A larger rotor stops faster becuase the leverage is greater since the point of the applied brake force is further from the center of the wheel. They also could provide slightly better fade resistance becuase of the greater heat dissipation area.

One reason a hydro brake could work better then a mechanical is because the mechanical brake cable housing could be compressing slightly. That is the theory behind the Nokon and other similar cable housings. Getting rid of the slight traces of compression could help improve braking performance.

I have no trouble locking my mechs, so power is not the issue. Ease of pull at the lever and modulation is where hydros really shine.

Really? I always thought a larger rotor would give better leverage and thus stopping. Although when i think about it, considering people have no trouble locking a 6" rotor on almost any system it seems moot and the heat issue comes into play with fade.

by that logic, V-brakes should be absolutely ridiculously powerful.

No because you apply the pressure differently.

Your reading comprehension is distressingly low. The obsession referred to a particular aspect of the braking system.

Your standard of proof is disturbingly low. You assert, therefore it is true.

As others have pointed out, well adjusted mechanical systems can easily lock up the wheel under load. You need nothing more.

By that logic V-brakes are pretty good given that the force on the pads is pretty low.

Al

Yes, in theory mechanical and hydraulics should have the same ability to apply force. The truth though is that if you have cables, you have friction, which isn't there with hydraulics. The smoothness of hydraulics could result in better stopping power because of better control. As you get closer and closer to the point of breaking loose, the smoothness of the hydraulics may allow you to maintain braking instead of locking up.

I reality it might not mean anything since the surface you are stopping on isn't usually consistent, so the difference may be moot. All I have is hydraulics, but I probably wouldn't mind mechanicals either. I would mind not having disc brakes since I do find them much better.

I have never experienced problems with fade on my brakes in real life - and I go down 3,000 feet of hill, controlling the descent with my brakes. This isn't a pure descent though, there are dips and rises along the way which gives things time to cool off. This is not to say it is a good idea to touch the rotor at the end of the ride.

I just jam my foot in the spokes.

Cuz I roll old school like dat.

If you use a good coated and lined cable system and know how to route them smoothly you won't have any real friction to speak of.

Ummm...wrong. Take a basic physics course sometime, or failing that, just read this from Hayes: https://www.hayesdiscbrake.com/hayesu_product1.shtml (look in the first highlighted box, number 3)

Rim brakes certainly benefit from the large diameter of the wheel, but they suffer from many other things that cause a degradation of braking power.

Ok, you didn't mention that assumption when you claimed my post was wrong and I missed your mention of it at the top of this page. I was thinking in theoretical terms of stopping the wheel faster, not necessarily stopping the whole bike/rider unit faster. A larger rotor does provide more powerful braking, wether or not that power is needed or can be utilized is another question. Sorry. I'm still right based on my thinking, and you on yours assuming that both or all systems provide the power to lock up the wheel.

Regarding hydro's...I have seen broken lines TWICE...once on the Mr. Toads downhill ride in Lake Tahoe and the other in the Foresthill area, near Auburn. One rider caught a branch and ripped the hydro hose right out of the reservour, the other rock crashed and damaged the connection at the rear caliper, leaking like a garden hose. Me likes cable as stated earlier, fixable on the trail. Yep, love the Avid BB-5's.

Larger rotor do provide more stopping power by simple physics principle of larger leverage ratio. If larger rotor does not provide more stopping power, all the motorcycle out there will use 160mm size rotor to stop a 165mph bike (not a good idea, unless you have a death wish). You'll see higher speed and mega horsepower motorcycles out there use bigger rotors to provide more stopping power and they also use dual brake pistons calipers.

Bicycles does not acheive speeds anywhere close to motorcycle speed so a simple single piston caliper and 160mm rotor is enough for 80% of mountain bike applications out there, downhill bikes will need 203mm rotors because of their heavier weight and more rolling momentum. Just because you can lock up a mountain bike wheel traveling at 15mph and weight 30lbs does not mean you can stop a 400 pound, 140 hoursepower, 120mph motorcycle with the same setup. Just think about it!

Brake rotors dissapate heat not just by its larger size/surface area but by holes/slots that is drilled into the rotor so it will have more contact area with air so heat can be tranfer faster.

Motorcycles are the forefather of moutain bikes, many breaking/ suspension theory and principals have been work out already, just look at how motorcycle is set up and it will answer many mountain bike questions.

I have ridden bikes with both setups and both worked fine...my bike has mechs. I havent ridden a bike with hydros long enough to notice any difference worth mentioning.

I agree with this statement. But I will also point out that the larger rotor with require less force applied via the brake lever to do the same job. Downhill riders often cite this as another huge benefit of the larger rotor. Their hands don't cramp up.

I think you're the one who really need to think about it. Just because you can lock up your bike with mechanical brake setup does not mean you will not stop faster with a hydrolic system. At what speed you're able to lock up the your wheels? 10mph? 15mph? and at what distance it took to come to a complete stop compare to hydrolics. For example if you can stop your wheel in 10 feet with your mechanical setup that use 160mm rotors and you switch to 203mm rotors it might help you stop your wheel in 8 feet.

Its not just because you can lock up your wheel that determines the braking power, its the distance that you can come to a complete stop. You might not feel the benefit of hydrolics and bigger rotors until you're traveling at higher speed with heavier weight.

Hydrolics are more powerfull becasue they can exert more pressure per square inch than what our hands can pull with cables. Its like power assit steering and brakes with cars. Have you ever try to steer your car with the engines off?

If you want to claim that in most mountain bike applications that mechanical brake set up is more than capable to bring you to a stop, that's fine. But to claim that hydrolics and bigger rotors will not provide more braking power and bring you to a complete stop in a shorter distance is simply wrong!

I know I said I was done, but that was just hilarious Mr. fjyang.

If you lock 'em up, you lock 'em up. You're still skidding across the ground wondering why you didn't go with 2.35's instead of the 1.95's that aren't hooking up enough to keep you from hitting that tree, hehehe.

It's ironic, but I was thinking more about what Mr. willtsmith_nwi mentioned. It takes less force at the lever with larger rotors...agree'd. It also takes less force at the lever of an Avid Code versus a BB7, or a Juicy 5 versus a BB7. (for example...no obsession with either )

That's what I meant about "more stopping power".

Sure, you can lock up the wheels with both but it takes more finger force to lock up the wheels with mechs versus hydro's. (properly set up and of good quality)

Either way...Mr. fjyang's comment was ammusing enough to bring me back into this pointless discussion. Lordy that was funny.

Obviously tires are part of the equation, enjoy your brakes, its a moot point and academic to keep going with this.

i'll +1 that.

if you can lock your tires, then you have enough power to stop your bike. it takes shorter to stop with traction it does locked up. having a bigger rotor won't change that fact; all it will do is make it easier for you to lock up your brake. so in a sense it does offer more braking power, but it won't change your stopping distance.

I need to throw in another 2 cents here. If you're skidding you're not STOPPING. Skidding occurs when traction is broken. Maximum braking force comes at a point just BEFORE you lose traction.

I think everyone needs to take a step back and re-read Sheldon Brown's Braking And Turning article

Feel free to keep your smarty pants comments to yourself I'll be happy to put you on a 50lb bike with 5" tires, 100mm rotors, 10" long brake levers and send you downhill at 45mph.

We're not done yet? What I'd mean by moot point and academic is like saying if we put a 100lb guy and 500lb sumo wrestler in a vacuum and see who has more power. That's what I'd mean by moot point and academic. Real world don't work like that becasue many variables are involved. I didn't attack you on my last comment did I? I'd have mechanical brake on my bikes and I also enjoy them for many years just like you do.

Anyone want popcorn?

Yeah, but hold the butter - some of these arguments are too slick for me...