What causes the brakes to lock up?

[daniel3507]

I'm really getting tired of the brakes on my truck. I just replaced the fronts less than a month ago because the rotors were really warped. It also had a tendency to lock up when braking too hard, especially when wet. I dont mean hard as in slamming on the brakes either. The new set up doesnt shake like warped rotors but just recently it has started to want to lock up again. I can feel and kind of hear a grinding when the brakes are being engaged and its slowing down to a roll. If i step on the brakes hard then it locks up and jerks around. I dont know what the problem could be anymore. What could be a cause of the brakes wanting to lock up? Its too the point where i worry about stopping if I run into a situation where I need to hit the brakes hard.

 

[adsm08]

Brake lockup is caused by more friction between the pads and rotors than between the tires and the road.

The rest of what you describe is ABS activation.


I would assume your tires are crappy.

 

[daniel3507]

Tires are a couple years old and are rotated almost every oil change and have lots of tread. The rear brakes are the only ones with abs correct?

 

[adsm08]

You should only have rear ABS, correct. The RABS system is kinda crappy though. It also infers wheel lockup by looking at how fast the wheels stop. If it thinks it is too fast then it kicks in.


Have the roads in your area been re-paved in the last year or so? Sometimes too much oil on the road surface will cause this, and it has been my experience that this can happen more if the roads have been repaved recently.

 

[daniel3507]

The roads haven't been repaved. It does it on any surface it seems. I'll have to look into the RABS and see if that's what's causing the issue I guess.

 

[Mark_88]

Did you by any chance change the flex lines on the front? If it is the fronts that are grabbing, it could mean your flex lines are flucked and need changing.

This happened on mine and there is a sticky or tech article around somewhere about how they become one-way valves that cause the brakes (rotors) to lock up. When you stop, they stay stopped.

Flex lines are easy to change and relatively inexpensive. They can cause rotors to warp and all kinds of extra expenses (like gas because your engine is fighting the front brakes) and worn parts. Added heat can help destroy front bearings and lead to the infamous front wheel separation.

Check that out...it might be the problem if it is your fronts that are locking...

 

[brokemechanic3000]

This has been a complaint from all of the rangers and explorers of this era. what i've done for my customers is to setup the rear brakes, then make sure the front is clean and lubed. I think there was a tsb on this.