E-bike Brakes thread, please add what you know

I found that the absolute braking power with properly set up rim brakes and disk brakes is about the same, but nothing can match the precision, sensitivity and repeatability of hydraulic disk brakes.

I've been using hydraulic disk brakes on a couple of my bikes for nearly two years, and I've never adjusted anything on them. That compares with my bike with rim brakes that's gone through three pairs of pads in the same distance, and loads of adjustments along the way. The effectiveness of the the rim brakes varies a lot depending on the adjustment and state of the pads.

With all brakes, whether rim or disk, you can improve the performance a lot by using decent pads. Most cheap brakes have cheap pads, which is why expensive cable disk brakes perform better than cheap hydraulic ones. If you put the same pads in each, you'll find that the hydraulic ones are better.

An important point for ebikes is the cut-off switches. It's very easy to install brake switches in cable systems. You don't have to use those crappy levers with switches. The "hidden wire" type fit in the cable just like a ferrule, and don't cost much. You can fit them at any position in the cable : either end, or anywhere along the length if you cut the cable outer.
http://www.bmsbattery.com/accessory/459-hwbs-hidden-wire-brake-sensor.html

The only hydraulic brakes that I've seen with switches are Tektro E-comp, or you can get an inline hydraulic switch from Magura, which is a bit messy to fit and requires that the system is bled afterwards. There's probably others now as ebikes become more popular.
http://www.ebike-easy.com/products/Bicycle-Parts/BionX-Press-Switch-for-Magura-brakes.html
 
I should have been more specific about my comment about a big fast downhill ride. The lame shit I do can easily fade the crap out of the cheap disks I have on my dirt bike. They would not be suitable for ski lift served DH riding where you bomb down huge descents. Or getting down really long paved routes at higher speeds. But they do brake with more precision than cheap rim brakes, and I can better keep from overbraking and launching with the disks. Or just skidding the tire. Fortunately, the kind of ride I do is still mostly within the capabilities of the cheap disk brakes I have. Nothing is worse on a big descent, than having a need for the brakes and suddenly they aren't there. Rocks and trees are not soft landings.

I don't do the kind of ride that would be likely to fade some very large diameter and robust hydraulic disks. Surely more metal surface area heats slower, and cools faster, so fade would be less of a problem. But that's not me speaking from experience. I'm assuming that would be the case.

Obviously, if you lock your brakes on loose surfaces, particularly your front wheel, you need to learn to ride. Just because you can lock certain kind of brake doesn't make any kind of brakes just as good in any situation. But if you can't lock em, they are crap.

There is a difference in several other categories, like ease of keeping it tuned for one. There are other kinds of issues with disks, you may overheat and warp the disk for example, or have trouble getting them to line up and clear a hubmotor cover. I definitely feel that the cheap disks give me a better fine touch on my brakes than cheap v brakes. I have experienced good rim brakes though, I had them on decent road bikes in my youth. Even in the wet, they worked fine. We used to gravity race in the rain on Emory Pass, a 10 mile 10% grade with huge cliffs to fly off of if your brakes didn't work well. I had no problems at all with Mafac racer center pulls on the bike. Those would lock a wheel on any surface anytime with ease. They had a great precise feel I don't get now from V brakes, so not locking them up was easy too.

Either rim or disk, good is good, average is average good, and crap is crap. You know at the first touch of your brakes which kind you are riding today.
 
d8veh said:
but nothing can match the precision, sensitivity and repeatability of hydraulic disk brakes.
Click to expand...

I'll bet you one drop of oil-- or heck, one drop of hydraulic fluid since you have some handy-- that you are wrong about that.

A little bit of contamination on rims doesn't usually affect braking much. Heck, rims are almost always at least a little bit contaminated. A little bit of contamination on a disc rotor is a whole other story. I've encountered very minor oil contamination of disc brake pads that I was unable to flush away with solvent or sand away with emery cloth, and I had to replace the pads. Tough luck if that happens in the middle of a difficult ride. Funny, though, if it happens because the hot disc rotor cooked some oil out of the hub's axle bearing grease. For this reason I believe disc brakes and sealed cartridge bearing hubs are natural companions.

If you brush a brake cable against a cable-actuated brake, it will still be as good as ever. But if you touch some hydraulic fluid to a hydraulic brake, bad things happen. Just a thought.
 
Really dig this topic :D

I've never seen so many facts about disk vs rim brakes like I see here :wink:

don't forget the main reasons why a lot of us use disks:
-rim brakes are rarely supported on "high end" frames, forks made for downhill / XC / freeride (and those are just the parts that we need/like to build 2kw+ ebikes) same counts for badass rims
-disks just look AWESOME! (no more crappy silver rim colour)

I've also seen someone mentioning the ebrake cut off being a problem:
it shouldn't be ;)

a reedswitch and a magnet mounted with heatschrink should fix that problem and is most likely cheaper then a dedicated system

314fmmr.jpg

(sorry been riding in the mud)
 
I don't know a single DH rider who would be willing to go back to rim brakes, despite most of them being maniacs about building light weight rigs. Don't get me wrong, rim brakes can work, but most of the time they let you down at the very moment you'd need them the most. Then, if you can ride 50 Mph a DH single track with both hands on the front brake, this might not be a turnoff to use rim brakes.
 
you are very welcome Spinningmagnets ;)

something that hasn't yet been covered about rim brakes:
it hurts like hell when the cable snaps or the screw breaks :evil: (specially the skin that is trapped between the lever and the handlebars hahaha)

there is a reason why nobody in the UCI DH world cup rides with rim brakes...

I've done downhill mountainbiking for a few years, going down offroad @ 70km/h+ speeds , braking as late as possible and can't really have a cable snapping at that moment :wink:

if rim brakes would be superior then we would also see motoGP happening with rim brakes :lol:

can't afford a tyre getting loose or popping due to the heat of the rim.... then I rather cook the oil in my bearings.
 
People keep coming back to off-road downhill racing-- but steep downhill slopes, unpaved surfaces, and racer-sized riders all sharply limit the braking forces that can be used without crashing the bike. It's like boasting about how powerful your bulldozer is because it can be carried on an airplane.

The riders who exert the highest forces and energies into their brakes are touring tandemists. Few touring tandems use discs except as backup or drag brakes, the same way they have traditionally used drums. The real stopping power comes from the rim brakes. Tandems are among the most expensive and lavish bikes available. If disc brakes were categorically stronger or more powerful than rim brakes, tandemists would have been among the early adopters, not the holdouts.

There are lots of reasons to use discs on a bike-- ability to use very wide tires or rims, ability to switch wheel sizes on the same bike, resistance to the effects of deep mud, relative cleanliness in persistent wet conditions, accommodation for weak grip strength-- but braking power isn't among them. Discs can strengthen brake lever response, but they can't strengthen braking power, all else equal.
 
3nslav3 said:
if rim brakes would be superior then we would also see motoGP happening with rim brakes :lol:

can't afford a tyre getting loose or popping due to the heat of the rim.... .
Click to expand...

dont you find it strange how all the pro road race bikes and teams still use rim brakes ?? :roll:

I suspect the answer is that there is no "one type is best for everyone" solution.
If the DH guys are convinced they are better off with discs,..thats fine
Road race teams obviously feel the rim brakes are better.
Some folks still ride with NO brakes at all ! :shock:
Most will use what they feel best suits their situation /budget/purpose..
 
Hillhater said:
dont you find it strange how all the pro road race bikes and teams still use rim brakes ?? :roll:
Click to expand...
Nothing strange about it.
It's called UCI
http://www.bikeradar.com/road/news/article/uci-open-minded-about-disc-brakes-for-pro-peloton-37068/

and related articles
http://www.bikeradar.com/road/gear/article/hydraulic-road-brakes-whats-the-point-37036/
http://www.bikeradar.com/gear/article/disc-brakes-the-future-for-all-bikes-32770/
Once component manufacturers start to offer integrated hydraulic setups and frame companies start optimizing designs for discs, we'll be left asking why it took so long. It's only due to legacy that we've all come to accept that squishing a couple of little rubber blocks against a carbon or aluminum rim is something other than ludicrous.
Click to expand...
:lol:
 
We don't use disc brakes because they are stronger, we use them because they are precise and reliable. Precision and feel is everything when time comes to stop or slow down in the shortest possible distance. Then, reliability under all conditions is what is making you sure that this shortest braking distance can be achieved all the time. Their even performance doesn't rely on a perfect rim and true wheel. The rotor is very quick to dry and sweep, and less likely to be corrupted by riding surface condition. Steel is making them stand the pressure better and longer, and rim brakes were much better when rims were steel but that was another era.

On a road racing pedal bike, no one would want or need the weight of disc brakes. The comparison doesn't stand. Even most ebikes are fine with rim brakes because their performance and use doesn't require better. Yet many here are riding an ebike that really is a light weight motorcycle, and disc brakes are not luxury for them. Some even use motorcycle brakes because the best bicycle disc brakes are not up to the task for their speed and weight.
 
Interesting thread. On my new build I used BB5 and 203mm rotors on the front, and on the rear, dual stage brakes. The rear lever activates regen first, then pulling more "V brakes" with kool stops second. This system replaced the BB5 and 203 on the rear. I can tell you the front disks are way better than the rear V brakes. In fact without regen, I don't think I would like V brake alone very much. Don't get me wrong, the V brakes and kool stops are a fine braking setup, but require much more input force to achieve the same level of braking, be it full lock or just mildly engaged. This increase in required gripping force means it's tougher to modulate, and in turn makes them seem less linear in application than a disk type setup. To me it feels like in the disk setup that the "brakes" are doing the stopping, where in a V brakes it seems like my hand is doing the braking by squeezing it so hard. Not a big deal since regen is my main brake (better than all of the mechanical brakes) but not 100% foolproof so the mechanical backup stays. I suppose any type of brake will have pros and cons however, each has it's place in cost, weight, and function.
 
Hillhater said:
Chalo said:
.... that 200 pound tangential load would be divided evenly among 18 spokes that get tighter and 18 spokes that get looser..
Click to expand...

Now here is an interesting calculation for someone attracted to force vector resolution...
assuming that 200lb (f) tangential braking load is reasonable, what load is transmitted to each of the 18 loaded spokes , considering that they are attached near perpendicular ( 5-10 deg ?) to the rim ..( and direction of the braking load )?
Click to expand...

Guys, since no one else took this on, i have done a rough calculation that results in a figure of an extra 153 lbf in EACH spoke if that 200lb stopping force is assumed .
This is base on a 680 mm tyre diameter and a 55mm diameter of the hub spoke holes that have to transmit the torque to the brake. ( dimensions taken from my bike )
Incidentally, in the same stopping situation, the disc caliper mount is seeing a load of over 900 lbf ! :shock:
Compared to the 140 lbf that each ( of 2) "V" brake mount would be subject to in the same situation :mrgreen:

EDIT:--
Chalo said:
... A front wheel can brake with a force equal to maybe, maybe 70-75% of the gross weight of the bike. So for a 300 pound bike + rider + luggage combination, you're looking at an absolute maximum of a little over 200 pounds tangential force at the contact patch
Click to expand...
Where does this 75% figure come from ?
In order to "lift" the rear wheel of a 300lb bike+ rider mass, the tangential braking force at the front tyre must be significantly MORE than 300lb since the C of G of that mass is acting somewhere between the two wheels ( say around the Bbracket area ?).
Simple force /distance ratio's imply that the braking force is much greater than the 300lb..probably more like double !
..So that 200 lbf could well be over 500 lbf :shock:
 
Chalo said:
People keep coming back to off-road downhill racing-- but steep downhill slopes, unpaved surfaces, and racer-sized riders all sharply limit the braking forces that can be used without crashing the bike. It's like boasting about how powerful your bulldozer is because it can be carried on an airplane.

The riders who exert the highest forces and energies into their brakes are touring tandemists. Few touring tandems use discs except as backup or drag brakes, the same way they have traditionally used drums. The real stopping power comes from the rim brakes. Tandems are among the most expensive and lavish bikes available. If disc brakes were categorically stronger or more powerful than rim brakes, tandemists would have been among the early adopters, not the holdouts.

There are lots of reasons to use discs on a bike-- ability to use very wide tires or rims, ability to switch wheel sizes on the same bike, resistance to the effects of deep mud, relative cleanliness in persistent wet conditions, accommodation for weak grip strength-- but braking power isn't among them. Discs can strengthen brake lever response, but they can't strengthen braking power, all else equal.
Click to expand...

there is a huge difference between braking at 30mph+ and 15mph, i dont see a tandem doing those high speeds

a tandem frame is very expensive and mostly custom/handmade, obviously something was done to keep the price / weight down,
 
3nslav3 said:
there is a huge difference between braking at 30mph+ and 15mph, i dont see a tandem doing those high speeds
Click to expand...

Tandems have the muscle power and gravity assist of two cyclists, but they only punch one hole through the air. Tandems are faster than single bikes on the flat or downhill. They tend to be slower on climbs.

So... tandems are faster than singles, they are too long to tip up from front braking, and they have less aerodynamic drag to slow the bike outside of using the brakes. They have the biggest need for braking power of all bicycles, and by far the greatest ability to use it. They use rim brakes for the most part. Draw your own conclusions.
 
im wrong about the speeds, sorry about that ;) i live on the flat and only see old couples on tandems overhere

but i do believe that a solid 4-6 piston disk brake system with big disks, good wheels and reinfored frame would be a good thing for a tandem

disks dont like to be dragged for to long due to heat, some disk brakes have vented disks and air cooled pads (see the latest saint brakes) should make a difference
 
Tandems are for pussies. We are talking about e-bikes here. READ THE F@#%ING THREAD TITLE. There are plenty of them with disc brakes anyway.

Stealth Bomber is a heavy e-bike capable of 80kph. Does it come with rim brakes? Do you see any reports of brakes not being strong enough?

If you think rim brakes are so good - go ahead, make a production e-bike with rim brakes and see if it sells.
 
For the manufacturers, only selling it matters.
 
I like a vibrant discussion with passionate advocacy for the speakers position.

I am happy for each rider to decide what style of brake they want to use. I most enjoy reading why each person likes the thing that they have embraced as "best" for their bike. I have seen tandems with discs, but...all the tandems that I have personally seen out in the real world were ridden on the street with a female on the back. I'm not surprised that all the tandems I've seen in person have had rim-brakes. Making a DH tandem would seem to be an unprofitable freak.

One point for discs I was PM'd: when riding through occasional splashes of mud on a downhill, some riders have experienced a higher frequency of rim-mud that was being flung off...but their discs (on bikes that have them) didn't seem to attract much mud in the first place. Of course discs DO get mud splashed in them sometimes, I'm just passing along one riders reason for choosing discs for themselves.
 
spinningmagnets said:
I'm not surprised that all the tandems I've seen in person have had rim-brakes. Making a DH tandem would seem to be an unprofitable freak.
Click to expand...

Maybe. There are suspended mountain tandems out there, but they are rare. Discs on tandems seem to occur on off-road bikes (where the usual off-road concerns apply) and lower than enthusiast level bikes (where the buyers probably assume that discs work better because they are discs). I was gobsmacked to discover that Co-Motion uses Avid BB5 brakes (which are not good even among discs) on their triplet bike. That seems like a bad mistake to me. One of my buddies who runs a fleet of pedicab trikes started off buying BB5s, but he quickly learned they weren't up to the task.

I wonder how any quality tandems can be profitable to make. The volumes are really small, and there are many different frame size permutations. Decent touring or racing tandems are expensive enough to make DH bikes seem cheap, though.

One point for discs I was PM'd: when riding through occasional splashes of mud on a downhill, some riders have experienced a higher frequency of rim-mud that was being flung off...but their discs (on bikes that have them) didn't seem to attract much mud in the first place. Of course discs DO get mud splashed in them sometimes, I'm just passing along one riders reason for choosing discs for themselves.
Click to expand...

I find it to be an act of self-respect and good bike husbandry to avoid riding in mud whenever possible.

Even in wet but otherwise clean conditions, rim brakes spray nasty filth all over the bike and rider, especially if fenders aren't used. Tires spray too, but the water they sling is mostly just water. Rim brakes squeegee off a dark-colored mixture of water, grime, and pulverized rim material. Discs are much cleaner, but they still get wet and they still wring off some black crud. That's why I have drum brakes on my rain bike-- they are very clean, and unlike rim or disc brakes, they truly don't get wet in the rain.
 
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