Question on brakes - JeepForum.com

 
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post #1 of 12 Old 08-31-2013, 05:25 PM Thread Starter
insaneinline
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Question on brakes

Ok here's my question if I'm going up a steep grade and have to come to a stop I press the brake pedal then if I hit the brake pedal again its like they stick almost like it prevents the jeep from rolling back and the pedal gets stiffer the more times I press and let off the brake pedal and press the gas pedal is this normal like a feature to prevent the jeep from rolling backwards or do I have a problem never noticed this before

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post #2 of 12 Old 08-31-2013, 05:30 PM
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Quote:
Originally Posted by insaneinline View Post
Ok here's my question if I'm going up a steep grade and have to come to a stop I press the brake pedal then if I hit the brake pedal again its like they stick almost like it prevents the jeep from rolling back and the pedal gets stiffer the more times I press and let off the brake pedal and press the gas pedal is this normal like a feature to prevent the jeep from rolling backwards or do I have a problem never noticed this before

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Sounds like Hill Start Assist, but nothing in your post or your profile says you have a JK.
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post #3 of 12 Old 08-31-2013, 06:46 PM Thread Starter
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Sorry about that yes I do have a jk with hill assist and I was wondering if that's what it may be

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post #4 of 12 Old 08-31-2013, 09:19 PM
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Yep, I tested out my Hill Start Assist today... LOVING the Jeep... Far better than my OffRoad Xterra!
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post #5 of 12 Old 09-01-2013, 07:53 AM Thread Starter
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Great that's one nice feature to have especially in pa

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post #6 of 12 Old 09-01-2013, 09:46 AM
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I'm going to use mine in the streets of Downtown Seattle today. Some STEEP streets there!
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post #7 of 12 Old 09-06-2013, 01:28 AM
Rtone1583
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As far as the brake pedal getting stiffer, this happens on just about every vehicle.

This is what is happening:

Two things are going on in this initial step.

1. By design the pistons in the calipers are made to pull back slightly into their bores when the brake pedal is released (this keeps the pads from resting directly on the rotors).

2. The rotors themselves are not 100% true and/or the hub does not run 100% true (talking about very minimal runout here and it is completely normal). This little bit of runout, though not felt by you, is enough to cause the rotors to bump into the pads which causes the pistons to be pushed just a little further into their bores.

Overall, between the two, the brake pads stand off from the rotors by a very small fraction of an inch while just driving down the road.

When you initially press the pedal to stop the pads have to travel this empty space before they hit the rotors and it is that short distance of empty space travel that you perceive as a soft pedal.

During a normal stop, where you have the initial pedal press and then let off and press the pedal again in relatively quick succession, the first two actions above don't have time to occur and the pads are kept right against the rotors so there is no empty space travel and the pedal feels harder on these subsequent pedal presses.

Hope this makes sense.
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post #8 of 12 Old 09-06-2013, 10:01 AM
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Quote:
Originally Posted by Rtone1583 View Post
As far as the brake pedal getting stiffer, this happens on just about every vehicle.

This is what is happening:

Two things are going on in this initial step.

1. By design the pistons in the calipers are made to pull back slightly into their bores when the brake pedal is released (this keeps the pads from resting directly on the rotors).

2. The rotors themselves are not 100% true and/or the hub does not run 100% true (talking about very minimal runout here and it is completely normal). This little bit of runout, though not felt by you, is enough to cause the rotors to bump into the pads which causes the pistons to be pushed just a little further into their bores.

Overall, between the two, the brake pads stand off from the rotors by a very small fraction of an inch while just driving down the road.

When you initially press the pedal to stop the pads have to travel this empty space before they hit the rotors and it is that short distance of empty space travel that you perceive as a soft pedal.

During a normal stop, where you have the initial pedal press and then let off and press the pedal again in relatively quick succession, the first two actions above don't have time to occur and the pads are kept right against the rotors so there is no empty space travel and the pedal feels harder on these subsequent pedal presses.

Hope this makes sense.
I understand #2, but can you elaborate on the design feature in #1 that makes the piston pull back a little when the pedal is released?
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post #9 of 12 Old 09-06-2013, 10:53 AM
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#2 is basically a suction effect from the hydraulic system that retracts the pads, thus they dont ride all the time wearing them.

am i right?

If it's not supposed to move and does use duct tape.
If it's supposed to move and doesn't use WD40
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post #10 of 12 Old 09-06-2013, 11:00 AM
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Originally Posted by bogleparsons View Post
#2 is basically a suction effect from the hydraulic system that retracts the pads, thus they dont ride all the time wearing them.

am i right?
#2 describes the pads/piston being pushed back by the little bit of run-out.
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post #11 of 12 Old 09-07-2013, 02:30 AM
Rtone1583
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Quote:
Originally Posted by bogleparsons View Post
#2 is basically a suction effect from the hydraulic system that retracts the pads, thus they dont ride all the time wearing them.

am i right?
This is correct as it applies to #1.
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post #12 of 12 Old 09-07-2013, 06:48 AM Thread Starter
insaneinline
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I thought it was the hill start assist when I started the thread but I wanted to make sure I never knew exactly what it was

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