I figured it was time for an update on the goings on over here. Like others on this form I am also working on a front and rear disc set up.
Fixed aluminum calipers are the only type I considered for this undertaking. A fixed rear with integral parking brake is the jewel in this crown, but it is flawed at best at the moment. The Wilwood Powerlite radially mounted 4 piston caliper seems to be the best choice from their line. It weighs just under 3 lb. Running 1.38" in the front and 1.00" in the rear yields a very similar piston area to the AR/NR of the 47. I am going to do a dual master set up.
My approach to the front was to repurpose the factory solid rotor. I have successfully milled the center away so that it can accept a 2 piece style aluminum hat. I am waiting on my fixed and floating hardware to come in from AP. The hat proved to be about 20% weight savings over the standard rotor. I plan to test this set up with a standard hub first so that I don't introduce too many variables at once. The next step will be to machine an alloy hub with an integral flange to accept the new rotor disc with floating hardware only. This will remove the need for 4 bolts and the associated material in the hub. I am also going to do a front bearing race spacer as I have read good things about it on here. It should be straightforward to mount a ventilated rotor to this hub as well if that is deemed necessary. Other improvements I am exploring on the front end include an aluminum steering arms for the upright & lightweight dust shields to help trim unsprung mass.
As we all know the rear is the problem child....
I have sourced Wilwood powerlite calipers with cable operated parking brake levers that actuate the pads. Wilwood developed them for miata people so everything seemed promising. I have read that some people had trouble passing MOT with the reduced hand brake capacity on incline, but these are the closest I have found to fixed calipers with integral p brake so I took a gamble. (Hi-spec also make a similar caliper, but Wilwood was much easier to deal with for me being in USA) The problem I have found is that the arms are too long to fit in the 13" TCS Wheel (Steel wheel is no better). I experimented by making a hat as deep as possible so the rotor has almost no clearance from the trailing arm. This is a very extreme proposition because it even removes the possibility of using a bracket to mount the caliper on the outboard side of the trailing arm. It is still not enough. Even with .375" of wheel spacers it still would not clear. The next step for me is to manufacture a new arm with a ball end receiver for the outer pincer which has a lower profile instead of the tall hook mount. I think I have a design that would not compromise too much on the clamping force of the lever.
This has led me down another tangent. I reverse engineered the rear upright to machine it from solid initially because of the intermittent quality of the castings. This exploit is best described by the expression that everything becomes a nail once you have a hammer... Once you consider making them this way it is easy to add extra mounts to it. I am exploring the idea of having an integral caliper mount or at the very least a modular mount for a caliper bracket. I would also add a clevis on the inboard side to allow the use of an upper link like Richard Mann has demonstrated for us. These changes would allow me to run CV axles and space the caliper as far out as is possible to clear potential problems with the 13" rim.
The 3rd option is to ditch the integral parking brake and fit 2 calipers. Standard powerlite fits easily without the arms. I don't really like this solution because it adds mass and cost that seem avoidable. Wilwoods MC4 parking brake weighs more than their 4 piston powerlite caliper....
With all that said...the smartest thing to do would be to run 14" or even 15" wheels. I have seen forged 15" wheels which weigh less than the alloy TCS rims. It would open the door for better tire selection as well. Miata guys use these exact calipers in 14" wheels so I imagine it could work for us too.
What do you guys think? I am convinced this is the Europa equivalent of the search for the holy grail and that my face will be melted off very soon for drinking from the wrong cup
