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Old 07-29-2014, 05:47 PM
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Originally Posted by 67Rally View Post

I don't want to switch to a floater rear.
Knock back is caused by the rotor pushing the pistons back in the caliper. Eliminate the movement of the rotor or allow the caliper to move with the rotor.

Wilwood's bearing retainers aren't exactly superstrong pieces, they usually bend slightly on installation and after that it doesn't take much for them to flex resulting in bearing end play and consequently knockback. Stronger retainer plates can be fabricated and careful machine work to maintain the proper bearing preload can go a long way in minimizing knockback.

Floating hub eliminates the rotor movement. You don't like that option, I get it. It's not inexpensive or easy at this point. It is the only surefire way that I am aware of to eliminate rotor movement.

The floating caliper sounds like a perfect solution. Late model Mustangs use a single piston floating caliper with a rotor diameter as large as 13.8" and have no issues with knockback. This is on a clip rear end with ridiculous amounts of axle end play. The key to a floating caliper working is that the force required to move the piston back must be greater than the force required to move the caliper on it's slides. If the piston pushes back before the caliper slides, you still have knockback. Even with a floating caliper, a residual valve may still be required.

What size wheels and backspace are on your car? Front and rear please.

Have you confirmed that the knock back is definitely coming from the rear? Misadjusted front bearings or spindle flex can cause this as well.

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