[dradernh]

This past summer, at the same time I had a shop install a jack point in the center of each side of my car, I also had them do something to get more air into the interior of my front brake rotors.

I did this because I’ve been experiencing very high rotor and caliper temperatures ever since I began running the car at the track. Even though there is air being ducted through the front bumper cover and into the area where the front braking components reside, little of that air is able to make its way into the center of the rotors and then out through the vanes. Without sufficient movement of air along that path, the rotors and calipers are going to get pretty hot - maybe hot enough to discolor the calipers and, possibly, burn them down.

Compared to the E36 and E30 that I used to run, there’s remarkably little room to channel incoming air to the center of the front rotors. There’s insufficient room for a 3” or 2” brake duct hose, and the car’s front knuckles/carriers effectively block almost all access to the interior of the rotors. Those parts can be seen at #2 in this realoem diagram: https://www.realoem.com/bmw/enUS/sho...diagId=31_0956.

The work the shop determined would be most effective in moving at least some air into the center of the rotors was to fabricate what they called an air “scoop”. This part can be seen in the photos immediately below.

This is a shot of the air scoop from the front showing its position relative to some of the suspension and braking components:

This one shows a close-up of the scoop; it gives an idea of how small the opening for incoming air is with the knuckle/carrier taking up so much space:


This shows the scoop from the rear, giving a glimpse of the brake duct exit in the bumper as well as showing once again the smallness of the opening into the center of the rotor:


The scoop is aligned such that it captures a portion of the column of air flowing out of the brake duct exit in the bumper assembly and redirects that subset of air into the center of the rotor. The shop told me that, relatively, it would have a greater effect upon caliper temperature than it would rotor temperature.

I’m not sure where I’ve managed to misplace the specific before and after temperature data; although, if I look at a rotor paint temp chart and a caliper temp strip, I’ll quickly be able to offer up the before and after temperature ranges for both components. If anyone wants that data, please feel free to ask, and I'll pull it together. The bottom line is that both the rotors and the calipers are running a decent amount cooler than they were, but nowhere nearly as cool as I’d like them to run.

Update: see post #20 for the before and after temperature data.

The next step is going to be to take out the caliper pistons and examine the dust boots and piston seals. Regardless of their condition, we’ll probably just go ahead and replace the boots and seals with high-temp units. The principal reason for this is that my next event will be a two-day open-lapping event at Watkins Glen, a much higher-speed track than is the track I’ve been running since I had the car built. That’s Mid-Ohio, a handling track with only one high-speed braking zone, whereas the Glen has five high-speed braking zones and places high demands on a car’s braking system.

FWIW, BMW sells a caliper repair kit that includes only the dust boots. If you want caliper seals from BMW, you have to buy new calipers. That’s not necessarily a problem, as Brembo makes the boots and seals that go in their calipers, but the shop tells me they need to take measurements before I can be assured of ordering the correct sizes of those parts.

In the event someone else ends up needing the data, I’ll post the caliper piston sizes here once they’ve been measured.

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Update: Here are three photos of a brake scoop taken when it was off the car: