Number of caliper pistons doesn't matter.

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DreamV4

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Surface of pistons is important. 3 sq.inch one piston works exactly the same as 2 pistons 1.5" sq. inch each and so on.
If master cyl. piston has surface .25 sq. inch and you push it 1", caliper piston 1 sq.inch or 2 pistons of same summary surface will move .25".
Let us hear what race guys say.
 

MaxMidnight

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Here we go, another one of Professor DreamV4's statements.

If the only aim was to move a piston a certain distance then your statement is correct.
However, the whole point of a brake caliper is to apply a force onto the brake disk and thus retard the machine it is attached to.

There are other factors that need to be considered; how much torque the pad can exert, i.e. the longer the lever the greater the torque will be. Remember Buell's rim brakes?
Whilst I may be wrong here, I would assume that the braking force across the face of the pad will reduce as the leverage it exerts will reduce as the distance to the mounting of the disk reduces?
Therefore the closer to the edge of the brake disk the greater the torque will be and therefore as multiple smaller pads can be place closer to the edge they will apply more braking force compare to an equivalent larger pad for the same pressure.

Brakes also generate a lot of heat which need to be dissipated. One route will be via the piston and into the caliper body. The two smaller pistons in the example proposed above have (if my sums are correct) a 41.7% greater diameter through which the heat can pass.

Larger pistons will also have more inertia so will take more effort to move them out and pushed back.

There may be other reasons that I haven't thought of.

It is also interesting to note that in motorsport and (as far as I am aware) most larger capacity motorcycle the multi pistoned caliper is used.
I don't think they would have done this is it didn't provide an advantage over one single piston.
 

02GF74

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To answer OP, I reckon the number of pistons doesn't matter, I'm sure it would be possible to have same performance from 2 piston brakes as can be achieved from multi-piston but the multi-piston calliper/disc would be lighter; and it's all about reducing unsprung mass.

There may be other reasons that I haven't thought of.
Having two or more pistons allows different diameter pistons to be used, which are used to compensate for pad were.

Shamelessly stolen from the internet.

The use of a smaller diameter piston at the side where the disc enters the brake pads will ensure more uniformity in the pressure distribution on the brake pads.

When the thickness of the brake pad is large compared to its length, there will be higher wear on the leading end of the pad. The frictional force acting on the disc contact surface and the reaction at the abutment of the pad will result in a turning moment on the pad, leading to higher wear on the leading end. The following figure explains the formation of uneven wear, and illustrates how a smaller diameter piston at the leading side makes the pressure distribution more uniform.


main-qimg-3162eb3d95e62310d8189415cf136b63
 

Parminio

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Surface of pistons is important. 3 sq.inch one piston works exactly the same as 2 pistons 1.5" sq. inch each and so on.
Experiment for you: try holding a 45 pound weight bar in the middle perfectly level using just one hand.

You can't. It'll teeter back and forth as you desperately try to balance it.

Now hold that same bar using just the thumb and index fingers of either hand in a circle spread apart. You'll do it with relative ease. (Unless you're a weakling.)

Here endeth the lesson.
 

V-Four

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Not true.

He actually believes he's smart and post ridiculously stupid things that are easily disprovable.

I feel as though he looks up facts, and then comes here and states the opposite for his amusement. Which I don't mind, as it gives me amusement as well.
👍


T$
 

Stephan

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Well Dream V4 has designed his zero torque engine, now he is working on some 1970's disc brakes. Will he complete his design with some girder forks, 27 inch wheels and some variable ratio pulleys for the leather belt final drive?
 

DreamV4

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If that's true it's somewhat demented. After all, what level of idiot does one have to be to enjoy looking like an idiot?
It looks like any brain effort is irritating you. While somebody has different opinion, you are just pissed off and want to insult a guy who started your painful and unsuccessful brain work. Don't burn your fuse, don't read my threads, find something simple to read.
 

DreamV4

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Well Dream V4 has designed his zero torque engine, now he is working on some 1970's disc brakes. Will he complete his design with some girder forks, 27 inch wheels and some variable ratio pulleys for the leather belt final drive?
Sounds very disrespectful to my Chinese scooter. :)
 

DreamV4

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Is Dreamv4 someone we once knew here? That's happened before. Remember that song-"I ain't got "Nobody"..............."
John H has Facebook, but who knows? He's sometimes use a different location and IP address.
I never had Vmax before, but always wanted one. I "land" in one forum or another, based on a project I am working on. Hopefully my Vmax will start flying in couple weeks or so.
 

Screwloose

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Erm, thought would jump in here just to re-cap and add in a couple of things on the subject of brakes. :)

My understanding is that surface area captured by the pots against the pads is the name of the game in stopping. But there are many other considerations due to a number of things like the fluid displacement volume available, the leading edge wear of the pad in comparison to the rotor direction, the pad flexing (especially as it loses thickness and hence strength), composite material of the pad as it requires strength or it flexes around the pots (especially as it wears), heat dissapation of pad(s), and the outer rotor (circular rotation velocity) faster at the outer than inner part of the rotor (like a propeller) so generating more heat at outer than the inner as more rotor surface area passes the pad per revolution. All this comes to heat, distortion, change of material properties permanent and momentary (rotor and pad), change of friction due to heat, trying to keep the wear even throughout the pad(s), and the list goes on.

Many considerations; good read. Interesting start to a subject that was very basic, but ended up a good education.
 

Parminio

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I tell you what the real issue with him is going to be: by the time he gets around to asking legitimate questions about legitimate Vmax issues we're all going to think he's still trolling and tell him complete crap.
 

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