Part 13
It has been 2 months since my last post. My car with ITB EFI starts easily and runs great without further tuning.
In the 16 years I have owned my 75 911 Carrera I have focused on more power and better handling but I have left the brake system stock. So I got to thinking, more go power needs more stop power and I began looking into brake system upgrades. After some research, I chose to upgrade my brakes with 4 piston units from Wilwood Engineering.
I wanted a conversion kit for both front and rear brakes that would allow me to retain the original 15 inch Fuchs wheels. From the Wilwood website (wilwood.com), I searched for brake kits by vehicle and started reading through the documentation for the front brake kit and the rear brake kit for my 75 Carrera. During this process of reading specifications and wheel clearance diagrams and then going out to the garage and taking measurements of my wheels and existing brake system, I discovered that my October 1974 build 1975 Carrera is fitted with "M" front struts and not the "S" front struts that the Wilwood vehicle selector guide assumed (M struts have 3 inch spacing for the caliper mounting bolts while S struts have 3.5 inch spacing). Fortunately, if I searched for a 1974 911, Wilwood's selector guide gave me the opportunity to select the M strut or the S strut and I was able to find the correct front brake conversion kit for my car. The rear brake kit selection was more straight forward as there is only one type (which uses 3 inch spacing).
Once I figured out what brakes I had, next was to choose either the 11.10 inch diameter rotor kit (stock size rotor) or the 12.19 inch diameter rotor kit for the front. Both kits were specified for a minimum 15 inch wheel so I carefully measured the inner diameter of the front and rear wheels, then compared those measurements with wheel clearance diagrams for each kit (11.10 inch front, 12.19 inch front and 11.4 inch rear). It turned out that the 12.19 inch big brakes would technically fit inside my 15 inch Fuchs front wheels but I would have just .090 inch clearance between the caliper and the wheel (Wilwood specifies .080 inch minimum clearance) which wouldn't leave room for the stick-on wheel balancing weights on the wheels so 12.19 inch rotors were out. I selected the 11.10 inch front kit and opted for slotted and cross drilled rotors front and rear.
I called Wilwood and placed my order. Boths kits were in stock and I received them 2 days after I placed the order (I live near San Jose, CA and Wilwood is in Camarillo, CA (near LA) so fairly short shipment). Both front and rear brake kits with tax and shipping cost just shy of $2500.
Wilwood provides clear and easy to understand assembly instructions, but just as with the CIS to ITB EFI conversion kit, you need a good understanding of the job and prior experience installing and working on brake systems is very desirable if not a must. I won't go into the same level of detail on the installation as I did with the ITB EFI, but be prepared to do several rounds to mock ups - put it together, check the fit and clearances, disassemble, adjust the shims and repeat until you have the caliper centered left to right over the rotor and the outer edge of the brake pads are flush with the outer diameter of the rotor.
A couple of more thoughts: Wilwood specifies red Loctite (highest strength thread lock) for the caliper mounting bolts which is great if you don't plan on having to remove them but I prefer to use the blue Loctite (medium strength).
The lower mounting bolt on the rear calipers is in a tight spot with minimum clearance from the cast aluminum hollow rear control arm and I had to use a 19 mm standard depth socket and a 3/8 inch drive non rachet bar to loosen the lower bolt (ratchet won't fit and a box / end wrench doesn't have enough clearance to move). Then after removing the upper mounting bolt and rocking the caliper away from the rotor then back to the rotor as I unthreaded the bolt with my fingers, I was able to finally remove the lower mounting bolt and remove the rear caliper. Then removing the rear rotor (by unscrewing the pair of flat blade screws - used a hand impact tool and hammer to get them loose) and removing (and discarding) the dust shield and you then have enough room to use an box / end wrench to install the new caliper mounting bracket.
I find it easier to work on one wheel at a time from disassembly, mock-ups, assembly, brake bleed and pressure / leak test. So I jacked up and secured with jack stands the right side of the car and did the right rear followed by the right front, then repeated the process of the left side of the car.
Original brakes
New brakes
Brake bleed set-up for one person brake bleeding
Repainted the wheel centers with black semi-gloss for freshened look
New brakes after two test drives with light and moderate brake cycles and begin brake pad / rotor bedding process
