Twinpot brake question

[FST4RD]

Was thinking about this today.
Why don't manufacturers use twinpot brakes on the front like Brembos on the back of an Evo or STI or like on the rear of an Altezza?
My thoughts is something to do with either cost or brake pad surface area?

[iOnic]

I don't really understand the question Can you rephrase?

[Lloyd]

Some do, most there is no point.

[FST4RD]

We'll from what I know manufacturers who use twin pot brakes on the front use calipers with the pistons both on one side.
Why don't they use twin pot calipers with opposing pistons?

[iOnic]

Ohh I get it now.

You want to know why manufacturers use sliding/floating calipers (pistons on the same side) over fixed (opposing pistons) calipers?

The main answer is because sliding calipers are cheap and easy to manufacture and wheel selection is better because they can fit behind a wider range of wheel offsets. Evo/STI Brembos are fixed calipers both front and rear not just on the rear.

[FST4RD]

Ohh I get it now.

You want to know why manufacturers use sliding/floating calipers (pistons on the same side) over fixed (opposing pistons) calipers?

The main answer is because sliding calipers are cheap and easy to manufacture and wheel selection is better because they can fit behind a wider range of wheel offsets. Evo/STI Brembos are fixed calipers both front and rear not just on the rear.

Ah never thought about wheel offset issues.

So is it possible to use a fixed twin pot opposing piston caliper from the rear of an evo, sti, altezza etc on the front of a car, even if it's more for wank factor more then anything?

[iOnic]

It's possible - not sure how well a caliper that small would dissipate heat when performing the majority of the braking on the car. They're not really designed for that.

FYI Evo (5-9 at least) Brembos have 2x40mm pistons in the rear calipers vs 2x40mm and 2x46mm on the front. Pretty sure STI's are the same.

[Lloyd]

There isn't really any point, the single piston setups will brake just as well. They'll have bigger pistons, and any force they exert will be applied to the other side anyway because the caliper is on a slide.

My old S2000 was only a single piston front setup and it braked like nothing else I've owned.

Though if you're going for wank factor, then go for it.

[LEAKER]

my 1973 toyota crown has 2 pot opposing front callipers.
It also has solid front rotors and drum rears and it has better braking than my st185 which doesnt really say much.
Just thought id mention it. Im only taking a wild guess but the callipers have huge pistons maybe 55 - 60mm. They only work ok because the offset on the disc is HUGE compared to newer cars so i would almost rely solely on that for the reason they are not used any more.

[FST4RD]

Ohh I get it now.

You want to know why manufacturers use sliding/floating calipers (pistons on the same side) over fixed (opposing pistons) calipers?

The main answer is because sliding calipers are cheap and easy to manufacture and wheel selection is better because they can fit behind a wider range of wheel offsets. Evo/STI Brembos are fixed calipers both front and rear not just on the rear.

Ah never thought about wheel offset issues.

So is it possible to use a fixed twin pot opposing piston caliper from the rear of an evo, sti, altezza etc on the front of a car, even if it's more for wank factor more then anything?

[Lloyd]

Anything is possible, but is it worth the effort/cost? Bear in mind it would need cert too

[FST4RD]

Anything is possible, but is it worth the effort/cost? Bear in mind it would need cert too

I wasn't planning on doing it.
More that I pulled up next to an Altezza today and was looking at the rear brakes and it got me thinking.

[RomanV]

It's like asking "Why arent all 4 cyl engines flat 4?"

Opposed twin piston calipers are uncommon for similar reasons... manufacturing complications for little tangible gain.

They need to be cast in two seperate pieces, machined perfectly flat on the mating surfaces, then assembled before they can be fitted.

Slider types require a lot less machining.

The 4 pot brakes like the nissan or brembo ones, in my opinion the main advantage over sliding twin pots is that you dont need to fart around removing the caliper to swap the pads, they can come straight out the top.

People say the braking response is better etc, but that's pretty impossible to quantify, especially with confirmation bias towards the $$$ someones just spent on their brakes.

The other main advantage is weight, I've got some aluminium 4 pot nissan calipers which are HALF the weight of a twin pot sliding caliper setup from an SW20.

I decided to switch from the twin pots to the 4 pots mainly so its easier to swap pads over in the long run, and save a little weight.
However would you like to know what deciding to do so actually acheived?

My otherwise well working car has been in pieces in the garage for the last few months because I'm too lazy to finish it off.

Should have just kept it how it was!

[iOnic]

Opposed twin piston calipers are uncommon for similar reasons... manufacturing complications for little tangible gain.

They need to be cast in two seperate pieces, machined perfectly flat on the mating surfaces, then assembled before they can be fitted.

Slider types require a lot less machining.

Not all fixed calipers are two piece. The Brembos being discussed in this topic are machined from a single piece of aluminium and there are lots of advantages to that. I do agree that slider calipers require a lot less machining though - that's why they are cheaper to manufacture.

The 4 pot brakes like the nissan or brembo ones, in my opinion the main advantage over sliding twin pots is that you dont need to fart around removing the caliper to swap the pads, they can come straight out the top.

That's one advantage but not the main advantage. As above, the Brembos are machined from a single block of aluminium. This makes them much stiffer than floating calipers (so you're not losing braking force through flex in the caliper or slop in the sliders). As you said they're also a lot lighter (a single Evo/STI Brembo 4 pot weighs ~3kg vs ~7kg for a MK4 Supra caliper or ~5kg for an S15 4 pot for example). They also don't suffer from tapered pad wear and are more reliable (you'll never get a seized/stuck slider). Sliding calipers also use thinner pads which reduces pad life (especially when you take into account the tendency for tapered wear). If you're doing trackdays this will be very noticeable.