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Mufasa in Training
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Discussion Starter #1
All,

I've been having some weird [lack of] rear lock-up issues that I'm guessing could be a bad caliper in the rear, or the MC not sending any rearward pressure. Basically the rear brakes will not lock up unless the hand brake is pulled.

Is there a chance anyone could help me look at it next weekend? If not, it's no biggie...
 

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Interesting Bryan, I have a similar issue but backwards. My breaks will lockup with the pedal but not with the handbrake. Pulling the handbrake feels as if it really does nothing except slowly slow the car down.
 

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That's because 99.99% of all handbrakes on passenger cars were not designed to be dynamic brakes. When adjusted properly, though, most do a good job of keeping a parked car parked. CNC Brakes makes some sweet hydraulic handbrakes for rally/drift.
 

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Very true Kyle, I think it isn't adjusted properly however. I'm trying to get the steel braided lines on before MATG, so I'll try and adjust them again. If I remember from my last brake change, we couldn't get the hand brake tight w/o the breaks squeeking all the time. I was reading on M.net last night how to adjust the parking break... I don't really understand the whole.. drive in reverse thing??
 

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Chris, let me know if you want a hand bleeding the brakes Wednesday night. I put the stainless steel flex lines in my car already. It's important to bleed the system starting from the correct rear caliper furthest away from the master cylinder and work your way forward.

I happened to have a factory workshop manual for the 2001 Miata handy. Section 04-12 discusses parking brake adjustment. Here are the steps (I've modified them slightly for clarification since you don't have the liberty of seeing the pictures):
  1. Make sure rear brake pads are adjusted properly. On the back of the caliper there is a manual adjustment gear. Insert an Allen wrench inside this adjustment gear and turn clockwise until the brake pads just touch the brake disc. Back off the adjustment gear 1/3 turn counterclockwise.
  2. Depress the foot brake pedal several times.
  3. Remove the plastic cover on the parking brake lever.
  4. Turn the adjusting nut to adjust the lever stroke.
  5. Pull the parking brake lever one notch, and verify that the parking brake warning light comes on. Release the parking brake.
  6. Turn the wheels by hand, and verify that the brakes do not drag.
 

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Mufasa in Training
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Discussion Starter #6
Either way, I gotta figure it out. The pedal feels like I'm not really hitting the brakes at all, and the car feels like it's not going to stop, even though it is. I already flushed and bled all 4 corners twice, so it's not bad fluid...
 

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Mufasa in Training
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Discussion Starter #8
What pads? How old are they? Could they be glazed or contaminated?
I doubt it. The pads (Cobalt GT-Plus's...think Axxis Ultimates made by Cobalt; Eddie was going to market them, but decided not to; I was one of the guinea pigs) in the rear have not been touched since the day they were put in less than a year ago. They seem to have a lot of meat left on them.
 

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I presume this problem is a recent development. Have you lubed the slider pins lately? This is required at least once a year to maintain proper braking performance.

Are you still running the rubber flexible lines? Do you see any cracking in them or any swelling? Has your brake fluid level in the mc dropped at all? Have you checked the junction block at the right rear for leaks? On rare occassion the piston can seize in the caliper but this usually happens to cars that have been parked in a grassy field for a while. It is possible for an internal mc leak but this is rare also.
 

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Mufasa in Training
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Discussion Starter #10
I presume this problem is a recent development. Have you lubed the slider pins lately? This is required at least once a year to maintain proper braking performance.
Yeah...it's pretty recent. The pins hadn't been lubed, and I'm still kicking myself for not getting my buddy to do it while we were working on them (he didn't think it was necessary because the caliper could wiggle freely on the pin and I don't know enough to tell him otherwise). Could it really just be a matter of the pin not being lubed properly? Wouldn't the hand brake no longer work?

Are you still running the rubber flexible lines? Do you see any cracking in them or any swelling? Has your brake fluid level in the mc dropped at all? Have you checked the junction block at the right rear for leaks? On rare occassion the piston can seize in the caliper but this usually happens to cars that have been parked in a grassy field for a while. It is possible for an internal mc leak but this is rare also.
The lines looked ok, and fluid levels have been fine (I checked it this morning in fact).

Hoping it's not the caliper!
 

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I have an exit I take on the way home that I have to be careful through. It's the only time on my drive home where I sometimes feel like my car isn't going to stop if I'm really trucking. It's just this one particular exit. I push the brakes and they feel like they're virtually non-existent. I get to the next light, hit the brakes hard again and I have full functionality. I can't figure it out.
 

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Mufasa in Training
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Discussion Starter #12
I have an exit I take on the way home that I have to be careful through. It's the only time on my drive home where I sometimes feel like my car isn't going to stop if I'm really trucking. It's just this one particular exit. I push the brakes and they feel like they're virtually non-existent. I get to the next light, hit the brakes hard again and I have full functionality. I can't figure it out.
Mine feel like that for almost every stop. It's almost like I have to floor the pedal to get any response. Two days ago, I was *rather* peeved and roared into a gravel parking lot and slammed on the brakes. As I'd suspected, only the fronts locked.

Something's definitely up...
 

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Mufasa in Training
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Discussion Starter #13
Gonna try lubing the rear sliders either today or tomorrow. Don't have a c-clamp to do the fronts again, but at least the lower front was done when the brakes were checked earlier.
 
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