Rear Brakes

[shoon]

replaced my rear calipers brackets and sliders with all new stuff because my ebrake kept sticking. And am left iwth a bunch of questions... sorry will try and keep it brief and to the point.

#1
While doing the job I noticed the brake pads have a single tab on them that fits perfectly into either of the 2 notches on the piston. Is the piston supposed to be rotated so that the tab lines up with the notch, or through normal operation will the pad line up and lock into the piston on its own?

So... if you need to wind the piston in to get it to retract, why would you want the pad to lock the piston from spinning? Does the piston need to spin in order to extend when you hit the brakes and through normal brake pad wear? or does the piston remain stationary (does not twist) and operate similar to the front calipers?

#2
After doing the job I noticed that there is a fair bit of drag when I spin the wheels with the ebrake released. How much drag is too much, and any tips on how to reduce/adjust this? The ebrake cable is already backed off as much as possible so this is not the issue.

#3
As far as the proportioning valve... I tried to push up on it by hand and it wont move. I would think its not supposed to be so stiff... Will having it stuck affect breaking significantly? It was my udnerstanding that this valve reduces brake pressure when the rear end dives down under hard breaking by restricting hydraulic pressure to the rear brakes, is this true?

#4
When bleeding the rear calipers, with the flex hoses off the calipers; there was a constant drip. With the flex hose installed on the caliper, and the bleeder screw open there was no drip. Doing a gravity bleed was not possible... the fluid would not flow. Is that normal on the rear brakes (because of the ABS or proportioning valve) or do I probably have collapsed flex hoses?


Thanks for any input!

 

[Bob Gervais]

#1- Line the groove in the piston up with the tab on the brake pad. This stops the piston from spinning. When you apply the ebrake, a screw turns inside the caliper and pushes the piston out. In normal braking, yes, it works like the front caliper.

#2- With the ebrake released there should be very little drag. Make sure you bottomed the pistons out (not just turned in enough to get the caliper back on), and that the tabs in the pads line up with the grooves in the piston.

#3- The rear bias valve doesn't move much, but you should be able to move the actuating arm fairly easily. Right definition, wrong end. When the front dives/rear raises, the bias valve applies less pressure to the rear brakes.

#4- When you were bleeding the rear brakes, were the rear control arms hanging? If they were the bias valve was closed, and would cause restriction in flow to your rear brakes.

If fluid flowed fine from the hoses with the hoses disconnected, then your hoses are not the problem. Your bleeder screws may be rusted/obstructed with junk and not letting fluid pass. Either clean them out or get some new ones.

 

[shoon]

Awesome, thank you!

I also noticed it was extremely difficult getting the calipers to tighten up (they are brand new) The brake pedal was rock hard (so properly bled no air in the lines) and yes the control arms were hanging.

Even with the engine running and boost applied it was still fairly difficult to get the pistons to extend, I had to pump the pedal a lot, and I was also engaging / releasing the ebrake to see if that would help.

Maybe I'll wind the pistons back in, and jack the control arms up a bit when I try and get the calipers to snug up this time.