BrakeExpert

Hmm, that is a consideration. Though they are lighter, they have the same texture as the stock steel ones, and have more surface area. They protrude more into the wheel, so they are closer to the air more outside of the vehicle. I guess this could help cool slightly more over the stock caliper by a little, we'd need an engineer to help run the numbers. I haven't done calc and thermo in quite a while

manuelisfun

That's an interesting consideration. I've always thought a bit of turbulence around the wheel area would be useful to move the air around even though it'd increase the car's overall Cd.

BrakeExpert

Nah, the width of the wheel from stock would probably be a bigger factor, but thats relatively negligable. Though more open spoked wheels could help a bit, the stock AP1 wheels aren't that hot.

ZDan

If you're judging a caliper's ability to reject heat solely by its WEIGHT, you're doing it wrong.

Suffice it to say, an aluminum 4-piston fixed caliper is going to do a much better job of rejecting heat from brake fluid than a steel single-piston sliding caliper, for a number of reasons.

BrakeExpert

I didn't say that, but it is about a third the weight, so that has to factor in at least a little bit.

ZDan

Spoon calipers don't weigh 1/3 of stock calipers, they're advertised as being a little over half the weight (still impressive!).
Aluminum does weigh ~1/3 an equivalent volume of steel.
Which does NOT mean that it isn't good material for brake calipers due to being too light! Quite the contrary, aluminum is far superior to steel for calipers (just like it's far superior to cast iron for cylinder heads).

Here's what you said:
>>>since they are lighter, they actually hold less heat than stock, so for fade resistance, they don't really help<<<

For one thing, you don't want the calipers to HOLD heat, you want them to efficiently REJECT heat. The spoons are going to do that much more effectively than the stockers for a few reasons:
1. Aluminum conducts heat much better than steel, hence it will take the heat from the fluid more effectively.
2. Greater surface area, more convective heat transfer (cooling).
3. Instead of one large-volume reservoir of brake fluid behind the stock caliper's single piston, you have four smaller volumes (of ~1/4 the volume), and the area of contact between the fluid and caliper body is going to be greater, which will further benefit heat transfer out of the fluid.

All that said, I don't overheat the fluid/pads at the track with the stock calipers, so I don't personally see a need to upgrade, and the upgrade wouldn't give me "better" braking as I can fully utilize R-comp tires with the stock system (i.e., I can lock the brakes at the end of a session).

But the Spoons absolutely WILL improve braking performance if you are at a power level that is too much for the stock system to handle.

BrakeExpert

I'm assuming using stock sized discs and pads, that the issue of boiling brake fluid isn't quite achieved, you'd likely want to have wider tires to allow the brakes to get to higher temperatures able to transfer enough heat fast enough into that fluid. So you are saying that the spoon calipers will allow the brakes to cool quicker and that will improve performance?

Antonov

^^^ huh?

ZDan

"huh?" indeed!
I have no idea why you'd WANT the brakes to transfer "enough heat fast enough into the fluid." You're not trying to cool the pads with the fluid! The pads can take much higher temperatures than the fluid can take. It is primarily air and the rotor that cools the pads (and, of course, air cools the rotor).
Heat transfer from the pads through the annular (ring-shaped) contact areas between the pads and the caliper pistons and into the caliper and fluid is going to be secondary as far as the pad is concerned. But of course this is where heat gets into the caliper. As far as the fluid is concerned, it's a lot, and at a certain point it will be too much for the fluid.

I'm saying that the fluid will be cooler under the same operating conditions with the spoon calipers than with stock.

y2k5S2k

I'm saying that the fluid will be cooler under the same operating conditions with the spoon calipers than with stock.

I have to chime in here, because I can't take it! The above is not true. Aluminum has a
larger coefficient of heat than steel, so the heat will "flow" into the Al. faster, but will also
flow out of the Al. caliper faster. i.e. Al. absorbs heat faster and dissipates that same heat
faster.
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So, input the same heat into both systems, and the same amount of heat gets to the
fluid; Steel resists the input, but holds it longer. Al. absorbs faster, but dissipates it faster.
The heat will flow more evenly throughout the Al. and make its way to the fluid, but some
will also flow out from the exterior. Net result: tests would have to be done to determine
which actually transfers more heat to the fluid; so many factors to consider: size of ea.
caliper (mass differences), piston surface areas (areas in contact with the fluid in ea. case),
piston materials (their heat coefficients) and many more.

However, this isn't the area of most concern regarding heating of the fluid; it's the
pistons. They see the heat first by direct contact with the pads and then transfer that heat
to the pistons; and the pistons are in direct contact with the fluid.
A really good way of keeping fluid cool is by insulating it from the piston/pad
heat source. Titanium spacer plates are great at doing this. Ceramic is good also, but coatin
the inside of the pistons with ceramics is kinda spendy--it's used in F1 and other race fields.
You'll also see this used with headers to keep the heat inside of the header and to direct
it out the exhaust.
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Sorry about the rambling on. It just isn't that simple. But of course, it never is.