Brake Ducting Rules Clarification

#1

I was just talking to Rob at Bimmerworld about installing their brake cooling kit on my '87 325is. He brought up the issue of their offset ducts and whether they are legal, since the rule below seems to imply that only a 3" dia. hole would be permitted in the air dam, not the larger, funnel shaped hole offered by the Bimmerworld system. I could make an arguement for either interpretation being legal.

9.3.13.7. Ducting to the brakes is permitted, and two openings in the front valance to allow the passage of up to a three (3) inch diameter duct leading to each front brake are permitted for this purpose.

On a related note, how have others of you dealt with this problem on this particular model? If I remove the fogs on a big bumper car with the gonzo air dam, there’s not much room behind the foglight hole because of a conflict with the body sheet metal. The little OEM air ducts at the bottom corners of the air dam seem like they don’t deliver much volume to the wheel well.

Thanks,
Sasha

#2

The rule states provides for openings in the valance which allow the passage of up to 3" ducts. I read this to say that the ducts/hoses themselves must not be greater than 3" in diameter. It says nothing about how large the external openings themselves can be. My car has the stock funnels (integrated bumper assy) leading to 3" ducts. I’m not very familiar with the layout of the diving board bumper assy’s, so I’m not sure how their stock ducts are set up.

#3

I replying not to interpret the rules per se, as our car is not yet ready, but, the ducts on my 240z track car sound like the ones described below. They are about 9 inches wide/5 inches tall, and they connect to a 3 inch hose for brake cooling.

Ed

#4

Lots of cars already in the series are using the Bimmerworld/RRT intake ducts and/or backing plates.

#5

Sasha, you’ll be legal with the Bimmerworld kit - the rules basically limit the size of the hose - your ducts leading to the hose can be massive.

As far as the sheet metal behind the fog lights, I’d suggest a little creative bending or cutting … A 3" hole-saw will do the trick perfectly.

-Vic
SO #325

#6

sdais wrote:

Steve is correct.

Carter

#7

just wondering, has anyone had any problems with overheating breaks or excessive brake fade!

#8

IIRC, Carlton melted a couple of rear pads.

#9

MikeD wrote:

I am building my 91 out for competition. Last year in DE’s I had overheating problems (car is still heavy). The cooling duct kit worked wonders. I did go with the BW kit and instead of isstalling their intake ducts, I attached the 3" hose to the back of the factor brake duct intakes just inside the fog lights. It’s working good so far…