Brake ducts/cooling

[TurboRA28]

Hi all, what can you tell me about brake ducts for cooling?

I've got RX7 4piston calipers with vented rotors on the celica but after 10 or so hard laps around the track I start to lose some pedal. Last outing I completely lost brakes all together, after a cool down they came back though.

So I was thinking about running some ducting from the front of the car using flexible piping and then making a plate or something similar on the strut like this -



Few questions.. Firstly is it worth it? Assuming so, do I point the air at the rotor, caliper, into the vents of the rotor??

Pic's i'm finding on the google machine seem to point the air closer to the hub/hat area of the rotor...

Another pic of a basic setup...



Thanks
Joel

[Big rob]

Point it into the vanes in the center brake disk like the picture you posted. This will create more flow through the disk vanes, increasing the ability for the disk to shed heat. In turn for the same braking force, less heat will be absorbed by your caliper and into the the fluid.

[TA22 1MZ]

Joel
Keep an eye on ebay in the US mate. search for NASCAR and there is usally someone selling this type of setup for a pretty good price. You can also get some nice big ducts to suit the front of our cars to suck up the air.

As Big Rob already mentioned, you wanna have it aimed towards the centre of the rotor so it can be drawn in through the veins of the rotor. If you end up making something yourself, go for a setup like the first pic, where you can clamp the ducting to the tube.

I'd be happy to swing you some $$$ if you do decide to make some up.
Talk soon mate

[ecko]

im also interested mate if you make something up

[TurboRA28]

Thanks for the info all.. I'll start to mock something up.
Cheers
Joel

[WDE_BDY]

Get decent pads, if you can only get 10 laps out of that setup there is a real problem.

Callum

[Draven]

at least you're only stopping ~1100kgs

I'm looking to create a similar setup before the next track day. From the forumsI've been trawling, centre of vanes = win. ~3" tubing, if possible

[The Real Roadrunner]

what pads are you running joel? if they are cheapies (bendix, ebc etc) grab some decent pads first like ferodo's or hawks (i believe craig is selling some ds2500's cheap) and test out the braking performance of them first.

if your losing brakes after 10 laps you have one of 2 problems
a) incorrect pad selection from a heat range perspective or
b) insufficient rotor mass to be able to absorb then dissipate the required amount of heat (energy) produced while braking.

ducting is a bit of a bandaid solution to the problem but can work, the undesirable affects the are increased heat cycling of the rotor and also can cause problems with over cooling the rotor to a point where the brake pads won't work efficiently.

also what fluid are you using? AP racing, Motul RBF600, Castrol SRF or is it just a cheap Dot4 fluid? decent fluid can make a huge difference from a boiling point perspective.

ask Draven how much of a difference going from a cheaper street pad to a race but streetable pad is, the difference is huge.

cheers
linden

[Draven]

I just re-read your first post.. if you're losing pedal, that's more of a fluid issue - get one of the brake fluids linden just mentioned.
And getting proper competition pads is BY FAR the best bang for buck mod I've ever done for my car. It's really nice knowing that your biggest concern when hitting the brake pedal is how far forward in your seat you'll slide, not if you'll pull up in time

edit: oh, and get a pyro onto your brakes so you can see what temp they're running at... that'll tell you what you need to change/upgrade

[YLD-16L]

Joel,

More details on your brakes would be good as we run similar times at WP, similar power but about 100kg difference in weight and my brakes are not as good spec as yours but I've not suffered fade even on 35+ days and doing near on 30 laps straight.

Front I run plain surfaced discs, 276x22 vented, DS2500 pads on single piston sliding calipers.

Rear are 256x9 solid with Lucas pads.

Nothign flash at all but nil issues either.

I had thought in the past about ducting too but as yet have not realised the need.

I just run Castrol Super Dot 4 fluid fresh each track day too.

[Draven]

also, do you have a turbo/hot thing cooking your master cyl?

[TA22 1MZ]

also, do you have a turbo/hot thing cooking your master cyl?

is on passenger side for him, so wouldnt of thought the MC is getting heat
how long since a good overhaul of the calipers and rotors Joel? Might be worth putting a new kit through the calipers along with fresh fluid and pads, before trying to go after something not relevant to the current issue

[allencr]

I start to lose some pedal. Last outing I completely lost brakes all together, after a cool down they came back though.

Pad heat problems go away when the temp. goes down and the pedal is solid.
Fluid heat problems do not go away until the system is bleed, unless you've got really nice fluid that reabsorbs 100%.

Edit for generalization.

[TurboRA28]

To answer some questions...

I am using Bendix ultimate pads.
Dot 4 fluid.
283mm / 22mm vented front rotors. Rear is St141, cannot remember exact sizing.
Inlet is on the MS side, so safe there.
I overhauled the calipers/rotors/pads etc around 4000km ago at most. Car hasn't seen much road time though, mainly track time.

So yeah, the problem does go away after car sits around for some time. When I pulled into the pits on one run the pedal went flat to the floor, 30mins later when I checked it was firm and good.

[TERRA Operative]

Check out Diesel /Truck suppliers for their black flexible ducting (black plastic with the spiral wire). It comes in various standard sizes (2.5", 3" etc) and is rated to +125 degrees or so. I use it for intake ducts and it's way better than the flimsy black stuff from Autobarn etc.