One of my 360R IVA failure points was that the steering rack gaiter caught on the side skin when the steering was going from lock to lock.
According to the IVA Tester’s manual “Steering components must not foul, or be likely to foul other parts of the vehicle under normal operating conditions.”. The problem was the wording “likely to foul”. Both my 360R and now my 420R steering rack gaiters can foul in some situations on full lock, and therefore I needed to enlarge the side skin hole for the steering rack gaiter. I also discovered this problem on a friend’s 310S SV chassis, when I helped prepare the car for IVA, about a year ago.
I applied plenty of masking tape to protect the paint, and slowly enlarged the hole so the steering rack gaiter no longer touched the side skin when going from lock to lock. Although the problem area was only at the 7 o’clock position, the enlargement was from 4 o’clock to 10 o’clock to maintain the shape. I used a dremel and finished off with sandpaper to create a neat finish. Releasing the tie rod from the upright gave me more room to make the enlargement.
My 420R only had this problem on the left-hand side and it was most obvious when raised and on axle stands. Maybe the left-hand side is more prone due to the asymmetric design of the steering rack gaiters used.
A quick application of touch up paint to restore the finish of the edge completed the job.