Temp reductions are really hard to measure. We used some temp sensitive paint initially and saw some reductions, but its hard to determine what color is what. C&T needs to get some of those stick on indicators that change color when a certain temp is hit.

I'm a firm believer in brake cooling, no matter which approach you take (DIY, C&T or other). There's a reason why virtually every race car out there uses brake cooling. :-) Directing at the rotor eye is definitely preferable, and it would seem you could get some uneven cooling if you don't. I don't know how big the differential would have to be to generate cracking, and whether or not the DIY setups would create that differential.

On the airflow, we ran the tubing from the duct up into the cockpit of my car to see how much air (anecdotally) we were moving. It was quite a bit even at 30-40 mph. No way to measure it precisely. The front in-bumper ducts are better placed for airflow, but I prefer to use one of those for the CAI.

UL

After 3" ducting used, my brakes have worked better than they ever have with even wear between inside and outside pads.

The hoses are generally directed to the hub area with 1/3 of the hose pointed to the rotor surface. I notice Hayashi's seem to be mostly toward the friction surface, and I havn't heard any problems there.

And as UL stated "It is also considered mandatory to run air ducts to the eye (center) of the rotor on any car used on track or in actual competition." as noted in an article about rotor seasoning.
<Rotor seasoning link.>

Chris,

thanks for the additional photo and thoughts. I really think 2" tubing will carry plenty of air, but it would be good to hear confirmation.


Shawn,

are you saying that you felt plenty of airflow with the C&T tire-spat ducts and 2" tubing? That would be great to know. Thanks.


Al,

more good feedback that ducting is worthwhile!


Harry,

great photos and details of your install. Those are very helpful! Especially good to know that the smallest NACA duct works well if flanges are cut down. Do you have a grille on there now? If not, do you wind up with a lot of debris in your brakes? Any thoughts or photos of routing hose through the driver's side bumper area?


Thanks everyone!

Ted

I have been looking at these DIY brake duct threads for a while and I'm ready to do the fronts, but I'm still not sure how to handle the rears. Any ideas/suggestions there?

I've actually noticed I have more heat problems with the rear brakes.

I don't want to use the faux ducts for this and I'm convinced that with my car as low as it is, I will break the C&T ducts. So I think I want to just get some naca ducts and mount them to the rubberized plastic pieces under the bumper. I figure if I mount them flush, they wont get much air, but if I angle them slightly, they should be fine. I'll use 2" tubing and route it to the eye of the front rotor.

But on the rear, I think I have no choice but to point the air at the inside surface of the rotor. And I have no clue where I should draw the air from.

Hi Ted, yes, there was quite a bit of air with the tire spat ducts and 2" hosing.

Rev, does your car scrape the stock spats? The C&T's have a little more clearance (maybe a half inch?). They also withstand abuse pretty nicely, as I've nailed one a couple of times not paying attention. I'd go for the fiberglass versions if you fear contact, as they are cheaper, easier to fix, and perhaps a bit more flexible.

UL

p.s. - They're really easy to install/remove at the track too. Takes all of 5 minutes a side and then just tuck the tubing away. Brake ducting on the street is pretty useless for all but the criminally insane :-) Oh wait, I leave mine on for the street.....

Rear brake overheating is another interesting issue.

Some have stated that the rear brakes should only overheat if the fronts are losing stopping power for some reason, and the brake bias is moving towards the rear. Others have seen heat problems in the rear, but aren't aware of any issues with the fronts at that time.

Who knows?

I scrape the front strakes pretty regularly, so I think I would destroy the C&T ducts inside of a week. I manage never to scrape the bumper, but the strakes scrape regularly and once in a while I slightly scrape the exhaust tips (although it's barely enough to even scratch them).

There have been a couple of times I've seen my rear brakes overheat (smoking, etc.). Once was on a mountain drive when I pulled off the road after a hard stop from 140 ish mph. I figure they were probably already plenty hot from mountain driving and then the stop from 140 to 0 probably was the kicker there. Also, I notice at the track that the rears seem to get pretty hot... but then again, I basically melted my fronts at the last track day, so Ted's theory that the rears overheat when the fronts stop working isn't a bad theory.

I can't find Naca ducts for 2" hose. Everything is for 3"...

What's the consensus on the best size hose to use? 2"? 3"?

Do I really need to use ducts, or can I just route the hose under the car and point it forward?

I'm thinking on the rears maybe it would be best to point the hose at the caliper instead of cutting the heat shield and pointing the hose at the inner surface of the rotor. Any thoughts on this? Might lead to less overall cooling, but there's a lot of surface area on the caliper and if I point the hose there, it will still get some air to the pads and the rotor. Thoughts? Really, it just seems easiest to me...

I'll chime in later on ducting, but I'll say a few things from what I've experience on the track.

the rear rotors heat up approximately 150-170 degrees hotter than the fronts. remember they are not vented rotors, so they do retain as much heat, and fail to dissipate as quickly than the fronts. even though some might think that if the fronts are overworked the rears will heat up - well, the rears have zero chance of getting ventilation without some user input like hecash or C&T's modifications.

the fronts, even though you aren't getting full blown air going into the faux ducts, this might work better, because I do not believe you'll need 90mph winds into the brakes, so some can pass right over the faux ducts. but that's just my take.

Hecash,

Very nice setup. I've got it on my to-do list.

I show the first racerpartswholesale NACA duct as part #SPA-D100, $15.99, 4"x8.5" opening. Does this sound right?

And #THE-SS300, 11' three inch silicon ducting, $64.99.

Also, have you had any problems with your powder coated calipers melting? Much of the powder coating on mine has discolored or dripped away from track heat. It's been much better after removing the dust shields, which will likely go back on when I have ducted cooling.

Rev, I think if you want to go 2-1/2" or 2", you buy the 3" NACA duct thn use the hose adaptors, #SPA-D103A or SPA-D103B $13.99 which snap on to the ducts.