1979-1993 & 94 Conv [Subscribe to Daily Digest] |
Gents,
My design is based on a pair of Wilwood 4 piston Billet Dynalite calipers and a 298mm rotor. Because of space restrictions I had to go with a slightly narrower rotor at 20.6mm, rather than the stock 23 mm. The new rotor is 18mm larger than the stock one thus increasing the leverage a bit. The two parts that required the most work were the caliper mounting adapter
and the brake hat. The new rotor is just a ring, no center portion, and
no one had the brake hat offsets I needed so I went the custom route. I ended up using a very hard aluminum alloy with a cross section of 7mm or more. Seems to be strong enough based on my testing so far. The caliper
mounting bracket is made from steel and is grossly over engineered.
With the standard caliper setup, the caliper mounting frame (aka the pad
holder) is threaded and the two M10 (maybe M12, I forget) bolts pass
through the hub tabs and then thread into the frame. In my case, again
because of space restrictions, I had to mount the adapter on the inboard
side of the hub tabs, thus I had to thread the tabs. I use M14 bolts to
hold the caliper bracket to the hub tabs and M10 to mount the caliper to
the adapter. The brake hoses caused me a bit of effort, but Paragon
Performance can make a set of custom hoses that will work nicely. (I
highly recommend taking your inner brake line off (Yeah brake fluid all
over the place) before you order anything and look at the hose end. It will have a convex or concave sealing surface at the end. There appears to be some differences across the years that caused a bit of confusion.) The
Calipers have 1/4-27 NPT female fitting on them. Using a Russell
adapter (several other companies make such hose adapters) that went from
a male NPT to a -3 with a 45 degree bend, I got the hose coming out of
the caliper at just the right angle. In my case I used a straight NPT
to -3 adapter on the wheelwell hose fitting (with a bit of help from a
NPT tap and with reference to the above comment on convex or concave taper confusion). (Just a piece of trivia, but a standard 10mm metric thread is almost exactly the same thread pitch as a 1/4-27 NPT) The brake hoses are off the shelf Russell -3 female on both sides and 15 inches long. If you go with Paragon Performance hoses, then the wheelwell adapter will not be required and the hoses can be slightly shorter. I had a problem of the hose rubbing on the wheel at full turn, but I made a small bracket that holds the hose out of the way.
The Wilwood calipers are available in two piston sizes. Basically you
measure what the stock piston cross section is and try and stay as close
to it as you can. This calculation is very important as the master
cylinder must have the fluid capacity required by the caliper pistons.
Too large a caliper piston and the pedal bottoms out or is soft. Too
little piston area and the pedal is too hard and braking power is
limited. I used the smaller piston size available as the larger size was too large I thought, but my pedal effort is slightly higher than stock, (It's not excessive by any means, just "firm") so I may have been able to get away with the larger pistons. Call it staying on the conservative side. The pedal is nice and firm as I have stainless steel hoses all around and has a nice progressive feel.
If you are interested in building yourself a set of these brakes, I have
the drawings. I need to get the car back up in the air to fix a minor rotor run-out problem that is causing some shuddering. Luckily with this setup, I can put shims between the hat and rotor to cancel the run-out. Wilwood actually recommends this approach.
And, lest I forget, I am using Wilwood's "Tan" pads.
I do have a few pictures, and can take more this weekend. If you want to see what it all looks like, send me your email address.
Regards:
Simon P. Coffin
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