On my bikes I find that I wear out the rear brake a lot faster than the front brake. In fact, I tend to avoid the front brake, and any time that I've used it exclusively, bad things would happen (like the rear of the bike flying over my head as I rush to get away from this flying heap of metal).

So I'm thinking... given that a disc brake system is just a pad that presses against the disc, has anyone considered attaching two completely independent sets of rear brakes to a single disc?

I suspect that one would need a single handle for activating both sets of rear brakes but I'm pretty sure it's not impossible. Apart from the obvious "your frame doesn't have mounts for two brake systems", are there any other reasons why this would be a bad idea? (Cost, weight etc. not being a factor.)

Clarification: my question is about the mounting of two sets of brake pads, specifically. I already know that two hydraulic lines can be merged (e.g., using Outbraker).

Clarification 2: just to reiterate (again), neither cost nor weight nor the complexity of the system are a factor for me, in other words I'm perfectly prepared to live with all of that, provided I get a more reliable, effective and powerful rear brake. The goal isn't just to reduce maintenance but to provide extra power to the rear brake.

Update 3: here's a photo

dual rear calipers

Update 4: I have accepted one of the answers below, but you should know that I'm definitely doing it -- going to install a second caliper on the rear brake, will probably also extend the size of the rear brake disc to the (rather expensive) Hope 203 rotor. Will post a picture and report when finished.

Update 5: someone might be reading this, so I wanted to give an update on something that I mentioned earlier - Outbraker, the two-hose variety. Basically this thing allows progressive braking with both calipers at the same time. I have installed it for a person who can only use the left hand for braking, and for that purpose it works rather well! The brake calipers no longer have a 'bite point' as the Outbraker acts like a time-delay mechanism.

Update 6: just wanted to post an update on the whole Outbraker thing. Long story short, v1 of Outbraker fell short of its described functionality -- it is actually pretty impossible to bleed, and it seemed to be losing air. Now, to be fair, Outbraker did send me v1.5 for free, but I haven't tested it, since changing brake lines is not a normal occurrence for me. So that's where we're at - nowhere. At least with Outbraker.

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    You should really consider using the front brake also. You’ll stop much faster.
    – Eric S
    Commented Feb 6, 2018 at 22:38
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    The redundant system that backs up the rear brake is ... the front brake. Commented Feb 6, 2018 at 23:10
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    Learning the physics of the braking process is also liberating as knowledge scares away superstitions and urban legends. Commented Feb 6, 2018 at 23:23
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    I applaud the maker of Outbraker (linked item) for their contribution to natural selection. It couples the independent front and back brakes removing redundancy. A failure (e.g. fluid leak) in the brake lever means no braking. I fail to see how it accounts for varying surface conditions, slope and rider weight distribute, so it will rarely achieve optimal braking (despite their claims). I see it as being extremely beneficial in a few limited cases - e.g. one armed riders, but able bodied cyclists should learn to use brake - its not really that hard.
    – mattnz
    Commented Feb 6, 2018 at 23:45
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    Not trying to disparage your riding, but it does sound like you need to work on your braking technique. In short, you should be moving your body weight backward (bum off seat, straighten arms and legs and "moon" to your 6 o'clock). The front brake should be on as hard as possible without breaking tyre traction AND without lifting the rear wheel. and the rear brake is there as a backup and helps to keep the bike going straight. The rear brake only has whatever weight is on it while braking, so that's why you push your bodyweight backward.
    – Criggie
    Commented Feb 7, 2018 at 10:18

6 Answers 6


The system you suggest has no benefit. The effectiveness of the rear brake is limited by the fact that braking moves your weight forwards and off the rear wheel. The brake you already have should already be capable of skidding your rear wheel. This tells you that the limiting factor isn't the power of the rear brake, but the grip of the rear tyre. Making the rear brake more powerful won't make you stop faster: it just makes you skid sooner. And bear in mind that skidding is not the fastest way to stop – that (and keeping control) is why cars have anti-lock brakes.

Instead, you need to practise using the brakes properly. If pulling the front brake sends you over the handlebars, you're pulling it too hard. Brakes are not binary: they're not just "on" or "off". Learn how much front brake you can use without endangering yourself (practise on a quiet street at gradually increasing speeds) and remember to brace against the handlebars as you brake so your weight doesn't flop forwards.

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    Good explanation of the physics of the process. It is worth underlining the final point of this reasoning once again: once your wheel is blocked and skids, the braking force has reached its limit and will not increase no matter how hard you continue pressing the brake lever. Another point, less obvious for those who missed their physics classes, is that "rolling" wheel friction is higher then skidding friction . Thus, it is counterproductive to block wheels. That is why cars have ABS systems Commented Feb 7, 2018 at 4:34
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    @Kaz I don’t think so. In the days before ABS was common, the advice was to let off the brakes and reapply them, repeatedly if necessary. ABS modulates very quickly, which allows you to stay right on the edge of the skid, getting maximum braking. Without ABS, you’re not going to be right on the edge but you should still be able to get more braking than a skid. Skids don’t brake you very hard because, as Grigory points out, static friction (the contact point of a rolling tyre isn’t moving with respect to the ground) is significantly higher than dynamic friction (tyre skidding across the ground) Commented Feb 8, 2018 at 9:48
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    By the way, folks, a wheel that’s not rotating because the brakes have been applied too hard is “locked”, not “blocked”. Commented Feb 8, 2018 at 13:48
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    @Kaz to clarify David's point, that was about cars, which take rather more than 2 seconds to stop if they start skidding (2 seconds is a reasonable approximation at a range of realistic speeds on a dry road, when skidding isn't all that likely)
    – Chris H
    Commented Feb 8, 2018 at 21:29
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    @Kaz ffden-2.phys.uaf.edu/211_fall2002.web.dir/ben_townsend/… This site has tables with static and kinetic friction coefficients for tires+asphalt. They show that if you are even moderately competent modulating your brakes, you are much better off not skidding, the difference between static and kinetic friction is so large.
    – Nobody
    Commented Feb 9, 2018 at 22:44

There are 4-piston disc brakes for bicycles that in a sense accomplish the same thing. Some have had 4 pads and others just 2 really big ones. The rotor's ability to manage heat is a bottleneck to the whole concept. You can of course get a bigger rotor, but at that point you're doing a lot of work to mitigate being nervous about the front brake, which leads to the next issue here.

The rear brake or brakes have slowed down the bike as much as they're going to once they lock the wheel. Getting that level of braking power in sufficiently demanding conditions isn't just a given, like how for example it sometimes might require a brake like the aforementioned 4-piston downhill/freeride brakes, but it's generally pretty attainable with existing designs.

Most cyclists who have been doing it for a while get pretty strongly opinionated against any brake system that downplays the front brake. The reason is that physics dictate that for the bike to stop as fast as possible, you need to stop the front wheel. It's best to develop mastery with the front brake, because you need it for emergency stops.

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    The physics of braking is so that the more the rear brake is efficient, the less "weight" comes to the rear wheel. Less weight means skidding starts earlier, which means the rear braking force limit is reached earlier. To keep rear axle weight high you will need to move the center of gravity closer to it, ideally behind it, to reverse the effect. But that is essentially turning the rear wheel into a front wheel! Commented Feb 7, 2018 at 4:45
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    @DmitriNesteruk It's physically impossible to stop a bike using only the rear brake in less time than it would take using both. You simply do not have the same efficiency when using only the rear brake. You will stop faster if you use the front brake too. Commented Feb 7, 2018 at 18:40
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    During my MC licence course I learned that ~90% of the braking power comes from the front wheel/brakes, this is because the weight is shifted towards the front when you brake. So it is a good idea to learn to primarily use the front brakes whenever possible. And yes, this applies to bicycles as well.
    – David
    Commented Feb 8, 2018 at 8:04
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    @DmitriNesteruk You're wrong for most riding. On surfaced roads, even in the wet, you don't really need a back brake (you might need to plan for not braking on bends, but that's a good idea anyway). On dirt tracks, the same applies. Of course it's a bit different on MTBs, but you haven't clarified what type of riding you're doing (not that it changes the conclusion: learn to use your front brake)
    – Chris H
    Commented Feb 8, 2018 at 21:22
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    @DmitriNesteruk Are you talking about mountain biking? Because on a flat surface it's easy to ride without a rear brake. Commented Feb 9, 2018 at 11:00

The easiest way to have a redundant rear brake is to have a rear coaster brake with a rim brake or disk brake.

One could argue that fixies with rear rim brakes are doubly redundant.

Of course as David Richerby is pointing out, the real problem is your lack of front brake control, not with your rear brakes.

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    Or rim + disc, but your solution means no need to mount a second lever. Of course a lot of fixies with rim brakes were designed to have flip-flop hubs with a freewheel on one side, at which point the rear brake is a necessity.
    – Chris H
    Commented Feb 7, 2018 at 6:59
  • Plus-sized rims on bikes typically do not support rim brakes. But it's an interesting idea! Commented Feb 7, 2018 at 7:54
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    Huh?? You’re thinking caliper brakes. Plenty of V brakes support plus size rims.
    – RoboKaren
    Commented Feb 7, 2018 at 15:49
  • @RoboKaren Plus-sized rims typically do not have an edge that is suitable for either conventional rim brakes or V brakes because there is no surface area to break against - they are flush with the wheel. They are typically marked as disc brake only. Commented Feb 22, 2018 at 7:23

Focusing on the question of adding two brake systems to the same wheel:

I had a tandem that had three brakes - front and rear hydraulic rim brakes and a hub-mounted cable-operated drum brake which was for limiting maximum speed on a downhill.

The drum brake was set with a barend shifter, and was very much Set and Forget for the descent. This is quite common with touring tandems, and rare but not impossible on a touring single bike.

There is nothing stopping you fitting Rim and Disk brakes to a bike, as long as it has proper stops on the frame. Bolt-on disk brake mounts are useless hacks so avoid them.

Some bikes have caliper, canti and disk mounts on forks and/or stays, so you could have up to six separate wheel brakes, plus a coaster in the rear or drum/roller brake on the front and rear. However some riders would call this a mild case of overkill.

Your main problem with anything above 2 brakes is control. You only have two hands, and trying to run two brakes with one hand is going to give extra cognitve load in an emergency. Partial workaround could be two hand brakes and a pedal brake.

Side note:, you have another speed reducing system which is your posture. If you're descending too fast, you can sit up and catch some wind with your torso, and splay your legs to catch wind with your legs. Being less aero will reduce your top speed to something less exciting and more manageable. Not a braking system as such, but a valid technique anyway.

Stern note: That outbraker thing sounds like it should slot in for your specific use, but its marketed as a way to control two separate brakes from one lever. In some jurisdictions, a road vehicle is legally required to have two discreet and unrelated braking systems, so separate front and rear brakes with no common components.

Upshot, the outbreaker would be illegal in New Zealand as their website describes it, unless the bike also has a coaster brake or a second brake on the other hand functioning separately. Someone who needs that functionality to work around a disability would be well-advised to get approval in writing, to guard against legal liability issues if they were involved in an accident that could be blamed on braking somehow. Insurers are weasels and would totally do that.

  • There is no issue with control in the set-up I describe, though. For example, you can have Front+Rear1 on one handle amd Rear2 on another. Commented Feb 8, 2018 at 19:36
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    A half-unzipped jacket is a very effective air-brake for sustained descents. Not only does it pretty much double the width of your torso, it approximates a parachute in shape and therefore drag coefficient. Just be sure to zip it up again before you start pedalling
    – Chris H
    Commented Feb 8, 2018 at 21:34
  • @ChrisH also great for hypothermia and potential pneumonia, I imagine Commented Feb 9, 2018 at 7:41
  • @DmitriNesteruk that depends on your conditions. Jacket in this context often refers to a thin rain jacket, as worn when layering, so while it keeps the wind off it doesn't provide much insulation (and we often get intermittent rain) here so end up with the jacket on and a bit warm.
    – Chris H
    Commented Feb 9, 2018 at 8:15
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    @DmitriNesteruk Pneumonia is a bacterial infection. Unzipping your jacket doesn't cause bacterial infections. Commented Feb 10, 2018 at 9:48

Some tandems are set up with two sets of rim brake pads, so that both riders can brake independently. But the limiting factor here is heat dissipation -- both rims and disks can heat up with prolonged braking to the point where braking effectiveness is compromised, and doubling up on the pads only speeds this process.

If you want maximal braking while minimizing the over-the-top risks of the front brake, and complexity is not an issue for you, consider the scheme I've suggested before: A front brake which is activated by the rear one.

Basically, the rear caliper would be on a lever, so that, when activated, it would rotate with the wheel for a few inches. This motion of the rear caliper would then be transferred to the front brakes to activate them.

So the front brakes would only be activated when the rear wheel has traction. If the front brake is too strong and the rear wheel begins to lift, then its traction is lost and the front brake is released. A sort anti-lock brake system.

  • Interestingly, ABS is a system that's been made real by Bosch for ebikes: bosch-ebike.com/en/products/abs Commented Feb 7, 2018 at 7:39
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    You just reinvented SureStop :) bicycles.stackexchange.com/questions/46241/…
    – ojs
    Commented Feb 7, 2018 at 19:16
  • I’ve seen tandems with disk brakes and an additional rim brake on the rear wheel for the second rider.
    – Michael
    Commented Feb 7, 2018 at 21:10
  • @Michael I'm no expert on tandems, but I wonder if the second rear brake is operated by the stoker to avoid the captain having too many brake levers, while existing mainly to avoid overheating a single braking system on long descents. Rather like Criggie's answer
    – Chris H
    Commented Feb 8, 2018 at 21:32
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    @ChrisH: Yes, that appears to be the case. Maybe it’s also for psychological reasons so that the stoker at least has some control over the vehicle ;)
    – Michael
    Commented Feb 10, 2018 at 8:30

Your initial issue you state is that your rear brake pads wear out "too quickly".

With bikes there is no hard and fast rule as to which should wear out first. In a car the weight of the occupants has little or no bearing on how the brakes wear. The vehicle weight will shift as it will while breaking as the occupants are a small amount of the total weight and can't do much to change how that weight shift will occur.

On a bike you choose how to apply the brakes (biasing front or rear as you will, in your case rear) and you control your body which weighs significantly more than the bike. Anyone who has ridden significant rock faces can attest that body position will greatly affect your braking performance and can be the difference between having traction or locking up a specific brake.

If (as originally stated) your issue is brake pad life (not stopping power) then you don't have a problem. Replace the pads as needed. I go through rear tires much quicker than front. Do I switch to a tougher compound? No. What I care about is traction. If that means buying new rear tires more often, so be it. It's a wear item and I need to replace it as I wear it out.

If braking power is the issue (which is stated later as a goal) then step 1 is rotor size. I had a hardtail with 180mm front and 160mm rear. With my braking technique at the time I found the rear brake did not have enough power. I increased the rear rotor to 180mm and it suited my style perfectly. Inexpensive and just what I was seeking.

On my latest bike I had 180f/180r. I found the front braking power and bite to be not quite what I needed/wanted. I increased the front rotor to 200mm and it's perfect for me.

If rotors don't provide sufficient stopping power it's time to look at pad compounds then brakes (lever/caliper). A 4 piston caliper is going to give more power than a 2, but it varies on brand and model. The brake brand and model used isn't stated so it's difficult to provide advice. If you are running something like Code, Saint or MT7 brakes and don't have enough power with big rotors I'd hazard technique is at issue. No racers to my knowledge run dual calipers. I won't call them redundant since with a shared hydraulic line they are not redundant. If one fails they both fail.

Brake pads are cheap. If that's your issue, but them in bulk to save on shipping (and learn to replace them yourself if you aren't already capable.. it's easy). If power is the issue, buy a better rear brake (for MTB something like SRAM Code, Shimano SAINT, Magura MT7 etc). You don't have to run matching brakes front and rear, so upgrading one isn't a big deal. Most people want the same feel front and rear, but it sounds like you aren't getting what you want out of one end, so changing just one might be the solution.

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