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How aggressively are you driving to get the knock back? I haven’t seen it … “yet”.
 

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How aggressively are you driving to get the knock back? I haven’t seen it … “yet”.
Hard turns. Also I have 200 series tires as well, so lots of grip. I am sure its my rear discs causing it. It's not as bad as it was but definitely still need to tap the brakes after a hard turn to reseat the pads.
 

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How aggressively are you driving to get the knock back? I haven’t seen it … “yet”.
Hard sweeping turns, rough gators. switchbacks followed by threshold braking, ya know the usual track stuff. In an effort to not buy a floater 9 inch. I shimmed the rear bearings 40 thou and that seemed to help. Next steps are knockback springs in the rear and big spindles up front.
 

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My experience with pad knock back on my car and a few close friend's cars:

- Panic inducing pedal drop can be caused by very small amounts of pad knock back. My friend measured it once by running back to back tests near his house. He found a safe place to do back to back left and right cornering that would reliably induce pad knock back. Then ran that same route and coasted to a stop without touching the brakes. He removed the wheels and measured the gap between the pads and rotors. I don't remember the number anymore but it was measured in thousandths of an inch (less than a tenth). My point being that it takes very little movement of the pads to create knock back.

- Anti knock back springs in the caliper seem like a joke. I have them and didn't notice any difference before and after. And I ask myself, if I'm holding the caliper in my hand to change brake pads and the springs aren't strong enough to push the pads towards each other then why would they do anything for knockback. They don't.

- 2-4 lb residual valves don't help. A friend had good luck with 8 lb residual valves to band aid his spindle flex problem. This was the same guy that measured his knock back amount above.

- Fixed calipers on a non floater solid axle are a really bad idea for autocross or track use if you are going to run grippy tires. My first year of driving it didn't matter as I didn't drive hard enough for it to be a real problem. After that it was there and never fully went away until I went to a full floater rear axle. The cheapest solution is to run a floating rear caliper. Wilwood sells one if you want to have it be the same brand as your fancy fronts but an OEM equivalent is fine.

- You need high quality front spindle bearings and they need to be adjusted pretty close to perfect. Loose or worn bearings will easily give knockback on the front with a fixed caliper. I use a bearing spacer on the front so I can tighten the spindle nut down tight without undue preload on the bearings. If you get repeated brake fade while on track then replace your front wheel bearings every 6-12 months. I had to do this until I found a better pad and rotor configuration that wasn't allowing so much heat to build up as well as transfer into the hub. Until I figured that out my clue to change my front wheel bearings is when I suddenly started getting small amounts of pad knock back.

- Wilwood sells floating 2 piece rotors. They can be a little noisy on the street but can actually help with minor pad knockback. I run them on my car. I could tell the difference before and after with these. I couldn't with the anti knock back springs.
 
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