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4-wheeled Disc Brake Systems
A big part of the safety equation is having great brakes on a vehicle. When you've got great brakes, you just drive that vehicle with confidence - knowing that they're always going to be there when you need them.
On late model vehicles - the last ten to fifteen model years - four-wheel disc brake systems have become pretty popular. There's still the odd vehicle around that has disc brake on the front and drum on the rear. And some people might associate that with an antiquated vehicle, but believe me, that system still works the best in a Canadian winter. It's the least in terms of maintenance. So, if you live in an area where you're driving on a lot of gravel roads, you might want to actually look for a system like that. However, we have to deal with these vehicles with the four-wheel disc brakes and they've brought along a whole host of service problems.
Interestingly, Saab cars, talking about Saab, they have an interesting feature on their vehicles. If you look on the underbody of a Saab vehicle, in approximately this area here, you'll notice a splash flap hanging down underneath the body of the car. And what that splash flap does for Saab is deflect a lot of the crud that's thrown up by the front wheels from reaching the rear wheels. And, specifically, this rear brake system. And it's that crud that's thrown up by the front wheels of a vehicle and billowing around and getting in the rear brake system that, in many cases, cause the breakdown of that rear disc brake system.
This Pontiac Grand Prix - this is my loaner car at the shop, that we're using today - this particular type of car is known for lots of problems in its rear disc brake system. But a lot of problems that happen with these cars are concerned with the rear brake caliper which is fairly exposed, as you can see here. Remember that this rear brake caliper - you can see the brake pads here, the outer pad and the inner pad - this rear brake caliper squeezes the brake pads together against the rotor. When you step on the brakes in the car, you hydraulically squeeze those two pads together against the rotor to apply the brakes on this particular wheel.
Some of the problems that can happen with these calipers is problems with the emergency brake cable that's integrated in here. The emergency brake cable is an alternate way of applying the brakes on this wheel for parking or for emergency situations. And that's a mechanical application of the rear brake pads. Here's a rear disc brake caliper off a car just like that Grand Prix that I had on the hoist. Some of the problems that afflict these calipers are obvious on this one. This slider right here, which should be able to move back and forth freely, no matter how hard I push on it, I can't get that thing to budge. You can get a glimpse of the pads here. And interestingly, the pads are still okay on this vehicle but everything else is gone wrong with the caliper.
Up here, the emergency brake lever, when I push against that, that lever should move forward and it should drive the inner piston out to apply the brakes on this wheel, that also, is completely seized and non-functional. So our emergency brake system wouldn't work.
And if I take the caliper out of the vice, you can see that the other slider - right here - the boot that protects it from the elements is charred and burned right off. What's happened here is because this brake caliper was seized on it's dragged the brakes and caused a lot of heat which has burnt this boot right off. That's partially why this one is seized over here.
If I pick up the rebuilt one that's ready to go on the car, and turn it over, you can see that when I just touch that slider right there, it floats back and forth the way it should. And that the boots are all nice and new. There's lubricant that's in this cavity that makes sure that this stays lubricated and to make a more effective seal with the boots.
When I put it in the vice and clamp it down, I'll support it a little bit, and you can see that when I apply the emergency brake lever - push against it - it moves in the fashion it's supposed to and it drives this piston out which pushes the inner pad in to mechanically apply the brakes on that rear wheel.
If you have a vehicle with four-wheel disc brakes system, sooner or later you're going to have to deal with re-building these rear calipers. Maybe your first brake job will be fairly minor - just pads, maybe machining the rotors. But sooner or later, these calipers on most vehicles with four-wheel disc brakes will have to be rebuilt. It adds up to a fairly costly brake job. For example, a caliper like this rebuilt: a hundred and forty to two hundred dollars each, times two if you have to do both rears. Fifty to seventy dollars for a set of rear brake pads, enough to do both rear wheels. The brake rotors, if they have to be replaced, cost can be quite high on those as well. And it depends very much on what type of car you're talking about. There's also a fair bit of labour and sometimes some rear emergency brake cables having to be changed, as well. So it all adds up to a fairly costly rear brake job on a car with four-wheel disc brakes.
And if you're coming out of a vehicle that had drum brakes on the rear, you're really going to have sticker shock when you get that first major rear brake job done on your four-wheel disc vehicle. But it's something you'll have to deal with sooner or later. That's just the way things are today in motor vehicles. And I'd like to thank Ed Olson down at Power Rebuilders in Oakville for loaning me this caliper. Ed, I've had it for a few weeks, but I'll get it bask to you on Monday, okay?
'Til next week, I'm Bill Gardner for Motoring 2002.
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