Wouldn't that be the rotor - not the A arm - pushing the piston back in the caliper? Or Excessive play in the spindle? Sorry for the rook question, but I never knew what was causing that in my 68 till I read the official knock back thread.....
If the caliper is in fact hitting the control arm, it would easily cause the knocback the opposite way it does conventionally. Normally there is deflection in the hub which causes the rotor to push the pads back against the caliper pistons. In this situation, the caliper hits the control arm and the caliper housing gets pushed towards the rotor pushing the piston into the caliper bore. Your caliper shouldn't be hitting your control arms. That could turn into a real safety issue.
If the caliper is in fact hitting the control arm, it would easily cause the knocback the opposite way it does conventionally. Normally there is deflection in the hub which causes the rotor to push the pads back against the caliper pistons. In this situation, the caliper hits the control arm and the caliper housing gets pushed towards the rotor pushing the piston into the caliper bore. Your caliper shouldn't be hitting your control arms. That could turn into a real safety issue.
Fortunately I am not driving it but to test the brakes. My idea was to extend the steering bump stop? Maybe extend the stop out an inch or so which would reduce my steering radius but that would prevent it from hitting my caliper and hopefully reduce the above issue as well. Sounds like the place to start! If you have any other ideas let me know-this has to be the most useful forum on the internet--thanks gents...
As long as the turning radius isn't compromised to much, sounds like the most economical fix.
What Todd said, just make sure you account for pad wear. As the outer pad wears, a floating caliper moves inboard the same amount, so you'll want to make sure that you won't make contact ever, even when the pads are ready to be replaced.
Brian Hobaugh SCCA National Tour June 2014
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