8 replies to this topic

[MMiskoe]

NA- 1.8 running stock brake parts (calipers, rotors, master cyl etc).

 

Problem - when the brakes get hot on the track, the fronts won't release.  They bind and often need to run over curbs/dragon teeth to get them to un-stick. 

 

Thing's I've tried

   - rebuilt calipers with "parts store" seals

   - rebuilt calipers with seal kits from Mazda

   - replaced calipers with "parts store" calipers

   - replaced hubs

   - swapped spindles

   - while the brakes are hot and the hub is hard to turn

          - open the bleeder - no change in resistance to turning the wheel, no fluid comes out

          - push the pistons back and the slides move easily

 

 

I've been running Miatas for 20 years now without any issues with brakes, but this problem has been nagging us for the past 2 years. 

 

Where are people buying replacement brake parts?  What tricks have people used to negate this sort of thing?

 

Any insight would be useful.

 

Thanks

 

[Jeff Wasilko]

I've had great luck with Drago's rebuilt calipers.

[LarryKing]

Are you using the OEM brake hardware? (The little metal clips that go in the caliper bracket where the "ears" of the pads ride, lubricated with brake grease)

 

I know a lot of people discard them, and say they are not needed. I have always used them with no issues.

[MMiskoe]

No clips/hardware, they always seemed that they would make this sort of problem worse. 

 

I'll check out the Drago calipers.

[Jim Drago]

NA- 1.8 running stock brake parts (calipers, rotors, master cyl etc).

 

Problem - when the brakes get hot on the track, the fronts won't release.  They bind and often need to run over curbs/dragon teeth to get them to un-stick. 

 

Thing's I've tried

   - rebuilt calipers with "parts store" seals

   - rebuilt calipers with seal kits from Mazda

   - replaced calipers with "parts store" calipers

   - replaced hubs

   - swapped spindles

   - while the brakes are hot and the hub is hard to turn

          - open the bleeder - no change in resistance to turning the wheel, no fluid comes out

          - push the pistons back and the slides move easily

 

 

I've been running Miatas for 20 years now without any issues with brakes, but this problem has been nagging us for the past 2 years. 

 

Where are people buying replacement brake parts?  What tricks have people used to negate this sort of thing?

 

Any insight would be useful.

 

Thanks

What brake pad compund are you running?? 

[bmarshall1]

Not Miata related but one time on an "86 Honda Accord. I replaced the MC, the plunger (from the brake pedal) that pushed in on the MC piston had threads, I decided to remove any play between the plunger and piston by using the threaded portion to remove any slop/clearance.  Unfortunately while driving the brakes and fluid heated up and expanded, there was no room for the plunger to move so the only way for the system to remove the pressure was to push the caliper pistons instead, thereby applying the brakes.  I had it towed home and once it cooled I could drive it (not far).  So I put some play back into the plunger/piston set up and wa'la, problem solved.

 

Also, how old are your lines, I have heard of  lines collapsing internally and/or separating from the outside layer and creating a one way valve.

 

Someone smarter than me might be able to say if the proportioning valve could cause this.  Both front wheels equally? Is one hotter than the other.  If you apply the brakes during this scenario does it still track straight or pull to one side. Generous lube on the slider pins?

 

Brake pad return hardware installed? Pads themselves binding in the caliper?  I will take a file to the metal edges of the 'ears' where they contact the caliper to eliminate any sharp edges that might grab.

 

So, likely you are either building pressure, unable to release releasing pressure, or something in the system is binding.  Let us know what fixes this.

[MMiskoe]

Sorry, got doing other things and this fell off the current list.

 

 

Pads - Hawk Blue, Hawk ER-1, Pagid yellow's.  All act the same in regard to brake drag.  We've reduced them all down to the backing plates.

 

Pressure build via fluid - I don't think so.  While everything is hot and the pads are binding you can open the bleeder and nothing changes.  If there was pressure on the fluid, opening the bleeder would remove it.  You're not the only one who has suggested this as an issue.

 

From what I can tell it is the piston binding in the caliper.  I was expecting that the Mazda seals would do a better job than the Dorman/parts-store grade, but they weren't appreciably better.

 

Another question for the collective group - with the bleeder open, and everything cold is there a measure of how stiff the piston is to push back?  Can you do it by squeezing it with just your hands? 

 

Drago calipers are looking like a decent option if they have good track record of behaving. 

[Tom Sager]

Sorry, got doing other things and this fell off the current list.

 

 

Pads - Hawk Blue, Hawk ER-1, Pagid yellow's.  All act the same in regard to brake drag.  We've reduced them all down to the backing plates.

 

Pressure build via fluid - I don't think so.  While everything is hot and the pads are binding you can open the bleeder and nothing changes.  If there was pressure on the fluid, opening the bleeder would remove it.  You're not the only one who has suggested this as an issue.

 

From what I can tell it is the piston binding in the caliper.  I was expecting that the Mazda seals would do a better job than the Dorman/parts-store grade, but they weren't appreciably better.

 

Another question for the collective group - with the bleeder open, and everything cold is there a measure of how stiff the piston is to push back?  Can you do it by squeezing it with just your hands? 

 

Drago calipers are looking like a decent option if they have good track record of behaving. 

 

A video showing brake drag on jackstands hot would be meaningful but tough to do in NH this time of year.  Hot or cold with bleeder closed you should be able to push back the piston into the caliper using channel locks pretty easily with 1 hand.   I've had a caliper or two drag over the years and just replaced them usually with East Street rebuilds and that has done the job.  A pad bind (cockeyed) or pin bind can do that but it sounds like you've checked that.  

[TylerQuance]

This could be caused by bent caliper brackets. If the brakes have ever been bled without the rotors landed flat against the hub with a lug nut, the force from the piston will not be acting normally to the rotor when you press the pedal.

Our single-piston floating calipers cause pads to taper and the drag gets worse every session until you replace pads again. I have found new seals do a better job keeping the piston straight in the bore. For a little while anyway.