The lower wishbone (also called the lower control arm) on the Fiat 500 is a common cause of knocking and banging noises from the front suspension. On this car the rubber ball joint insert had slipped out of position and was knocking against the subframe on every bump. Left unchecked this will worsen quickly and can become a serious safety issue.
What makes this job trickier than a standard wishbone replacement is that part of the front bumper and an underbody brace bar need to be removed to access one of the wishbone mounting bolts — but once you know the process it's very straightforward.
Classic Symptoms to Watch For
- Loud knocking or banging noise from front suspension
- Noise worsens over bumps, speed humps and rough roads
- Clunking when turning the steering
- Visible rubber tearing or displacement on the ball joint
- Excessive play or movement in the lower arm
- Failed MOT on suspension component
Tools You'll Need
Step-by-Step Guide
Remove the Wheel & Inspect the Ball Joint
Raise the car and remove the front wheel on the affected side. With the wheel off you can inspect the lower ball joint directly. Look for the rubber boot — if it has split, slipped out or you can see the ball joint moving excessively, replacement is required. On this car the rubber was visibly displaced and knocking on the subframe.
Release the Bumper Corner
To access the brace bar bolts you need to partially release the front bumper at the affected corner. Remove the four Phillips screws from the inner wheel arch and the T30 Torx screw where the arch meets the bumper. Then remove the T13 Torx bolts along the top of the bumper (four bolts top, four bolts bottom) at the corner — you don't need to take the whole bumper off, just release it enough to pull the corner away and access the brace bar bolts behind.
Remove the Underbody Brace Bar
Raise the car fully on the ramp. Move the wheel arch liner to one side for access. From underneath you'll see the brace bar held on by four 15mm bolts — apply WD-40 if they're rusty and give it a few minutes before trying to undo them. With those four out, remove the two further 18mm bolts and one 16mm bolt. Use a pry bar to free the brace bar if it's stuck, then remove the support bar held by two more 16mm bolts. The brace bar can now be lifted clear.
Move the Washer Bottle Aside (Driver's Side Only)
If working on the driver's side, the washer bottle sits in the way of extracting the brace bar. Undo the two 10mm bolts holding it in place and slide it to one side — you don't need to disconnect any pipes, just move it enough to slide the brace bar out.
Remove the Lower Wishbone Bolts
With the brace bar out of the way you now have clear access to the wishbone mounting bolt that goes horizontally through the subframe. This is what all the previous work was for. Remove this 15mm bolt. Then remove the 17mm bolt at the rear of the arm and the 18mm bolt at the front. The wishbone should now be free — if it's reluctant, a pry bar will encourage it out.
Fit the New Wishbone
Offer the new wishbone into position. Start all bolts by hand first — never use an impact gun until all bolts are hand-tight to avoid cross threading. Apply a small amount of copper slip to the bolt threads if the old ones were heavily corroded, to help the next person who has to do this job. Get the arm roughly into position, locate the bolt holes and start each bolt loosely.
Pre-Load the Suspension Before Final Torque
This is a critical step that many people miss. Before fully tightening the wishbone bolts, use a trolley jack to raise the hub to approximately normal ride height — this pre-loads the suspension bushes in their natural position. Then tighten all wishbone bolts to the correct torque spec with the suspension loaded. Release the jack only after all bolts are fully tightened.
Refit Brace Bar, Bumper & Wheel
Refit the brace bar and support bar, starting all bolts by hand with a dab of copper slip on corroded threads. Tighten all bolts down evenly. Refit the washer bottle if moved. Bring the car down and push the bumper corner back into position, locating the tabs into the wing correctly before refitting all the Torx bolts and Phillips screws in the wheel arch. Refit the wheel and torque the wheel nuts.
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Job Summary
What to expect on this repair: