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My pre-1988 brakes tutorial to end all tutorials - c900
I have used a 1986 C900 as a daily driver for around six years now. It was only recently that I got to the bottom of the issues I've been having with the front brakes. As many of you know from the Saabsite tutorials and angry grumblings from friends, these front calipers serve as handbrake and service-brake, using a handbrake that acts on the disk through the caliper itself. To a technician not familiar with the calipers, they can look very strange.
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But they are quite simple, and the handbrake's performance need only be tested in-car to prove its worth to a skeptic. Because it acts on the front brakes, the handbrake can still provide up to 50% of the car’s normal stopping power in the event of a total brake failure. By comparison, a rear-handbrake system only gives about 20% of the power, while de-stabilizing the car when used in an emergency. The fact is, when in good repair, the front handbrake works a lot better than a rear handbrake!
A certain amount of basic knowledge is necessary to work on these calipers. This knowledge is, more-or-less, applied by the Bentley repair manual. I am providing the equivalent for those who do not have access to this large book. But I’m also providing a lot of other, more specialized information that even the so-called “pros” do not have. It is the result of six years of c900 ownership, three different front-brake problems, two rebuilds, and four sets of calipers.
I hope someone gets some use out of it.
Difficulty: 2.5/5
Tools Required:
-19mm socket, probably a deep one
-Breaker bar
-Pliers of some kind
-Large, flat screwdriver
-Torx driver to remove rotor (this is in your toolkit in the trunk if you don't have one)
-Coat hanger or piece of wire to hang caliper from suspension spring
Parts Required:
-Caliper grease
-Caliper seals, possibly
-Possibly o-rings for the lever hole
-Dot-4 brake fluid, possibly
-Possibly pads
Torques:
-Front caliper to swivel member: 81-96 ft-lbs
-Wheel lug nuts: 66-81 ft-lbs
A word on removing and re-installing calipers to insure safety-
Both on front and rear calipers, between the caliper and bolt heads, there is a so-called "locking plate". This thing is just a sheet of metal with two holes:
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But it's very important. This plate's ends should be bent over to rest against the flat sides of the two caliper bolts. Failure to do so could result in your caliper bolts coming loose and the caliper falling off. I've been in a car when this happened. It's very dangerous, because it could cause the affected wheel to entirely lock up, resulting in a loss of control. If you find that your car does not have locking plates, make some out of sheet metal with a tin snips or similar. They are essential to your safety. When re-installing calipers, be sure to bend the locking plate's ends over the bolt flats once again, to ensure that the bolts will not come loose.
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Problem 1: The Sticky Handbrake
When I bought my car, I was warned not to apply the handbrake, or it would stick on and get very hot. If the cable is free in its housing (it usually is) you probably have a seized handbrake lever on the caliper. The handbrake lever is the metal piece, which you can see close-up in this photo, that the handbrake cable pulls to apply the brake.
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This sticky-handbrake fix will require jacking up the car (either with jack and jackstands or with your spare-tire jack) and taking a front wheel off.
The fabled Bentley manual says nothing about how to tear down the calipers and un-stick this lever. The Saabsite and Townsend might have told you that the only cure is to buy new calipers, but they are wrong. Un-sticking this lever is something I can do in about an hour. If it's your first time, you might take two.
Step 1. Remove caliper from car
Unscrew the two mounting bolts on the back. They are 19mm, same as the lug nuts. There may or may not be a "locking plate" between them and the caliper body, so take care of this as I mentioned in the first post of this thread.
You can hang the caliper from the front spring using a coat hanger or other wire, so it doesn't dangle and damage the brake hose.
Step 2. Remove the caliper yoke from the caliper.
Some like to remove the rotor and then re-mount the caliper, figuring that the car is a good place to work on the caliper, because it’s bolted on sturdily. This is easy enough to do, just take off the two countersunk-screws (either Torx or Phillips) that hold the rotor on, then whack the rotor a few times with a soft mallet and off it comes. The rotor needs to be out of the way. Then remove the pads by taking out the retaining U-clip using a hammer and punch. Remove the handbrake cable from the yoke. This requires taking off a circlip, which is usually defeated with a screwdriver.
Then, you're going to need to pound the yoke out of the caliper. You should wiggle the handbrake lever as you do so. Its shaft needs to come out of its hole, as you can see here.
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Pound gently, and it should come off, pulling the handbrake lever out with it. The lever’s spring will be released, so you should remove it earlier. A funny arched wire will also fall out. Set these things aside.
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Now the caliper should look like this:
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As you can see, it’s just a big cylinder with two pistons, one in either end. The handbrake mechanism pushes these two apart via a complex jacking mechanism I’ll explain in my next post, below. For this simple fix, you won’t need to go into it.
Step 3. Clean-N-Grease
Clean up the lever's pivot shaft. Look in the hole in the back of the caliper piston. See where the lever goes in? Squirt some caliper slide grease in this hole. Don't be shy now you've got it apart! Be generous!
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Clean off the lever's pivot using solvent and a scouring pad or similar. God knows it's rusty or corroded or gummed up.
Also, clean the caliper yoke slide tracks using a file or similar. Not too aggressively, just touch them up.
Extra credit consists of prying the O-rings (there are 2) out of the lever's pivot hole and replacing them with new from the hardware store.
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Step 4. Reassemble!
Insert the lever (without its spring) back into the greasy hole. Marvel at how silky smooth it is to turn. Now squeeze the pistons together while operating the lever (might need a clamp or some channel lock pliers to do this), to make sure the lever pushes the pistons out of the cylinder a bit. If not, you’ll need to go deeper. See my next post in this thread.
Take it back out, and insert it with the yoke and arched wire at the same time, so it’s just like it was before you took it apart.
Put in the pads, their retaining pins, and their anti-rattle clips as they were before. Hopefully you won't need to wind in the piston, but if you do, go for it. Everything should fit just fine.
Step 5. Install on the car!
If you didn’t take the caliper hose off, you don't need to bleed the brakes or anything. Just put the caliper on the car again, torque the mounting bolts up to spec, FOLD OVER THE LOCKING PLATE, and away you go!
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Performance Modifications
The best, most cost-effective, easiest performance mod consists of doing the above to get your existing brakes working right. The following mods are much harder, require guesswork, and are not well-tested. Mod at your own risk! :)
So your brakes are operational. They're working well, but you still want more. You clearly need to mod. Some would change to the later, rear-handbrake setup, and use front calipers from a 9000, but if you want to ice-race with those old square-seat soccerball wheels, that's not gonna be possible. Also, you can't run Incas, Shelby Minilites, or the infamous Manholes with a new-style lug pattern. Therefore, this post is a collection of everything I know about modding the pre-1988 brakes for performance.
Switch to vented
First thing you can do is to add vented rotors. To do this, you need, AT MINIMUM, caliper yokes, wheel hubs, and of course the rotors. The hubs for vented differ from those for non-vented, in terms of dish or offset. These need to be pressed in and out, so you may be better off just changing the whole swivel member and ball joints. Once that's done, you will need to mount the discs, and then the calipers with different yokes, and you'll be set. I did this to my car in about 3 days, with numerous problems and setbacks, so you should be able to do it comfortably in that amount of time.
Racing calipers
If you've got vented rotors and still want more power, there are a few options people have tried. The first is to use some aftermarket Wilwood Superlite calipers. I don't approve of this. Wilwood calipers are for racing. They work well under demanding conditions, but they are not really meant for daily driving, as they have no dust boots. In fact, the decision not to use dust boots is a trade-off. Dust boots often melt under extremely high-heat conditions, which is why racing calipers don't use them. Unlike regular-use calipers, racing calipers don't age gracefully, and I don't know how they cope with sitting and not being used, especially in wet or wintry conditions. After searching some Honda forums, I found numerous references to Wilwood calipers on daily drivers lasting only a year between full rebuilds, and some posts describing calipers randomly blowing seals on the track. It sounds like a bad trade-off to me.
Rallyists argue that, since the Wilwood units withstand a rally, they must be able to withstand daily use, but I believe they are usually rebuilt shortly afterward, and closely watched throughout--not the kind of care a daily driver's brakes are going to receive. That said, these provide amazing stopping power, so if you want good brakes for your race-build, non-street-legal 900 or 99, these are for you. Here are some pictures of a Wilwood setup.
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I believe they don't work with Inca wheels (possibly also not with Soccerballs), and they require some spacers to get the caliper offset right, as you can see in the first picture. As you can see, even this guy doesn't have the offset quite right, but that's likely because he wanted as much wheel clearance as possible.
A durable, more cost-effective mod
Legend has it that FRONT calipers from a 1990 Subaru Loyale will work on the rear. These also have front-handbrake, so you'll be effectively doing a rear-handbrake conversion without changing the axle or knuckles. Legend also has it that the four-piston calipers from a mid-1980s Toyota 4x4 pickup. I know that the calipers from a 1986 V6 4wd pickup will definitely work, so you just need to cross-reference with that in mind and then go to a junkyard to see what you can find. You will need to re-drill the caliper holes larger than original. I don't know about wheel-fit with these.
If you want higher-performing set of calipers, these are your options. All use stock disks, and you'll need to change the proportioning valve even if you only change the front calipers, and definitely if you change the rears. Changing the proportioning involves disassembly of the master cylinder and adjusting a pin, but I don't know the specifics. You can also buy an aftermarket proportioning valve, but then you'd have to re-route your lines and not have diagonally-split brakes anymore, and that would be silly.