Brake System Design and Optimization: Brake Lines
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Brake Lines
05.09
| 00:00 | - We've talked about how we build and regulate hydraulic pressure for the brakes and now we need a way to distribute it throughout the system. |
| 00:08 | This is where brake lines come in, they're responsible for transferring fluid and pressure throughout the system and providing a fluid path between components. |
| 00:18 | Brake lines fall into two categories, solid and flexible. |
| 00:22 | The solid lines are used to link different parts of the braking system together where no movement is required. |
| 00:29 | As such, they're normally made from steel, stainless steel or copper nickel tube that's bent to follow the contours of the chassis and bodywork. |
| 00:38 | Flexible lines also known as hoses are used where we need to transfer fluid to moving components, most commonly the brake callipers. |
| 00:46 | Outboard callipers are attached to the suspension which is obviously moving relative to the chassis as we make our way around the track. |
| 00:54 | On the front axle, the suspension is also being steered which also requires the lines to move. |
| 01:01 | In the OE world, most flexible brake hoses you'll come in contact with will be rubber based but in the motorsport industry, braided stainless steel lines are the go to. |
| 01:11 | While the rubber based hoses are chosen in the OE world primarily for cost reasons, they do have some downsides we'll discuss shortly. |
| 01:19 | The brakes hoses will generally connect to the solid brake lines somewhere near the inner wheel well. |
| 01:25 | This helps to minimise the length of flexible hose in the system which we want to do for a few different reasons. |
| 01:32 | Solid steel lines are going to be more damage resistant than flexible hoses in most cases. |
| 01:37 | Meaning we should be using them whenever possible. |
| 01:40 | However, from a function perspective, compliance is another important factor. |
| 01:45 | We've discussed compliance in its own module previously but in the context of brake lines, this is where the hose or line swells and changes shape due to the internal hydraulic pressure. |
| 01:56 | When this happens, it requires more fluid to be displaced in order to raise the pressure in the system and that requires more brake pedal input by the driver. |
| 02:07 | For consistency, feel and confidence of the driver, we always want to limit excessive brake pedal travel. |
| 02:14 | Rubber hoses expand a lot more than steel line does in response to internal pressure. |
| 02:19 | This means manufacturers, while they're willing to accept more compliance in the system at high pressures compared to motorsport, still want to minimise it. |
| 02:28 | This is the reason you'll see the rubber hoses being kept as short as practical. |
| 02:33 | As we've touched on a few times already, this is why braided stainless steel brake lines are so popular in motorsport. |
| 02:40 | As they expand far less due to internal pressure, giving us less compliance overall. |
| 02:45 | To allow the solid brake lines to be joined to other components, you'll generally find tube nuts at each end of the lines. |
| 02:53 | This is a nut that slides over the line where the end of the line has been flared. |
| 02:58 | This nut screws into the component, pressing the flared end into the matching part of the component thereby creating a seal. |
| 03:06 | The flare is used to add strength and integrity to the connection and improve the seal. |
| 03:11 | There are a few different types of flares and although single flares do exist, they shouldn't be used for brake lines and are actually illegal for road use in most countries as they aren't able to withstand high pressures and will crack and leak easily. |
| 03:26 | Double flares, also known as SAE or inverted flares, create a much stronger, more secured seal connection. |
| 03:33 | Bubble flares which are sometimes referred to as ISO or DIN are also commonly used with success however a double flare is still a more durable and reliable option and is therefore the go to for brake hard lines in motorsport applications. |
| 03:49 | One last thing that's worth mentioning here is routing options for the brake lines. |
| 03:53 | In some OE applications, the brake lines are routed diagonally, meaning the front left and rear right are on one circuit and the front right and rear left are on another. |
| 04:05 | This means if there is a hydraulic leak in one circuit, at least one of the front brakes will be able to provide some stopping force. |
| 04:12 | This is important as the front brakes always provide more of the total stopping power compared to the rear. |
| 04:19 | A downside of this is the car may be difficult to control during braking as the brake force is uneven side to side. |
| 04:27 | The conventional way that a motorsport style brake system is laid out is for the front and rear systems to be plumbed separately. |
| 04:34 | This is something we've touched on previously but this allows us to modify the front and rear brake pressure independently of each other. |
| 04:42 | In summary, brake hoses are responsible for transferring hydraulic pressure between the different components in the system. |
| 04:49 | They can be either solid or flexible depending on what part of the car they're used in. |
| 04:54 | Braided stainless steel hoses are preferred in motorsport applications over rubber based hoses and the way the brake lines are routed will determine whether you can vary the hydraulic brake bias front to rear easily. |
