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Old 01-05-2013, 03:05 PM   #11
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Join Date: Jul 2012
Location: Liverpool
Posts: 1,524
My Ride: 320i SE Coupe
Do calipers/brakes normally become less efficient/effective over time? I guess a rebuilt one is different than one that doesn't show any problems?
For the record. Yes. Most things with seals do. When caliper seals leak it may not be noticeable. Minute leaks might accumulate behind the boot and dry up. Calipers get jolly hot. Nevertheless, air gets into the system past the seals and instead of the hydraulic force from the pedal acting on the piston it squashes the air instead leading to a reduction in the force available for braking. So it depends on the condition of the caliper left behind. It generallly works on this premise. You find it necessary, for some reason, to replace one caliper. Assuming both calipers are of the same vintage, it is only reasonable to propose that internal seals wear at the same rate in both calipers over time. There are other factors, of course, that might accelerate the deterioration of one with respect to the other : split rubber boot for example and corrosion preventing the piston from fully retracting. But in an ideal world both calipers should apply the same force to their piston and thereby to the pads at the same time resulting in the same traction between pads and disc. The whole point of changing both discs, both sets of pads and both calipers when they need replacing is so that they are the same vintage at the outset and so that they act and deteriorate uniformally. Like I said, you need to ensure that both are properly bled and, if the problem persists, you need to check the remaining caliper, pads (for contamination) and disc. Its all about ensuring uniformity of applied braking. Although, as most have already pointed out (myself included), it is most likely you FCABS.

Last edited by RayPooley; 01-05-2013 at 03:41 PM.
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