- My model of MX-5 is: _ NC1 2006 Sport
- I’m based near: __ Wirral/Liverpool
- I’m looking for technical help or recommendations on: __ Faulty handbrake mechanism on new rear caliper?
Hi,
I had a rear caliper seize on me about a month ago so I bought a new set of aftermarket rear calipers from MX-5 parts for £140 and fitted them myself along with new slider pins and shims (pads and discs are about a year old).
Everything seemed to work great until my MOT a week ago where it failed due to insufficient handbrake reserve travel (and a hole in the rear sill but I’m getting that welded shortly) and was advised to adjust the handbrake.
I got both the rear wheels up in the air and began doing half turns on the handbrake mechanism inside the car and then rotating the wheels by hand to check when they’d lock up however I noticed one side will lock up completely while the other will still spin with some effort and never seems to completely lock even at max clicks and a significant tighten in the cabin.
I’ve looked at each caliper (photos attached) and it seems the side which won’t lock up has a lot of tension built up in the handbrake cable so does this mean the caliper’s handbrake mechanism is failing to push the piston enough to lock the wheel?
The pads on each side have pretty much the same thickness left and I’ve inspected the caliper but can’t see anything else that might be causing it. I’ve driven about 300 miles since installing them so don’t think bedding in is the issue although that would be a nice easy fix.
Is the caliper faulty or is it something else?
Passenger side works fine:
Driver side isn’t locking properly:
Any help would be appreciated 
The next thing I would check is the handbrake cables.
If one is failing internally it would pull less on the caliper.
You need to adjust the calipers. First, disengage the hand brake. Then loosen the adjuster on the handbrake handle end. Next, adjust the brake calipers themselves until the pads just start to catch. Finally, test the handbrake and tighten the adjuster so it holds after maybe 3 clicks.
How do you adjust the calipers individually? I thought this wasn’t possible on the NC
The pistons are threaded. And usually would be wound clockwise when putting new pads on. As you are using old pads that have perhaps worn unevenly, due to the old calipers, You may have to turn the one that is not applying anti-clockwise to balance it out. Probably the best option though is to just get new pads.
Can you just depress the brake pedal to push the caliper piston out?
Agreed - the NC does not have caliper handbrake adjustment like the earlier cars.
Using the brakes settles the pads to the disc.
If those two pictures were taken with the handbrake lever in the same position - It’s just an observation but the drivers side bellows ( cable cover ) is compressed much more than the passenger side one.
Do the two adjusters at the handbrake lever seem to be about equal ( same amount of thread sticking out ? )
I am wondering if the driver side cable is too tight and the fluid is not getting through easily to self adjust the rear calipers.
With the rear wheels off the floor - Handbrake off fully - I would get someone in the car to lightly push the brake pedal and see if both rear brakes apply the same force.
The manual says that the handbrake operating lever on the caliper MUST return to the stopper nut when the handbrake is released.
The photos were both taken with the handbrake at 8 clicks, I interpreted the driver side bellow being more compressed to mean that despite the handbrake operating lever being pulled sufficiently by the cable (you can see in the photos it’s actually being pulled further than the passenger side), the caliper piston isn’t pushing against the pads hard enough in response and therefore the lever reaches maximum travel without pressing the piston enough to lock the wheel. If the handbrake operating lever was stopping in the same position as the passenger side I think the more compressed bellow would look the same as the passenger side.
I’ll check to make sure both rear brakes apply the same force and also if the stopper nut returns when the handbrake is released. I can only see one adjuster nut in the cabin so can’t comment if both adjusters are equal.
Bought some brand new pads too to see if that’ll do anything, I’ll update tomorrow
Sorry - my error - different car in mind - You are correct - only one adjustment nut at the handbrake lever.
I would back off the handbrake adjuster until you are sure BOTH calipers have their actuator levers at the stop.
Then pump the brakes until both sides have the pads against the disc.
Only then - adjust the handbrake adjuster nut until you see that the cable is about to take the caliper lever off the stop.
Thanks for your help, I checked both sides and the driver side caliper lever wasn’t on the stopper nut when the handbrake was disengaged. I loosened the adjuster nut until it was on the stopper but unfortunately it’s way too loose even at max clicks and obviously if I tighten it it won’t function correctly as the lever will no longer hit the stopper with the handbrake full disengaged. New pads also made no difference unfortunately.
Decided to put the old driver side caliper back on temporarily as it wasn’t the one that originally seized and the handbrake immediately fixed itself and locked simultaneously with the passenger side even without tightening the adjuster nut meaning the new caliper was indeed faulty (my own fault for buying the cheapest option 
)
Glad you found the issue - shame it was a new part.
I decided to do my own caliper refurb using kits from Frentech.
Brakes now feel like new.
