Interesting to see this old trait continuing with the mk4, my mk1 had the same symptoms when I got it. Took a while to track it down but replacement pins solved the issue. What also solved it temporarily was to liberaly grease the old sliders with lithium brake assembly grease - did you apply some to the new pins when you put them on? that might get rid of the last bit of noise.
Bob is the oil guy and myriad others say not to use lithium or other non rubber freindly greases on slider pins. Is there a rubber friendly lithium version?
Yes, used all the grease supplied. I suspect if the car itself was noisier the caliper rattle wouldn’t intrude. It only makes a muted clonk over the worst bumps now. Specially fitted pins, perhaps extra plating to make the diameter larger?
Not sure I can be bothered, but experimenting would be cheap enough.
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Apologies, I’ve just looked and I think it’s silicone based rather than Lithium 
Bit late to this, as we have been away. I have a similar problem that has been ongoing for 2+ years. Have ordered the same pins and will feed back. I also have new bump stops, that I have yet to fit, however new pins are less effort to will try that first. The car is a 3.5 sport, so don’t want to replace the shocks at £220+ per side, if possible. One cause of knocking I found was the jack in the RHS compartment in the boot, mine is now wrapped in bubble wrap and tightly fastened. As others I have found less noise if someone is in the passenger seat.
Puddle, I’ve now taken the pin thing to its logical conclusion, fully fitted pins machined from a larger diameter pins set. They are a sliding fit and have quietened the knocking hugely, but not completely. Interesting that you’ve noticed it’s quieter with a passenger, so is mine I think. It’s a Mk4 rather than 3.5.
Assume the pins must be the same for 3.5 and 4? Mine are for a nominal 10mm diameter bore in the caliper bracket, the plain pin has the largest clearance, it’s about 9.65mm and the flatted one 9.85mm. Noticeably quieter after fitting two of the larger pins instead of 1 small, 1 large.
Good luck!
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Well had a result from Mazda UK about the top rose bush on the rear hubs , they are paying 70% of the cost to replace both the rear hubs so I’m well pleased with that
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Thanks for letting us know 
just collected my Mazda from the dealers after having new rear hubs fitted it feels like a different car now with no knocking and noise from the rear , it was worth getting the hubs changed as the knocking was getting more and more frequent.
also a big thanks to Pentagon Mazda of Lincoln for sorting this out for me
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Thanks for the update. If I have any problems like yours, I think I may well be going to Lincoln , Chris
It’s worth going through Mazda UK which is what I did and I managed to get the work done via good Will , which Mazda paid 70% of the total cost
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Having carefully examines all the bushes in my rear suspension plus improving the fit of the caliper slide bolts, I did a search of the internet for Bilstein problems. The only common themes were harsh ride and knocking noises, not just from Mx5s but also others, mainly BMWs.
Not much other detail except some claimed new dampers, either Bilstein or other makes cured the noises. Having exhausted all other avenues I cracked and bought a new pair of Bilsteins, these specifically
https://www.bilsteinsuspensionstore.co.uk/bilstein-b6--sport-damper-24249584_p31599783.htm
Took the old ones off and tried to make a comparison moving them by hand - no appreciable difference. So, somewhat depressed, fitted the news ones with no real expectation. Test drive this morning, silence, bliss! Turns out 50k old dampers are not as good as new ones, even if totally leak free.
Here’s my assessment. Dampers have two operating conditions, a slow movement that relies on fixed orifices to damp, and a fast movement [eg sharp bumps in the road] where deflection of washers in the damper further control damper speed. The less control there is over wheel vertical speed and tyre bounce, the more likely it is that the brake caliper will be ‘rattled’ creating the clonking noise. No idea what wears to lower the damping effect.
Anyway, £260 well spent…
Question for those who took their cars to a dealer. Did you ask them to cure the noise, or something more specific, like actually changing the uprights? I don’t imagine any manufacturer is going to come right out and say ‘no we didn’t change the uprights, but we did fit new dampers cos we know that’s the problem’. A good check would be to read carefully what they say on the receipt for the work done. Just a thought…
Now that’s got me thinking… Anyone else???
As I understand it, motor oil has intact polymer chains when new and those chains get chopped up with use and age, reducing the viscosity and effectiveness of the oil
It may be this that causes the reduced damping over time.
Motorcycle fork oil is supposed to be changed at intervals, so it may well be that changing your dampers for new ones will be beneficial even if there is no apparent wear or leakage.
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We are saved, just how do we get this?
My two week old ND2 has just started knocking today… from the rear… and it goes silent when I brake - please let it not be this!!
There are two things that I’ve found to cause knocking on my car, the brake calipers on their slider pins and also the drive shafts have a small amount of movement that seems to cause a similar knock when moved with a sharp tug axially. In the end what the car needs is to be as noisy as previous models in the engine and exhaust department, would drown out the other stuff. Mine is ‘silent’ with the hood down, but the odd knock can be heard with it up, all to do with acoustics I think.
New rear dampers helped my car, but won’t be an issue on a 2 week old machine (you’d hope!)
Two weeks old (not s/h?) don’t mess about, it’s under warranty, take it back to the dealer and let them put it right!
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My 3.75 has had an annoying knocking noise since purchased at 50K miles. After 2.5 years solved, jacked up the car and lifted the dust shrouds covering the tops of the shock absorbers. I found a plastic cover on the shocks that was probably originally glued to the absorber, both of mine were loose. As a trial I have squeezed grease in - result is after 2 years no more knocking. Also check out a loose jack in the boot, this too can give a really annoying noise.
Hope this helps.
Ps - sun out = roof down
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So after a look under the following night after the noise started I found the rear callipers (with handbrake assembly) to move freely and discovered the 4 rear calliper bolts to all be a little more than a 1/4 turn loose.
Sorted now and no trouble at all. To mention I understand these mustn’t be FTight due to the heat and expansion cause from braking?
Cheers
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