Hello! I’m new to the MX5 scene, owning an NB since July. I bought it with only 21K miles but after using it as a daily it has developed some issues I believe from being in storage by the previous owner.
I just changed the front bearings but still hear some similar noise. How do I know if it is the rear bearings or the differential bearings?
Thanks!
Bearings at such a low mileage? I wouldn’t have thought it very likely at all but I suppose you never know. Have you, er, checked the MOT history of the car? Is that mileage legit? I have never EVER heard of wheel bearings degrading from a vehicle being stored, only driven. Since it is a similar noise, are you sure it isn’t a different issue entirely, such as brakes, which can go a bit funny if not used in a long time.
The easiest way to tell if it is the wheels or diff is simply to listen. If you’re feeling brave, jack up the rear of the car, start it and get them spinning.
To test wheel bearings: Jack up the relevant end of the car. Spin the wheel. Do you hear any grinding that is not coming from the brakes? Bearings that have shed their grease will give a constant smooth grinding noise, always reminds me of a roller coaster. You will hear the roller coaster at lower speeds as you’re driving, and it will turn into a resonating whine at higher speeds. Next, grasp the wheel firmly and move the wheel by pushing and pulling perpendicular to the car, then shift your grip 90 degrees, so if you were on both sides you’re now at top and bottom and repeat the motions. If a wheel bearing has worn out, you will get a (normally quite subtle) amount of play when you do this. Bear in mind that if it is a bearing, you will get play around the entire rim of the wheel. It is easy to get confused because all sorts of things can cause play, like control arm bushings and tie rods to name a couple, although these parts generally give you more side-to-side play than top-to-bottom.
As for differential bearings… Unless the diff is or has leaked a lot of oil, I really wouldn’t be too concerned about your diff. Mazda seem to have been able to provide incredibly capable differentials for decades now, and it’s one part I’ve never had to deal with on a 5.
I would top up the gear box and diff oil just to be sure they are not ‘low’. Ideally you should change both.
If you do the above instructions (grasp the wheel firmly) and feel some play then get someone to push the brake pedal firmly and see if the play goes and returns when the brake is released. If this is the case then it is 99% certain to be a worne wheel bearing.
Awesome, I’ll try these! Thanks!
Not on a MX5 so far, but I have had two vehicles I was convinced had a wheel bearing issue, which was in fact tyre wear! Seems some tyres cause a similar noise/rumble as they wear, before they become illegal.
When I took it to a tyre specialist they confirmed ‘sounds like wheel bearing issues, doesn’t it?’ It was noise related to speed (but not a tap like there was a nail in the tyre)
That said for sure the tests suggested in the thread should confirm if there’s a real problem with the bearings.
Thanks, everyone, for your input! I was able to change the passenger side rear wheel bearing and that was it! It progressively got worse so I just did it myself and the car rides smooth now.