Rear End: Assembling the Lighter Mini Subframe
The iconic Bogus 2 rebuild project continues at Mini Sport Ltd.! In our previous guide, we delved into the steering rack. Now, let's shift gears and focus on bringing the rear suspension of this classic Mini back to life.
Assembling the rear subframe on a bench not only simplifies the process but also reduces the risk of damaging the shell. Here’s a step-by-step guide to ensure a smooth assembly.
Assembling the rear subframe on a bench makes life easier and reduces the chance of damaging the shell. Initially, only the trunnions are fitted, as the heavy rear radius arms make subframe installation more difficult.
The mounting points for the rear trunnions were covered during powder coating, so they needed cleaning before fitting the trunnions. The threads were also checked and cleaned with a wire brush, nut, or dye if necessary.
An ultra-light alloy DSN Classics trunnion kit was fitted, shown here with replacement steel trunnion pins and Mini Sport poly bushes. The trunnion pins are standard Mini items. Apply some copper grease on the shaft and thread to prevent the trunnion from seizing. The trunnions are fitted with a Nyloc nut, but not finally tightened until the subframe is in place at all four corners.
Forward Pin Adjustment
The nut on the forward pin is not fully tightened before the subframe is bolted into the shell. Since nobody seems to make the two-pronged tool needed to lock off the trunnion pin, improvisation is required.
With all the trunnions fitted and positioned in the direction of their mounting points, the rear subframe is ready to be fitted. The front trunnion mountings need to be cleared after the shell has been painted. It’s critical to get some copper grease into these captive nuts, as this is a rust-prone area of the shell.
The heelboard in the British Motor Heritage-supplied floor pan needed modifying during trial fitting. Access to the captive nut wasn't possible without elongating the hole before painting. A Dremel is useful for this job, but protect the thread carefully.
Lifting the subframe is at least a two-person job due to the nuts and bolts alignment required. Get at least one bolt in each trunnion first before attempting the second to avoid scratching the paint. Take care when inserting the mounting bolts into the heelboard captive nuts. Support the subframe to relieve the load off the bolt. These points are crucial for suspension geometry, especially for older captive nuts that are difficult to replace if stripped
With the rear subframe in place, tighten the front and rear trunnion Nyloc nuts before fitting the radius arms. Before installing the radius arms, fit the new knuckle joint into each arm on the bench. Ensure the knuckle joints are properly packed with grease, using a new nylon cup.
The Mini Sport adjustable rear camber/tracking brackets had to be modified to fit the DSN leading trunnion. This modification is due to the more bulbous outer radius of the trunnion compared to standard camber brackets. Tighten the adjustable rear camber/tracking bracket. Fine adjustments will be done once the car is back on the floor and fitted with its correct wheels.
Apply copper grease to the inside surface of the connecting rod between the rear cone and knuckle joint. This ensures the cone remains removable in the future. Apply copper grease to the outer shaft at the cone end. When positioning the offside Adjusta Ride cone, ensure the grease nipple is accessible to avoid difficulties posed by the battery box.
When fitting the rear Spax dampers, they were found to foul the edge of the radius arm. Trim the upper edge of the arm to clear the damper. Mini Sport prefers not to use the steel cup washer at the top of the rear damper mount rubber bush, as it causes chatter. Let the bush sit against the wheel arch surface to minimise noise.
Ensure the damper top thread clears the fuel tank when the Mini is on its wheels. Trial fit a standard tank to verify. Finally, fit the Mini Sport dry-suspension-specific handbrake quadrants. Remember to secure the quadrant shaft with the tiny split pin and washer.
Don't miss out on the rest of the Bogus 2 Series!
This blog series is your go to for a guide to taking your Mini from a bare shell to a road-worthy classic. Check out the rest of the series for tips and advice from our Mini Experts for every stage of your Mini restoration!
Need help or advice on upgrading your Mini's rear suspension? Contact us today for expert guidance tailored to enhance your driving experience. Let's restore your Mini together!