amount stopping power as the rim brake levers. Additionally, I found the 105 gear shift levers would contact my fingers when stopping in the drops (even with reach adjustment fully out). Unfortunately, there was no free stroke adjustment on those 105 shifters. Perhaps that may have allowed me to firm up the levers a bit.

However, after riding a new bike equipped with Shimano Ultegra R8170 12 speed disc groupset, I was eager to see if the new Servo Wave braking technology included in Ultegra R8170 would feel better. Quite simply YES, these new Ultegra R8170 disc brakes feel MUCH better to me, offering more initial stopping power with less lever pull than the old 105 hydraulic disc brakes. In every respect they feel better than my old rim brakes. But that in itself is not the main reason I changed to disc brakes.

Disc Brake Advantages

I believe the biggest advantage of disc brakes is how the braking works and feels nearly IDENTICAL in wet or dry conditions, unlike rim brakes which stop and feel different in the wet. In comparison I find there may be a short delay with rim brakes before the braking starts and then you need to pull the lever harder to get the normal amount of braking. If your are using rim brakes, be careful when drafting a rider with disc brakes in wet conditions, they will be able to stop a bit earlier, you don’t want a rear end collision. Other advantages of disc brakes include;

• No wear on your carbon wheels when stopping as there is no brake track.
• Carbon wheels can be designed more aero and built lighter as no brake track is required.
• If you are using an inner tube, you can choose any tube material you like. Latex tubes are not recommended for carbon clincher wheels when using rim brakes due to possible heat related punctures.
• If your wheels are out of true, it won’t affect braking performance on disc brakes. However, I recommend fixing any wheel that is noticeably out of true. If it is due to loose spokes, other spokes will usually be tighter and could break, ending your ride earlier than planned.
• As the bicycle industry has standardized disc brakes for road bikes, you will have more choices for future frames, wheels and groupsets.
• Bike frame designs are not subject to the same limitations of rim brake bikes. They do not require a bridge at the seat stays and spacing between fork legs and rear stays can be wider to accommodate larger tyres.
• Wheel thru-axles provide more rigidity to improve cornering stiffness.
• Hydraulic lines can be routed at more extreme angles than cables with less effect on braking performance.
• Less effort pulling the levers to stop the bike.

Disc Brake Disadvantages

I think the major disadvantage of disc brakes can be the loud squeal when stopping! Unfortunately, the pads/rotors can easily become contaminated which is usually the cause of the noise. Simple ways to contaminate the brakes include touching the rotor or pads with your fingers, allowing these parts to come into contact with bike products like degreasers, oils, grease etc. To be safe, I now remove both wheels from the bike before cleaning the drivetrain to avoid risk of contaminating these parts. I have also experienced pistons that do not retract fully after braking. It’s pretty simple to fix, but not something you would experience with rim brakes.

Other disadvantages of disc brakes include:

• Potential to bend the rotor when travelling with the bike or other possible other causes like crashes or mishandling. The rotor usually can be trued.
• Disc brakes add weight to the bike which no one really wants, but it’s only a small amount when looking at your overall system weight ie. You, your bike, accessories and clothing.
• Not as easy to travel with the bike ie. bike bags, removing rotors etc.
• Shift lever hoods tend to be more bulky which may not suit you.
• Bleeding hydraulic disc brakes requires extra tools and it’s a bit more complicated than working on rim brakes. It shouldn’t be required often, but situations to do this may include;
  • Swapping stems or handle bars if your brake cables are internally routed.
  • Replacing or working on headset bearings if your brake cables are internally routed.
  • You decide to replace with clean brake fluid as part of a service.
  • Changing brake pads may require a bleed if an earlier bleed was performed without using the correct brake block spacer and the pistons cannot be retracted enough to fit the new pads.
  • You get a leak or air gets into the hydraulic lines.
  • You want to strip down the frame and hoses are internally routed.
• Pad clearance is still fairly tight (even though it was increased in R8170), so the pads can rub on the rotor if;
  • Rotor is not true or warps due to excessive braking heat.
  • The caliper piston(s) don’t fully retract after braking.
  • A bit of contamination gets in between the pads.
  • The brake caliper is not centered to the rotor.

This sounds like a lot of disadvantages, but a lot of these situations shouldn’t occur that often. Regardless, it is a lot easier to clean and maintain bikes with rim brakes, they’re not as sensitive and just simpler.

Disc vs Rim Brakes: Stopping Power and Modulation?

In the dry, I can stop in about the same distance on either rim or disc brakes, but they do feel different at the lever. In the wet however, no contest, disc brakes are superior. Many reviewers will say that disc brakes have superior modulation, you have more feel at the lever and can brake later with more confidence. I will say disc brakes certainly require less effort, but I believe your braking skill (and feel of the brakes) really comes down to practice and familiarity. I recommend practicing emergency braking in a quiet side street to develop this skill. In particular, get to know your front brake as it does the majority of the stopping (ie. when braking the weight moves forward, so there is less weight & grip on your rear wheel). Be gentle using the rear brake to avoid lock-ups and skids under hard braking. Learn the braking feel of each lever and braking grip of each tyre by hard braking only using ONE lever at a time. No matter what your braking system, practice and familiarity will help you get the best out of it.

Conclusion

There are a lot of pro’s and con’s when it comes to disc brakes versus rim brakes. Ultimately, I believe the Shimano Ultegra R8170 hydraulic disc brakes are superior to rim brakes in both feel and stopping in the wet, but they require more work and caution to keep them running smoothly and quietly, plus they are heavier! But if you ride in the wet, disc brakes are sensational. If you only ride in the dry, then rim brakes still offer fantastic performance.

About Me.

I have been riding and working on my own bikes for many years now. I wanted to share my experiences, knowledge and research with others. My aim is to inspire people to get involved in all aspects of this amazing sport. Cheers.

Comments.

I welcome reader feedback in the comments section. Should you wish to suggest an amendment, please include a note advising the source of your information so that myself and other readers can ascertain the accuracy of your information. Note: Trolling or argumentative comments will be removed as they are counter-productive.