Braking Bias (front vs rear force applied)

BuickGirlFromMars

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Right now, if i want to change how my car distributes braking, I can easily do it by reversing and stopping.

Then if I drive forward, my car now will stop much more balanced. IE back brakes sharing a good amount as front.

if i drive for a few days or use my parking brake, it will now heavily bias the front, so much so you can feel the rear start lifting off the ground and it getting very sway-y like it wants to kick out

They are not adjustable brakes like a drum brake, so I dont know what you can do to "balance" them and have it stay. Im stumped
 

JoeBlog

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I would suspect that the ABS module has something to do with that. Since the majority of the cars’ weight shifts forward during braking, the ABS system would need to compensate somehow to ensure “balanced“ braking occurs if it gets activated. Of course, I just got over two-weeks of COVID, so my brain cells could be randomly firing with no logic whatsoever. You decide.
 

BuickGirlFromMars

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i decide maybe. i did the ABS test feature on my tech 2, it passed.
my wheel sensors make sense, dont ever deviate.

i use ABS and traction, they work.

But maybe when i changed caliper it didnt bleed perfectly? I didnt bleed extensively because i got in car, had the pedal have constant pressure, prefilllled caliper, installed with bleeder cracked, and never let off pressure till it was a stream, closed bleeder, reput pedal up,put pressure on, cracked and did a full push down closed it and called it good. feels like no air, but i could be wrong. ive only had a few cars, most had bad lines or brake pedal feel. no new cars
 

2007LucerneCXL

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On the ABS it may need to be cycled which with the TECH2 it should be available, not sure if that was or is the problem but air in the ABS doesn't always bleed unless the valves are in parked position. This may help in regards to the ABS.
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BuickGirlFromMars

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On the ABS it may need to be cycled which with the TECH2 it should be available, not sure if that was or is the problem but air in the ABS doesn't always bleed unless the valves are in parked position. This may help in regards to the ABS.
I did that procedure i should have clarified. being i have a tech 2 i did that first. maybe it needs tk be done last?
 

2007LucerneCXL

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This is a little out of my of my area as I don't know all the GM ABS but if yours can be parked in the home position that would allow straight through bleeding as far as beginning or end now I would be needing to check a manual lol, but parking the ABS would be the beginning.
 

techmann

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If your braking pressure is not even between front and rear, it is your proportioning valve. The ABS keeps the brakes from locking up in a panic stop. When you hard stop your brake pedal and feel the pedal go down and then push up repeatedly, the ABS is working.
 

BuickGirlFromMars

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I KNOW HOW abs works, Sorry lol. SOmetimes you guys think im new to cars. Ive replaced a lot of components and ive wrenched a lot and i own a lot of cars, but the diagnostics and the how to is what im more still navigating. if i havent run into an issue ive unlikely dealt with it, my first 2 cars didnt have ABS from factory and my 2 following cars had brakes i never touched lines or fluid on.

I know how TCS, magnasteer, ABS, etc function, but this unique issue ive never had i guess making sure it is not some other possibility.

Techmann, would it shift between front and rear bias? I can change it anytime by braking in reverse or forward. If i brake in reverse, my car will brake straight and take a little longer, if i brake forward hard enough i will kick out rear and it will stop on a dime but feel unstable because rear tries to lift off

and sadly i dont think the Tech 2 offers park position for this style ABS, i looked into it, and the bleed procedure calls for ABS bleed AFTER mechanical bleed and even a caliper replacement requires both bleeds, not just one(Like I did) so i will start there before changing parts
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HotZ28

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Have you replaced the front & rear pads/rotors with the same equipment/style & friction?
 

BuickGirlFromMars

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Uh...thats a good question... when i had to un-f$%k my rear brakes, i had to junk my AC Delco ceramic pads for whatever AUTOvalue had on shelf, it was 25 dollars for the set. Rotors werent FUBAR, so I sent it. currently the rotors are smooth again and no vibration.

What do you think that is doing?
 

2007LucerneCXL

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If this is the same vehicle with the rear proportioning valves it's a different system than most have delt with and if it's unique on how the system is bleeding it may be a shop manual explanation? Rubber hoses can create funky braking if collapsed because of age along with the seals in the master cylinder, not answer's just other items to consider looking at.

Oh, seeing how you own and can use a Tech2 that's above most vehicle owners of any gender LOL.
 

BuickGirlFromMars

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i do know the hoses were... ignored by the shop when i had asked them to do all four, they did front 2. but prob for best considering how it wasnt done correctly. Definitely not opposed to replacing rear hoses... but i was looking to buy 99 fsm, f$%k it im ordering them
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2007LucerneCXL

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Unfortunately on older vehicles braking systems it's usually the weakest link on part replacement that will show up. Replace one line or section and the others will rear their ugly head as I had assume I've solved a problem only to have another show up because the new part was actually working properly.
giphy.gif
 

BuickGirlFromMars

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Unfortunately on older vehicles braking systems it's usually the weakest link on part replacement that will show up. Replace one line or section and the others will rear their ugly head as I had assume I've solved a problem only to have another show up because the new part was actually working properly.
View attachment 25445
my lines are new and my front hoses are new
 

techmann

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Buickgirl, I was just giving you my 50 + years knowledge of working on cars, didn't mean to imply you knew nothing about ABS, but as to your reply , " SOmetimes you guys think im new to cars. Ive replaced a lot of components and ive wrenched a lot and i own a lot of cars," I shall not insult your intelligence again.
 

BuickGirlFromMars

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Buickgirl, I was just giving you my 50 + years knowledge of working on cars, didn't mean to imply you knew nothing about ABS, but as to your reply , " SOmetimes you guys think im new to cars. Ive replaced a lot of components and ive wrenched a lot and i own a lot of cars," I shall not insult your intelligence again.
no no not you so much, more so regulars around here. for example one day i asked for recommendations on a trans cooler and i had a few people breaking down the concept of them and why its good to run them more than individual product recommendations. i dont think its malicious or people think im dumb lol it just probably the way i word it combined with the fact its not common for girls to be into it all
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BuickGirlFromMars

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issue was strut and control arm bushings, front, worn and binding up. Rear braking shifted weight off them.
by front i mean only the frontward one on both arms, so the rear-ones were good. odd.

Struts were caused by mechanic.... yeah im not happy.
 
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