andrewhake

Instead of aiming your duct specifically at the caliper, removing the dust shield and aiming it toward the center of the rotor should work better.

davidc1

Exactly correct!

spdracerut

The heat is generated between the heat and rotor. My guess is the rotor material conducts heat better than brake pad material, so most of the heat will go into the rotors.

Looking at this thermal image of rotors and calipers, you can see the rotors are much hotter than the calipers:


In the top level motorsports, air does get ducted to the caliper too. NASCAR stock cars have big ducts on their calipers. You can see the duct on the top of the caliper on this ALMS M3:


On WRC cars, they actually use water-cooled calipers on tarmac stages. So yeah, in extreme cases you do need cooling of the calipers, but the rotors should be cooled first as they heat up more.

andrewhake

New front rotors and pads for me tonight, and look what I found:









Tiny little brake cooling channels in the front under tray. For the future I am planning on extending the curved section down with an addition piece, to at least go as low as the front wheel diffuser, and see how far it can extend towards the wheel hub without rubbing anything. That with a nice guide mounted to the front control arm to help focus the air at the center of the rotor. Could be a really nice and clean brake cooling solution.

Seriously could be as simple as buying 2 more front wheel diffusers, and screwing them right into the under tray, bending them to follow the curve.

Croc

i appreciate constcructive and informative replies.
"How much more explaining does it need?" doesn't help when no real explanation was there.

i understand that - but it seems you guys dismiss that friction happens between the rotor and the pads.
you're only talk about rotors but completely dismiss pads.
and pads heat the caliper, heat the braking fluid.
where the evidence that rotor needs extra help on cooling and pads/calipers are not important?

so things are not that simple.

especially when rotors cool themselves and pads are not.

anyway - in the thermal picture above it looks to me that rotor is hotter than caliper.
so i"ll start with the rotors and will see....

robrob

The rotors are hotter than the calipers so the temperature differential between the cooling air and the rotors is greatest so you get more efficient cooling. Since air supplied to the rotor hub flows through the entire rotor you're also getting much more surface area between the cooling air and the hot rotor.

The brake pads act as an insulator (Raybestos pads were made with asbestos for that reason) to reduce heat transfer from the pad contact surface to the brake caliper.

Croc

again.

talking about heat insulation - following recommendation here i started to use titanium pad shims - and IMO they make a good improvement in this area.

Reapur

The vanes of the rotor are turning and pumping air into the heart of the caliper already. If you're directing air into the center of the rotor/hub you're killing two birds with one stone.

With our cars this is all that's needed. In more hardcore pro racing like ALMS both components are cooled because they actually need to. Caliper cooling is not needed before rotor cooling.

con40

I'll try to take a stab at this. Comes down to thermodynamics. Ignoring differences in exact pads, calipers, and rotors materials and design; this is my understanding:

At the contact point between the rotor and the pad, the rotor will be slightly hotter (because the pad is effectively sloughing off onto the rotor. Same way that when you use a powered sander on wood, the wood gets hotter, and the paper gets worn. The pad and the rotor have very little space between them, so you aren't really going to push cool air between them. Thats why you want to direct air to the exposed rotor. Cool that, and the cooler rotar will reduce the heat generated between the pad and rotor during the next braking event.

Now for the calipers. They are either aluminum or steel, or some alloy (I'm sure somebody can clear this up for me). The brake pads are effectively attached to the caliper and have to transfer heat though the caliper and cool through the caliper to the air. Steel radiates horribly, and aluminum a little better. Either way, the brake pad will transfer heat to a cool rotor much more quickly (its spinning, and acts as a much larger contact surface). If you wanted to cool the brake pads through the caliper, it would have to made of something very different with aluminum or copper fins to let the heat off. Take a look at any cpu heatsink online to understand how the metal would have to be cast.

May be some holes to these concepts, welcome somebody picking through it. Also, I'm very excited to see an AP2 brake duct solution. Not very often are there mods that make you faster (slow down faster) and actually improve reliability.

WASPcomposite

Hi Guys,
I have been following this thread for a pretty long time and decided to make brake cooling kits for AP2 and if everything goes as planned possibly put it in production. Last night I got around making foam plugs for both sides and I should have the prototype done early next week, and hopefully install them on Alex's s2000 (momofoolio) for I believe Extreme Speed Track Event at BW in couple of weeks. here are some pictures of the foam plug, it can be used with 2.5" diameter ducts. I will update everyone with more pictures as I go.
Bryan