2017 ND RF 2.0 rumble

  1. My model of MX-5 is: 2017 ND RF 2.0 Sport Nav
  2. I’m based near: Crewe
  3. I’m looking for technical help or recommendations on: Rumbling noise.
    Hi. My beloved 2017 RF has recently developed a kind of rumble, wondering what it might be and if it’s something to worry about and/or get fixed. Some details:
    Car has a full main dealer service history, 19,000 miles on the clock, I’ve owned it since ~6,000 miles, about 2 years. Never been tracked and not driven especially hard. It’s got a Mazda warranty on it.
    The noise started suddenly about 500 miles ago, it wasn’t there on the way to the town but it was on the way back. I heard it initially above ~40 mph but I can now hear it above ~35. Not sure if it’s getting louder over time, as I’ve obviously become sensitised to it. Tried recording it on the phone and on the dashcam but it comes out indistinct.
    It is road speed dependent, getting faster and noisier as road speed increases until wind noise drowns it out at about 70. It is unrelated to engine speed or which gear the car is in and still happens when coasting with the clutch in. The noise does not change when loading up one or other side of the car when driving enthusiastically round bends.
    It’s not tyres, as I replaced the original Bridgestones with new PS4s a couple of hundred miles ago as the former were down to 3mm. It’s not the A/C fan either. Difficult to tell where exactly it’s coming from but it feels like it’s more from the rear of the car rather than the front. So I’m thinking propshaft or diff. Are these known weaknesses for this model?
    Would be interested in others’ thoughts on here as to probable cause and any ideas what needs to be done? Turning the stereo up drowns it out very effectively but I’d prefer to know what it was and get it fixed. TIA.
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Sounds like a wheel bearing rumbling.

Needs putting on a lift or jacking up and each wheel spinning by hand to listen for noise or free play.

If it’s not that, could be worth changing the diff oil, it’s only 1 litre and an easy job. Although diffs tend to growl when in gear and you come of and on the accelerator.

Do previous MoTs mention anything about wheel bearings or play?

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Thanks, I’ll jack it up at the weekend and give them a spin. Nothing on the MOT (which was only 700 miles ago), no advisories or remarks about them at all.

Surely, into the dealer?

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Agree with Nick D, it has a Mazda warranty so take back to the dealer and if possible get a technician out with you on a drive and point out the noise.

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Thanks. Yeah, I’ll do that once I’ve had a look myself at the weekend. The dealer wants money up front in case it’s not a warranty claim (no doubt the wear and tear clause will come in there somewhere), and they’re miles from where I am.

As others have said here it sounds like it could be wheel bearing failure. I take it the car is no longer under manufacturers warranty and that the warranty is the dealers own warranty/insurance. You need to check the details of the warranty that you have to see if the wheel bearings are covered. A wheel bearing going after 19K miles is not acceptable as wear and tear. Typical rolling element bearing life follows a “Bath Tub” curve and consequently it is not unknown for them to fail prematurely. If they don’t fail prematurely they can be expected to last a long time before bearing race fatigue failure occurs.

I have a friend who bought a brand new Audi A6 at the end of 2020. After 8,000 miles both rear wheel bearings failed. The car has now done 20,000 miles and the rear wheel bearings have failed again.

Prior to the Audi he had a new Kia Sportage which he owned for 3 years and 50,000 miles, he never had one problem with it.

Wow. That really is poor. The design specification of the bearings must be inadequate for them to fail that early. One, can be accepted as “infant mortality” but four in 20,000 miles is completely unacceptable. Is he driving around with his boot filled with bags of cement/sand?

No, he just commutes to work 6 days a week 20 miles each way with only him in the car. He also does some long distance journeys just him and his wife 200 miles each way to visit relatives.

He is very carful with his cars and they are never driven hard.

There is a lot of Weibull going on here!

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So here’s a little update. Car went into the dealer, they test drove it and experienced the noise. They then lifted it in the workshop, ran it stationary while it was up there, went over everything, even with a stethoscope on the diff, etc. No excessive play in anything, nothing about to fall apart. A little bit of surface rust on the inner side of the rear discs. They drove it a couple more times on different road surfaces and agreed it is not road surface dependent. Their conclusion is that it can only be the tyres. According to them, the new PS4s are a much harder compound than the factory-fitted Bridgestones and that’s the cause. Yet the problem didn’t start when the tyres were first fitted. It started suddenly. Thoughts?

Standard dealer reply . No fault found

Surely if it was the tyres causing the problem everyone on here running PS4’s would also be moaning about the noise ? and they’re not.
On other cars I’ve had they were noticeably quieter than what they replaced, and not an issue.
Could you try another set of wheels/tyres? It wouldn’t matter what tyres were fitted.
Hope you get to the bottom of it.

recently we had a PX ford focus that we swore had a bearing problem on the back, coincidentally got a puncture so new tyres for it (we only do pairs for safety) and no longer any noise from the back. I was shocked at the difference the tyres made.

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The Focus and the Volvo C30 (same platform) have had an issue with the rear tyres feathering and becoming ‘noisy’. Apparently it was the rear steering set up that was to blame.
:heart:

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@Overdrive Exactly, which makes me think it’s not the tyres.

@Mad_Malc The PS4s were brand new and the problem showed up after about 600 miles on them. I’ve done about another 400 since. They’re definitely not feathered. I’ve seen feathered tyres before on the front of my BMW.

I agree with you. I was explaining the likely cause of the issue that ‘harco’ had experienced.
Have you tied swapping fronts to rear to see what happens?
:heart:

This is a good point. We have a Yeti that was fitted with some sort of Michelin tyres at the front. A rumble from the front got worse and worse and I was convinced it was a wheel bearing. I jacked the front of the car up and rotated the wheels to see if I could hear anything. I also checked for play. I began to suspect the diff. Anyway at that point we thought we were going to trade the car in shortly, so we ignored it. However in the end we didn’t trade the car in. A few weeks later car was due it’s MOT. The front tyres were getting towards their legal limit so they were replaced by some Kumhos before the MOT. Voila! The rumble disappeared completely.

So yes, there is something to be said for checking the tyres :crossed_fingers: :+1:

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