ABS kicking in significantly increases brake distance?????? - JeepForum.com
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post #1 of 8 Old 12-03-2018, 09:18 PM Thread Starter
2007laredowk
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ABS kicking in significantly increases brake distance??????

I recently upgraded the brake system on a 06 wk, (rotors, pads, braided lines, etc.), the difference is very noticeable, the front end dips easily (as in brake force, no suspension problems here) which before happened only under hard or very hard braking, very good results.
The problem now is that I'm braking and all good, firm and sturdy stopping power, as soon as the ABS kicks in it feels like it lets go the wheels, the brake pedal just stops moving like it locks in place and the ABS does the rest of the job but a very bad job doing so, it increases brake distance in a significant amount, very crucial under emergency braking. Is this normal? Is that the way the ABS works in this truck? I know it prevents the wheels locking up but damn it does the absolute opposite to make it happen, just let's them keep going. Any sort of adjustment the ABS system has?

Thanks.

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post #2 of 8 Old 12-04-2018, 06:44 AM
wave_crusher
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The abs should only be kicking in if it senses wheel stoppage on one or two wheels while the others are still rotating. If that occurs then you only control as to when the brakes apply, not how much pressure. The ABS will determine how much brake pressure is put on, and which wheels get it.

It will increase brake distance because it's not stopping all movement, it's there to prevent wheel lockup, which will happen, especially with fancy new brakes that work *like that*. So it's actually doing exactly what it's supposed to; except with the new brakes the wheels are more likely to lock up completely hence why the ABS is kicking in more. You would need to take it to the dealer and they might be able to adjust the ABS control (not sure if that's a thing or not).

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post #3 of 8 Old 12-05-2018, 07:19 AM
Nejeep
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I would suggest you bleed the rear brakes again (assuming you did that with the upgrade). It sounds like the front brakes are doing all the work to the point of locking up under heavy braking (ABS engaging).

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post #4 of 8 Old 12-05-2018, 09:33 AM
acabtp
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dunno what kind of surface you were getting the ABS to engage on, but remember with the stopping distances it will always be:
distance for hardest stop w/o engaging ABS < distance for stop with ABS engaged < distance for stop with tires locked up

the coefficient of static friction is always higher than dynamic (sliding) friction. when the wheels are sliding part of the time (ABS is engaged) the stopping distance will be longer than if they are not sliding at all (powerful controlled stop w/o locking tires or engaging ABS). on surfaces like snow/ice the difference between static and kinetic friction is huge so it would really be noticeable as longer braking distance. on wet asphalt they are closer, and dry asphalt closer still, so the difference in braking distances would be less noticeable.

the point of ABS like implemented on the WK is to help you keep some of your steering authority by not allowing the front tires to stay locked, allowing you to steer out of danger rather than slide into it. it does not provide the shortest possible braking distances, though more modern ABS implementations on newer cars are getting better at this.
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post #5 of 8 Old 12-05-2018, 08:58 PM
Walt
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Quote:
Originally Posted by Nejeep View Post
I would suggest you bleed the rear brakes again (assuming you did that with the upgrade). It sounds like the front brakes are doing all the work to the point of locking up under heavy braking (ABS engaging).

The ESP and braking system on the WK cause the rear brakes to take more load than earlier disc brake systems. Normally, the rears wear out faster according to one of the local off-road shops here. It was true on my WK also.

If yours are now spongy, consider "reverse bleeding" the rear brakes to force any bubbles up and out to the master cylinder reservoir. I saw this new system advertised and it intrigued me: it allows one person to bleed from the caliper upward....wish I could remember the name/brand of the system.

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post #6 of 8 Old 12-08-2018, 04:39 PM Thread Starter
2007laredowk
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Thanks for all the input, looks like I'm going to bleed the brakes again just to be safe, they were definitely bled when the upgrade was done since the hoses were replaced. The pedal feels normal, solid and firm, no spongyness or hardness. The doubt was mostly because when I've seen videos of cars testing brakes you can see when the front leans forward and the car keeps braking without locking the wheels indicating the ABS is working, firm and steady braking, but in this truck I feel like the wheels let loose just to avoid locking up nevermind increasing the braking distance, but if it's normal I will just have to be careful when emergency braking. It wasn't much of a test but just getting to see how the brakes worked under different circumstances, but this was done in slightly wet/slippery pavement road and pavement with some loose gravel.
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post #7 of 8 Old 12-08-2018, 04:57 PM Thread Starter
2007laredowk
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To reverse bleed I would need to buy equipment, is the traditional pump the pedal, open the bleeder, close the bleeder, release the pedal, repeat, method enough?
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post #8 of 8 Old 12-08-2018, 06:17 PM
Walt
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Quote:
Originally Posted by 2007laredowk View Post
...is the traditional pump the pedal, open the bleeder, close the bleeder, release the pedal, repeat, method enough?
My experience says no (but I've never had to do it on my WK). It takes 2 people: One (1) to push down and hold the brake pedal and 1 to perform the bleed and close the bleeder valve before releasing brake pedal pressure. First person pumps up the system pressure again. This method prevents any "back-sucking" of air into the hydraulic system.
Between bleeds, verify that the brake fluid level remains high in the master cylinder reservoir.

My 2 cents worth.

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abs , brakes , power , race , speed

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