Your thoughts on (bicycle) disc, as opposed to rim, brakes?

wayover13

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I'm kind of souring on disc brakes and am even contemplating taking the disc brakes off one of my recumbent tandems* and replacing them with v-brakes instead. What are your thoughts on the pro's and cons of the two types of brakes? In my experience disc brakes perform slightly better in stopping power and in wet weather. But they're more trouble to maintain than rim brakes; the pads, for example, don't last as long, are more expensive, and are more difficult to replace.

So, what say you?

* I have electric assist on the tandem in question, but it's a lower-power, low-speed system.
 
I agree. Imo decent hydraulic is the only way to get the most from discs, and the pads still wear faster- any benefits are likely lost on your bike, making vbrake the best choice if you're able.

We were just talking about this in depth in two recent threads. You could search recent titles for brakes. Tandems were mentioned at least once and concensus was vbrakes are the most common best choice.
 
Sorry to be obtuse, but have you looked at the sturmey archer drums?
They have a lot going for them & unlike disc or rim brakes, when they're off, they're off!
 
Depends on the situation.
First, just to clarify, stopping power is actually a function of the tire. The tire's grip on the road is what stops the bike. A bike's maximum stopping power is reached when the tire is at the point of lockup. All brakes just allow you to modulate that power and maintain control, while dissipating the kinetic energy of the bike as heat. So in that regard, all brakes that can skid the tire have equal stopping power. Any advantages a brake has are in other areas.

Rim brakes are great at low speeds. essentially a rim is a giant disk. Since there is more surface area, they dissipate heat better and run cooler. their pads are optimized for cooler temps and so can use a thicker pad since heat retention wouldn't be an issue. they can also operate at a lower pressure since they have a higher mechanical advantage stopping the wheel near the tire instead of near the hub. Both of those factors means the pad will last longer.
Also because they operate so close to the tire, they have the highest degree of precision and offer the greatest potential for razor sharp modulation. There's a reason many stunt bikes use rim brakes, as they offer unparalleled precision.

Also in their favor, they are one of the lightest weight braking options. They also can be placed in the shadow of the frame, and are one of the most aerodynamic braking options. They also put no stress on the spokes, so a lighter weight wheel can be built.


They have downsides. If the rim isn't true, or if the rim gets damaged on a rock, bump, log, pothole, squirrel, or other road hazard, the effectiveness of the brake is reduced. That loss of effectiveness is exacerbated by high speeds. The faster you go, the more critical a perfectly straight smooth rim becomes. There is risk in running a rim brake at high speeds because any thing that effects the wheel can leave you with poor to no brakes.
They don't play well in the wet, and they do abysmally in the mud. Unfortunately rims are prone to get wet and muddy, especially off road.
Also, wind, water, snow, ice, mud, etc can change the temperature of the rim. that effects the way the brake pads interact with the rim and effects modulation consistency. The amount of hand pressure needed to stop the bike won't always be consistent.
In general, it takes more hand pressure to operate a rim brake than a disk brake. they take 2 or more fingers to use for most people


Disk brakes don't offer the same laser precise precision, but they come damn close. More like razor precision. They are up away from the wheel, so mostly immune to the mud and gunk on the road or trail. they also designed for self cleaning, so they are more tolerant of mud, snow, water, blood, guts, and the general whatever that gets splashed on them along the trail. Just about anything that could damage a wheel and still leave the bike mobile won't hurt the disk, so if the tire holds air, and the wheel can turn, it should be rideable.
Since the pads are designed to work at high heat, and are designed to generate their own heat up to a point, they are less effected by the environment. changes in environmental temperature are less of a percentage of their total temp so cause less change in performance. A mech brake like a BB7 takes 1 finger, a hydraulic brake can be operated by a butterfly fart.
Disk brakes take less hand pressure to use than rim brakes.

On the down side, Disk brakes eat expensive pads. they need a heavier hub and thicker spokes. While damage is rare as they are fairly protected, even a millimeter bend in a disk might put a bike out of service. They weigh more. They cause more aerodynamic drag. And they just aren't as precise.


As for maintenance, I think it's a wash. Rim brakes need perfect rims, that means a fanatical attention to keeping the wheel running true. But disk brakes need constant pad, cable, and/or fluid maintenance. As someone who rides both, I don't think either is better.
 
bobc said:
Sorry to be obtuse, but have you looked at the sturmey archer drums?
They have a lot going for them & unlike disc or rim brakes, when they're off, they're off!
Leave it to a Brit to drag in the Sturmey-Archer name! :) I hadn't thought of drum brakes--though it would certainly be worthy of consideration if this were a new build. I was probably thinking only of disc versus rim brakes because, this being in relation to an existing bike with already-existing wheels, buying and building new wheels is not something I'd like to contemplate. The Sturmey-Archers, as I'm understanding it, come only built into hubs--necessitating not only purchasing the hubs but rebuilding wheels. There do seem to be add-on drum brakes (drag brakes), though Arai, the main manufacturer, apparently stopped making them some years ago. So far as I can tell, the only add-on drag/drum brake now available is made by Karasawa.

Thanks for all the interesting input thus far, guys.
 
Drunkskunk +1 8)

I would use rim brakes if my rear wheel was more true, more of the time. Prior bike has had V-Brakes and Kool Stop? or similar pads and the braking was excellent. The next run about, non assisted bike will have BB7 to try out mech disc brakes.

Have you considered a disc brake with a larger pad (i.e. switch to a four pot set up) and levers with pad adjustment? Just a thought.
 
wayover13 said:
bobc said:
Sorry to be obtuse, but have you looked at the sturmey archer drums?
They have a lot going for them & unlike disc or rim brakes, when they're off, they're off!
Leave it to a Brit to drag in the Sturmey-Archer name! :)
Hah - they've been Taiwanese for a long time..... Sorry, got the impression you were rebuilding - I just 'rediscovered' the bike drums a couple of years ago & wouldn't choose anything else now, either on my bikes or the greenpower racers.
 
I have found from experimentation that HAYES ACE disk brakes are the most effective brake for Ebikes. I have bought several on Ebay for very reasonable prices. Big and wide. I use 2 old cut up disk brakes as spacers. And they work GREAT.
 
Here is my experience...

I currently ride about 20 miles per day rotating between 4 bikes:
1 set of 203mm disc hydraulic brakes, 1 set of 203mm disc BB7s, and 2 bikes with Salmon Kool-stops (a 26er and a 29er)

My commute is relatively hilly. There are several hills where I achieve 40mph on the descent (without throttle, but I usually accelerate beyond 40mph on the faster bikes) before hitting the brakes for a stop sign at an intersection at the bottom of the grade before it flattens out! Coming from a motorcycle/racing background I really enjoy braking late and testing my equipment and there is rarely traffic at the four way stop in case I miss the mark and can't scrub all the speed. This is full force braking to a stop from 40+mph on a 12% grade that I practice everyday. I have not done any calculations or research, but I assume from a classical mechanics standpoint it is a scenario that will meet or exceed the upper limits of braking exertion that bicycle systems are designed to meet.

The main difference I notice between the disc vs. rims is that on that first section I mentioned above, I can cause my rim brakes to heat up and vibrate and squeal loudly before coming to a stop. It gets ugly. I can't imagine most riders would purposefully approach these limits of traction on a downhill section at these speeds unless emergency braking or if they have a similar section near their house like mine that they enjoy regularly testing. After I encounter this dreaded squeal on the rim brakes it takes another 2-4 miles of stop and go traffic before the salmon Kool-stop pads stop squealing and start acting normal again. Yes, I have tried sanding both the pad and the wheel multiple times and readjusting the angle of the pad to the wheel. The rims are also perfectly true. It is very, very repeatable on both bikes and has been for many sets of pads. Again, after some riding they become totally normal again. I have zero issues with either of the disc bikes on this same section of hard braking ever and I typically achieve faster speeds on the descent because those brakes are on faster bikes that can accelerate beyond 40mph.

I will also note that wet weather riding sucks a lot more with the rim brakes. Your mileage will vary, but this is my experience after years of testing and daily commuting on both setups in all weather conditions. I thought it would helpful since tandems have high demands on brakes. The fastest I have been brave enough to go without my wife going ballistic on our tandem was 36.6mph... Luckily I didn't have to do a hard stop from that speed and got to use the energy for attacking the next hill!!! :)
 
disc brakes cost about 4 times as much as v-brakes and provide questionable extra stopping power. and about 5 times more hassle.

people who say disc brakes totally destroy v-brakes are suffering from post-purchase rationalisation.

a good set of cartridge pads (pads that fit in a metal housing) are just as good as good if not better than disc brakes for numerous reasons.

1. cost
2. easily adjustable.
3. easily viewble (when pads get low and need replacing)
4. discs mean for narrow spoke width at axel (meaning weaker wheels)
5. discs stop the axel not the rim putting excess stress on spokes when braking.
6. most ebike brake levers are short pull (designed for use with vbrakes)
7. discs weigh more and add more unsprung weight
8. disc pad material is easily contaminated, completely negating all stopping power

the only bonuses i can see to disc brakes are....
1. they look cool
2. v brakes wear out your rim over time.....disc brakes dont

my ebike goes 35-40mph......i tried discs (non hydraulic) and almost instantly went back to v brakes. because they didnt stop me properly plus of all of the above.

so i dont want to hear "my discs(hydraulic) are mint, so much better than v brakes" when they do exactly the same for about 4 times the price.
 
jimmyhackers said:
people who say disc brakes totally destroy v-brakes are suffering from post-purchase rationalisation.

Did you read my post above? I have an open mind to both and it is absolutely not the case for me. On my bikes with disc brakes, the brakes are one of the smallest line items and the price is inconsequential to the total build cost. If you are going to build an ebike with rim brakes over disc brakes and plan to do thousands of miles per year then you are being penny wise and pound foolish. I question how much you ride as Koolstop pads at $15 per wheel adds up pretty fast over the years and will totally displace the cost of disc brakes whose pads last much, much longer, especially under hard riding.

jimmyhackers said:
a good set of cartridge pads (pads that fit in a metal housing) are just as good as good if not better than disc brakes for numerous reasons.

1. cost
2. easily adjustable.
3. easily viewble (when pads get low and need replacing)
4. discs mean for narrow spoke width at axel (meaning weaker wheels)
5. discs stop the axel not the rim putting excess stress on spokes when braking.
6. most ebike brake levers are short pull (designed for use with vbrakes)
7. discs weigh more and add more unsprung weight
8. disc pad material is easily contaminated, completely negating all stopping power

1. See my post above.
2. Rim brakes are actually harder to adjust than hyrdraulics and have the slight edge over the BB7's. I also have to adjust them way more often due to my demanding riding and routes.
3. That's good since I have to change rim pads way, way more often than the discs'
4. Irrelevant on my builds (I am using DH and MC rims)
5. Irrelevant on my builds (I am using DH and MC rims)
6. Ebike brake levers are shitty. If you need them use a magnet and hall sensor.
7. Not a concern on an ebike when you are added dozens of pounds of batteries and motor.
8. This has never happened to me on ebikes, trailers, motorcycles, cars, trucks, etc. This happens to people who don't know what they are doing.

jimmyhackers said:
my ebike goes 35-40mph......i tried discs (non hydraulic) and almost instantly went back to v brakes. because they didnt stop me properly plus of all of the above.

Did you even burnish the pads and give the rotors time to bed-in?! If not, then you did yourself a huge disservice. Try your rim brakes on a steep mountain road at 40mph and see how you like them...

jimmyhackers said:
so i dont want to hear "my discs(hydraulic) are mint, so much better than v brakes" when they do exactly the same for about 4 times the price.

You are going to keep hearing this from the world. You can try to stick your head in the sand, but it is a newer and better technology. If rim brakes were so good we would be seeing motorcycles that use them... not the case. The closest I know of would be the radial brakes on the discontinued Buells, but that is still more of disc-ish than rim-ish. The point I am making is that as our ebikes become heavier and faster and we ride them harder the advantages to disc brakes become more extreme. Under normal n00b riding conditions I am sure rim brakes are totally fine. I listed a condition where I hit their limit and I am also tired of readjusting and changing pads at $15 a wheel all the time... DIfferent strokes for different folks. I think we all can be a little too dogmatic about our personal choices regarding our builds at times.
 
With the exception of Avid BB7s, my experience with, and impression of, all mechanical disc brakes is that they are junk found on B.S.O.s. I'd take the shitiest rim brakes over the mechanical discs I had the misfortune to use.

Disc brakes work well in rain and mud (we get a lot of that here) so they win for me. I hear some that squeal and hear of the need for regular adjustment and bleeding. That would put me off.
 
jimmyhackers said:
1. cost depends on what brakes you are specifically referring to
2. easily adjustable. Generally mine pretty set and forget. So new pads every 12 months, bleed, align, done. No further adjustment required.
3. easily viewble (when pads get low and need replacing) becaus so look in the calipers, it isn't hard
4. discs mean for narrow spoke with at axel (meaning weaker wheels) err what?
5. discs stop the axel not the rim putting excess stress on spokes when braking. True. Arguably a heavier gage of spoke is require for greater strength increasing wheel weight.
6. most ebike brake levers are short pull (designed for use with vbrakes) so use a sensor with the existing levers. Most ebrakes levers, certainly those supplied with most kits, are rubbish anyway
7. discs weigh more and add more unsprung weight depends what brakes you are comparing. The difference is immaterial. If I have a wee before riding on disks it would be the difference.
8. disc pad material is easily contaminated, completely negating all stopping power no man! Rims are far easier to contaminate! Discs are further away from all the mess.

It sounds like you had a poorly set up set of discs...
 
Rim brakes have a few fundamental advantages when they work for a given application:
Like for like, they'll always cost less than discs
You can change pad materials for different feel or power
Rim brakes are usually easier to service
They can be repaired easily in the field
The whole system is inherently lighter
Non-disc wheels are inherently stronger and stiffer
Wheels are much less fragile than disc rotors

Disc brakes have some situational advantages:
They are independent of tire width
A disc braked bike can use different size wheels than originally equipped
Many discs are hydraulic, and those are insensitive to hose length or routing problems
They can stay farther out of deep mud or water when that's a factor
Some disc brakes require very little lever pressure (good for weak hands)

Rims and rotors both wear out in abrasive conditions, and they cost similar amounts, but rotors are much simpler to replace.

For me, the bottom line is that discs prevail for fatbikes, wheel size retrofits, or sloppy riding conditions. Rim brakes are cheaper, lighter, more versatile, and generally easier to live with.

Anybody who'll lay down a hundred bucks a wheel for discs without first spending twenty bucks a wheel for new pads and professional adjustment on their rim brakes simply can't be trusted when they assess which one works better. They don't know because they didn't really try.

A propos Punx0r's comment about mechanical discs, TRP Spyke and Hayes HMX-1 are on a par with BB7 in terms of performance. Most mechanical discs, as he points out, are total junk that cost double, weigh double, and work half as well as reasonably good rim brakes.

Make no mistake, they have similarly underachieving peers among hydraulic discs.
 
Rim brakes are also superior to replace spokes with - one less thing to remove before replacing a spoke.

Disc brakes are superior when the rim goes out of true...
 
I've never ran disc brakes, but currently run rim brakes on an ebike in NYC. My top speed is 25mph+, 28MPH on downhills.
I run a front U-shaped brake booster in the front and use aluminum fishbone brake housing for both front and back to reduce line compression. I've never had a problem with stopping power, and can lock up the rear wheel when ever I want.

In terms of wet weather issues, there is definitely a point during heavy rain, it seams as if the brakes have to clear off the water from the rims before I'm able to start slowing down. But during most wet conditions the biggest issue I have is usually the tire sliding on the pavement and not the brakes.

Rim wear is an issue, but only after 10 or so years depending on how much you ride. I didn't realize I had worn the brake wear indicators off my rims until I recently replaced them, but I've had the same wheels on my bike for almost 20 years with casual use.
 

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ive turned to the dark side.

mainly because my rims were finally reaching the end of their wear bar and i didnt fancy paying for 2 new double skinned rims and going through the hassle of relacing two wheels. (my rims are lightweight now :lol: )

i already had most the parts, still cable operated single sided calipers, tektro brand. (low end of the scale)

i did fork out for a 200mm rear disc.....which if anything is too good. i can lock up the rear waaaay too easy.

its going to be the same story for the front.... ive replaced due to warebar closeness and also the hub bearing was deteriating slowly.
ended up relacing the rim onto another front hub i had with disc attachment.

but again, ive only got 160mm discs to hand and they are....terrible. worse than v brakes again.

im wondering if i should get a 180mm for the rear and put the current 200mm rear on the front. or just do 200 front and back.

in heinsight a few of my points dont exactly hold true, and they do look cool.
 
And thats all that matters, looking cool.

Start with 200 front and whatever you got for the rear, and if its not enough buy a 200 for the rear.

jimmyhackers said:
and they do look cool.


Rim vs Disk brakes, its all a matter of what you have setup on your bike. Flip a coin, its no big deal unless your hopping rocks doing a stationary wheelie on a boulder, or rocking down a double black diamond ski run in the middle of summer.

pssst btw there is such a thing as 220 rotors ;)
yw
 
Thats doable on a bicycle, I think I seen it once posted here on es.
I would have no clue what key terms to use to search for something like that.

amberwolf said:
Or you could go Buell:
 
Except rim brakes can gunk up with mud, a minor draw back. I like the fact its all very reasonably priced, I would only jump into mechanical disks if I had bb7's or similar.

Why do roadies prefer v-brakes over disk brakes?
 
calab said:
Except rim brakes can gunk up with mud, a minor draw back. I like the fact its all very reasonably priced, I would only jump into mechanical disks if I had bb7's or similar.

Why do roadies prefer v-brakes over disk brakes?

Discs can junk up with mud if they get it on them, too. They have a little more ground clearance is all.

It's worth noting that a single drop of oil can permanently ruin disc brake pads, whereas rim brakes are fairly tolerant of oil contamination. This is especially relevant for hydraulic discs that use oil.

Roadies never used V-brakes for the most part. They used caliper brakes, and some still do. Discs may have predominated recently, but caliper brakes are still equally effective, lighter in weight, and compatible with lighter and stronger wheels.
 
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