C4 ZR1 Front Disc Upgrade
My car came with 11" disc from the factory. Ages ago, I upgraded the car to the 12" 1LE brakes by installing spindles off of a 84 Pontiac Parisienne wagon and calipers off a 77 Trans Am. Pretty easy and effective update but just didn't cut it by modern standards. Over 10 years ago, I started to look for an upgrade and the Baer racing track kit was the hot set up at the time but was out of my budget at the time. I found Flyby racing offered brackets for 13" C4HD (same as ZR1 and GS) brakes on a second gen and sourced a rare GMPP brake kit spec'd for the C4 ZR1 on ebay and it sat in my basement for a decade.
By 2020 standards, this does not represent a state of the art update but I had 80% of the parts and Covid quarantine provided some time. 13" dimpled, curved vane rotors would be more than I would need. I was able to source the necessary hubs, brake lines and lug nuts from Keith at Custom Works Performance to finish the job.
I saved my original spindles which now needed to be cut to clear the new aluminum C4 caliper. I used a combination of a sawzall, 4" angle grinder and rotary burrs to finish up the spindle mods, drilled and tapped the dust shield holes for the Flyby brackets. I then brushed off the flaky rust, rattle can painted the finished spindles and it was pretty much plug an play from there. Outside of a major change in the toe setting which will require an alignment, I am pretty confident in this set up.
Update: System worked great out of the box and had tons of initial bite even when cold. The only downside is the track ready brake pads spit out a ton of brake dust. I mean the dust was crazy! I don't know what brand they were but they got replaced by a set of Powerstop Z26 pads. The Powerstops eliminated the dust issue but I ended up losing the hard initial bite feel. That has been my experience with virtually all Powerstop pads I have used and somewhere along the line, these are likely to get replaced.