# Thread: Hydraulic Guru's...a question (or five) based on Hope's

1. ## Hydraulic Guru's...a question (or five) based on Hope's

I think I know the answer to this already, so I suppose I'm looking for affirmation.

The question...What's the REAL difference here?

Let's compare different models of Hope brakes brakes. Mono Mini, Mono Trials, Mono4 and Mono6. First, let us suppose that this comparison involves only 180mm rotors and identical pad compounds. All brakes other than the Mono Trials have the same piston area, giving them the same hydraulic leverage ratio. (The Mono Trials has a larger slave piston, increasing the ratio and making for MUCH more powerful brakes). Given the same hydraulic ratio, there are two obvious differences, pad contact area, and the ability to absorb heat.

Does pad contact area relate directly to stopping power? Since the same amount of overall force would be present in any one of these brakes (excluding the MT) the difference here seems to be in the pressure of the pad on the rotor. Given the same input force, doesn't the pressure decrease when surface area increases, giving us the same end result? Say if you're able to pull at 25lb at the lever on a Mini vs. a Mono6, the pressure at the pad is the same, right?

2. ## Same area ?

I thought the Mono had 2 pistons, the mono4 had 4 pistons and the 6 had 6.
I dont know the specs of the brakes, but if each piston was the same X-section area then the force exerted by each piston is the same for the same pressure generated at the master cyl.

So each upgrade on the Hopes would bring an increase in the force exerted at the brake
caliper.

eg. Each piston is 1 sq inch.

So 100 psi at the master would generate 100lbs at the mono, 200 at the mono4 and 300 at hthe mono6.

Originally Posted by smudge
I think I know the answer to this already, so I suppose I'm looking for affirmation.

The question...What's the REAL difference here?

Let's compare different models of Hope brakes brakes. Mono Mini, Mono Trials, Mono4 and Mono6. First, let us suppose that this comparison involves only 180mm rotors and identical pad compounds. All brakes other than the Mono Trials have the same piston area, giving them the same hydraulic leverage ratio. (The Mono Trials has a larger slave piston, increasing the ratio and making for MUCH more powerful brakes). Given the same hydraulic ratio, there are two obvious differences, pad contact area, and the ability to absorb heat.

Does pad contact area relate directly to stopping power? Since the same amount of overall force would be present in any one of these brakes (excluding the MT) the difference here seems to be in the pressure of the pad on the rotor. Given the same input force, doesn't the pressure decrease when surface area increases, giving us the same end result? Say if you're able to pull at 25lb at the lever on a Mini vs. a Mono6, the pressure at the pad is the same, right?

3. I was wondering at the same thing as well. Some say M4 is just as powerful as M6, but M6 has more modulation due to the toe-in effect of the series of pistons in different diameters.

If we disregard the fade resistance and the heat dissipation effect of multi-pair pistons brakes. The only remaining difference should be the fartherness of the leverage distance exerted by the pistons of smaller diameter.

I'm not sure how relevant is this, but let me point out that the LEVERAGE exerted by the single pair of BIG opposing pistons calipers (Mono Mini) on 180mm rotor is less (at least slightly) than the LEVERAGE exerted by double pairs of SMALL opposing pistons (M4) calipers on the same 180mm rotor,even though the overall aggregated piston areas between the two brakes are the same.

Let me illustrate this:

Mono Mini, a Single pair opposing piston brake (2 BIG pistons).
Mono M4, a Double pair opposing piston brake (4 SMALL pistons).

The area of 2 BIG piston = the total area of 4 SMALL pistons

Imagine: BIG piston = a quarter coin, SMALL piston = a dime coin.
This is a valid comparison because a quarter has exactly twise the area of a dime.

Their respective leverage distance will be:

Mono Mini equivalent: 180mm minus the radius of a quarter coin ~ about 168mm
Mono M4 equivalent: 180mm minus the radius of a dime coin ~ about 171 mm

Doesn't sound like a big difference, but certainly a measurable one.

I hope you can picture what I'm trying to say....

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