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Dragging Rear Calipers

Discussion in '308/328' started by jsumnertx, Jul 26, 2025 at 1:53 PM.

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  1. jsumnertx

    jsumnertx Karting

    Dec 9, 2004
    164
    Austin
    #1 jsumnertx, Jul 26, 2025 at 1:53 PM
    I've got a dragging rear left caliper at a minimum and it looks like the rear right also has an issue. Looking for some advice on next things to do

    About 9 months ago, I had a problem with what I thought was the e-brake being overtightened and dragging. Got it loosened up and the dragging went away. Then a month ago it felt like the rears weren't fully releasing when I happened to use the e-brake (I usually leave it in gear and try to avoid the e-brake altogether) but after some jostling of the car, over some rr tracks, it seemed to go away. Last straw was earlier this week when I drove home a mile from a car meetup and again the car would slow down in neutral. By the time I got home, I could feel some pulsing as if the rotor was warped and the left rear had heat and burning brake smell.

    So, up on the lift. Checked the ebrake cable and it was loose enough not to be activating the brakes.
    Wheels off I could rotate the right rear rotor back and forth 10 degrees or so by hand. The left rear rotor could not be moved by hand

    Left rear (the one that was hot and burning) removed the e-brake cable altogether, loosened the inner 4mm hex screw a few full turns (counter clockwise). Loosened the outside 13mm nut + 4mm screw a few turns and got a little liquid dribbling out. Then I could push back the outer piston by hand and remove the pad but couldn't retract the inner piston. Wear was extremely uneven.

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    So for the left side, a couple of questions:

    1) Seems like next step is a caliper rebuild? Or is there something else I should check that could be causing this?
    2) With the pulsing, that would mean the rotor is warped and I should replace the rotor. Or do I check something before doing that?


    So then I figured I'd check the right rear even though it wasn't hot or smelling to get a comparison. Removed the pins and found also very unequal wear.

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    In this case I need some help with the adjustment screws for the passenger/right rear to see if I can get the pistons pushed back.

    1) For the inside 4mm adjustment screw, I'm not sure if it unscrews clockwise or counter clockwise. Turning firmly either direction results in no movement and I don't want to force it and strip out the screw
    2) For the outside 13mm nut + 4mm screw, similar problem. If use a socket to turn the 13mm nut, it moves a bit but the resistance is the same both counter clockwise and clockwise and I don't want to force it. I could try putting the 4mm hex wrench in the screw and then a 13mm crescent wrench in the nut to turn them against each other but would help to know if I'm going ccw or cw with the 13mm nut.

    Once I do that, is there something else I would check in the right caliper or are we also looking at rebuild there?
     
  2. bl10

    bl10 Formula Junior

    Jun 8, 2011
    442
    Chatsworth, CA
    Full Name:
    Barry Leavengood
    #2 bl10, Jul 26, 2025 at 6:28 PM
    The clearance adjusting screws are a little fiddley. On my 78 US 130K miles if backed out to far they will leak. You certainly need new pads if nothing else. The only time I've seen uneven wear, when the calipers were working correctly, was if one clearance screw was backed way out. If you have all 4 screws backed out, one side is left hand but I can't remember which, and can't rotate the rotors (I use a short bar between lugs if I have the wheels off) there is definitely a problem.
    I adjust mine about once a year (3 to 4 k miles) by turning the screws in until its tight against the rotor then backing it out until I get just a little drag. Like adjusting the brakes on old drums. I try for about 1/4 inch movement at the lever with the cables off then take the slack out of the cables.
    Something some don't realize is that if the clearance screws on the e-brake side (inside) are backed out to far its possible for the e-brake levers to go over center and cause drag. I have seen cruddy (won't rotate) pully's on the e-brake cables cause uneven tension on the e-brake calipers.
    I replaced the caliper seals on mine, after it sat for 14 years, because one of the e-brake gizmos started leaking after I got it running again. The back calipers use Porsche 814-6 (cyl) seals, the fronts use Porsche 911 seals I think.
    Many threads about all this plus Birdman's site.
    Good Luck.
     
  3. jsumnertx

    jsumnertx Karting

    Dec 9, 2004
    164
    Austin
    #3 jsumnertx, Jul 26, 2025 at 7:26 PM
    Two updates:

    I didn't loosen the inner adjustment screw properly, leading it to actually not be loosened at all. That could be the reason the inner piston won't release. Need to try that again tomorrow.

    For the outside adjustment screw, the Porsche 914 thread had a good suggestion and picture for creating "Special Tool VG13MM" that I'll try tomorrow.

    http://www.914world.com/bbs2/index.php?showtopic=90625
     

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