Rear brakes wear quickly - do I need redundant rear brakes?

Question

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

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.

Answer 1

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.

Answer 2

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.

Answer 3

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.

Answer 4

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.

Answer 5

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.

Answer 6

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.