Binding front brake

[chadz]

Hi
I've got a problem with the front nearside brake binding.
The caliper, disc, pads all new 3 years ago and greased using the correct grease on caliper, and pads to aid movement. The guide pins top and bottom lubricated and caliper moving/ sliding as normal.
Before putting wheel on rotated to ensure not binding.
Spreader springs in place and working. On the road after braking a couple of times the brake is binding. Excessive heat and very noticeable retarding of forward movement. Any ideas what is going wrong?

Chadz.

[blackyb]

Pistons seized would be my guess.
Strip her down and see of the piston pushes back in easily. The piston should as far as I know, move back into the housing slightly after the brake pedal has been applied, when they start to seize, the dont.
Either buy a rebuild kit ( did this to a former mx5 we had, not too hard to do) or for ease and speed, get a new caliper ( if its the piston then I would replace both sides)
But what do I know, according to the wife NOTHING USEFULL.

[chadz]

Many thanks.
The piston did go back in with a rubber lube on the seal and silicon grease on the exposed part of the piston. No visible corrosion. As you said the piston must be the culprit.

Chadz.

[blackyb]

When we bought our current mk1, it had the same symptoms. As it was then our 2nd mx, I ordered two rebuild kits, stripped both calipers down, cleaned and rebuilt them with new seals and pistons. Never had a problem with the fronts since.

[Mazda Mender]

Are you 100% sure it's not a brake pad sticking? .
Now for the last 3 years have you serviced the brakes with a routine refresh ...clean,regrease, reset and bleed air out of the calipers? If you have just done them the once 3 years ago..? Then chances are it could be a slider sticking, pad on the slider clips, or pot rusted on the inside.
M-m

[chadz]

Hello and thanks for your suggestions regarding my binding brake.
When I changed the caliper etc 3 years ago I used the correct Girling brake hose clamp to prevent the brake fluid leaking out.
I believe this has resulted in the rubber hose collapsing inside and forming a one way restriction, not allowing the pressure to ease when the brake pedal is released.
The hose would have been 21 years old so even using the correct tool the crushing effect has caused the damage above.
I will remove the wheel, pump up the brake and see if it is binding. If it is I will open the bleed valve to see if the reduced pressure in the caliper allows the disc to rotate without binding. If so, the hose must be the problem.

Chadz

[GlennyGills]

Sounds like excellent detective work - hope you solve the problem

[chadz]

The plan was implemented and I have to report that the brake is still binding.
Greased up with plenty of movement on the slide pins, disc revolving nicely, engine started, brake pumped and disc held tight. Caliper nipple opened, no change, so not the brake hose. A few taps on the caliper body with soft hammer, bingo disc turns, no binding.
But that is no good because when the brake is applied again disc is clamped tightly when brake pedal released.
Because the caliper is in my opinion OK I am going to change the hose anyway 'cos it' s 24 years old and the caliper is just 3 years old.
Is the answer to my problem something I have overlooked?

Chadz.

[blackyb]

Not an MX but bro in law had a Mitsubishi 4x4 with sticking brakes, after checking the calipers by applying the brakes first, brakes stuck on. Undid the bleed nipple and brakes eased of. Process of elimination it was in this case the master cylinder which we stripped down and rebuilt..

So you could try that first and see if the brakes ease. Brakes on and off, check! if stuck undo the bleed nipple and see if it eases off, if not then I stick by my original diagnosis, piston sticking, caliper might only be three years old but if moisture is in the system, they soon rust up internally especially if subject to little use and long layups.

I would swap out both calipers for new (not cheap bay of E) and give the system a right good bleed so she has nice clean fluid in. That said, i'm a little OT when it comes to our MX.

[Mazda Mender]

The only time I have had a OE brake hose collapse inside is from being clamped off for a long long time, not a couple of days or a couple of weeks, I have had people here to sort that were stupid enough to clamp a braided S/S hose which they do not understand after explaining ,that it is just a plastic tube with S/S braid around it and is simply to stop flex for direct pressure to the caliper pot, so clamping crushes it.
Like I say ,I would be very surprised if it is the OE hose at fault, but everyday can be a learning day, what did you use to clamp it ? and by any chance are we talking about the so called large "sports brakes" ?.
M-m

[chadz]

Standard brakes. I used a girling hose clamp where 2 round bars clamp together.
I have sent for a replacement caliper, hoping it is a sticking piston.


Chadz