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What are Shocks? What are Struts? Which Does Your Car or Truck Use?

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Hey, everyone. Let's talk today about suspension, shocks and struts to be more specific. What do they do?

So, I laid out here on our mighty little table suspension parts, new stuff, old stuff, so struts with complete assemblies and then we also have spring-mounted shocks. And I'm going to explain to you the differences, what the difference is, what they do, and why, and our lovely, shiny new ones. We're going to break them down for you.

So, I want to start with rear shocks, real basic rear shock. I've got two different types of shocks here for the rear, and this is how they come when they're packaged. They come with the strapping on it. That's because these are compressed with gas and oil. All depends on which one you have. So, what you do is you just compress it. You can hear the sound in there of the oil, gas, and then it extends to its full extension. Now, when you put a new shock in, just a quick notion, you want to call...they call it starting the shock. That means you have to compress it about three times to get all the gases mixed. So, after three times of what they call starting it, you'll feel that it gets harder to compress it. If you don't start the shock, try to say that one, what you can end up hearing is a rattling sound, and it might go away maybe about 100 miles, 200 miles. All depends on the kind of road you live on because that shock will keep doing mini starts, and then finally all this gets activated and it's like it'll become the ride that it needs to be. So, as you can see, it's getting more difficult for me. So, here is a different rear shock type, more likely for a truck or mid-size SUV. And we'll see just how far out this extends from where actually it was compressed. So, a lot of people don't know how big a shock is, you know. They don't get into the car. They don't look. They don't understand it. Look at that, puppy, huh?

So now that I showed you what a shock is, let's go look at where it is located on the car. So, here we are underneath a pickup truck, and this is the rear suspension or rear differential, but more importantly, here is the shock, and it is mounted to the bottom of the differential. And then there's always a mounting block on the top, usually on the frame or the body. Now, what this does, a lot of people misconstrued what a shock does. They think that it holds the suspension of a vehicle up, and it actually doesn't. It's exactly in the word. It's a shock. It absorbs the shock of the vehicle in the ground. What holds the suspension up on this particular vehicle is called a leaf spring. Now, I'm sure you've heard of leaf springs or coil springs. Most trucks will have leaf springs, and some large SUVs or passenger cars have coil springs. The old days, back in '70s, even cars had leaf springs.

So, I want to explain to you real quick what a leaf spring is, and what it looks like, and what it's made of. So, if you go to the back of your truck, this is the leaf spring. It's mounted on what they call a shackle, which is mounted to the frame, and then it goes over the differential. These are what they call mounting U-bolts, and it mounts to the top over here in the front of the frame. Now, these are steel bars, and as you can see, this is called a four pack, one, two, three, four. Four leaf springs. They will always be the curved ones, and then the straight heavy plate on the bottom. That steel is...see how it's bent into almost a U-shape, that holds that car up. So, that's exactly what it's doing. It's holding the car up like a beautiful piece of artwork.

So, let's talk about coil springs. Not leaf springs, we just looked at those, but now we're going to look at coil springs, and this is what it is. It's pretty simple and it's lightweight, but this is a compressed spring that holds...this isn't a differential because it's front-wheel drive. It's just the rear suspension, which is a crossmember solid steel tube. We have the leaf spring mounts here, and then the shock. Now, if I was to take this shock out, this car would only drop about a half-inch. This is not what makes a car drop to the ground. These are what make the cars drop to the ground. So, some people take these and they put shorter ones in. They have those cars you see go around. People have low rider cars. That's what they do. They modify the suspension by taking the original ride height and shorten it up. But this will take all the bounce from going down the road. So, a lot of people don't understand is with front-wheel-drive cars, the rear of the car is extremely lightweight. It's usually a short compact car and it's for gas mileage, handling, wheelbase. Can go into a deep theory. But if this isn't working properly and it doesn't have the right charge inside with the gases, it's weak and what ends up taking the absorption of the road bounce is the tire, and you'll get a tire wave, choppiness, lack of rotation, and a bad shock.

All right. So, I told you I was going to tell you what's going on on the inside of this. Let's do it. Real simple. Metal casing, it's a tube style, and you can see how here they weld the mounting bracket to it. And there's going to be a rubber center here that helps take it. The main bolt goes through there. The same with the top. So, this is just an outside shell. Sounds like a bell. So, struts have rubber boots. We'll get into that. But right now, on a shock, usually 90% of the time it's steel unless you've got to see the rubber one right here, but this eventually can break down, get holes in it, and then dirt will sit on top of that shock and ruin the seal as the piston goes up and down. But let's see what's happening underneath that boot. There is our shock. So, this is the main casing that I was talking about, and inside here is compressed gases. Some of them are oil, but on this particular model that's gas, and this is the actual rod. So, on the inside of this tube, this rod goes down in right about here maybe there is a round washer with a rubber seal and another washer, and it's bolted to this rod. So, as this rod compresses, which I can't do because this is a high functioning gas shock, so as this rod compresses, it acts like a plunger. The gases are on this side and on the top is air. Sometimes the oil mix. And as that plunges down, it compresses only so far, just like a piston in an engine, and it won't allow it to go down any deeper, so it pushes it right back up. So, this piece will rock back and forth, absorbing the road shock, thus the word shock.

Let's talk about struts, types of struts, what they do, and how they work. So, here we go. We have a regular used struts. We have a full-size strut, and these are called spring-seated shocks. And I'll tell you the difference and why they make them. So, I put a strut in our strut machine so I can take it apart and you can watch. And this is how they're assembled and what they're made of. So, I'm all set up here, ready to go, and I'm going to compress the spring. So, here we have the strut housing. The whole cartridge comes up, has this base and the rubber seat, and the coil spring mounts. This rubber piece does have a seat in it where that spring ends up right there. So, you have to line that up if you are to take one of these apart. Strongly recommend using a machine. They do have tools that are just bolts with hooks. You have to be extremely careful because these are under a lot of pressure.

Okay. So, when this strut is mounted in the car, top part, this being called a strut, not a shock assembly, I'm going to show you the difference. This is a strut, spring-loaded, gas-powered piston in a cartridge, but this is strut mount. And the difference between a strut mount in a spring-seated shock is that the mount moves. So, when you turn your steering wheel, this is mounted up inside the fender wheel, usually in the engine compartment, and when you turn the steering wheel, this stays attached to the knuckle and it lets it turn. So, this part will be turning in the car, and this is mounted stable inside the engine compartment. And that's how it turns. Sometimes these in here have a bearing that goes bad and you'll hear a grinding noise. When you take a corner over bumps, they go [vocalization]. Pretty good, huh? A lot of times it'd be internal bearing on the strut cap. Hold the strut. And do the mounting nut. Take the strut cap off the top half. Here is that bearing I was talking about. And let the strut come right out.

So, let's discuss the insides of a strut. So, you have the cartridge and inside here with this steel shaft is the piston. Just like a shock, it has a coupler on it with rubber seals, another coupler on the top, and it's just like a plunger, comes down and up. And in here is chargeable gas that charges by pressure. You have your base mount, rubber mount, your spring, which is still in the compressor, then you have your top mount with another rubber mount. That's going to go on top. Goes like this with the spring on and the rubber stays there. Now, this is the strut mount bearing. So, it's a two-piece bearing. There's little ball bearings inside these two pieces of metal so it will spin. Has a nylon casing around it. That goes down next. You center that, and then the top strut mount. Go on. Sits down on that bearing, and that's where it gets to ride. Once the spring is in here and there's pressure, this base plate stays in place and doesn't move. Just the top moves, but because I wasn't created with three arms, I can't show you on the camera. And then the lock nut, which, of course, gets torqued down to the manufacturer specifications. But that is what's going on inside your strut. That is the whole way about it. Now, that's why you can purchase a strut assembly and get a whole assembly with a new spring, everything is done. Take it out as one piece and put it in as one piece. You would strongly need a tool to take the spring apart. They do make little compression bolts with hooks on them. Scary, but they do work. I've used them. You just have to be careful and very precise. So, assembly is kind of for me are the way to go.

So, I want to talk about what you should purchase if you're going to replace your strut yourself, even if you don't, if you pay someone to do it, but I strongly recommend if you do the assemblies, you can do it yourself very easily. One thing I strongly recommend if you get the assembly, get the links. The links are attached to the assembly right here, and these are easily... They're inexpensive. They're easily... They get a wear item. They wear real fast. You don't want to strip this out, taking it out and putting a new strut in, then you get on the road and you hear a little noise. And guess what? The bushing inside here is worn-out too. Inexpensive. Do it as a pair, highly recommended. If you're going to do the strut without the assembly, and you're going to do...compress the spring yourself, if you know the spring is in good shape, it's not cracked in any way, you're going to put the old spring on a new strut. Strongly recommend buying the strut cap. This item right here is one of the highest wear items on a strut, and that is due to the pressure they put under from that spring in this little bearing right in here. This is under so much pressure that... It's inexpensive again to replace the cap with the bearing when you do just a strut replacement. So, when I replaced this whole strut assembly, I knew that I was going to replace the link, so I left it attached to the strut and just undid it right at the sway bar. Easy-peasy. One, two, three, four, five, six. Six nuts and bolts and out of there. No problem.

So, here we have a front strut assembly on a front-wheel-drive vehicle. This is what it looks like from underneath. So, you have the whole strut assembly, comes down, and it bolt right here to the knuckle, and here's the link. The link is attached to the strut and then bolted here to the sway bar. And that's why I undo it from the bar and leave it on the strut and replace it when I do a strut. So, here we have rear suspension on a front-wheel-drive vehicle, and we have a rear coil spring that's separate from the shock, and then the link is separate. So, if I was to do just shocks here, I wouldn't bother with the link or spring assembly. I would do just my shocks.

So, now let's talk spring strut assemblies, the difference between them. Mainly, most of the differences. That the cap itself does not spin like a strut. So, it's stationary in place, spring-loaded, high-pressure gas. So, if you don't know what you have, a strut or a spring assembly shock, just look and see if you have an upper control arm. If you have upper and lower together, more than likely you have a spring-seated shock.

So, here we have a spring-seated shock assembly inside a vehicle. Now, as you can see, we have a lower control arm, upper control arm. This is mounted to a steady place. Doesn't pivot. And up there, it is mounted to the top of the shock housing, which is welded to the frame, so that doesn't spin either. So, now you know you have a stationary spring-seated shock or strut, shall I say. It's all one assembly. These, I strongly recommend replacing them as an assembly because this spring is so tense, compressed so tight, and it's a narrow spring. You definitely need a specialty tool to compress that. The old fingers with the bolts, it's really difficult. So, do yourself a favor, save yourself some time and fingers, and get the whole assembly on this one. And when replacing this, there's nothing really that I would recommend other than doing a quick visual. The link is separate, so you don't have to replace that. The control arm is separate. The upper control arm is separate. You just basically undo the bolt, follow procedure, and remove it.

So, in completion with what's in a strut and shock, when do you know when to replace them? Like, what's the problem? Well, one, noise, two, leakage, and age. So, if they are of long age, some cars can go up to 120, 130 all highway mileage, you might not need to change them at all, but if you have rough roads, a lot of potholes, dirt roads that you travel a lot, you're going to hear them break down a lot sooner. You'll start hearing noises. You'll notice maybe on an inspection, they'll say your strut is leaking. So, those are times when you need... When they leak, they're losing the compression, and they no longer will take that absorption of the road. So, noises, oil leakage, and handling too because that's a key part of steering is the suspension, is the strut assembly or shock. So, pay attention to the steering, feel it out, and have fun.

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