One of the wear points for MX-5s, be they NA’s, NB’s or NC’s, are the front wheel bearings, especially when you do track days and use R-Spec tyres. Every few meetings there is always someone who has a front bearing collapse or start rumbling.
My NC had 160,000k up on the clock before the front left bearing started making a noise. This is the bearing that takes all the load at Wakefield. Ralph’s NC bearing collapsed after 50,000k when we were at Winton, luckily Ralph trailers his car to the track.
With the NC you can’t just replace the bearings as you could in the earlier models as the hub is a sealed unit. You have to replace the entire hub.
There are a couple of replacement options for the NC and the price varies accordingly;
Mazda OEM NC hub,
aftermarket NC hub,
Mazda OEM RX-8 hub (2009+ model),
aftermarket RX-8 hub (2009+ model).
If you have time, importing from the US or UK saves you a lot of $$$. The OEM hubs are around the same price for the NC & RX-8.
The 2009 and up RX-8 hub is a direct replacement for the NC hub. Avoid earlier model RX-8 hubs as they have a different ABS sensor attachment.
The advantage of the RX-8 hub is wider outer bearings designed to support the much heavier RX-8 and therefore able to stand up to the added loads of R-Spec (and slick) tyres when used on the track.
The photo below shows OEM hubs. On the left the NC, on the right the RX-8.
Look at depth from the face of flange carrying the studs to the bearing You can see the NC’s flange is around 5mm wider making the outer bearing narrower.
Also note that the where the hub fits into the hub carrier (pink grease area on NC hub), the shoulder length is a few millimetres shorter on the RX-8 hub.
This hasn’t cause a problem on the race NC running slicks so I’m not expecting a problem with my R-Specs.
Now for some instructions on how to install a new hub.
You will need the following tools:
Sockets 17mm, 14mm, 12mm & 10mm, ratchet, hammer, punch, a broad screw driver to use as a wedge and a Phillips head screw driver.
Jack up the car and remove the wheel.
Undo the brake calliper (2 x 19mm bolts) and swing it up and sit it on top of the upper wish bone. Tie it there with a piece of rope.
Use the Phillips head screw driver to remove the two locating screws holding the rotor to the hub and remove the rotor.
Remove the ABS sensor and cable from the hub (10mm & 12mm bolts)
The hub is held in the hub carrier with 4 x 14mm bolts. Loosen all 4 bolts until there is a 2mm gap between the shoulder of the bolt head and the hub carrier.
Use the hammer and tap (read whack) the bolts to force the hub from the carrier. The hub can be rusted in place so this may take a little force. Tap top right bolt, then bottom left, then top left, bottom right and on so until all the bolt heads are touching the carrier. You may find it necessary to turn the steering wheel to rotate the hub so you can get a good swing at the bolt head to get it loose initially. You may need the punch (or something similar) to get at the top front bolt.
Then wind the bolts out another 2mm and repeat the process but use the flat headed screw driver as a wedge between the hub and the brake shield on the opposite side from where you are tapping. This stops the hub twisting back into the carrier on the side you just worked on. Keep this up until the hub pops out of the carrier.
Clean up the carrier where the hub sits with some steel wool to remove any rust.
Apply a thin film of high temperature grease. I used calliper pin grease. This will help on the off chance you need to take the hub out again.
TIP: When reassembling, position the ABS opening hole on the hub at the top and then push into the hub carrier. This then aligns the four hub bolt holes which aren’t concentric, with the hub carrier holes.
Reassemble the reverse of removal. Job done.
