Bigger brake discs/rotors

[militantmandy]

With good modulation you can also apply very little braking force gradually which is great for steep techy rocky decents, if it grabs you're going over the bars.

Modulation IMO is more important than outright braking force

I agree with some of that, but outright power is definitely the most important thing for me. On long, steep descents, more power means less effort, means less hand fatigue, means more confidence. A relative lack of modulation can be overcome with improved technique. That said, I still find Saints/Zees to be too sharp for my preferences, although I am sure I could get used to them.

 

[urastus]

With good modulation you can also apply very little braking force gradually which is great for steep techy rocky decents

I'm in the modulation camp, but not in this instance . I ride a couple of long steep techy rocky descents most days - that's why I put metal pads on the back. Usually it's a quick grab on about a meter of flat before a mess of washouts and rock. That meter is just part of a second. It's like that all the way down - squash and quick grab, let go and go light over, squash and quick grab, let go. My bum is back (I'm still balanced) so I never slide. Before when I had resin, the back brake was cooking because I had to hold harder and more often.

The better I ride the less I consider modulation important for mtb. It's not like riding on the road - we push the bike down into corners to get on the side knobs while we stay up; bang on the brakes, push the bike down. It's all pretty aggressive. As mtb riders, we generally squash the bike hard and brake; it doesn't last long and it's hard to lose traction when you squash.

 

[emtbPhil]

Kinda completely missing the point

Power and modulation are not related at all - you can have both, you can have one, you can have none.
The more modulation the brakes offer the easier it is to get a precise amount of braking force without going too far and locking up.
Power needs no explanation but is typically a combination of rotor size and pad area. You can get more power from calipers with bigger pads the same as you can get from going up in rotor size.

Then there's heat dissipation. Which again is affected by pad size, compound, caliper material, cooling fins, rotor size, whether the rotor is a split rotor or a single piece... etc.. etc..

I'll agree to disagree but if you're braking style is nothing, slam on, nothing, slam on.... you will eventually break traction on wet/muddy sections or throw yourself over the bars.

It's good for doing skids in the car park to impress the kids though

 

[Alexbn921]

Kinda completely missing the point

Power and modulation are not related at all - you can have both, you can have one, you can have none.
The more modulation the brakes offer the easier it is to get a precise amount of braking force without going too far and locking up.
Power needs no explanation but is typically a combination of rotor size and pad area. You can get more power from calipers with bigger pads the same as you can get from going up in rotor size.

Then there's heat dissipation. Which again is affected by pad size, compound, caliper material, cooling fins, rotor size, whether the rotor is a split rotor or a single piece... etc.. etc..

I'll agree to disagree but if you're braking style is nothing, slam on, nothing, slam on.... you will eventually break traction on wet/muddy sections or throw yourself over the bars.

It's good for doing skids in the car park to impress the kids though

Yes and no
Power and modulation are not related. More power is generally a good thing as there is an optimum lever force for maximum control. Also less lever force reduces fatigue. Most riders never learn their brakes or try powerful brakes and think they lack control.

Lack of power (Sram) does not equal control, it just means you have to crush the leavers and have crappy brakes.

Pad size has NO effect on power. NONE! Larger pads last longer and small pads wear out faster. The total friction is identical. There is a small heat dissipation benefit to larger pads.

The speed you ride and the steepness of your mountain will have a big impact on the power you need and the optimun range of power. All can be tuned with rotor size and pad compound.

Sram brakes get significantly better with Trickstuff pads (power and control). Shimano also benefit from Trickstuff pads in the modulation department without losing any power.

Setup and bleed have a huge effect on feel.

Also initial grab and modulation at lockup and completely different things.

I ran some Sicc rotors with composite pads and it was the best modulating brake I will ever ride. They don't increase friction coefficient while stopped so they can transition from stop to spinning with no reduction in lever pressure. Absolutely amazing performance that nothing on the market can match. It's too bad they couldn't solve the technical issues and went out of business.

 

[militantmandy]

That's what I said



Whut? Yeah a more powerful caliper will assert more force with less finger force, but if you apply more force with less finger force you are by definition losing granularity on the control.



This is nonsense. All sram aren't lacking in power...



This is absolutely mind-boggling nonsense.. Brakes convert movement into heat by applying a friction between PAD AREA and ROTOR AREA. The reason you get more braking force when you change the rotor size is you have moved the force applied further away from the pivot (center of wheel). You get more braking force with bigger pads because there is MORE SURFACE AREA CAUSING FRICTION.


I'm out... you can literally google all of this.
I'm off to tell the BTCC team that they're wasting they're time with 6 pot calipers and massive discs.

I have no horse in this race, but from Google:

"Although a larger area of contact between two surfaces would create a larger source of frictional forces, it also reduces the pressure between the two surfaces for a given force holding them together. Since pressure equals force divided by the area of contact, it works out that the increase in friction generating area is exactly offset by the reduction in pressure; the resulting frictional forces, then, are dependent only on the frictional coefficient of the materials and the FORCE holding them together."

Why doesn't friction depend on surface area?

Ask the experts your physics and astronomy questions, read answer archive, and more.

www.physlink.com

Interesting, as I would have naturally assumed bigger pad (or contact patch between pad and disc) would equal more friction. Also, I cannot speak to the voracity of that site.

 

[emtbPhil]

Most of that was bordering on nonsense.

The speed you ride and the steepness of your mountain will have a big impact on the power you need and the optimun range of power. All can be tuned with rotor size and pad compound.

Yeah 4 piston calipers just look nice.

Also initial grab and modulation at lockup and completely different things.

No they're not

But by pad size I meant as a generalisation that bigger pads means bigger calipers which means bigger pistons

Piston size does effect brake power.

 

[emtbPhil]

I have no horse in this race, but from Google:

"Although a larger area of contact between two surfaces would create a larger source of frictional forces, it also reduces the pressure between the two surfaces for a given force holding them together. Since pressure equals force divided by the area of contact, it works out that the increase in friction generating area is exactly offset by the reduction in pressure; the resulting frictional forces, then, are dependent only on the frictional coefficient of the materials and the FORCE holding them together."

Why doesn't friction depend on surface area?

Ask the experts your physics and astronomy questions, read answer archive, and more.

www.physlink.com

Interesting, as I would have naturally assumed bigger pad (or contact patch between pad and disc) would equal more friction. Also, I cannot speak to the voracity of that site.

Yeah I was forgetting that I didn't mention piston size in the original reply. If you increase the friction face and the piston size behind them, you get more power.

But I can't see any way you would put a bigger pad on a bike with a small caliper. Unless you bought a bigger pad and filed it down to fit in a single piston calliper and stick out of either end... but then you're a lost cause lol

I deleted that cos it's getting ranty. There's so much nonsense in here about "have the most power you can get and just hammer on" that I've lost patience with arguing on the internet

 

[militantmandy]

Yeah I was forgetting that I didn't mention piston size in the original reply. If you increase the friction face and the piston size behind them, you get more power.

But I can't see any way you would put a bigger pad on a bike with a small caliper. Unless you bought a bigger pad and filed it down to fit in a single piston calliper and stick out of either end... but then you're a lost cause lol

I deleted that cos it's getting ranty. There's so much nonsense in here about "have the most power you can get and just hammer on" that I've lost patience with arguing on the internet

For the sake of your mental health, that might be a wise move!

 

[Alexbn921]

Piston ratio X friction coefficient X leaver force = power.

It is possible to have grabby brakes that modulate at the limits. I never said it was a good thing.

I rode in Moab on sram code ultimate brakes and they where great. No need for face melting power and the feel was excellent.

Back home they are scary and my hands hurt. They didn't have the initial bite or power I needed. I swapped them to xtr 4 piston. I want and have adapted to right now power with 220 rotors.

 

[urastus]

Piston ratio X friction coefficient X leaver force = power

if we're getting into physics, consider rotor size alone! It's simply a longer lever. Even with the modulation argument, bigger rotors will take you in that direction. A longer lever = more finesse, TO SLAM IT HARD . Ooops, brain fart ; it will give you more finesse

 

[Alexbn921]

if we're getting into physics, consider rotor size alone! It's simply a longer lever. Even with the modulation argument, bigger rotors will take you in that direction. A longer lever = more finesse, TO SLAM IT HARD . Sorry for that; it will give you more finesse

Truth! I like big rotors and I can not lie. On my mountain bike I run +20 in the front for the better feel in the rear.

 

[Redlemon]

This is entirely wrong, with all due respect

Spent years building race cars - what modulation allows is for you to use 98-99% of braking force without locking the wheel up
With poor modulation you would get to 80 or maybe 90% and then lock up - as soon as you lock up you lose all braking force as the tyre has lost traction with the surface

With good modulation you can also apply very little braking force gradually which is great for steep techy rocky decents, if it grabs you're going over the bars.

Modulation IMO is more important than outright braking force

You're right on it!

I really don't get the hype about Shimano brakes where you're getting hit with a 80% power surge at bite point, but then with nothing left in the tank to control yourself. Combine that with their sometimes vague bite point and you get a nice recipe for a disaster when riding on some steep slabs/rocky descents.

It's the worst feeling ever not being able to properly modulate on steep stuff.

 

[Alexbn921]

Shimano modulate better than Sram at higher power levels and don't feel grabby after you learn the power curve. If any brake is setup wrong it will feel like crap.

Sram has a smoother ramp up, but requires too much lever pressure at threshold.

Trickstuff brakes have a very progressive ramp with a massive amount of power. They are the best I've used.

 

[Redlemon]

Shimano modulate better than Sram at higher power levels and don't feel grabby after you learn the power curve. If any brake is setup wrong it will feel like crap.

Sram has a smoother ramp up, but requires too much lever pressure at threshold.

Trickstuff brakes have a very progressive ramp with a massive amount of power. They are the best I've used.

I'll side with emtbPhil here as clearly you're not aware of what's going on lol, I'll stop it there and leave the article below so you may read a little bit on the topic.

The best MTB disc brakes – 14 MTB brakes in comparison

We tested the 14 newest and most powerful MTB brakes - in the lab and on the trail.

enduro-mtb.com

 

[Alexbn921]

Clearly I don't know shit. Did you even read the article?

Having lower deceleration values on very steep terrain is what you want.

RAM Code RSC demonstrated deceleration values on the dyno that fell short of the big hitters.

SRAM Code R It’s not a DH bruiser like some of the bigger hitters on this test. I have a set of these brakes.

Guide Ts struggled a little on steep terrain.
– Underpowered

Few brakes can match the distinguished heritage of the Shimano Saint, a brake that has been trusted by the world’s fastest riders.
– Too powerful for inexperienced riders

I'll see myself out.

Edit:
Trickstuff Power+ pads (they are compatible with Shimano pads) scrub speed effortlessly, no gradient or demand is too much.

I use these on all my brakes. They transform the sram setups and are slightly better that the Shimano pads.