- My model of MX-5 is: 2000 NB
- I’m based near: Fife
- I’m looking for technical help or recommendations on: Rear brakes binding with new pads
On the rear the nearside brake is fine and rotates with a little bit of rubbing but doesn’t instantly come to a stop, so good enough.
The rear outside brake though? The outside pad (non piston pad) is right up against the rotor. When the wheel is tightened up, it’s a complete bind and that the car can’t even rotate it when the car is on jacks.
I’m not sure how to diagnose this. I thought perhaps the rotor is warped but it’s an even bind all the way around, so I would have thought that means the rotor is concaved but it’s not (used a rule across the surface). Is there anything else that could be causing this? The mounting bracket looks fixed correctly and doesn’t have spacers or anything, don’t think that material can bend and is more likely to break if it was under stress?
Any advice? Currently hovering over the buy button for a replacement set of brakes + rotors but I have a feeling that’s not the issue.
Have you fitted the new pads and did you adjust the caliper/handbrake correctly?
Did you also check for free movement in the slide pins, assuming you did the fitting?
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Yep. Slide pins are clean and move freely (with no pads in ofc). Caliper is wound all the way out, handbrake is off. The piston is no where near the rotor, but the non piston pad is right against it.
Worth noting, the wheel moved freely with old pads, but those had <2mm of life left so I’m not surprised that it did lol.
Brake pad spec sorry, Mintex 1144. I’m just taking a closer look now, I think some pictures might help. Will snap some and attach them to OP.
It actually looks when I’m putting the bottom slide pin in, I’m putting pressure on the caliper to align the bolt with the thread and perhaps when I remove this pressure the slide pin is not sitting straight. Maybe.
You have wound the caliper piston back then on again with a 4mm allen key in the rear of the caliper?
Did you fit loose shims…not always needed
Yep. I’ve complete reset the brake more than once. 4mm adjuster all the way out, push piston back in with tool, fit to car and without even touching the adjustment the outside pad is right up against the rotor. If I tighten the wheel, it binds.
No shims on these pads.
I’ve made a bit of progress in identifying what I think is the problem. When I put the pads in and let the brake rest in it’s natural spot, I have to push down slightly to align the bottom slide pin with the thread, I’m assumign that once everything is tightened up that perhaps there is upwards pressure which is causing the slidepin to not run true in the slot.
I also noticed that it looked like the top of the pad was pressing against the caliper, so I ground away a tiny little bit of the top of the pad backing material and now the brake sits almost inline with the thread.
I’m thinking something is bent?
You don’t push the piston in with a tool on Mk2 rears, you wind them in/out.
Around 1 min 50 secs in on video…
Well that would explain why it won’t go in any further, good news is I didn’t force it in with the tool, it was already all the way in, sooo, that’s lucky lol.
I’ve snapped some pics, first pic you can see that the pad is right up against the rotor. I have pushed the rotor flush as if the wheel was secured. It rubs
This pic here is the opposite side with the caliper wound all the way out. The caliper simply can’t come over far enough. I know there is corrosion on the piston, I’ve already had the seal off and it doesn’t appear to extend into the housing.
What could be causing the outside pad to sit so tightly on the rotor like that? The other side is fine, like it rubs ever so slightly but not enough to be of concern.
Wind the piston out onto the disc. I would hold the disc in place with a couple nuts so it’s fits flush to the hub before any adjustments.
So done this, ran it out until it locked up then backed off 1/4 of a turn. Can see light ever so slightly through it.
I’ve been at this point a few times, from here it is still binding, needing a bit of effort to turn with the wheel off. With the wheel on, it’s binding heavily. I also tried giving the brake a good stomp to make sure the caliper is sitting true but still the same.
I’ve managed to solve this. I just don’t think the tolerances in the pads are great.
The actual caliper itself was pressing down on the pad, which of course was pressing it into the spring clips nd preventing them from moving. In order to get the bottom slide pin in, I had to apply light pressure to align the threads. However when you let go, I now had the inside of the slide pin bore pressing against the slide pin, causing even more bind.
I modified the pads slightly:
So the great area is where the caliper was putting pressure. I skimmed that with a cutting disc and removing a hair of material, and now the pads fit perfectly with zero binding, wheel does a good turn before stopping.
I’m not sure if this is because these pads are from the Finish Line on eBay and are perhaps not subject to the same tolerances as buying them retail? Not sure, just glad they are now in.
I remember (it was approx 12 year ago) buying some Mk1 rear pads for replacement they were a very tight fit. I took a very slight amount off the location tabs much the same as you describe. In the end these pads started to chatter eventually, I could hear them hood down at slow speeds.
I bought some of a different make in the end and all good from fitting, the fit was perfect.
I suspect the same is going to happen because now they aren’t seated against the top of the caliper, well one is because I was less agressive with the cutting wheel but I don’t think it really matters, car is only driven at track and noisy pads is the least of my issues with this car.
I appreciate all the help.
