Baja Bug
Rear Suspension Update
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Page 6
"Final" Details Now that the car has disk brakes on all four corners, a larger bore master cylinder was required. The stock master cylinder worked fine for front disks/rear drums but wasn't up to the task after installing the rear, 4-piston calipers. The stock master cylinder provided enough pressure but not enough fluid volume to actuate all the pistons in our brake system (we replaced the calipers that came with the micro stub kit with Wilwood calipers that have smaller pistons to mitigate the problem somewhat). We felt that it was important to retain a "dual-circuit" configuration (front and rear "circuits" independent of each other - a failure in one doesn't affect the other) and that limited our choice of master cylinders; there are numerous dual circuit master cylinders available but the only one that would fit in the stock location is the "large bore" VW master cylinder (20.6mm diameter bore vs. the stock 19mm). We installed the new master cylinder and the brakes now work perfectly with a "high and firm" pedal. This is the same configuration as our race car brakes and they have served us well throughout many races - they'll be fine in a pre-runner as well.
Rear Bumper Fabrication
We bolted the case and the driver's side cylinders and head to the transaxle so that we could measure for a new rear bumper. Since the transaxle is in a slightly different location than the previous one and the engine mounts to the transaxle, we need to build a new bumper to fit. This mock up allowed us to see exactly what the shape needed to be in order to have clearance for the muffler and room to install a UMP air filter.
In keeping with the "old school" theme of this build, Trevor wants the bumper to look like a "5 unlimited" bumper from the 1980's. The photo above shows the basic configuration we're aiming for - we'll design our own to fit around Trevor's "Porsche " engine and UMP air filter.
Once we designed the shape of the main bumper "hoop", it was time to bend it up. We use "Bend-Tech" software for determining where each bend begins and the correct bend angle so that we end up with a usable part rather than an expensive steel pretzel....... Our JD Squared Model 3 bender has served us well through race car and pre-runner builds. We converted it to air over hydraulic actuation and the addition of a digital bend angle display makes creating roll cages and bumpers easy.
This is the basic configuration of the new rear bumper, ready to weld. We'll be adding some tubes for side impact protection next time. It was getting late in the day and we didn't want to start on that yet; we need to mock up the entire engine and exhaust configurations before we can proceed - lots of things to work around. We think we've been successful in creating a look similar to the "old school" 5 unlimited bumper we were going for.
The bumper is nearing completion - we just need to add mounting provisions for the brake lights/turn signals and the UMP Supertrap air filter. We'll wait on the air filter mounting until the engine is reinstalled permanently so that we can get the location and routing of the ducting just the way we want.
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