How do our S3 cars' calipers work? - Alfa Romeo Bulletin Board & Forums
 
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post #1 of 5 (permalink) Old 03-02-2015, 03:17 PM Thread Starter
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How do our S3 cars' calipers work?

just thought- our calipers dont have any "sliding bolts" like Ive seen on other cars. These sliding caluipers are what allow the pads to retract away from the disc (right?).

So then how do our brake pads retract away from the disc after we press brake then drive off? Just wondering cuz otherwise, discs should become worn prematurely, right?

Thanks

87 spider veloce

Last edited by Joe Papa Sr; 03-02-2015 at 04:11 PM.
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post #2 of 5 (permalink) Old 03-02-2015, 03:46 PM
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The square cut O-rings grip the pistons. When you apply the brakes hydraulic pressure pushes the pistons outward slightly distoring the O-rings. When hydraulic pressure is released the O-rings pull the pistons back slightly.

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Last edited by ghnl; 03-03-2015 at 05:03 AM. Reason: typo
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post #3 of 5 (permalink) Old 03-02-2015, 03:47 PM
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Quote:
Originally Posted by Joe Papa Sr View Post
Still rebuilding our caliper and just thought- our calipers dont have any "sliding bolts with booties" like Ive seen on other cars. These sliding caluipers are what allow the pads to retract away from the disc (right?).
That's a floating caliper. Usually they have only one piston on one side: the caliper moves on a sliding bolt so that both pads make equal contact.

Spider fronts have a fixed caliper: there is a piston on each side, and both pads move independently towards the disk so the caliper doesn't have to move.

In both cases the retraction is the same. Once you remove the pressure on the pads, the pads (or pads & caliper) move such that they're no longer exerting any force on the disk. They remain just barely kissing the disk, but this doesn't cause any significant wear.

Tom

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post #4 of 5 (permalink) Old 03-02-2015, 04:10 PM Thread Starter
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good to know. thanks, guys.

87 spider veloce
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post #5 of 5 (permalink) Old 03-03-2015, 04:38 AM
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Correct. Be glad our Alfas have this style. The double piston concept is a better, and more expensive, design. Sliding caliper brakes are used as a cost reduction since there is only one piston per caliper instead of two. This is much less effective if the caliper doesn't slide when the brakes are applied. When this happens, you effectively only have one of the two brake pads in the caliper pushing on the disc. My motorhome has disc brakes, but they are sliding caliper design, and the sliders need periodic maintenance to function properly.

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Originally Posted by Joe Papa Sr View Post
just thought- our calipers dont have any "sliding bolts" like Ive seen on other cars. These sliding caluipers are what allow the pads to retract away from the disc (right?).

So then how do our brake pads retract away from the disc after we press brake then drive off? Just wondering cuz otherwise, discs should become worn prematurely, right?

Thanks


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