Rearbrakes, what is normal?

[alfredhamstra]

Hi all, have a discussion with the shop were i buy my stuff
Its about rearbrakes. I got a new set and problem is that the caliper dont come out when I move the handbrakelever.
Vendor sais it is normal that it dont.
Im lost…
In my opinion it has to move out so to be sure that there is also good brakes with thinner getting brakepads.

Or are the new brakes a new design that the calipers move out more while braking instead of handbrakelifting to accompensate thinner pads?

[18Fiatsandcounting]

We're talking about your Fiat spider, right? The rear brakes have a self-adjusting mechanism to make sure the piston still contacts the brake pads even as the pads wear down. That's the good news. The bad news is that this mechanism often stops working, and the solution there is to rebuild the rear brake calipers.

As the rear pads wear, the self-adjusting mechanism should adjust so that the handbrake still works. And yes, moving the actuator arm for the handbrake mechanism should move the piston out from the caliper (to press on the brake pads). It's not much movement, only about 1 or 2 mm. If you have the wheel off and you move the actuator arm by hand, you should feel the pads grabbing the brake rotor. If they don't something is wrong internally with your caliper.

-Bryan

[alfredhamstra]

Thanks for the reply. When the rears are free from the car than i can move the lever easy but the cilinder comes out 1mm or so and goes in again. And not getting more out each time i move the lever. They are new and the seller sais its normal. But they should go out like one inch and even more they pop out or not?
Hard to explain…

[alfredhamstra]

Bryan, what I try to say is that each time I move the lever, the pistin goes out like 1 mm. After moving it 10 times it sticks out 1 centimeter. Moving more it will drop out. That is indeed the system to correct for thinner pads.
My vender sais it doesnt work like that, it gets out 1mm and moves also back in same each time you move the lever.
He sais the disckcompensation happends also while normal braking.
He sold 250 items and never had any complaints so I am questioning myself now, just need a second pair of brains...

gr
Alfred

[18Fiatsandcounting]

Hi Alfred, you might both be right, in a way. Here's how I recall the rear caliper function:

With the caliper off the car
When you actuate the parking brake arm, the piston should move out about 1mm as you state. When you release the arm, it might remain in that position, and then when you move the arm multiple times, the piston will slowly move out until eventually it would fall out of the caliper if you moved the arm enough. My recollection though, is that the piston moves back in when you release the arm, but there may be differences with the calipers for the newer cars.

With the caliper installed on the car with the pads and rotor in place
When you actuate the parking brake arm, the piston should move out about 1mm. However, it should be pressing against the brake pads and so it can't move out any further. Moving the actuator arm multiple times should just cause the piston to press against the pads and then release each time you release the arm.

I think it matters more what the caliper/piston does on the car, so you might install the caliper and see how it works.

-Bryan