Front caliper install
The Passat front calipers bolt up quite nicely to the stock 924 steering knuckle. Hooked up to the upgraded stainless steel brake hose, they make it look like we finally have a serious braking system.
A couple surprises came up during the installation. The left and right calipers are basically mirror images of each other, and they have unique part numbers to avoid confusion between them. They are designed so that the bleed screw sits on the bottom of the cylinder in the installed position so when the brakes are bled, sludge and other debris can be cleared and all old fluid eliminated. On the Passat caliper, the hose fitting also sits on the bottom of the caliper adjacent to the bleed screw.
Upon completing the driver side caliper, it became obvious the brake hose fitting was going to interfere with the control arm in a left turn. At full droop with the car in the air, the wheel can barely turn, scraping the hose against the control arm as the rear of the knuckle turns in. Installed this way, we would probably eventually lose steering or the brake. So, the obvious solution is to swap the driver and passenger side calipers so that the hose connection (and bleeder) sit at the top of the caliper. This is one of those details too rarely documented (remembered?) on mods like this one. So here it is – you need to install 1990 Passat calipers upside down and backwards on the Porsche 924.
the other little surprise was discovered after torquing down the two mounting bolts on the steering knuckle. The hub wouldn’t spin. Closer examination reveals that the caliper dust cover, a thin metal disc attached to the steering knuckle on the inboard side of the brake rotor, doesn’t quite clear the slightly larger calipers. There is a section cut out of the dust cover to accommodate the stock Porsche calipers. But with the Passat calipers, when you bolt them down they squeeze the corners of the cutout into the rotor, interfering with the brake mechanism and effectively seizing the caliper. One solution is to remove the dust cover entirely – it isn’t really a necessary component. However, removing it requires first removing the rotor, which on the Porsche 924 is also the wheel bearing. It’s not a big deal, but it’s a pain unless you have bearing work to do or an extra hour on your hands. Another solution is to grab some pliers and bend back the offending corners.