I had exactly this problem, brake judder and overheating. It was sticking slider pins on one front caliper (I replaced the other side as well and that was better, but not much). I replaced the caliper (which had corroded) and the pins. I found a great narrow wire brush (like a wire bottle brush) which attached to my drill and used to thoroughly clean the inside the slider housing with a liberal dosing of brake cleaner (very satisfying). Only £12 on ebay and well worth the money (link copied below). Calliper should slide really freely when greased with the correct grease supplied in the rebuild or pin kit (you can purchse a calliper rebuild kit that includes pin rubber, pin dust covers and grease on MX5 parts or ebay for about a tenner)
This happened to me on my NC and it was a sticking front brake calliper. Gently put your hand near to the offending wheel hub, it will be hot it the calliper is sticking.
Just happening to me at the moment went for a quick spin Monday realised the car wouldnt roll back when on slight incline and when setting off felt like on flat tyres…Took out last night car now rolling but noticed the front left extremely hot guess how I found out !! Dont know if Its stuck sliders or caliper with one minute seized next free??
When one of my calipers partially seized i found that the pistons had slight corrosion on it. This caused drag and prevented the piston moving back into the caliper.
As a very quick temporary measure I popped the piston out cleaned it up, put it back in the then bled and pressure checked it for leaks.
The calipers have been completely stripped and overhauled since then though.
The inside surface of the brake disc was also heavily corroded with only partial wear on it. So even if the visible surface of your brake disc looks ok have a detailed look at the inside surface.
Treat servicing the brakes as an annual event, strip clean inspect and lube with the correct product.
Like Trigger says, look after your broom, same with brakes.
I’ve seen some brakes over the years not been cared for, one of my earlier cars (not MX-5) in an atrocious condition, that’s because they were only looked at (visually) instead of a proper strip clean inspection.
Sometimes you pay for the work but they don’t always do it.
The pins arrived a few days later than anticipated.
The one i freed up last week (drivers side lower) was as tight as a yorkshiremans wallet… again
The passenger side lower had no lateral movement but would rotate.
I replaced all 4 pins this afternoon and the issue appears resolved.
Well done on sorting it out👍.
It’s all here on the forum somewhere…
I was convinced it was a problem on the rears though.
Just goes to show.