Rear brake grabbing early

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Hatchetf15
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Rear brake grabbing early

Post by Hatchetf15 » Tue Oct 08, 2019 11:21 am

Gents,
My C2 left rear is locking up a little early during threshold braking, just before I start easing up. Stock rotor and warm Akebono pads. PSM off. Straight line or turn either direction. ATE fluid has less than 2000 miles. Any ideas on a fix?
Cheers,
Mike

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gnat
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Re: Rear brake grabbing early

Post by gnat » Tue Oct 08, 2019 11:27 am

Time for a caliper rebuild?

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Hatchetf15
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Re: Rear brake grabbing early

Post by Hatchetf15 » Tue Oct 08, 2019 12:27 pm

Could be, Gnat. They have 90k on them.

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5chn3ll
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Re: Rear brake grabbing early

Post by 5chn3ll » Wed Oct 09, 2019 11:40 am

Is alignment/camber correct on that corner? If the contact patch is smaller than it should be, the brakes may be overpowering that tire and locking it up.

Is the tread wear pattern the same on both rears?

In neutral on jack stands, does the problem wheel turn as freely as the non-problem side? Any bearing play/grind?

Understeer: You will hit the wall with the front end.
Oversteer: You will hit the wall with the rear end.
Horsepower: How hard you will hit the wall.
Torque: How far you will move the wall.

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Hatchetf15
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Re: Rear brake grabbing early

Post by Hatchetf15 » Thu Oct 10, 2019 2:10 pm

5chn3ll,
When I get home next week, I’ll put it up and check bearing and caliper...bleed that corner just cuz. Fresh alignment (just -1.8 on the rears), fresh suspension everything and new-ish AS3+ shoes. That side didn’t chirp at all with the 19’s and PS4S.
Hatchet

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5chn3ll
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Re: Rear brake grabbing early

Post by 5chn3ll » Fri Nov 08, 2019 8:44 am

Anything ever come of this?

Understeer: You will hit the wall with the front end.
Oversteer: You will hit the wall with the rear end.
Horsepower: How hard you will hit the wall.
Torque: How far you will move the wall.

"Reading daily intel briefings is for p*****s."
-DJT


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Hatchetf15
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Re: Rear brake grabbing early

Post by Hatchetf15 » Sat Nov 09, 2019 5:06 pm

So I thought if left rear is the grabby one, was it that brake late to the party, or the right rear? Thinking about all the reasons made my brain ache. So...

Eventually got done with troubleshooting on Thursday. Bearings, alignment all good. Going on assumption rear brakes are mostly mechanical issues, not hydraulic; I pulled both rear wheels. I pulled both calipers and used spreader to seat pistons. Eyeballed all the pistons for any variances. I cleaned both calipers and rotors and pulled the pads. Cleaned around the pistons with Dawn. Even wear (to be expected cuz they’re new) on pads.

I siliconed the pins and put pads in exactly the same on both sides, torqued the bolts to exactly the same number. Basically took as many variables out as possible between sides. Fixed! Not gonna comment on what coulda been the culprit cuz I’m not that car-smart.

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Re: Rear brake grabbing early

Post by FRUNKenstein » Sat Nov 09, 2019 9:28 pm

Glad to hear you got it resolved. Thanks for the update.
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5chn3ll
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Re: Rear brake grabbing early

Post by 5chn3ll » Mon Nov 11, 2019 2:56 pm

Voodoo mechanics FTMFW...

Understeer: You will hit the wall with the front end.
Oversteer: You will hit the wall with the rear end.
Horsepower: How hard you will hit the wall.
Torque: How far you will move the wall.

"Reading daily intel briefings is for p*****s."
-DJT


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Hatchetf15
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Re: Rear brake grabbing early

Post by Hatchetf15 » Mon Nov 11, 2019 3:30 pm

Sometimes ya just gotta flash dem chicken bones! But really I wanted to get both sides the same, in case the problem didn’t get resolved. I even pulled and cleaned/moly lubed speed sensors. I guessed it was something simple. If the problem happens again, I’ll just summon the loa.

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