Brake Cooling - An uphill battle

[Cat in Hat]

Over the last 5 years my car has slowly become more and more of an event car and less like a road car. The metamorphosis has included weight saving, significant suspension upgrades and some power gains. All in all the car has been very successful...I have had very few reliability issues and a lot of success in a lot of events. The one single weak point has been keeping the brakes cool.
Unfortunately my "Home" race track (Zwartkops raceway) is notoriously hard on brakes and challenges race cars in every class.
This thread is intended to be a journal of what has been done in an attempt to solve this problem. Fortunately a lot of events that I take part in do not include many consecutive laps around a track, but are more like a time attack format, gymkhana or hill climb so the brake cooling is not a problem. But from time to time consecutive hot laps are necessary and this is when the problem arises. This past weekend's rally was such an event.

The current brake setup has been in place for some years : OEM Brembo calipers, DBA series 5000 rotors, Performance friction pads (full race spec), Performance friction PF665 brake fluid, braided brake lines.
I have tried various brands of brake fluids to try prevent fade and found Endless 660 to be the best so far.

This setup on its own works well for about 3 or 4 hot laps, but brake fade inevitably ends the fun there and then.

Mod 1. Roo ducts. These were fitted without any ducting to the Roo intake and also no ducting to the wheel hub. The fog light covers were removed to allow air to pass into the ducts. Result = no improvement

Mod 2. Roo Ducts with intake ducting and ducting from the Roo to the centre of the wheel hub/rotor. This seemed to help a bit but it still did not allow me to do more than 3 or 4 laps.



Mod 3. Added bigger - home made intakes to Roo ducting. Still no improvement.


At this stage I decided to take a closer look at the aerodynamics of the intakes because there seemed to be no reason why the ducting had such an insignificant affect. I mixed up a bit of paint that would not dry quickly, placed a few dots around the intakes and went for a drive. I left the one intake as it was and on the other I fitted a small lip to the outside of the intake hoping to deflect more air into the ducting. Here are some pics of the experiment...I only wish I knew how to mix a better paint brew for the exercise:?

Paint spots before driving



Paint spots after a drive

no lip with lip (deflector)


The lip that made a noticeable difference to the air flowing into the intake.

 

[Cat in Hat]

The results indicated that the air "hitting" the car was being pushed past the front of the intakes and not actually going into them. Fitting the outside deflector was not really ideal, so I looked at different options. The NACA duct seemed to be the obvious choice because this was an intake designed to "fold" air into itself from a low pressure zone across a surface. I was sure this would do the trick.

It turns out I was wrong: this pic was taken in the time control point at the end of a 5 lap Special Stage this past weekend. The temperature paint actually caught fire :tard:

So the next step will have to be some kind of deflector to force more air into the fog light intakes. We have a track day in a few weeks time...Ill post the results.

My brake supplier happened to be a spectator at the rally and said to me that he thinks my rotors were reaching about 750 deg C. (1400 F):-o

 

[ZachTTLM]

Are you able to take a picture to show how you have the ducting to the wheel hub set-up? Also I thing a lip to deflect the air into the inlet would help as you have mentioned. But my curiosity for how the ducts at the hups are set up is if you can have a way to get the cool air right too the rotor and to as much of the rotor as possible without losing it before it does the job it is to do.

 

[Cat in Hat]

Apologies for the poor quality pics but you will get the general idea.
The ducting runs from the Roo duct to a modified dust cover plate .

 

[Grinder34]

I'd be interested in the ducting further up. Like from the fog bezel to the roo duct!

 

[Grinder34]

Is there any reason why you've stuck with the Brembo caliper? I've been doing some rough number crunching, and it appears the high cost of a BBK (lets say $2500) could/would be offset by the significantly cheaper cost of pads (up to lets say $100 less per set. in reality it might be even more!). After 25 sets of pads you'd pay for the bbk. Plus you could/would get larger rotors for better heat dispersion.

Please tell me why my thinking is wrong, because its making me want a BBK (that I cant afford)!

 

[Cat in Hat]

The obvious solution would be a BBK but it comes at a price... As you have noted.
I would also need to get two sets of 18 inch wheels and the cost of 18" tires is considerably more here.
We know that the cars braking won't be better with a BBK it will just brake as well for longer. I am also concerned that using bigger wheels will have an impact on the way my car handles, and I am very used to the car as it is.

Having said that I may be in luck. Due to my rally results I have been approached by a brake kit manufacturer to discuss a potential sponsorship for 2013. So a BBK may be in my future

 

[finallymysti]

i track quite alot. my main tracks are njmp and pocono. i have rooducts to quantum motorsports hub adapter kit. i use fog lights bezel from a wrx. i use ferodo ds1.11 pads and motul rbf 600 fluid. i don't get fade unless its above 80 degrees outside. and if it is it usually doesn't happen until the 20-22 minute mark. so on a 1:40 track that equals at least 10 hot laps. however, i have seized both my front calipers so there you go.

 

[ZachTTLM]

The pics aren't working for me.

 

[Cat in Hat]

The pics aren't working for me.

Post edited - pics sorted.

We have a race team here that runs two 2008 model cars in a series called "Production Cars". They have had to go to extremes to cool brakes at the short Zwartkops track...they actually inject a water mist into the centre of the discs. This is in addition to a huge AP racing BBK and ducting.
The problem is that as the car gets faster so the heat generated increases dramatically.
I think the formula for calculating the heat generated is : mass * 1/2 velocity squared.

 

[finallymysti]

i just looked at that track and it doesn't look to bad.

 

[ZachTTLM]

That was going to be my next suggestion with the water mist. You could set up an auxiliary washer bottle and run a hose with a nozzel to mist the system down. I have a customer that is inquiring about this as well.

 

[Cat in Hat]

i just looked at that track and it doesn't look to bad.

It's a very short lap, here is an onboard video of a lap. BTW I have shaved about a second off that time since 2010. Another problem is that ambient temps at this track often get above 30deg C.

@Zach - It wont be too difficult to set up at all, maybe a system triggered by the brake light switch. The idea would certainly be to spray the water into the centre of the rotor where it could move through the centre cavity and cool both sides. The race team also commented that they were concerned about the discs cracking with the water spray but the discs have been fine...no twisting or cracking at all.

 

[Td_d]

It definitely gets mosty toasty here in summer, and that track cooks in December / January.

 

[Grinder34]

The obvious solution would be a BBK but it comes at a price... As you have noted.
I would also need to get two sets of 18 inch wheels and the cost of 18" tires is considerably more here.
We know that the cars braking won't be better with a BBK it will just brake as well for longer. I am also concerned that using bigger wheels will have an impact on the way my car handles, and I am very used to the car as it is.

Having said that I may be in luck. Due to my rally results I have been approached by a brake kit manufacturer to discuss a potential sponsorship for 2013. So a BBK may be in my future

I'll be interested in what, if any, bbk you end up with.

You dont always need 18" wheels/tires for a BBK. I'm looking into a Stoptech ST-40 which clears the OEM wheels.

 

[Grinder34]

Just wondering if you'd tinkered with your brake setup at all in your summer months. I will be installing ducts shortly and would like to learn all I can before tackling that project!

 

[randyzimmer]

Hi, Randy with the RooDucts here, lots has happened in the last couple years.
We have a tough track in Canada and we tried NASCAR 12VDC fans blowing 60MPH air constantly.
No secondary hose.
Laps increased from 3 with Brembos to 4 with AP to a whole tank of gas with fans on the APs.
I think Brembos with fans would do the same.
They draw some amps and are pretty loud but they sure do the job.
The Brushless are trick but the brush ones work fine for us.
Tell Ashley I sent you.
http://prosystembrakes.com/catalog/index.php?cPath=28&osCsid=6f8563822ad8123ee0e6d42349cfe95a

 

[Cat in Hat]

Brake cooling continues to be a problem for myself and a number of my customers (who mostly run BBKs) As you start to get quicker around the circuits so the weak points start to show. For example a customer was running a 1'13" lap around the circuit mentioned earlier in this thread. At this pace he coud run lap after lap without any brake fade and his pads and discs (rotors) lasted a long time. His driving and handling have improved and is now running a 1'10" lap. Now his brakes are not up to the task, they are starting to fade, the pad compound/rotor combination is becoming an issue where he either has excessive wear on the pads or on the rotors depending on what compound he uses.
unfortunately our currency exchange rate (10:1) to the USD makes brands like AP and Alcon unaffordable for most of us so we use a locally manufactured setup www.powerbrake.co.za
the cooling fans are an interesting option.

 

[Grinder34]

What are the vanes like on those rotors? I really like the stoptech rotors for their efficient design.

As for ducts:
I personally havent installed my roo ducts yet (thanks Randy), but a buddy of mine had DIY brake ducts with an undermount naca inlet, and recently switched to the Roo duct and said his brakes were considerably cooler with noticeably less fade. While not a technical measure by any means, he that with the old duct he'd get off the track and his wheels were too hot to touch for even a second. With the Roo ducts you could leave your hand there for quite a few seconds before the heat became too much.

 

[Spamby]

Traction control on or off for you guys?
Pads advertised max temps your using is up to snuff for your tracks and tires?