Editing Line lock

==Introduction== A line lock or launch control is used to lock the (usually) front brakes without needing to apply continuous pressure on the brake pedal. ==Uses for a line lock== ===Burnouts=== If the line lock is used to lock only the front brakes, that leaves the rear brakes free to spin in a water box prior to starting a drag race. A front wheel drive vehicle would lock the rear brakes. This is especially helpful for a manual transmission vehicle. ===Drag race launch control=== If using a line lock for staging and launching, the engine RPM has to be kept below the point where the front tires would be pushed by the rear tires. This isn't a problem when doing a burnout- the tires are wet for that. But once the vehicle is in the staging area the tires are hot and sticky, plus the track is (usually) prepped with traction compound. That adds up to a situation where the rear tires are going to almost always going to be able to overpower the front brakes or the front tire's traction to the track, especially if you have wide sticky rear drag tires and/or skinny front tires. A line lock can also work as a way to launch a vehicle when drag racing. If plumbed into the ''rear'' brake line out of the master cylinder, it can be used to prevent the rear brakes from applying. This allows a modulated amount of front brake to be used that will let the driver keep the rear tires spinning while the car rolls forward however fast the driver wants. This can also allow a quicker drag race reaction time and ET than using a foot brake that controls all four wheels because the rear brakes are not in the system. Once the button that controls the line lock is released, all four brakes will work normally, allowing safe stops at the end of the track, unlike when the rear brakes are mechanically backed off to keep them from applying during a burnout or during a drag race launch. It is also possible to use a pair of line locks, one on the front brakes for burnouts and one on the rear brakes for staging. Using a rear brake line lock can allow an automatic transmission vehicle to load the torque converter harder than just the front brakes would allow without the rear tires either spinning or pushing the fronts. A line lock can also be used to launch the vehicle by using it on the front brakes, just like when doing a burnout. If this is done it must be kept in mind that the engine will tend to push the car no matter how much front brake force is applied; the rear tires almost always have more traction than the front tires are able to control, so the front tires will either slide or roll if enough throttle is applied. Also, if this technique is going to be used during a race, the driver first needs to practice so he can cut a decent light (have a decent driver reaction time, in other words) because the reaction time of the ''vehicle'' will be different than if launching using the foot brake normally. Obviously the best launch will be made using a trans-brake, but that's not something everyone wants or even needs and the cost and installation complexity is much greater than for a line lock. A manual transmission vehicle can use a line lock in much the same way as an automatic-equipped vehicle, along with being able to load the drive train with the clutch without worrying about rolling out of the starting beams. Loading the drivetrain can be easier on parts and reduce breakage from the hard hit a manual transmission can produce. ==Plumbing a line lock== [[File:Line lock plumbing.jpg|thumb|700px|left|Typical dual reservoir master cylinder system]] <br style="clear:both"/> ==Wiring a line lock== ===Selective switching between a pair of line locks=== The set/release button is often placed on the shifter. It can be used along with a toggle switch to select the front or rear line locks. But for using either the front or rear brakes one at a time, a single pole double throw (SPDT) switch could be used; it makes a complete circuit when in either the "UP" or "DOWN" position. One position would be the front brakes, the other position would be rear brakes, for example. There would be an arming switch to power the line locks up, the toggle would select which line lock received that power. From the interweb: A Single Pole-Double Throw (SPDT) switch connects one terminal to either of two terminals (three terminals in all). A Double Pole-Single Throw (DPST) switch has four terminals that connect or disconnect two pairs of terminals simultaneously. And a Double Pole-Double Throw (DPDT) switch (six terminals) connects one pair of terminals to either of two other terminal pairs. Locking all four brakes might help if the launch RPM was too high for the front tires/brakes to hold the vehicle from moving in the starting beams. ===Wiring the dash brake warning light=== [[File:Line lock brake light wiring diagram2.jpg|thumb|700px|left|Wiring in the dash board brake warning light to indicate when the line lock is activated]] <br style="clear:both"/> [[Category:Brakes]]

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