Why Disk Brakes Are Better Than V Brakes on a Mountain Bike

Disk Brake vs V Brake in MTB
Update: You might as well skip this post and go straight to the comments section where Remus made it clear why disk brakes are more efficient than V brakes.

There's a reason why disk brakes are better than V brakes on a mountain bike and it has nothing to do with the usual arguments: no mud and no water reaches the disks thus the braking is more efficient - unlike the rims which easily gather mud, sand and water while crossing streams, making it harder for the cyclist to stop the bike (not only that but the brake pads and the rims themselves are worn out by the abrasive materials caught between them, which not cool...).

But the real reason rim brakes are less efficient than disk brakes consists of a simple truth pertaining to physics: it's a lot easier to stop an object moving in slow speed than it is to bring to a halt an object moving in higher velocity.

The vectorized image above depicts a mountain bike wheel equipped with a disk brake system. Notice that the two points (A and B) travel different distances in the same time unit until they reach their destination positions (noted here as A' and B'). Based on this observation it can be stated that, given a certain spoke (radius) of a bicycle wheel (circle), each point of the spoke starting from the hub (center of circle) to the outer margin of the wheel (rim) has its own speed when the wheel is spinning. The further from the center, the higher its speed.

Think of it this way: no matter how fast the wheel is turning, the rim will always spin faster than the brake disk (which is smaller in diameter and has the same center) even though both the disk and the rim (and all points on any given radius for that matter) perform the same number of rotations per time unit. Example: One full spin of the wheel happens in one second - the speed of the valve (taken as a point on the rim) is about 200 cm/second while the speed of the corresponding point on the disk brake is about 60 cm/second.

Since the braking force is applied so close to the wheel's hub there is a need for sturdy spokes in the wheels that have disk brakes on them. Unlike the normal wheels on which the rim is designed to withstand erosion and friction (features needed for V brakes), disk brake wheels come with stronger spokes (double spokes) that distribute the braking force towards the tire without breaking the spokes themselves.

Wheel Rim for Mountain Bike
As a side note you may have the disappointment to find that medium bikes that have disk brakes (mechanical system, not hydraulic) do not have such strong rims. So while your bike brakes efficiently you might see that the wheels loose the round shape easily after bumpy downhill rides. This happened to a friend of mine who has a Kona Fire Mountain. A smart thing you can do is replace the rims (or the whole wheels) with ones that are designed for V brakes - they are stronger due to thicker walls; also the sharp U or V section profile makes them hard to bend/break.

Kona Mountain Fire 2009 Bike

Another reason the disk brakes are desirable is because they are thin and ventilated. Also the travel of the brake pads is shorter than in the case of V brakes - the pads are closely positioned sideways from the disk as to apply friction on it after a travel of not more than 2 mm. The holes in the disks allow a better ventilation letting the heat (caused by friction) escape more efficiently.

The rims get hot (after a long downhill ride with V brakes) and transfer the heat to the tires which is not necessarily a smart way of getting rid of heat. While I haven't heard of tires exploding or melting due to hot rims I think we all agree the disk brakes manage to take care both of stopping the bike faster and not damaging the tires through heat transfer.

The same physics law that makes the rim of the wheel move faster than any point situated closer to the center of the wheel is responsible for the noise of the helicopter rotor blade. Some of the noise that we hear in a flying helicopter (bang bang bang) is a series of sonic bangs caused by the tips of the blade which travel through air at supersonic speeds. The longer the blade, the faster the speed of its tip (rotations per minute being constant). Military forces are working to reduce this noise for stealth operations -
long-range propagation of helicopter noise can alert an enemy to an incoming helicopter in time to re-orient defenses.
Read more about helicopter noise reduction and rotor noise (see page 4).

Want to learn more? Check out a cool article where you can learn about the benefits of having disk brakes on your mountain bike - weight and other technical aspects are being taken into account as well.

Keep riding your bike. And since you love biking so much, why not learn to design your own mountain bike T-shirt or jersey?


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  1. Hi,

    I beg to differ on this one!

    First of all, the angular speed is the same at the disk point and at the rim point.
    What you were trying to say is that the travel of the brake pad (the arc length) is longer on the rim than on the disc for the same amount of rotation. So it is the same angular speed (measured in rpm, radians per second etc) both at point A and point B. Just the arc length AA' is larger than BB'.

    Secondly in concern of the efficiency of the brakes we are interested in the force needed to stop the wheel depending on the position relative to THE AXIS OF THE WHEEL. And here we get to the torque concept.

    So lets say
    the torque needed to stop the wheel (lets call it Ts) its the same at any point from the axis point (lets call it X) to point A. The only variable is the brake force needed at a given point.

    So we have the following relations
    At the rim (point A) : Ts= Fa*XA therefore Fa= Ts/XA
    (Fa is the force needed to stop the wheel at point A, XA is the distance from axis to point A)

    At the disk point

    So per example let say that at a specific moment, the torque needed to stop the wheel is: Ts=10 Nm.

    So let's calculate the forces needed at each point.
    Fa=Ts/XA; Fa= 10/0.3; Fa=33.3N
    Fb=Ts/XB; Fb= 10/0.1; Fb=100N

    So, the braking force needed at the disk is higher than teh braking force needed at the rim!
    You can try it yourself by trying to brake the wheel at the disk and at the rim points, you will see the difference.

    Also, in automotive industry the brake disks of cars get bigger and bigger ...

    Needless to say that Fx equals plus infinity...

    We need more braking force but disk brakes are more efficient, hmmm thats a bugger!

    It's all in the materials used.
    The rims are made of aluminium and the rim brake pads are made of rubber.
    The disk is made of steel and the disk brake pads are made of asbestos (maybe mixed with metal particles, just like in the auto world)
    So the disk brakes are allowed to heat more than the V brakes, maintaining efficiency.

    Another factor is the brake caliper.
    The disk brakes have a proper brake caliper which is not allowed to expand, unlike the bike framework that holds the Vbrake components...

    I hope you'll undestand, i am not an engineer :D

    1. Though it is true that the Angular velocity is the same, the linear velocity is different. I would say the article is not wrong in stating this. It clearly states that the distance the rim moves is greater than the distance at the disc brakes over the same amount of time. Though you are correct in stating that this means they have different arc lengths, they do in fact have different velocities. Velocity is distance/ti

  2. Wow! This clarifies it all now.

    Indeed the force necessary to stop the wheel is grater at it's center - I was aware of that but I never thought further into the physics of the process. So I figured since the disc moves slower relative to its disk pad brake that must be the real reason why it's more efficient than V brakes.

    Thanks for this awesome explanation!

  3. The best thing would be a disk brake near to the rim, but also your braking can only stop as quickly as your tyres and grip allow.

  4. just Lol...............total non-scientific post..
    Do you can explore where you count the leverage action happens when braking with a disc......try ..pull your front wheel > make a spin the fron wheel > try to stop it by your hand at the Rims and thereafter try at the disc rotor......lets see which one stop more easyly
    .......i dont think who post these he/she is a biker or such he didnt have a good bike or else......the same non-scientific post with rims too.....do you wana say DH/DJ/Fr/AM riding rims are poor than a XC-V rims or such.......hahahahhahahah

    1. Just as I said in the update man, my post is crap. Read Remus's comment above - I agree the force is much higher at the hub. I was just speculating - thinking out loud.

  5. Seems simple enough to me, common v-brake bikes used for heavy duty purposes need some box rims with THICK brake tracks, made of good steel or alloy, maybe with upgraded wear surfaces (ceramic! It's been done), and upgraded pads (they are called Kool stops).

    Discs are great, but v-s are still great for XC and road riding.

    1. Yeah, I'm a V brake guy but I may upgrade. :-)

      Love your bike engines, man!

  6. Larger diameter discs are more powerful than small discs, and you can't get a larger diameter 'disc' than the rim!

    Sadly, STYLE has pushed disc brakes to become nearly universal on new bikes when the brake type should really be determined by the bike type.

    The heat transfer issue can only be a factor if you weigh 300lbs and do long downhill riding slowly. I've had some very long, steep downhills where I had to brake the whole way due to hikers - and was concerned about the heat build up... the rims were hot, but certainly not to the degree of becoming a concern for the tire. Remember, the rim has many times the surface area of a disc, so radiates the excess heat much faster. Disc brakes can also fail due to heat, it's just not a threat to the tires.

    The truth is a GOOD rim brake setup brakes far more powerfully than ANY disc. Pads have improved a great deal since the advent of discs - and ceramic coated rims are worth every penny - they do not get as hot, do not transfer heat as much, are more consistent in water/mud, and DON'T wear out.

    Still, if I had a downhill specific bike I would use disc brakes for one reason - more control near lockup. Because the disc IS smaller more force is required for lockup, so a wider range of force is needed between 0 and lockup - resulting in a wider range of power that can be applied more precisely. This could result in fewer slideouts or end-o's! Plus, who cares about weight on a downhill bike?

    BTW Constantin - good on you for admitting when you're wrong! - and think twice about your riding style before you 'upgrade'.

    1. "The truth is a GOOD rim brake setup brakes far more powerfully than ANY disc"

      What?????????? Are you retarted? Dude you sound like you never even tried disc brakes. If that were the case, there would never be disc on a bicycle. You see it as a STYLE when really it's a revolution for bicycle brakes. Quit worrying about weight. Disc brakes outperform any other brakes OVERALL. You need to accept "changes" in this world. I ride with disc brakes for 2 years now. Before that I was on v's of all kinds and under. Used "GOOD" expensive "PROFESSIONAL" rim brakes on a bike that cost over 1k and installed by professionals and honestly, they have no chance against disc. I know this from experience, I'm not here to give BS. People such as yourself and myself have our opinions, but really the laws of physics know what is better no matter what you prefer. What's better is better. Can't argue with that.

    2. That's what Carlmon, said. Disk is better. My assumption and (crap physics explanation) was wrong.

  7. Hey, Carlmon! You're so right on the lockup - never thought of that but makes sense.

    But I guess, as Remus said, the theory that braking is nothing else than transforming one type of energy (kinetic) into another (heat which is then "lost" in the air) still stands, right?

    I'm asking this coz if you said the ceramic rims don't get that hot, then what does that mean? How's the energy transforming in that case?


  8. Constantin- it's the difference between conduction and radiation. There is no significant contact with anything to conduct the heat away from your wheel, so the energy can only be dissipated by radiation - which happens faster at higher temperatures.

    The ceramic coating does not conduct the heat as well as raw aluminum (think space shuttle tiles). This results in keeping the heat at the surface (rather than going into the rim and tire) where it radiates much faster because of higher surface heat. The energy is radiated quickly into the air and brake pads - which is why there are different formulations for ceramic pads that can tolerate the heat.

    Uncoated aluminum is a very good heat conductor, so it rapidly absorbs more of the heat into the center parts of the rim, where it can store and build with prolonged braking, rather than radiating to the air.

    The Mavic ceramic rims I had on my old mountain bike had much better wet braking than any non-coated rim, and were less grabby when dry - I suspect due to a slight texture on the surface. Of course wet braking is less than dry, but it is significantly better than the panic of zero braking on a wet bare aluminum rim! And after a decade of hard use there was no sign of wear at all.

    My newer mountain bike has regular rims that stop quite well with Koolstop salmon pads - though more grabby than the ceramic rims were.

    Ceramic rim brakes might be the best choice for an all-mountain bike (including downhill) due to a balance of control, heat, and weight. If I ever need to replace my rims I'll go ceramic.

    Ceramic rims are more expensive, but not nearly as expensive as all that is needed to 'upgrade' do discs.

    1. Got it! Gotta look into ceramic rims this coming summer.

      Good point on your "style driven bike trend" on your first comment. Indeed there's a breed of bikers who like to "flash" their discs. :-)

      I'm a cycling enthusiast in general, but I do enjoy a good sweaty uphill ride just to live the thrill of a speedy downhill drop later on. So ceramic rims seem to fit my "style".

      Thanks so much for taking the time to reply!

    2. Forgot to mention to contact me, Carlmon (there's no email info on your Blogger profile). Cheers!

  9. Carlmon says "Still, if I had a downhill specific bike I would use disc brakes for one reason - more control near lockup. Because the disc IS smaller more force is required for lockup, so a wider range of force is needed between 0 and lockup - resulting in a wider range of power that can be applied more precisely. This could result in fewer slideouts or end-o's!"

    This is very true but is it just down to brake force and control. Is there any physics involed relating to the position of the braking force relative to distance from the wheel center. I believe that end-o's more than slideouts are affected by some 'rotational' 'center of gravity' issues here?

    1. Can't actually answer your question...

      But it's clear now (for me) that the larger the disk, the easier it is to brake. So as the breaking margin of the disk is further from the center of the wheel you need to apply less force to brake.

    2. Cliff- what you're talking about here is braking torque, and the only thing that can cause an end-o is braking torque exceeding your torque in the opposite direction due to gravity.
      Remember, torque is the length of a lever times the force applied to that lever.
      If it takes 50 foot-pounds to stop you in 20 feet it makes absolutely no difference whether that force is higher nearer the center or lower near the rim if the torque is the same.
      The longer moment arm of a rim brake only makes exceeding the required torque to end-o easier.
      Speaking of end-o's, I had a rather painful one a few months ago, so I switched from the koolstop salmon pads to koolstop black. Salmon pads are very aggressive, but I found the hard way are too easy to lock when you panic!

    3. Now I know that I don't know too much about these things...

      Half of what you're saying is "alien stuff" for me. :-) I'm not actually a technical mountain bicker. I just cycle and I love downhill but that's where it all stops.

      Carlmon, please contact me.

  10. In my opinion, disc brakes are far more superior from experience. I use mechanical disc brakes with 160mm rotors that came stock on my bike. Got it in 2011 and was my first bike with disc brakes. Before that, I used nothing but Vs and under. The difference is WOW. Let me give you all a scenario on how I feel between riding with disc brakes vs V brakes. When I ride with v-brakes and try to stop, especially in rain: (the scene from spiderman when he tries to stop the train). When I ride with my mechanical disc brakes during all weather conditions: (Magneto stopping a train). Now with hydraulic disc brakes...I don't need to say more. I couldn't care less about weight or cost. I may not "need" them but I want them. Saved my life a couple times from cars that don't know how to honk and slow down when coming out of alleys. Disc will replace V brakes in the future. We are in the very process. They are getting cheaper, lighter, and installed on more bikes every day. Even road bikes. I don't need a scientific explanation for why they are better. V-brakes are old technology. Doesn't mean to stop using them. People still use CD and cassette players to this day instead of ipods and mp3 players. I still listen to vinyl.. It's whatever preference the person seeks as long as it does the job. But one will be more superior than the other and will do the job better and more efficient. To conclude this, I personally will NEVER go back to v-brakes. Will upgrade to hydraulic eventually.

    1. I hear you, man! Good point. A friend of mine has hydraulic disk breaks and he said he'd never go back.

      After I tried his bike - I totally agree.


  11. I feel I need disks on my race bike 'cause going fast in the city and not knowing when a car may pull up in front of you sucks. But I don't want it to add too much weight so I think it would be good to have disk in the front and V in the back. sort of like I have double disks in the front of my motorbike and only a single disk in the back.. would it work?

    1. Yup, Saytac. If you wanna save weight, the disk on the front wheel is the best way to set up your bike.

      That's coz when you break, the inertia makes most of your weight press on the front wheel - thus you need better breaking power there. Be careful though - you may fall on your face if you press too hard on the front brake. :-)

      I guess this happen to most of use at least one time.

      The front suspension also helps to dissipate some of the kinetic energy while breaking so your breaking distance will be shortened with front suspension.

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  13. I would like the opportunity to purchase a mountain bike with rim brakes. I like rim brakes better than disc brakes. The last time I checked at my local bike dealer all quality mountain bikes come only with disc brakes. Why not let the consumer have a choice? Follow the money. Rim brakes work great and need less maintenance and adjustments, and are much easier to work on meaning fewer repairs and less need for bicycle repair shop visits. Ok, disc brakes are better. I think it depends on what perspective you are making your judgement. From my experience, I have found disc brakes to be a nuisance and distraction from the pleasure of bicycle riding because they require so much attention. On the other hand rim brakes don't.


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