ReX-8

How many pistons there are on the front brake? rear brake?
2 on each of the front and 2 or just 1 on each rear brake?

The Beav

i think it's two piston in the front one piston in the rear

Ahura

This is one thing that slightly dissapoints me. Even though the RX-8 have gotten rave reviews about its brakes, why did they choose to go with a single piston caliper when they've been using 4 piston calipers for years now on the RX-7?

Good Duck

1 piston per rotor all around.

wakeech

because the number of pistons doesn't matter, it's about the difference in surface area... more pistons doesn't inherently mean that there is more area than a two piston caliper, but if you assume that the 6p calipers are maxed out on the area they can cover, then yeah, obviously they'd have a greater hydrolic advantage.

Sputnik

Don't forget that the way that sliding calipers work, they effectively act as if they have twice as many pistons. So, in other words, a 2 piston sliding caliper is roughly equivalent to a 4-piston fixed caliper of the same piston size.

---jps

babylou

Some people just love to bitch. Every published report I have read gushes about the brakes and the test numbers back up their words.

However, there are other reasons to have multiple pistons other than increasing piston area. With multi piston setups one can better able compensate for caliper deflection and can eliminate caliper floating systems. The flip side is multi piston calipers are heavier, significantly more expensive and contain more areas for reliability faults (each piston plus the hydraulic fluid crossover).

Why should Mazda go to the trouble of doing a fancy multi piston Brembo (the Bose of brakes) brake setup when they can match it for less weight, less dollars and more reliability?

wakeech

:D very well put.

Quick_lude

I'd rather have an option for steel braided brake lines and high performance pads/rotors over Brembo calipers.

MikeW

Differential bore calipers pistons are an advantage, so the front should have two pistons, come on an Oldsmobile Alero has dual piston front brakes(non differential piston bore, I think)

The Rx-8 better have 'steel braided brake lines' stock. Even the Dodge Intrepid has those.

http://www.stoptech.com/faq/data/faq13.html

http://www.zeckhausen.com/testing_brakes.htm

Digisan

Awesome analogy!

What about Baer brakes, any good?

Cheers

babylou

I didn't mean to say that Brembo brakes are poor quality. I only meant that in many peoples minds "Brembo" connotes superior brakes, like Bose does for many in regards to stereos. The reality isthere are other brake manufacturers and stereo manufacturers of equal quality.

RomanoM

Hi, just want to chime in on this issue. I used to be a brake engineer with Teves Brakes (better known as ATe Brakes) and then Ford.

The only practical reason to go to a fixed caliper (and in reality the number of pistons has nothing to do with it) is the better overall pedal feel and packaging advantages.

A slider has some inherent "defects" in it's design that create inconsistencies in it's performance. Because of the way a sliding caliper works the inboard pad and outboard pad do not have the same force curves. This means the 2 pads do not apply the same force at the same time on both sides of the rotor. Also, inherent in the design is greater "dead travel" or "lost travel" from the fact that the pads need to be father from the rotor than with a fixed caliper.

There are also some "real world" disadvantages of a slider that can be overcome, but would increase mass and cost substantially.
These being stiffness (a slider flexes more) and the ratio of caliper size to piston area is less (thereby limiting the number and area of the pistons). Plus the added friction from the sliding, which adds to lost travel. However, these "real world" disadvantages are not huge. In the end only racers and car geeks (like myself) would care or notice.


There is one myth about fixed v. sliders, that is that fixed calipers produce more braking torque or resist fade better. The type of caliper has nothing to do with either.

Braking torque, where the caliper is concerned, is a characteristic of overall piston area and nothing else. If a slider and a fixed have the same piston area, they will produce the same force. Heat transfer to fluid through the caliper has much more to do with material selection than design.

These myths are not just urban legends, they have come out of the fact that in the market almost every fixed caliper out there is made of aluminum and at least 4 piston design. While sliders are typically cast iron (though there are a few made of Al). The OE sliders are usually much heavier and with greater tolerances, giving a great advantage in pedal feel and weight to the more expensive and better built aftermarket fixed calipers.

In the end a fixed caliper, like Brembo, AP or Stoptech has the advantage (usually) of far less mass, far better pedal feel, easier modulation and better fade resistance(<--very minor). But not necessarily shorter stopping distance.

This however is a matter of economics and marketing. With the right engineers, management and budget a cheaper sliding caliper system can work just as well.




Regards,
Michael

My Brakes Website: http://mysite.verizon.net/romano.michael/

TerenceT

good to have Romano here...

glad to see lots of wrx immigrants too :D

rpm_pwr

great post! thanks

P00Man

so in other words the rx-8 has great brakes that arent fancy.
i wish they made them look cool though, like painted them black or something with rx-8 on the calipers, thatd be cool

as a side note
what about ceramic brakes, or carbon fiber? think i haerd somewhere that f1 cars have carbon fiber brakes.

also, what makes "big reds" so strong? is it actual tensile strength of the materials or sheer stopping power?
________
Vaporizers reviews

RobDickinson

F1 brakes (carbonb fiber) ar totaly not sutable for road cars.

They need a lot of heat in them to get up to working temperature, something the average road car will just not see.

Oh and they tendancy to shatter when they get to thin probably would cause a problem or two.

Lotus in the UK launched the Elise with MMC ceramic/aluminium brakes. This was because of a deal with the supplying company to get them cheap, as on their own they were to expensive to use.

The MMC breaks worked extreemly well in the dry, but not so good in the wet, and had a habit of melting when you drove them extreemy hard (read - heavily tracked). This on a car that weighs 700kg (1400llbs) - and there BIG breaks on that car

StealthTL

iTrader: (1)

Ferrari use ceramic brakes on their new model, the Enzo.
The DISK is also ceramic! the pads look kind of normal (huge, but normal!) a kind of grey color, but the disk looks more like a clutch - because it too is greyish.

Maybe you can get some for your '8', the pads go for $6000 a set, and the disks are a steal at $2300!
S

RomanoM

1. What makes fixed calipers so good is just sheer stiffness. The fact that they are either 2 halves bolted together or in less common and far more expensive circumstances monobloc. Porcshe uses monobloc calipers a lot. Monobloc just means the caliper housing is made as one piece.


As far as carbon brakes, there is Carbon-Carbon, which is what F1 cars use. These are completely useless on a street car. The cold friction is horrible. These rotors require carbon pads.

Then there's carbon-ceramics (CCM) or just plain "ceramic" these are not pure carbon and work very well all the time. But very expensive. They will work with most pads.

Now, Brembo it seems has perfected a new manufacturing technique to produce carbon rotors that will have most of the benefits of the CCM at only 30% more cost than the current 2-piece rotors Brembos sells. Or about $350 each. The great benefits are very long life, 100,000 miles should be no problem, and for all purposes the end of brake fade. And are 1/3 lighter. They can use any pad on the market.
These are not the same rotors as those on the Ferrari Enzo CCM (carbon-ceramic) rotors.

mlx8

[QUOTE=RomanoM] ..... Braking torque, where the caliper is concerned, is a characteristic of overall piston area and nothing else. If a slider and a fixed have the same piston area, they will produce the same force. [QUOTE=RomanoM]

I thought rotor diameter - a bigger radius providing a longer "lever" - was an important component in determining braking torque.

mike

Gord96BRG

In this more-than-one-year-old-thread , he says "where the caliper is concerned". You are correct, the rotor diameter is an obvious factor, but he was only referring to the clamping force that the caliper can generate, when comparing a fixed vs. sliding caliper of one, two, or 4 pistons - total piston area is all that matters, as far as caliper comparisons are concerned.

Regards,
Gordon