Caliper Rebuild Time.

"Berang" (berang) 10/08/2015 at 00:10 • Filed to: brakes, saab 96, this old saab

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Yeah. Those are supposed to be like that.

So one of the calipers has been leaking the past few days which I didn’t notice until one day the brake pedal went halfway to the floor on a steep hill. O . K .

I already knew the problem was a corroded piston because I had made a note of it when replacing the wheel bearing. It wasn’t leaking then, so I figured I could put it off. It was leaking now, so I ordered the rebuild kit with a new piston and set to work today.

Mmmm parts. These calipers were made by Lockheed and used in some old Austins (the landcrabs I think) and also in the SAABs. I have never seen anything like them on any other car ever. The friction material is cut at an angle for some reason - and one end of the caliper rests on a hinge... as the pads wear down the whole caliper pivots until finally the pads are worn flat - no more angle. Why? Because England.

Popping the piston out. I don’t have any fancy compressed air. So I remove the caliper from the knuckle, remove the pads, set the caliper on a box so it’s not hanging by the brake hose, and pump the pedal until piston pops out. Just make sure the brake resevoir is full before doing this so you don’t suck air into the master cylinder and end up having to bleed that too.

One of the cool (and I use that term inaccurately) things about these calipers is that the cylinder detaches from the caliper. ??? Shitting fuck if I know why. But it does make the thing easier to take apart. Modern calipers are not built like this. They usually have a dust boot. This one does not have a dust boot. It has a rubber outer seal, and an inner rubber seal. The outer seal is held in by an easily damaged round piece of tin. This is held in by an interference fit. I thought I would be clever and put the new tin piece in the freezer to make it pop into the cylinder. I destroyed the new one trying to get it in. So I reused the old one. Recycling. It’s what’s for dinner.

New rubber and new piston fitted into the cylinder! I used a very light coating of disk brake grease on the piston to help get it into its tight new home. You should be able to push it in by hand. If not, something is wrong. On this type of caliper both seals will fit in either outer or inner position - but they should only be fitted one way around, with the solid “flat” seal going in the inner position. Don’t mess ‘em up.

Caliper all back together. Success! Put it on the car, bled, and tested. No leaks. Car stops in a straight line.

Here’s the gross old piston:

No wonder it was leaking.

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For reasons: this post is intended for amusement value only. It does not contain complete information and should not be considered instructional advice. Don’t try this at home kids, I am a trained amateur.

Berang > Berang 10/08/2015 at 00:38

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It does sort of look like a horseshoe crab amirite?

DasWauto > Berang 10/08/2015 at 00:47

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Neat idea with the pivoting calliper actually. When brake pads wear they often end up a bit wedge shaped because the force of braking pulls them back (you know what I mean) in the calliper, if effect pulling the leading edge toward the rotor and keeping the trailing edge in lighter contact. This seems to be a neat solution or pre-empting of that wear pattern, though I’m sure it has it’s own issues, otherwise it’d be more widely used.

*fairly extreme example pictured but point made

mattc993 > Berang 10/08/2015 at 00:50

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At first I was like DAT SLIDE PIN DEFLECTION WTF.

And then I was like.....hinged caliper wear wat?

Berang > DasWauto 10/08/2015 at 00:54

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I think the big issues were 1: if the pivot wears out, gets gunked up, rusts, or otherwise sticks - problems ensue. 2: these brakes do not like going backwards and were notorious for squealing when the car was moving backwards.

Urambo Tauro > Berang 10/08/2015 at 00:54

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Thanks for sharing. When I first saw that picture, I immediately figured you had a caliper bracket problem. What a weird design!

With-a-G is back to not having anything written after his username > Berang 10/08/2015 at 01:03

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Don’t let it go to your head, but it’s posts like these, in all their humble yet bold amateurness, that keep me coming back to oppo.

DasWauto > Berang 10/08/2015 at 01:07

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Extra mechanical complexity usually does open up more places for things to go wrong but I hadn’t even thought about braking in reverse. In normal running the pads would bite more strongly with the thicker ends as the braking force will torque or twist the calliper in relation to the rotor. In reverse the pads will then operate more with the thinner ends of the pads as that twisting force works in the opposite direction, quickly wearing those edges out and exposing the backing plate to get in contact with the disc and squeal.

Again, it’s a neat design. I think the twist that braking force applies to the calliper actually helps apply more force on the pads, making the brakes more effective and requiring less braking pressure from the driver, useful for un-boosted brakes (assuming the Saab doesn’t have a booster). Am I right in thinking these brakes are not too strenuous to use for manual brakes? You seem like the man to ask that question as I have far less experience with unassisted brakes on a car (read: none)

Berang > DasWauto 10/08/2015 at 01:17

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By 1973 they were using a booster. In normal driving they require very little pressure - that’s not to say they’re very strong though, just that you don’t have to push the pedal down to the point where it gets firm to get the brakes working. I don’t know if that has anything to do with the calipers though. I have driven a ‘68 which did not have the booster, but it was so long ago I don’t remember it much. It did have a typically stiff pedal feel, although I don’t think it needed too much effort.

I have a feeling bean counters and engineers looked at it again and asked why they were making the calipers more complex for the sake of throw-away brake pads.

desertdog5051 > Berang 10/08/2015 at 03:32

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I followed your instructions as you presented them. My brakes failed and my dear old grandmother died. You will be hearing from my lawyer. :)

kanadanmajava1 > Berang 10/08/2015 at 06:31

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I haven’t seen this kind of caliper before. But I haven’t been messing with British stuff much. My friends have plenty of old Saabs but I guess I could have missed this one.

It’s either a brilliant or a completely ridiculous solution. I cannot decide which.

Tohru > Berang 10/10/2015 at 07:08

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Don’t camber your brake calipers.