Installation of Front Brake Duct for an E36 M3

 

I have a 1995 M3 which I occasionally take to open track events. In an effort to help prevent both brake rotor warping and excessive brake pad wear I decided to install ducting to provide fresh air directly to the rotor center. After a bit of research and some good advice I chose to buy the TMS backing plates and the Bimmerworld Flange and Flexible Hose Kit. I was replacing the front bearings on my car and this allowed me to choose any backing plate. The TMS backing plate matched the Bimmerworld Flange (both use 3-inch flexible hose), is priced reasonably and is a nice design. The Bimmerworld Flange Kit allows you to quickly and easily install and remove the flexible hose in the fender well for track events. Very nice!

The installation of the backing plate is very straight forward and there are on instructions provided. Once the bearings are off the spindle you simple unbolt the factory backing plates and replace them with the TMS backing plates.

To install the Bimmerworld kit I followed the procedure on the Bimmerworld website. But, as you will read below I made a few changes, some of my own and one important one recommended by Neil Maller.

The TMS Backing Plate installed on the spindle. The driver side plate (shown) installed very nicely. The passenger side plate required the enlarging of the three mounting holes to fit properly.

The bearing has now been installed. This part of the job, removing and replacing the bearings was simple.

The rotor and caliper have now been installed. The backing plate needed a little bending since it was rubbing on the rotor at a few points. A couple of big screwdrivers and some prying solved the problem.

This is the side view of the hub and rotor assembly. The opening for the ducted area has a tight fit with respect to the suspension components as you turn the steering, but it works fine.

I purchased an adjustable routing tool from Home Depot for about $13. It is designed to cut through plastic and it did an outstanding job! You simply attach it to a drill, set the cutting tool for the diameter you wish to cut and that’s it. It took only a few minutes (if that) to cut each hole in both the fender liners and the factory brake ducts. Easy!  

The driver side, factory duct after I cut the opening for the flexible hose. Using a tip I got from Neil Maller, I cut two holes in the factory duct using the tool shown in the previous picture. I then used a razor knife to cut away the plastic between the two holes forming the opening you see above. This method is a deviation from the Bimmerworld website instructions. Bimmerworld’s website instructs you to cut the factory duct in half and attach the flexible hose to the end of the duct. I think the procedure above is superior for two reasons. First, the duct is left mostly intact and is still supported at both ends when you re-install it in the car. Second, the hose exits the duct at a better position and angle to meet up with the flange.

The flexible hose and factory duct assembly. With the oblong opening in the factory duct the hose fits in very nicely! Note the two small holes (in the upper left of the duct in the picture above) I drilled in the factory duct. I needed some way to help anchor the assembly in the car since it now requires more support to remain in place due to the flexible hose pushing back on it when it’s installed in the car. I used a heavy zip tie to provide support and the holes above are for the zip tie as you will see in the next picture.

The assembly installed in the car, driver side. Note how the zip tie provides support. On the passenger side I used two zip ties to secure the assembly. Use trial and error in your car.

The Bimmerworld Flange has been installed in the inner fender liner and the inner fender liner has been installed in the car. I followed the Bimmerworld website instructions. It is a tight fit. The Bimmerworld Flange kit did not come with the nuts and bolts to attach it to the car. This required a trip to the hardware store which I did not appreciate since it came as a surprise. The kit should either come with the nuts and bolts or at least inform you that you need to buy them beforehand.

HIGHLY RECOMMENDED!!

While you are at the hardware store I highly recommend you take one of the fender liner screws with you (they are all the same) and buy four that are longer by at least a 1/4 or 1/2 inch. Two of the screws on each side of the car come up from the bottom blind and screw into the fender liner below where you have installed the flange. The factory screws are too short to reinstall unless luck is on your side. I also purchased a few large washers to reinforce the fender liner screw that is located directly above the flange (you cannot see it in the picture above) and the screw that is located at the front, upper, outer part of the fender liner. I had been warned that the area of the fender liner above the flange is susceptible to tearing itself apart so I’m hoping this bit of reinforcement will prevent that.

You will also note that the bolts on the flange are facing away from the wheel well. I did this to simply give myself a bit more clearance since I did not want to worry about the tire hitting it.

The completed job! Not bad huh? The hose takes about five minutes to install I have discovered. It’s much easier to install if you turn the wheel as shown above when you install it. With my suspension and tire/wheel combination I can turn the steering wheel about one full turn before the tire starts to crush the flexible hose. Let’s just say you will get good at three point turns at your events. Once on the track it’s not an issue at all. You simply have to remember while you are in the paddock. In case you are wondering, there is no way at all you could run the car with the hose installed on the street. It wouldn’t last your first drive to the grocery store.

As an interesting note, the picture below is the “before” picture. Note the changes.  

All in all I’m happy with the changes. I had a bad wheel bearing so this was for me the optimum time to perform the ducting installation. If I had not been replacing the bearings I would have purchased the Bimmerworld backing plate since it does not require you to remove the bearings. If you buy a backing plate besides the TMS or the Bimmerworld and you use Bimmerworld’s Flange Kit, make sure the backing plate is designed to work with 3-inch diameter hose since the flange is designed for 3-inch hose.

With my method of installing the flexible hose in the factory ducts I do not have a true seal between the factory duct and the hose and some of the air which enters the factory duct is able to escape past the hose, missing the path to the backing plate. For my next event I’ll just simply block off the area in the factory duct behind the area where the hose meets it and fix this problem.

Steve Grigory
sgrigory@pacbell.net