35 replies to this topic

[Site]

The radius of the small pistons is 19 mm which works out to an area of 1,134 sq mm x 2 pistons = 2268 sq mm

The radius of one large piston is 24 mm which works out to an area of 1809 sq mm

 

Two small pistons > one large piston

 

the point i was making was that you can actually get brake callipers which may have 2/4 even 8 pistons pistons...but their cumulitive area is actually less then one or two large pistons...in your case with those measurements you are correct, but what happens if the small pistons have a radius of 15mm? they cover an area of 1413mm² so your one large piston actually covers a larger area...so the one large piston, accompanied by a larger MC would actually give a better spread of force....

 

but following on from what people have mentioned, the 2 smaller pistons would actually give you a larger force per unit area than the one large piston, given you are using the same sized MC etc...

 

i still stand by saying i would prefer numerous smaller pistons spreading the force onto 2 points of the pad, giving an even spread onto the disc rather than one massive force onto the middle of a pad....

[icebox187]

Why doesn't anyone in the honda community seem to understand hydraulic systems? The larger piston surface area will give you more clamping force with the same mc. A larger mc will actually reduce the clamping force and reduce pedal travel. http://www.engineeri...aws-d_1274.html

[Screech]

Why doesn't anyone in the honda community seem to understand hydraulic systems? The larger piston surface area will give you more clamping force with the same mc. A larger mc will actually reduce the clamping force and reduce pedal travel. http://www.engineeri...aws-d_1274.html

Sounds like what I was saying/thinking...

 

 

...I was thinking the 2ea 1.5" bore would apply the most force for the given input pressure on same sized master cylinders, but I've never really studied that area of mechanics. My thought was when you push a fluid a create 5psi of pressure in it that the slave cylinder(s) with the larger surface area would have more of that 5psi reaches the moving part. Granted, it would also require more input to reach the 5psi. On the flip side I would think the 2ea 1.25" would have the least clamping force, but would require less movement of the input to reach 5psi in the fluid. Maybe my thoughts of translating of a classic fulcrum and level to fluids is where I get messed up....

[cbstdscott]

In spite of the snarky comments, I am committed to the community we have created here. 

 

Use the information I have shared as you seen fit.

 

Scott

[icebox187]

Sorry.. Didn't mean to come off snarky. It's just that I've seen so many threads about big bore master cylinders and nobody seems to understand that they are reducing the potential clamping force. Screech, yes, it does seem that you get it ☺. Scott, stick with the plan of twin pots on stock mc. If the fronts lock up too easy, or the increase in pedal travel hinders driveability, then consider a bigger mc.

[Site]

Why doesn't anyone in the honda community seem to understand hydraulic systems? The larger piston surface area will give you more clamping force with the same mc. A larger mc will actually reduce the clamping force and reduce pedal travel. http://www.engineeri...aws-d_1274.html

 

good link actually...so the key thing to look out for is the the actual area of the pistons rather than the amount you pistons you have have (which is partly what i was getting at in my first post)...but either way its nice to learn something new every day...

[icebox187]

Umm Scott...   
 
You're right, the two smaller pistons do have a larger area than the other single piston caliper. However, it's not necessarily about how much 'more' area you can apply to the back of the brake pad. While that does help in better distribution of that same pressure to the brake pad, it will do nothing to contribute to better stopping power without the proper pressure applied.
 
With the same pressure applied to the brake calipers, whether they be single piston, dual, quad, or whatever, the one with the smallest 'area' will apply the highest pressure, or clamping force, to the brake disc. The only way more brake caliper piston area will give you more, or equivalent to what you had prior, stopping power, is if you use a larger bore master cylinder.
 
Then you need to consider the brake pedal ratio.
And then there's the rear brake pressure that just changed due to the larger master cylinder. Etc, Etc...
 
All this info is easily available out there on the interwebs.

My problem was with this post in general. It's totally wrong, but the right answers are easily available out there on the interwebs.

[Site]

Sorry.. Didn't mean to come off snarky. It's just that I've seen so many threads about big bore master cylinders and nobody seems to understand that they are reducing the potential clamping force. Screech, yes, it does seem that you get it ☺. Scott, stick with the plan of twin pots on stock mc. If the fronts lock up too easy, or the increase in pedal travel hinders driveability, then consider a bigger mc.

 

ive got to ask how does a big bore MC reduce the clamping force? Youve just said a larger piston in the calliper has a larger force as the same pressure is the same...so wouldnt the pressure be the same with the larger MC giving you the a larger force again?

Edited by Site, 31 October 2014 - 10:45 AM.

[icebox187]

good link actually...so the key thing to look out for is the the actual area of the pistons rather than the amount you pistons you have have (which is partly what i was getting at in my first post)...but either way its nice to learn something new every day...

Not completely, the multi piston calipers also have better distribution, so if I had to choose between a single and a twin pot caliper with the same combined cylinder size I would go with twins. Also, it isnt all about the cylinder size, its the ratio of input to output cylinder.

[icebox187]

The big bore mc reduces potential clamping force by decreasing the input/output ratio.

[Site]

Not completely, the multi piston calipers also have better distribution, so if I had to choose between a single and a twin pot caliper with the same combined cylinder size I would go with twins. Also, it isnt all about the cylinder size, its the ratio of input to output cylinder.

 

ah i see i agree on having the twin or 4 pots etc over one large one if they have the same total area....

[icebox187]

You can also play with the hydraulic press calculator at this site to get a better idea of force multiplication ratio: http://hyperphysics....pasc.html#hpcal

[Andy69]

You guys are looking at this from the wrong angle.  The advantage of multiple piston calipers has nothing to do with clamping force.  The advantage of multiple calipers is that the clamping force is more evenly distributed over the back of the brake pad, enabling the use of larger pads over what you could use with a single piston.  This, arguably, is the better way to go to increase brake performance as a larger friction surface means a larger area of contact with the brake rotor.  Since the kinetic energy removed by stopping your X lb car from Y mph in Z feet never changes, a bigger contact surface means less generated heat per unit of surface area and better heat dissipation, resulting in less brake fade.   One thing I am certain of is that piston size and number is not a terribly important factor in stopping distance if you already have enough braking power to lock the front wheels.  In short, it is doubtful that you would see much difference between single piston and multiple piston brakes on the same vehicle with the first heavy stop.  But after multiple heavy stops?  The difference would be dramatic.  That's the main advantage of the Integra brakes on my CRX - multiple and repeated braking events over the course of a 25 minute club race (the car is a former ITB Regional Champion), but for what I do, autocross, I'd be willing to bet I would not see a difference in switching back to the stock brakes.

 

Drag racers used to love drum brakes over disc brakes.  Why?  Less fade, because of the larger surface area of the shoes, the larger mass of the drum, and  the subsequent generation of less heat because of the larger contact area, the greater ability of the larger components to absorb that heat, and the greater dissipation of that heat.

Edited by Andy69, 31 October 2014 - 11:49 AM.

[Screech]

Well, if you put stock brakes on the front with stock pads sizes you will notice a difference from the Integra brakes. Integra pads have much more surface area. I've currently switched to the 94 Del Sol S brakes as the off the shelf pad options are much better than the 1G Integra and about the same size. I would rather the 94 Del Sol S over the twin pots mention is OP for one reason, its a wear component and having replacements within a day or two is nice. 

[PuddleSkipper]

Scott, thanks for sharing, did something similar with my car (EF). I did a brake swap before work, swapped the fronts from stock LX calipers to EX calipers. IIRC I had already done the rear DA disc brake swap before this (due to time I have to do things in stages). The EX calipers were definitely bigger calipers and because I did not have time to swap the prop valve or the MC (both still stock at this point) I experienced lower pedal pressure and increased travel on the pedal. It wouldn't get firm until the bottom end of the pedal, so, make sure you have absolutely no air in the system and give yourself plenty of stopping distance. Also, just a note, once you experience this you are going to want the bigger MC. Once I swapped in the integra 40/40 prop valve and a 15/16" EX MC and finished it off with stainless steel brake lines (from ebay: cheap) I am VERY happy with my brakes. Great pedal pressure, or right for me anyway, and reduced pedal travel which is probably what impressed me most. I also was going to swap to the EX booster but last minute decided to keep the stock LX booster, but I like the smaller booster with a big MC, gives me a better feel on the brakes. So experiment, have fun, and be safe!