Let's talk about brakes

veloman said:
Why not take the travel lane at those speeds?
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Well I was being courteous to the drivers around me. Remember as much as I hate cars, they are still bigger than you and you don't want to start a fight with someone much much bigger than you. : ) also it is a fact that the road is a 45mph section so I would need to be maxing out just to keep up with the traffic.

Yeah I go around that corner much more cautiously now. It is not worth the risk.
 
John in CR said:
Hillhater said:
John in CR said:
It's not the stopping power that brings rim brakes into question, it's the fact that a big enough hill can get those rims so hot that it pops the tube. Next would be the constant fiddling with them to keep them working properly.
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in 55 years of cycling....( but only 30 or so with "V" brakes !)
Never had a tube pop from hot rims ( boy, do discs get hot though !)
Never worn through a rim
Never had to "constantly fiddle" with adjustment.. ( once every few weeks, at the adjuster on the lever ..whilst riding !)
very rarely had to replace brake pads
and never had any problems with spokes or nipple seats !
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Ah, the old "It never happened to me, so it can't happen" rationale, just like the RC Lipo is safe guys. I've never had it happen either, but I know it can because it has happened to others.
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Controlled tests by BIKE magazine of Germany have shown that most bicycle disc brakes fail at sustained energy levels lower than those that cause problems with normal rim brakes on normal rims. Make those rims bigger and heavier than normal, as many of us do, and the margin gets even wider.

Discs have only one advantage with regard to actual stopping: Some of them can yield more stopping power for a small lever effort than any rim brake. None of them can stop harder than a good rim brake, because all brakes are constrained by the geometrical limits of the bike layout or the limits of tire traction. And as instrumented testing has confirmed, discs are at a disadvantage when it comes to continuous energy dissipation.

Thus, what people are really saying when they claim that disc brakes are categorically stronger or safer than rim brakes is that they have baby princess hands and are incapable of operating normal rim brakes to their potential. Or else what they are saying is that they can't be bothered to make their rim brakes work right because it's better to acquire $200 worth of new gee-whiz brakes than $20 worth of pads and adjustment. The latter is a fallacy because discs fall into disrepair too-- sometimes just because they got a tiny droplet of chain oil, suspension oil, or their own hydraulic fluid on the rotor.

Discs are often easier to implement on bikes with very fat tires, or unintended wheel sizes, or rims that lack sidewalls. Discs allow a bike to accept any wheel that fits within the frame or fork. And discs are somewhat better at staying clear of deep mud, pig manure, mango puree, or whatever sort of muck characterizes your riding surface. But these are reasons to use discs, not ways in which they outperform rim brakes.
 
I would love to see them test an avid BB7, nuke proof brand ceramic pads and the hope floating rotors. I have had those literally glowing a bright cherry red doing repeated 70mph torture test stops until failure. The part that fails? The grease and paint burns out of the caliper pivot and the action becomes stiff. Before it failed, it stopped a 300 pound bike+rider three times from 70mph. If that's not good enough for most non high powered racetrack folks, I dont know what is.
 
BATFINK said:
If in trouble I jam the sole of my shoe on top of my tyre and burn my shoes to a crisp until I stop ;)

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Ha ha, i remember those days, though they are now a very distant memory.

Back to the original poster....., The brake manufacturer 'Hope' make great hydraulic brakes for bikes.
The V2 has recently been upgraded from a two piston calliper to 4 piston(V4), it has wide and long pads 'sintered' giving best stopping power. They even do vented discs like high performance cars have to help dissipate heat away from the disc. The front V2 with 203mm hope v2 disc has noticeably excellent stopping power. These brakes also use 5.1 dot fluid. Remember that dot 5.1 and the expensive vented discs are mainly used for long performance purposes to stop brake fade when used for downhill riding for long periods of time
 
What do real MTB riders think of rim brakes?

Well, I just came across this post (scroll down to #6):
Alright, seeing how you bunch of tight asses ain’t putting you money where your anything is it’s time to do a proper mother-ducking sales pitch. Get ready to have you panties blown off b*tchs.

This bike here is the greatest f*cking bike ever made, it rare alloy composite carbon frame is impervious to losing, thats right......LOSING. Steve Peat road this thing and was quoted from an unreliable source saying “This thing is the raddest mother bitch facing downhill, freeride, XC, god damn motorcross rig ever built, I can’t handle it, it’s speed carrying-ness ability scares me’’. Matt Hoffman once quadruple double and a half back flipped this thing over a burning bus filled with lingerie clad lesbians licking each others nipples whilst playing electric guitars.
This thing goes like corn through a goose, it’s shiny too, so when you take it home after impulse buying the shit out of it the missus will mistake it for diamonds and then her clothes will blow off and her rack will double in size. As well as that she will finally think you are interesting cause now you have the craziest half vintage/old shit bike around and the fact she thinks it’s made of diamonds means every time you piss her off cause you’re off winning the World DH cup, spraying champagne in podium girls faces and not at home changing the nappies and mowing that thing you call a lawn you can just chip off a bit of the frame off and give it to her and she will think the sun shines again from the 2 white half moons you call you ass again.
And V brakes, mother f*cking V-BRAKES!?!? When’s the last time you saw these on a championship winning rig? 2 decades? You know why? ‘Cause they were BANNED for being too good, that’s why. They combine the stopping power of a cat on lino with the grip of a slab of butter sliding down an oiled lingerie models back and all with the feel and progression of getting your fingers smashed with a hammer. Only when you need to slow down do you need more than two hands squeezing on the lever to get them to work, and then they won’t even lock, ‘cause sliding is slow. And slow this bike aint.
This bike will change your life, women will worship you. Men will try to murder you to steal it. And I will be richer. Your life will soon be VERY exciting; you’ll be dodging bullets whilst fondling boobs and at the same time winning DH, XC or motocross races.

Well, after this little sales pitch your no doubt frothing at the mouth and you wallet is as excited as a seal in a fish shop, so stop being a cheapskate and get yourself real hard ass, bad ass and any other sort of ass XC World Downhill championship cup diamond encrusted sex sled bike designed by Jesus and Babe Ruth.

Peace out!

P.S Some of the above points are lies, others are complete Bullsh*t.
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Do you think an ebike really needs strong brakes, like 4 caliper downhill brakes?

Reason I ask is I am looking for a set of disc brakes for a new build and can buy the shimano XT disc brakes or the Shimano Zee/saint brakes for around the same price. Seems like the Shimano XT gets great reviews, many people recommend the XT over the saints if your not using a downhill bike. basically it seems that the XT brakes just have a better feel for them.

But I was thinking about it, does an ebike really need those powerful 4 caliper downhill brakes? A downhill brake is made because you are always braking going downhill and have to fight gravity where an ebike your usually just braking on flat grounds.

The other issue is with really strong 4 caliper brakes you stand a greater chance of going over the handlebars in a panic stop.

I am unsure here, go with the 2 caliper XT brakes or get the 4 caliper zee/saint brakes because an ebike needs all the braking it could get?
 
I've had shimanos fail in the same manner in two different bikes. Luckily not during a panic stop. No more shimanos for me. I switched to Avids. So far so good. I'd rather have a powerful brake, than a failed one. Whichever brake you choose, just make sure its a quality one.
 
On a normal Ebike? Any brake that can skid the wheel is fine. On some high powered Ebikes, you may have heat disapation issues. In those cases larger brakes can help shed the heat better and avoid brake fade, but thats not nessessary with a conventional Ebike.

If a single piston brake can skid the wheel, then a 4 piston will have no more power. Braking force is entrily an aspect of the tire's adhision to the road. What does matter is that some brakes allow better modulation, allowing the rider to keep the wheel closer to the point of skidding with better feel and feed back so they can brake more effectivly, but thats not a strength issue.
 
It's certainly worth getting hydraulic disk brakes. I have several types and find Shimano XT really good.Mine are BR-M775. There's several different versions of them, all different.
 
The faster you go the harder to slow. Good quality dual disk brakes never hurt anybody, hydro vs mechanical even better. But can they fit if you are planning a hub motor and multi speed cassette?
 
On fast e-bike heat in the breaking system is the main problem i think. I also have the Shimano Saints BR M820 and the braking power is very good. The cooling fins on the brake pads are superior features which help to get out heat very quick.
I use the Shimano SM 99 RT Rotor which also cools down very fast, but i think it will wear out fast because of the aluminum between the "two dedicated" rotors. If i didnt had a centerlock wheel hub i would have taken this 224mm rotor:

http://www.hayesdiscbrake.com/brakes/parts-accessories/disc-rotors/v9-rotor/

You should also keep in mind the Saints do have 2-finger levers which can be a problem if you have a twist throttle (magura are very wide) so you may not reach the lever because its to far away from your finger.. But every type of thumb throttles schould always work fine (i use AWI 5k).
 
You need extra powerful brakes on an extra powerful ebike. In other words, if you build a flyweight motorcycle, you need the good brakes to stop from 50 mph or so.

If you ride a bike with 1500w or less, I'd say the rim brakes on the bike in walmart still work good enough. They will stop you from 30 mph fine.

Part of why I say this, is because if you ride like brakes will save you, the best brakes on earth won't save you. You have to steer around that car while under braking, just like you have to do on motorcycles. Those that don't have that skill in their bag of tricks whack into that car that frocked them.

In off road riding, or a racetrack, then you tend to work those brakes hard and it's obvious that the longer you go before they fade the better. My off road bike had cheap tektro disks, and I had to just get used to no brakes on some trails. The tough spot would fade em every time.
 
Ebikes need stronger brakes because they have more momentum (due to the added weight)

I don't like the idea of using rim brakes on mid powered bikes where the hub is laced into the wheel.
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If you are lucky enough to spend most of your time on a bike path, take advantage of a roller brake.
They suck for hard stopping but are great for gradual decreases in speed.

The best thing you can do (if unable to buy hydraulic) is a good quality cable that doesn't stretch and putting in some effort to adjust your system.
 
My last ebike was a 3 speed Raleigh with rim brakes, I once hit the side of a truck that ran a red light at an intersection that I certainly could have avoided with better brakes. I was doing 20 mph and it really caught me off guard how poor the rim brakes were on that bike.

That said, any decent disc brake (hydraulic or mechanical) should be just fine. If you can afford the Saints they're awesome, but probably overkill. I run a pair of Avid BB5's on the front of the KMX now and I'm completely satisfied with the braking performance. No doubt hydraulics feel better but mechanical discs will lock up the wheels.
 
I wasn't really happy with the performance of my brakes until I got a 203mm rotor for my front Avid BB7.

I've only experienced brake fade twice since then and that was going down some seriously steep fire trails (15-30% grade). I daresay mechanical brakes will stand up to more abuse than hydraulic, although the brake feel is not as good and you have to adjust them occasionally.
 
My main issue is brakes like the Shimano saint are supposedly very powerful and may feel too grabby for most riding. Something like the Shimano XT may be less grabby.

I find that an ebike doesn't need all that much breaking power. Most of the time you coast and with the resistance from the hub motor the bike doesn't coast very far. Why have super grabby breaks when most of the time you don't need them.

Good point about the small levers and thumb throttles. I am actually worried about this issue as I use a thumb throttle.
 
The question is: How fast, how heavy, and where do you ride ?
Brakes need to match the bike's performance and riding conditions.

I use Hope M6 Ti with 224mm rotors and EVO levers on my new build, and I find they are just right.
 
andrew.box said:
If you can afford the Saints they're awesome, but probably overkill.
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with the Saint 4 piston and 203mm 99RT rotor i have never stopped my 21,6" OD frontwheel for so far - even if i pulled the lever very hard. I think on very heavy and fast e-bikes no bicycle brake on the market is overkill they are more too weak!

If you really need good braking power you have to go with a dual brake fork and dual brake wheel hub...
 
There is a conflation of three issues here: force, power, and energy. Disc brakes are not categorically better at braking power, and are inferior at dissipating energy, compared to rim brakes. Where they excel is in generating maximum braking force at the wheel with minimum input force at the hand lever. That can be a good thing or a bad thing, but is good up to a point.

Hydraulic brakes, by not incurring the usual static friction losses of a cable-operated brake, are particularly good at delivering braking force per lever force. So hydraulic disc brakes are the best of both, in terms of converting lever force to braking force.

But force isn't power, nor is it energy. Braking force is usually limited by bike layout and tire adhesion, not the capabilities of a good quality brake. Once you skid the rear tire, that's all the rear braking force you get. Once you tip the bike up on its front wheel, that's all the front braking force you get. V-brakes, cantilevers, dual pivot calipers, and discs can all reach that threshold.

Braking power is a function of rim linear speed and braking force, and it is proportional to braking force unless heat loads affect the friction properties of the brake, e.g. disc or drum brake fade or rim brake pad melting. Good quality brakes of whatever kind usually resist major heat effects on braking until they approach their maximum limits. The rate at which heat can be evacuated from the friction material is the main factor in its ability to deliver large amounts of braking power, which is why metallic disc pads are better in this regard than organic pads, and why aluminum rims are better than steel or wood for rim braking.

Braking energy, and the ability of a brake to withstand and reject heat energy, is what matters most in regard to brake failure. And this is where discs fall behind rim brakes most dramatically. A 200mm disc brake rotor weighs about 225g and is made of stainless steel, which has about half the specific heat capacity of aluminum. The aluminum rims that are relevant to what we are doing run from about 600g to over 1000g, meaning they have five to ten times as much heat capacity as a large disc rotor, along with a much greater area through which to reject that heat to the ambient air. So it's no surprise that rims rarely get too hot to touch, while disc brake rotors do so routinely.

Rim brakes fail when the pads melt or when the tires get soft enough to blow off the rims. Disc brakes fail when the pads fade or burn away, hydraulic fluid boils and locks them on, or when plastic parts in a mechanical brake melt and prevent the normal operation of the brake.

in my twenty-five years plus of riding bicycles with commitment, and over twenty years of servicing them, I have never once witnessed a braking related tire blow-off, and I have only seen pads melted on department store BSOs with terrible cheap pads, or else bikes with painted or powdercoated rims. I have seen critical fade of both drum and disc brakes, though, many times. That is because the total energy required to bring a disc or drum brake to operational failure is much lower than that required to do the same to a rim brake on an aluminum rim. It does not require nearly as extreme a set of conditions to get to that point. I burned my first set of stock Hayes organic disc pads right down to their backings in less than 20 miles of steep but normal Seattle city riding with a 400+ pound gross weight. (The EBC Gold metallic replacement pads have lasted for thousands of miles with variable loads.)

To get more specifically to the OP's question, yes the brakes on a fast e-bike should be powerful, because momentary loads in the case of panic stops from maximum speed are very high. Whether your brakes need to have unusual energy dissipation is a matter of the terrain you ride on (are there large elevation changes?) or whether you are racing in conditions where the brakes don't have time to cool down between hard stops from high speed. But do not fall into the trap of believing that one species of brake is categorically better than another in all ways. The job of hauling down a fast, heavy e-bike in normal traffic conditions can be done by many different disc and rim brakes. And there are many different disc and rim brakes that would fail to do an adequate job.

A good baseline for the performance levels that make sense for a fast e-bike would be decent Shimano or Tektro V-brakes with Kool Stop pads, or Avid BB7 discs with metallic pads. Hydraulics might feel better to you, but they won't help you stop harder unless your hands are so weak as to be the limiting factor in your braking.
 
Chalo said:
But force isn't power, nor is it energy. Braking force is usually limited by bike layout and tire adhesion, not the capabilities of a good quality brake. Once you skid the rear tire, that's all the rear braking force you get. Once you tip the bike up on its front wheel, that's all the front braking force you get. V-brakes, cantilevers, dual pivot calipers, and discs can all reach that threshold.
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with some heavy hubmotor in the backrim its not as easy as you think to reach this threshold...
You are right that some good rim brakes might have better braking characteristics but the main disadvantage is the durability and effort (cost) to change them (lace new rim etc).
 
And not having to buy new rims with re lacing the motor.... rim brakes destroy rims. And how much more do you use brakes on an ebike compared to a normal bike?

Regen is your friend for long down hills.
 
That one was really good Chalo.

One reason I like the slow dd motors, is that on the long big mountain descents, even without having regen enabled, you get a maximum speed from motor cogging that allows a good rider like myself to nearly never touch the brakes. Works great in the big rocky mountain passes. Works great going down the shorter but still steep hills in daily riding too.

I've yet to wear out a rim using rim brakes in a lifetime of riding. But if you ride in mud, it could be a real problem. It's just too dry here to get grit stuck in the pads for long. But then again, I never ignored a dirty pad for more than a few blocks. You can hear it when you have a grain of sand dug in there.

As for " I was going 20 and it really caught me off guard", Why did you not see that truck was about to run the light? You trust a stupid traffic signal to keep you safe or do you watch those evil 5000 pound hunks of steel like they are trying to kill you?

Personally I'm watching those cars, I'll stop at a green light when I don't like the look of one car. However, I don't doubt your brakes sucked too. I'll go on record right now that I won't ride a bike with poor brakes. Some cheap caliper brakes are incredibly poor. It has to do with the leverage designed in. Proper maintenance helps a lot, but you can't safely ride those bikes faster than 10 mph or so.

But I have found that with fresh pads, even the cheapest v type rim brakes can be quite good.

Repeating till you hate me for it. Once you are going motorcycle speeds, you are going to be limited by the rubber and when it skids if you lock er up. You better be thinking dodge that truck rather than stop in time. I'd have died by 20 if I hadn't learned that skill before moving from bicycles to motorcycles at 15. It would have helped though, if I'd had even a tiny bit of control over what my throttle hand did then.
 
I don't really like v-brakes at all, I think they're just too inconsistent. The only rim brake pads I ever liked were the Kool Stop Salmon pads. even then performance was not great in the dry (after you get a bit of grit on the rims, which transfers to the pad), and simply terrible in the wet.
 
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