- My model of MX-5 is: 2.0 NC Sport Tech
- I’m based near: Fife
- I’m looking for technical help or recommendations on: Rear Brake Caliper
Hi,
After getting some rust issues sorted on my car, (plus some shiny new coilovers and front discs and pads added) I have finally got my car back and its been great to drive it again. The mechanic who was doing the work said that one of the rear caliper’s was seizing, so could do with a replacement (I believe OSR). He said he greased up the sliding pins, but I have noticed a decrease in my mpg since collecting it. I used to be getting around the 30-33mpg mark and I’m now barely getting 26mpg. I’m pretty new to working on cars, so I don’t have a lot of experience when it comes to diagnosing problems.
But from my understanding, to fix a seized caliper, would it be ok to just replace the sliding pins or do I have to buy a whole new caliper as well? From the service history that came with the car, it seems to have had both the front calipers and OSR caliper replaced in 2021. So unless something random has happened since then, it should just be the sliders that are seized?
Would it be a bad idea to replace them with used but still useable calipers, as I’ve seen some on eBay for £50, compared to some other places wanting £100+. Could there be anything else causing the decrease in MPG? It could probably be the weather (as its never the warmest in Scotland!) but just thought I should ask.
Many thanks for any replies
Well first thing to check are the temperatures of each brake disc, are they even. Talking rears they never really get very hot, in normal use possibly just warm. If you have one that is hot but the other just warm you have a problem on that hot side, something binding. Usually points to seizing slide pins or seizing caliper.
Determining which needs a brake strip down, clean and the proper grease used.
Used reconditioned genuine Mazda calipers can be had for around £70 last time I looked, add shipping and probably a return your seized caliper fee which will get added then deducted upon return.
BTW test the heat on the brake however way you want don’t burn yourself or use a temp gauge/probe thingy.
I’d greased my sliders and the pad clips but both front discs got hot over the winter. My car was put on the rolling road they use for MOTs and I was shown which wheels were binding when hot and how it affected braking efficiency. A proper dismantling and clean up (by someone who does this for a living) with proper grease/ lubricant did the trick and cost me an hour’s labour for each wheel. No need as yet for any further work/replacements.
My calipers look like the originals and have done 75,000 miles.
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I have just done a refurb on all 4 calipers.
New everything ( pistons, seals, slide pins, springs, pad shims etc )
All in - appx £100
It is doable DIY if you are reasonably handy with the tools.
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Took it on a quick 10-15mim drive up to temp, then took the temperature of the rear and they were both around the same ( ~30°C when I measured). So I’m thinking it’s not anything to do with a seized caliper. Back to the drawing board I guess!
Cheers for your help
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Are there any instructions for servicing the rear calipers? Struggling to find anything! Although I think it might not be necessary at this moment in time! (Definitely going for red calipers tho, they look awesome!)
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I couldn’t find anything MX5 NC specific but they are no more complex than many manual handbrake rear calipers.
You will need a piston wind back tool.
Some long reach circlip pliers for the large circlip holding the handbrake mech in.
Having said that - if your handbrake is feeling ok - just do the main piston and seals - far easier job.
This is the kit I used - very comprehensive and all the parts fit as expected
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Short bursts of driving just a few miles aren’t good for decent mpg especially in winter. It’s been pretty cold recently which affects mpg, longer warm up times. Aircon on or off, heat on full or low all adds to more fuel use. Mine’s over 30mpg atm, I use mine for longer burst of travel probably 30 miles each way.
I was hoping it was to do with the weather and driving distance. That reassures me a bit more that all is ok!
Thanks for your help!
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I’ll have a look, cheers!
As a wind back tool, I used a G-clamp and a large socket when I redid mine. It was a front wheel that became obvious by a judder at speed and tyre temperature gauge showing over 30 degrees C
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I wouldn’t try that on the rear calipers - unless the rear pistons are rotated and pushed at the same time you will damage the handbrake mechanism.
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A simple tool like the one below is all that’s needed. Use the plate as normal on the tool for the rears to wind back. For fronts use as packing an old brake pad to push on against the caliper piston.
About £14 from Screwfix, does my NC and daily drivers calipers front/rear.
