knock while braking
10-12-2010 | 04:05 PM
#1
Thread Starter
Staging Lane
Joined: Aug 2010
Posts: 54
Likes: 0
From: Houma,La
knock while braking Ok so within the last week or so I've noticed that wen I brake(only happens wen lettin off the brake pedal,not pushin brake pedal down) I can hear wat sounds like a knock.happens wen lettin off the brake fast,if I let off slowly I can't hear the knock.and this only happens wen I first start driving the car,after a good 5-10 minutes of riding if I press the brake on and off I don't hear it.
I'm thinkin maybe sum10 can be loose,hopefully this isn't a big problem.wat do u guys think.
I'm thinkin maybe sum10 can be loose,hopefully this isn't a big problem.wat do u guys think.
10-15-2010 | 07:05 AM
#5
If it's always a single knock, I'd suspect a loose component in the rear suspension (LCA, shocks, etc.) more than the brake.
As you apply the brakes while rolling, the momentum causes the vehicle to tilt forward, letting weight off the rear end. It is during this moment that a play at the rear suspension could polarize and slam back upon release of the brakes, causing the knock/tap. In this case, you wouldn't necessarily hear a knock when first pressing on the brakes because of the resistant depression of the front suspesion, allowing for a smooth forward tilt but a hard recoil. On the other hand, if it's a brake (loose pad/rotor, sticking caliper), you would expect there to be occasions--however rare--when the knock either happens more than once or not happen at all.
So the key in audio detection is pattern and persistence. Observe whether the knock ever occurs when going over a bump without using brakes, whether you can ever get the knock to happen more than once at a time, whether there's ever a time that the knock doesn't happen at all. However, despite these specifics, conclusive diagnosis can only be obtained through visual inspection. Fortunately, this will be easy to accomplish as you need only to stop by a Midas or Meineke for a free initial inspection. Furthermore, a conclusive deduction can likely be made after a look at the rear suspension for anything loose. If nothing is found, then it must be the brake(s).
As you apply the brakes while rolling, the momentum causes the vehicle to tilt forward, letting weight off the rear end. It is during this moment that a play at the rear suspension could polarize and slam back upon release of the brakes, causing the knock/tap. In this case, you wouldn't necessarily hear a knock when first pressing on the brakes because of the resistant depression of the front suspesion, allowing for a smooth forward tilt but a hard recoil. On the other hand, if it's a brake (loose pad/rotor, sticking caliper), you would expect there to be occasions--however rare--when the knock either happens more than once or not happen at all.
So the key in audio detection is pattern and persistence. Observe whether the knock ever occurs when going over a bump without using brakes, whether you can ever get the knock to happen more than once at a time, whether there's ever a time that the knock doesn't happen at all. However, despite these specifics, conclusive diagnosis can only be obtained through visual inspection. Fortunately, this will be easy to accomplish as you need only to stop by a Midas or Meineke for a free initial inspection. Furthermore, a conclusive deduction can likely be made after a look at the rear suspension for anything loose. If nothing is found, then it must be the brake(s).
