"WHAT EVERY DRIVER SHOULD KNOW!"--Chapter One: Brakes & Bearings. DFO 851_1 10 July 1979
--Part 3 of "Have Faith Will Travel!"
1. BRAKES: THE TYPE OF BRAKES THAT ARE USUALLY USED in American cars, & in a lot of other cars too, operate on the principle of what is called a drum on the inside of the hub & about a foot in diameter. It's just exactly like a sauce pan that's about 3 inches deep, except it has a hole in the bottom for the axle & the hub & so on.
2. IT WORKS ON THE PRINCIPLE OF USING WHAT ARE CALLED "BRAKE SHOES." These metal shoes have a curved surface which is exactly the same curve as the inside of the drum & which, when it's in good condition, is covered by a piece of asbestos which is riveted to the surface of the shoe. What we call the sole of the shoe. This strip of thick asbestos is usually about a quarter-inch thick or somewhere around there. There are two shoes inside of each brake drum.
3. WHEN YOU PUSH ON THE BRAKE PEDDLE THE HYDRAULIC SYSTEM CAUSES THE SHOES TO PUSH OUT against the inside of the drum. The shoes push out & push the brake linings, which is the asbestos, against the inside of the drum. They are kind of a soft lining, & they're asbestos so they won't catch fire. It gets very hot because of the friction required to stop the wheel.
4. NOW IF THE BRAKE LINING GETS WORN CLEAR DOWN TO WHERE THE RIVETS SHOW THROUGH, THEY BEGIN TO SCORE THE DRUM. They wear grooves on the inside of the brake drum which is bad for the drum & cause the brakes to scrape & shriek. Then if the asbestos lining gets worn down so far that you're just rubbing on the brake shoes alone, it's metal to metal & it's very bad, 'cause if you step on the brakes real hard there's so much friction it can make those metal shoes virtually red hot, or your brake drum red hot. It's a very dangerous situation. That's why they have these thick asbestos linings on the soles of the shoes. So when your brake shoes get down to where the lining's nearly gone, where it's just shoe against drum, that's a very bad condition.
5. IF THE BRAKES MAKE ANY KIND OF A SCRAPING NOISE OR SHRIEKING NOISE when you put them on, that means that your brake lining is virtually gone. Either the rivets or even the metal of the shoe itself are wearing right against the drum. They wear right through the asbestos & press against the drum, & it makes this terrible shrieking, scraping noise you hear sometimes. Trucks have it a lot because they wear their brakes out so fast with their heavy loads.
6. IN THE STATES THEY'RE SO SAFETY CONSCIOUS THAT IF THEY HEAR YOUR BRAKES SHRIEK THEY'LL PULL YOU OVER & give you a ticket, 'cause it's dangerous!--And you have to have that repaired within one or two weeks time or your ticket becomes effective & you're fined! You have to bring back to the police the ticket & the garage bill showing the work is done before they'll cancel your ticket. (Maria: That's a good idea.)
7. IT'S A VERY DANGEROUS THING IF THAT LINING WEARS OFF, because then you've just got metal against metal & it makes a horrible noise. Not only that, the brads & irregularities of the surface of the sole of the shoe were not meant to be the braking surface, & will wear grooves on the inside of the brake drum. This can cause uneven braking or even brake failure, or if it's the front wheels it can cause your car to pull sharply to either side when the brakes are applied.
8. ONE WAY YOU CAN TELL IF YOUR BRAKES NEED RELINING is if even though they adjust the brake pedal as much as they can to give you as much brake as you can get, if there is too much throw: That's what they call the distance between where you start to push the pedal & where you feel the pedal is hard & is applying the brakes.
9. IF THE DISTANCE YOUR BRAKE PEDAL GOES DOWN BEFORE BRAKING IS TOO GREAT, ONE OF TWO THINGS IS WRONG: Either you're low on fluid, there's a leak in your hydraulic system, or your brake linings are worn too far. Now if you've got plenty of fluid & your hydraulic brake system is not leaking & you have to push the pedal down almost to the floor before it applies the brakes, then you need new brake linings.
10. SO IF YOUR BRAKES HAVE GOTTEN THAT BAD, usually you have to have new shoes, & new linings, & they have to do what they call "turn the drum." They put it on a metal lathe & they have to take off a real thin layer of metal from the inside of the brake drum to get it all smooth & even all the way across again.
11. EVEN WITH BRAND NEW BRAKE LININGS, IF THEY HAVEN'T TURNED THE DRUM in other words cleaned off with a metal lathe the inside of the drum so it's perfectly smooth, shiny & almost polished, it's still got the grooves in it & your brakes will make the funniest noises. They'll make high pitched squeals (whistles) like that--not scraping, but those funny little grooves in there will make a high pitched whine or squeal.
12. (MARIA: UNDER WHAT CIRCUMSTANCES WOULD YOU HAVE TO GET A NEW DRUM?) If the things are that bad that you have to get a new drum, well, usually the wheel is shot. Maybe in some cases they can separate the drums from the wheels, but the drum usually is welded onto the inside of the wheel & is a part of the wheel, so you'd either have to get a new drum or you have to get a new wheel, one or the other.
13. (MARIA: DOES THAT HAPPEN OFTEN?) That's a pretty serious case.--Usually they're not that far gone. That drums are pretty thick & they can stand some scoring & they just need turning, need lathing to even them off inside.
14. THERE'S A SPECIAL MACHINE THAT TURNS DRUMS OR LATHES THE INSIDE OF THE DRUM. I've watched them do it many times when I've had that happen to my brakes, especially on big heavy cars that take a lot of braking. We always had big heavy cars, so frequently we'd let our brakes go too long & it was too late & they had to not only change the shoes but have the drum turned, which was an extra labour job of course.
15. THEY PUT THE WHEEL RIGHT ON THIS MACHINE, on a kind of an axle, & the machinery slowly turns the wheel as the cutting blade of the lathe starts on the outside of the drum & slowly goes in until it has cut completely across & the inside is perfectly smooth.
16. THEN WHEN YOUR NEW BRAKE LINING FITS YOUR NICE NEW POLISHED BRAKE DRUM THERE'S NO SOUND at all, absolutely no sound of any kind. It's just perfectly quiet & smooth & grips perfectly. So it is a big job.
17. WE CAN'T LEARN TOO MUCH ABOUT CARS. I can hear cars go down the street making noises & tell you what's wrong with 'em. I heard one the other day going by with the wheel bearings shot & if the guy doesn't do something about it pretty soon he's going to lose a wheel!
18. (MARIA: HOW CAN YOU TELL IF A WHEEL BEARING IS SHOT?) You can hear the grinding, sort of a rattle inside the hub of the wheel. If they don't grease the wheel bearings frequently, at least every 10 thousand miles, they'll go dry & burn up!
19. I'VE SEEN BEARINGS JUST GROUND TO POWDER INSIDE THE WHEELS BECAUSE THEY DIDN'T GET 'EM RE-PACKED, or weren't watching! The mechanic can claim he repacked it good, but it's something you can't see you can't tell. You gotta stand right there & watch them, to see that they do it. (Maria: Even if you don't know anything about it, you should stand right there & watch them?) If you stand there & watch, they don't know whether you know anything about it or not, & one thing about it, you'll sure learn a lot. That's the way I learned mechanics, watching mechanics work.
20. (MARIA: SO WHAT CAUSES THE WHEEL BEARINGS TO BE SHOT?) NO GREASE! (Maria: You just have to get regular greasing?) Yes, every 10,000 miles you're supposed to have the wheels pulled off & the bearings repacked.
21. THE BEARINGS OF THE WHEELS CONSIST OF LITTLE ROLLER BEARINGS WHAT THEY CALL NEEDLE BEARINGS.--Little rollers on the hub of the wheel that roll around the axle. That's what makes it possible for a wheel to turn. Even on the old ox carts & first most primitive kind of vehicles they had to grease their wheels. Even if it was nothing but the center of the wheel straight on the wooden axle, they had to put grease on it.
22. IF YOU LET IT GO SO LONG THAT THE GREASE DRIES UP & it's all gone, then very soon, because of all the friction of the rapid rotation of the wheel, the bearings burn out. They get red hot & they go to pieces!
23. SO YOU HAVE TO PULL THE WHEELS EVERY 10,000 MILES & CHECK THE BEARINGS. Sometimes there's still plenty of grease, they don't have to repack it & it's not any major job. Sometimes, a lot of the garages just repack 'em by hand, just push the grease in by hand, but a good garage has a machine.
24. YOU SET THE BEARING IN THE MACHINE then put a big wad of grease on top & pull that lever down & "Whueet!" it just packs or squeezes the grease throughout the whole bearing. So they don't even have to take it all apart.
25. BUT IF THAT GREASE DRIES UP, THE BEARING WILL BURN UP & THE WHEEL WILL COME OFF! (Maria: It just flies off?) Flies right off! It's the bearing the holds it on, the bearing & a nut, the axle nut. The bearing is on the inside of the wheel & the wheel is held on the axle by the bearing. The axle is the rod that goes into the wheel.
26. THE WHEEL IS HELD ONTO THE AXLE BY THE BEARING & the bearing is held onto the axle by this big wheel nut, great big nut, probably the biggest nut on the car but you! It has to be on very tight or all the vibrations & rotations could unscrew it & off comes the wheel!
27. SO IT'S GOT A PIN THAT GOES RIGHT THROUGH THE NUT & THE AXLE, all the way through, to prevent the nut from unscrewing. If that nut comes off, the bearing comes off & the wheel come off! If you have no grease in there & it burns up & the bearing goes to pieces, then the bearing could slip right over the nut & the wheel comes off!
28. MY BROTHER HAD A FRONT WHEEL COME OFF WHEN HE WAS DRIVING ABOUT 60 MPH, & it was just a miracle of God that he managed to stop in time! It didn't actually come completely off, but he heard this horrible rattling noise & the wheel was just turning about with the axle stuck loosely through the middle of it! It hadn't come completely off hadn't fallen right off the car, but it was no longer attached! Let me tell you, it's dangerous! But you can hear it: There are certain sounds that you recognise if you're a mechanic & know anything about a car at all.
29. WHEN A WHEEL BEARING BEGINS TO GO BAD, THEN IT'S TOO LATE TO REPACK IT. The wheel bearing has burned out because you didn't have enough grease on it. It makes this crunching, squeaking sound as you roll along, especially if you just roll easily, not rapidly, but at a slow roll takeoff pace. Or as you are stopping, you'll hear this grinding sort of squeaking noise in the wheel.
30. WHEN YOU HEAR THIS KIND OF A CRACKLING NOISE IN ONE OF YOUR WHEELS, sort of a crrockle scrape grind crrockle grind, you'd better stop quick because you're going to need a new wheel bearing as well as repacking! In several cars I've driven I've burned out a few bearings because somebody didn't properly grease the bearing, or we went too long.
31. BUT YOU CAN HEAR IT KIND CRACKLING & GRINDING IF THE WHEEL BEARING IS GONE. Course that's too late, then you've gotta replace it, but at least the wheel has not come off, & you hope it hasn't done the axle or the wheel any damage. So all you have to do is buy a new bearing.
32. A WHEEL BEARING CONSISTS OF QUITE A FEW PARTS: There's a container ring--I've forgotten some of these terms I used to know. Then there are the bearings in between the container ring & the center ring. They're usually roller bearings--little short tube-shaped bearings--& they roll around between the inner ring & the outer ring. So the outer ring rolls around the inner ring with these bearings in between.
33. IT'S THESE BEARINGS THAT MAKE THE WHEEL GO AROUND. I've talked about bearings before. If it weren't for roller bearings there wouldn't be any wheels & there wouldn't be any machinery, & there wouldn't be any cars & there wouldn't be hardly any motors, because all wheel's have to turn on bearings. Of course they sell books for amateurs on cars & show you pictures of all these things.
34. I THINK ONE OF THE MOST IMPORTANT COURSES A BOY COULD POSSIBLY TAKE IN HIGH SCHOOL IS CAR REPAIRING, where they learn all about the various parts of the car & the names & operations & how to repair it & everything else. I just learned through experience, years of experience, watching mechanics work & having things go wrong. (Maria: Are those things the most common things that can go wrong with your car?) Well, they're two very common things & very serious things.
35. EVERY 10,000 MILES YOUR CAR NEEDS TO HAVE THE WHEELS PULLED, bearings repacked, drums inspected & the brake linings inspected, to see if they're okay. If they're not worn too much, then you can put the wheels back on & maybe get another 10,000 miles out of them.
36. USUALLY ABOUT EVERY 20,000 MILES YOU HAVE TO HAVE NEW BRAKE LININGS. In other words, about every other time they repack the wheels with grease, you have to have new brake linings. And they're not very expensive.
Copyright (c) 1998 by The Family