My Cantrell Motorsports Brake Duct Kit writeup (with BBK)

[Car54]

Originally Posted by VictorH

I have this same brake duct system on stock rotors, calipers and track pads. This is one of these items that's difficult to draw a conclusion. Like the OP states, it's probably helpful but hard to know without back to back testing under the same conditions. I've never had brake fade at VIR so ducting kit made no difference there. I've had brake fade at Road Atlanta and I still get it with the brake duct kit. Do I go longer before fade starts? I don't know. Do my pads last longer? Not that I can tell. The one thing I can say with a fair degree of certainty is that once I have fade (not just a little but good rippin' fade) that the recovery back to usable brakes is quicker with the ducting kit. So hard to tell how much it helps without data, but it does help, though in the stock brake form, it's certainly no cure for fade on certain tracks were fade is an issue.

Just curious but where do you usually get fade at RA? Seems like an easy track on brakes to me, but I've never driven anything over 250hp there.

[lutfy]

Originally Posted by Car54

Just curious but where do you usually get fade at RA? Seems like an easy track on brakes to me, but I've never driven anything over 250hp there.

Interesting. I was there early in March and drove the snot out of the car there. At the back straight somewhere past 150MPH braking for 10A was not an issue.

With Motul 600 fade is not an issue. My current stock rotors last me around 8 days before cracking up to the circumference. Issue is pad wear. I can go through a set of PF01 in 1 day (full threshold braking) and went through a set of PF08s in one weekend. NOT COOL! (no pun).

For me, the stock brakes are good (no fade) its just that I go through pads SUPER quickly. I thought about cooling ducts as well but have decided to get a custom 2 piece rotor (stock caliper) without any silly drills etc (which eats up pads) and heat treated (for longevity).

Cheers,

Lutfy

[jacobe92]

I don't think it's over kill to install brake ducts w/ BBK. I like your rotor size . I have the same set up. Front 365mm rear 345mm.

[Modena NYC]

Originally Posted by VictorH

I have this same brake duct system on stock rotors, calipers and track pads. This is one of these items that's difficult to draw a conclusion. Like the OP states, it's probably helpful but hard to know without back to back testing under the same conditions. I've never had brake fade at VIR so ducting kit made no difference there. I've had brake fade at Road Atlanta and I still get it with the brake duct kit. Do I go longer before fade starts? I don't know. Do my pads last longer? Not that I can tell. The one thing I can say with a fair degree of certainty is that once I have fade (not just a little but good rippin' fade) that the recovery back to usable brakes is quicker with the ducting kit. So hard to tell how much it helps without data, but it does help, though in the stock brake form, it's certainly no cure for fade on certain tracks were fade is an issue.

It's interesting that VIR, a very fast track you get no fade, even stock with no ducts. Maybe BMW engineers really did know what they were doing for the street then with the brakes on this car.

I am nervous to even attempt stock brakes on the track with this car.

[VictorH]

Originally Posted by Car54

Just curious but where do you usually get fade at RA? Seems like an easy track on brakes to me, but I've never driven anything over 250hp there.

Well, at Road Atlanta you generate a lot of heat in the back straight slowing down for the 10a-10b complex (walk to that location and watch how red/orange peoples brakes get there) and then again on the front straight entering turn 1. For me after a good 3-4 laps with no traffic I get notable fade slowing for both turn 5 and turn 6 even though both of these especially turn 6 are reasonably fast corners. If I don't watch the brakes I'll get more and more fade on subsequent laps, but I'm not usually trying to see how hot I can get my brakes and will back off a tad or more often than not, traffic slows you enough to have full brakes back in less than a lap. I'm running Pagid RS-19s front and rear and Castrol SRF (this year only, don't think it's any better than Motul) on otherwise stock brake system (except for ducting).

[knolow]

Great Thread. I am getting an E92 for the track and am thinking of doing this, it has to help in some way even with a BBK.

[radiantm3]

Originally Posted by knolow

Great Thread. I am getting an E92 for the track and am thinking of doing this, it has to help in some way even with a BBK.

This is an old thread and my car has gone through quite a few updates since then. I still have my cantrell kit on, but the ducts are being mostly blocked by my GTS splitter. I can say with strong confidence that the ducting works because I was able to brake hard all day long with my bbk + ducting (and I'm brutal on my brakes). When I had the gts splitter put on I started to get a little bit of brake fade (although nothing too serious) because the ducting was blocked. I have to manage the heat in my brakes just a bit more now.

[knolow]

Originally Posted by radiantm3

This is an old thread and my car has gone through quite a few updates since then. I still have my cantrell kit on, but the ducts are being mostly blocked by my GTS splitter. I can say with strong confidence that the ducting works because I was able to brake hard all day long with my bbk + ducting (and I'm brutal on my brakes). When I had the gts splitter put on I started to get a little bit of brake fade (although nothing too serious) because the ducting was blocked. I have to manage the heat in my brakes just a bit more now.

Thanks for the info. I will follow the DIY thread on the self fab/install brake duct.

I will have the same issue you have now as I have the Challenge GTS front lip (without the brake duct holes). My way around this is creating vents that are angled and hang slightly lower than the under carriage profile.

[Car54]

Originally Posted by radiantm3

This is an old thread and my car has gone through quite a few updates since then. I still have my cantrell kit on, but the ducts are being mostly blocked by my GTS splitter. I can say with strong confidence that the ducting works because I was able to brake hard all day long with my bbk + ducting (and I'm brutal on my brakes). When I had the gts splitter put on I started to get a little bit of brake fade (although nothing too serious) because the ducting was blocked. I have to manage the heat in my brakes just a bit more now.

Fade must be coming from all that extra downforce!

[JYost]

Very Nice!! Clean Install!

[CSBM5]

Originally Posted by VictorH

Well, at Road Atlanta you generate a lot of heat in the back straight slowing down for the 10a-10b complex (walk to that location and watch how red/orange peoples brakes get there) and then again on the front straight entering turn 1. For me after a good 3-4 laps with no traffic I get notable fade slowing for both turn 5 and turn 6 even though both of these especially turn 6 are reasonably fast corners.

This reminded me of being at the Walter Mitty Challenge in 1981 at the driver's meeting where Brian Redman was leading the meeting. His comment way back then was something to the effect of "if your brakes feel the least bit weak going into 6, be careful for the end of the back straight because they probably won't be there for you." Of course back then the back straight was crazier than today also as the plunge down the "elevator shaft" (as we called it) has been filled in and they rerouted the approach to the bridge with the chicane. Way back then you used the huge uphill into the bridge for a good portion of your braking, and of course the bridge was actually a turn with the apex sitting right underneath it coupled with an awesome track out on the other side.

Someday I'll get back to RA and drive the new layout (well, new as in 15+ years old now I guess).

Brian was a stickler back then in that driver's meeting about brakes as one would expect given the year and state of brake design at that point. He suggested becoming familiar with how your car felt when doing a quick tap of the brakes in the middle of the back straight, and suggested everyone pay close attention.

Unfortunately, a guy in a ~1974 Capri lost his brakes going at the end of the back straight that year, careened over the hill and end-over-end tumbled down toward the pit entry (there was only one pit, the one on the outside of the track back then). He had to be airlifted out.

Which brings up more of the story as the Mitty organizers decided to "slow down" the back straight by putting a cone chicane you had to negotiate on the section just prior to the downhill plunge. I was in the very first session out with that "addition", and on the 2nd lap, a 911 about 4 cars in front of me lost it in that cone chicane and slammed head first into the Armco on the right side of the track, totaling the car (driver ok). Needless to say the cones were promptly removed.

Sorry for the aside guys, it's too easy to tell stories when your aged.

[bigjae1976]

Dang, I missed this thread?

Interesting tests on the ducts. I agree with Porschefile (why wouldn't I?) that you really need to get the temps right after a hot lap. I had a Zionsville radiator in my 330...peak temps were a tad lower but the biggest benefit was that the water temps would decrease much faster after a hot lap and I could run longer at that peak temp vs the OEM radiator which would begin to become overwhelmed after about 25 minutes.

The bimmerworld E46 backing plates had a flange on the side which was very close to the inside of the rotor hat. According to their website (Turner or BW) this reduced air leakage and directed more air towards the center of the rotor. Then the air would be passed through vains between the rotor disc surfaces which would cool the rotor better and more evenly.

I'm not an engineer but that design looks like its only cooling the back side of the rotor. Have you noticed uneven pad wear? I would imagine the outer pads are wearing faster if that's the case.

[SneakyDeeky]

Can anybody else see more pictures than just the first one? I'm bummed cuz the iPad and Mac Mini won't load them.

Great thread and content, though as I've been wanting a BBK (like everybody), but having a hard time justifying the cost so I did a search on brake cooling to see how effective this approach was when coupled with primo pads, lines, fluid, and rubber. Take away from the debate looks like it helps, but not as much as the better engineered BBKs out there.

Thanks for the data collection and write-up, Radiant.

[WinterSoldier]

Great thread! Just received my kit from Cantrell, will install next weekend using these instructions.

[WinterSoldier]

Installed Cantrell kit a few weekends ago...just getting around to posting results.

[jfo122]

Originally Posted by WinterSoldier

Installed Cantrell kit a few weekends ago...just getting around to posting results.

Any on-track feedback? Issues with rubbing?

[WinterSoldier]

Originally Posted by jfo122

Any on-track feedback? Issues with rubbing?

Newly installed, so just in town driving. No rub lock-to-lock on the stand, we'll see how it fares under duress at Barber in April.

[FogCityM3]

Have the kit also, you can get it not to rub with a good install. The "corner" of the bottom of the wheel well where the ducting comes up should be cut as in radiants photo and you should zip tie tightly to the control arm. I also ran some duct tape around the tubing just in case, but so far, no issues. Running 255 in front 19x9 ET 20. Also, if you have the performance splitters, they will cover half the hole. I cut the bottom of the splitter and added a small foam block underneath to create a higher pressure "zone" but still probably not getting max brake cooling effect. Will say it is a PITA install (I had a shop do it and it took them a while) and not sure I would do it again, unless I were a true track rat vs going a few times per year.