bikeman2005

Just wanted to know what is the main performance difference between disc and V brakes. I'm a noob and thinking about getting a bike with just the Vs for money reasons. However, I was wondering if it would be worthwhile to save for discs. Also, if I were to get discs, at what price do they start becoming worth it. I'm of the understanding it is best if you are going to get discs to not go to cheap on them. Thanks.

LowCel 

The biggest difference is how they perform in wet / muddy conditions. In these conditions disc brakes are much more reliable. As far as which brakes to go with if you are serious about your riding I wouldn't go with anything below Avid bb7's.

Raiyn

Here we go again. We just did this last week.
The following has been reposted by me more times than I care to admit
Why are discs better than rim brakes?

The difference is friction. Friction is of course the force acting against the momentum. Friction under all circumstances will be greater in a disc system than a rim system. Not even ceramic rims and their pads can compare to the sustainable friction of a disc system. Not to mention the effects of inclement conditions on rim brakes.

Let's start by taking a look at the physics involved. There's a law of physics that states how an object in motion has a certain amount of energy due to its momentum. This energy is called kinetic energy. In order for this object in motion to stop or slow down, it must lose some or all of its kinetic energy. It does this by converting the kinetic energy to heat.

It's pretty simple. At your wheel you have a metal disc and a set of friction pads. The pads squeeze or push onto the metal. When this happens, you create friction. Friction generates heat, of course. Since the wheel is turning, then the kinetic energy of your momentum is converted to heat at this point and discharged harmlessly into the atmosphere (with a slight loss of pad material), and your bike slows down. The faster it is going, the more heat is needed to stop it. The more pressure you apply to the pads, the faster it can discharge the kinetic energy. The disc aids in the discharge of the heat generated. The surface area of the rotor allows heat to dissipate more quickly.
Rim brakes work well, but they have a hard time shedding heat well enough to prevent fade when used really hard. Brake fade occurs when the brake overheats dramatically; braking power is vastly reduced. The fact that rubber compound rim brake pads can only sustain so much heat and pressure before they break loose is another key point as is the fact that disc pads, being made of a more durable substance, are not prone to the same failures.
Facts[*]Disc brakes handle heat load and dissipation better than calipers. [*]They don't transfer the heat generated directly to the rim, like calipers. [*]Disc rotors are MUCH cheaper to replace than an entire rim (as low as $17).[*]As far as being able to lock a wheel: yes you can lock a wheel much easier with a disc than you can a caliper of any type, however if your brakes are PROPERLY setup, you also have greater modulation with less effort than any caliper system ever invented.

Next time:

Brian

Yeah, what Raiyn said. But cheap discs are a headache, and should be avoided.

[bEn]

eg. Promax

Brian

And Tektro.

wheelhot

What about Avid BB5?

Brian

Good stuff. Easy to set up, good mudulation. Strong enough to stop a tandem. And, just to make you happy, economical.

xenochimera

i think the only difference between a bb5 and bb7 is that the 7 have adjustble calipers??

wheelhot

Whats the difference is braking power between BB5 and BB7 and Juicy 5 and 7 during raining?

Drunken Chicken

The same that there is during dry (i.e., Juicy's have better modulation and more power, but are hydraulic, which makes on-the-trail repairs hard, etc).

ankush

i think what he meant was what is the difference between the bb5 and 7 and then, in a different comparison, between the juicy 5 and 7. and as far as i have read, basically the 7's have more tunability options over their counterpart fives?

would someone please correct/verify?

Drunken Chicken

Ankush: Could be, the post wasn't very clear. Anyway, you're right, the Sevens have more adjustability over the Fives.

seely

Yes, the only difference that I can detect between the BB5's/7's is the setup. Braking power, with the limited time I have had on both, has been very comparable, but a lot depends on setup, if you've faced the brake tabs, if the pads are contaminated, if the pads are broken in, etc, etc.

You are less likely to cut the end of your finger off with BB5's (still sore + bitter).

*RANT/TANGENT WARNING*
In all honesty, I firmly believe brakes depend more on proper setup and levers than the actual brake itself. The crappy Hayes mechanicals on my P.1 are DIALED. They feel great, and anyone who has ridden it would tell you that too. Why? I took the time to face the tabs, true the rotors, and ran full housing front and back with a quality Avid lever. With the old Hayes levers, they never felt all that great. So in short, there are a million factors at work that play into brake feel/setup.

wheelhot

Hey thanks for the info, technically i just want to know the braking power of Avid BB5 and 7, Avid Juicy 5 and 7 during raining and about their durability in trail biking and i have another question, can i use a hydraulics lever on a mechanical disc? If can, will my mechanical disc work better then using a dial lever?

Brian

You cannot use a hydraulic lever on mechanical discs. Hydraulics push fluid through a hose to acutate the brakes by moving the pistons inward. Mechanical brakes use a lever that pulls a cable to actuate the arm that moves a single piston inward.

wheelhot

Oops, which cable do u think is the best for mechanical disc brake? and must i change my hub if im going to use discs?

Brian

You'll need a disc-compatible hub. Any cable will work, as long as it's a brake cable.