I can't seem to find this information. I'll probably just yank the caliper and put the micrometer on it if no one knows. But I thought I'd throw out the question to save me some time just in case someone knows.

 

Front Disc Brakes: Ventilated, 11.8 in. (300 mm) diameter; 1.1 in. (28 mm) rotor thickness
Rear DiscBrakes: Solid, 11.1 in. (282 mm) diameter; 0.35 in. (9 mm) rotor thickness

 

I think he's looking for piston. One gripe about this car is how it's single pot... they should atleast throw two in there.

 

Why????

When you put your foot down on the peddle you can't tell if it has 1, 2 or 7 pistons.

 

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LOL WHY NOT.... you have to have at least 1 piston =)

I think CLS/ACcord/TL all have 2 pistons

 

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LOL :o who told you that you cant tell the difference?

 

oops..didn't read the request clearly...sorry Steve.[

QUOTE=NiteQwill]I think he's looking for piston. One gripe about this car is how it's single pot... they should atleast throw two in there.[/QUOTE]

 

No problem. I knew the disc sizes as that is pretty easy to come by. The caliper piston is not listed anywhere that I have found. I guess I will just pull it off and mic it.

 

Nope, a single large piston on the CL-S.

 

Ah, but you can tell a difference if done properly.

 

 

I am not sure the stock size, but Steve, I think you need these for your CL.

 

I put my foot down, the car stop. How can you tell how many pistons the caliper has????

 

By looking at the caliper. The amount of pistons determines the braking force your car has. A 2 pot caliper is superior to 1. Many aftermarket brakes can be had with 4 (Astroboy's above pic for instance) or more pots (or in the case of the Brabus posted a few days ago 12 ). This is the money-part of "on-the-dime" braking.

 

Those are very nice and something like that will be employed at some time. But initially I have something simpler in mind.

 

How quickly or rather, how short of a distance does it stop?? Can that be improved upon?? The idea is to increase braking performance.

 

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my scion has 108 hp and when i step on the gas, it moves....... S600 V12 Twin Turbo can do the same... so i am guessing you canNOT tell the difference either then.

 

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Awww... i guess i over estimated CLS :o

 

go drive a car w/ 4 piston calipers and step on the gas, and then go jump in your scion, tell me you can't feel a different. It's not that you can hit the brake and go "oh that's a 4 piston caliper". But you'll definately tell the difference going from a car w/ smaller brakes

 

I would think that the tires/contact patches play a bigger role in how short/quickly the car stops - the stock cl brake system has sufficient power to activate the abs with no modifications.

I would think that the various caliper/rotor characteristics help determine how consistently and confidently you can repeatedly stop from speed.

I was under the impression that the general purpose of multiple pistons was to spread the clamping force more evenly across a broader brake pad. as I understand it, this is why multiple piston calipers use smaller pistons on the leading edge of the brake pad than those on the trailing edge.

in addition, I can tell you from personal experience that 1 or 2 piston "floating" or double-action calipers (like those installed on the cl) are less rigid than 2, 4, 6 or 8 piston "fixed" or single-action calipers, and that difference in rigidity is readily apparent in the amount of pedal/lever force required to acheive a given level of clamping force at the pads (due to the energy wasted by flexing the floating-type calipers).

on motorcycles, at least, the switch from 1 or 2 piston floating calipers to 4 or more piston fixed calipers also results in an increase in piston area, requiring a resize of the master cylinder in order to maintain an adequate balance between brake lever travel and caliper clamping force.

anyway, I'm pretty sure that I've heard somewhere that the real benefit of high performance, multi-piston caliper setups is in consistency of brake feel (ie, no "slop," especially in conjunction with braided ss lines and fresh brake fluid). this consistency of brake feel, combined with the superior heat absorption and dissipation capabilities of quality aftermarket performance rotors and sticky tires, should yield repeatable short, straight stops from speed.

but I could be wrong about all that...

 

Does Smitty have his old stock calipers laying around? That would be the easiest to measure. The other way would be to go to the dealer or a parts store to measure a replacement part.

 

zipee seems to not know that much about breaks or how they work

 

 

You seem to not know much about spelling the word BRAKE

You take a break at work, BRAKES stop your car.

Oh i'm almost forgot.....









:noob:

 

You are correct as I was taking the simplistic approach in an explanation. Also, I was not necessarily referring to what I am doing; just the general concept of better braking systems. Although there may be actual benefits of decreased stopping distances; scrubbing off speed quicker before locking up, the consistency is what I am looking for.

 

Maybe, maybe not.....but I know how to spell it.

Tire adhesion and ABS are the limiting factors in stopping. If the ABS kicks in or you lock the wheels you have gotten all the breaking force you can use.

 

Correct, the clamping force has exceeded the tire adhesion capability for the given surface. In normal driving this is never an issue as I have always had enough clamping force to lock the tires. But that doesn't necessarily indicate that I can lock the tires at higher rates of speed or under higher braking temperatures.

We should clarify; the number of pistons does not alone change anything. The combination of components can change performance but more importantly for my concerns, consistency.

 

It is worth noting that the number of pistons is meaningless, it's total piston area that counts. The reason for 4 piston calipers is that you can get get more piston area in the caliper with 4 smaller pistons than with 2 large ones.

If consistancy (high speed fade) is the issue I would suggest that temperture control via slotting/drilling/venting is the first area to look at. More pressure through hydraulics is also an area to explore as is alternate pad material.

One consideration is that brake systems generally work best in a fairly narrow temperture range, you can easily over cool or use too hard a pad and get poor results at lower speeds. You may have to find a middle ground.

Carroll Smith's writings are over 30 years old but still some of the best on the subject.

 

not necessarily - this would only be true where the pad is very rectangular or eliptical in shape - a single piston provides maximum area when used with a square/round pad.

since the shape of the brake pad itself has an influence on the braking performance, there are multiple reasons for 4+ piston calipers: (1) to allow more even pressure across longer rectangular/eliptical pads, (2) because opposed piston (fixed) calipers are more rigid than their single-piston (floating) caliper counterparts, and (3) they look badass. ()

 

Well, yes and no. It depends on the pad as tankmonkey mentioned. Also, your idea of increased piston area discounts that the master cylinder is already selected. IF total piston area is increased the pedal will require greater travel and most likely a soft feel. I'm actually shooting for the same total piston area if not slightly less.

One idea of more pistons is to cover more area of the pad instead of just the middle. Again, this is in addition to what tankmonkey said.

The other suggestions are already being considered, but thanks anyway. However, they were not pertinent to the thread subject so were not brought up.

I am planning on pulling the caliper tonight and mic the diameter.

 

zip it!


ziiiiiiiip


zzzzip it!

zzzzzzzzzzzzzzzzzzz....!


He was asking for design reasons, and or technical data. Hard to make technical decisions without knowing the data. Your just guessing otherwise...

yes, I agree scalbert more pistons evenly distributes pressure over more of the pad. Nearly impossble to do without a round brake pad to match, or a oddlong shaped piston.

 

Scalbert, did you try an PM Smitty about his calipers? I'm sure he still has his stock set laying around somewhere and could measure them much easier than you removing yours.

 

Yep, he is checking into now.

 

Quite the helpful community we have here isn't it?

 

You want the fronts and rears sizes or just the fronts?

I misunderstood your post...

 

Just the piston size of the front caliper at this time.

 

:crying:

im gonna cry someone is making fun of me over the internet

 

okay, as soon as I get up to my garage in the next couple days I will measure it for you.

My calipers are sitting there collecting dust.... Would you like me to send you one of them?

 

I'll get the measurement tonight. It'll only take about 30 minute and I was going to be in the garage anyway. This way I can get an exact measurement with my Mitutoyo digital micrometer. Thanks anyway.

 

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Somehow i think u misunderstood what i was trying to say.

AND i own a car with 4 piston caliper (brembo) so i know the difference...