NA Miata MX-5 Front Wheel Bearing / Hub Assembly Replacement

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In the previous Failure Points segment, I discussed a recent front wheel bearing failure on the Super Touring 6 Miata. This failure was abrupt, and there was no indication of issues before the session. And as promised, here are the steps to replace the front wheel bearings on the Miata. A surprisingly simple process.

Choosing a Replacement

Front wheel bearings are a known failure point for Miata’s, particularly on racecars. Replacements come in two forms. First, the front bearing can be purchased separately and pressed into the old hub. Or buy a new hub assembly with the new bearing already in place. It is far easier to replace the entire hub.

Front wheel hub assemblies come in two variations, factory replacements and aftermarket. As this was my first failure, I opted for the factory replacement from the auto parts store. I was limited on time to make the event at Nashville Superspeedway, so I had to drive a distance to an AutoZone that had 2 hub assemblies in stock. Cost was around $91 each. However, if you have more time, they can be purchased online for almost half that amount.

The aftermarket hubs are quite a bit pricier and are marketed as the ‘last front hubs you will ever need!’ At $629 per side, they better be. However, they do seem to live up to that statement and you can read more about them at Good-Win-Racing.

The Miatahubs billet front hub assembly sold by Good-Win-Racing for the NA Miata.
The billet Miatahubs sold by Good-Win-Racing are super nice with ARP studs already installed.

Removing the Old Hub

Replacing the front wheel bearing/hub is a straight remove/replace operation. To remove the old hub, you must first remove the wheel, the caliper and bracket, and the brake rotor. The wheel lugs are 4 x 17mm and the caliper bracket is held on by 2 x 14mm bolts.

Now the hub is exposed and as you can see from the video, mine was shot.

Using a flat-head screwdriver, pry the silver cap off of the spindle to expose the spindle nut. The spindle nut secures the hub and bearing to the spindle. I had to tap the screwdriver into the edges to work the cap off.

The spindle has a slight indentation, and the spindle nut should have a slight deformation into the indentation. This prevents the nut from backing out over time. Using a pick or screwdriver, pry the indentation back up and use a 29mm socket to remove the spindle nut.

I used an impact gun for this part, but a breaker bar will work as well.

(Fun fact: the spindle nut on my car was only hand-tight and led to premature wear. One of the myriads of reasons I no longer let allegedly ‘reputable’ shops touch my equipment anymore.)

NA Miata front spindle nut after the wheel bearing failure.
The portion of the nut highlighted by the arrow was supposed to be centered over the circled spindle indent. You can see an attempt was made to bend the outer ring at some point.

Issues with Removal

My wheel bearing ate itself and as a result, some ball bearings where split and deformed and I believe that caused additional damage to the inner bearing race. The inner race was stuck to the spindle, and I used an air hammer to knock it off.

NA Miata MX-5 hub removed with the damaged ball bearings from the wheel bearing exposed.
The crushed ball bearings along with the loose ones made the wheel bearing very unhappy on the NA Miata.
Air hammer being used to knock the inner race off the front spindle of the NA Miata MX-5.
My favorite tool made quick work of the last remnants of the wheel bearing.

Installing the New Hub

After removing the entire old hub assembly and stuck bearing race, clean the old grease off of the spindle with a rag and apply new wheel bearing grease. Then slide the new hub on and reinstall the spindle nut. Use a socket wrench to tighten the spindle by hand. This process will snug the rear of the hub to the knuckle stop, securely setting the bearing on the spindle. Use a torque wrench to tighten the nut to 120 – 130 ft-lbs. Finally, notch the outer ring of the spindle nut into the indentation of the spindle. A flat head screwdriver and mallet work well here.

New wheel bearing grease applied to the front spindle of the NA Miata.
The new wheel hub comes greased but a little extra on the spindle won’t hurt.
The new front hub assembly was installed on the NA Miata MX-5.
The shiny new front wheel hub installed on the racecar. And yes, that is a harmonica attached to the tie rod. One of my fellow racers was being a prankster.

(Note: Not pictured but worth noting, I used the air hammer to knock the abs ring off of the base of the new wheel hubs. My car doesn’t have abs and the ring removes easily.)

Once the new hub is installed and tightened, ensure it spins freely and with little resistance. Then replace the cap over the spindle nut. Finally, reinstall the brake rotor and caliper.

Brake rotors and caliper reinstalled after replacing the front wheel hub and wheel bearing on the NA Miata MX-5.
The finished product, new wheel hub and bearing sitting behind the old equipment. Note the shorter wheel studs on the replacement.

Swapping the Wheel Studs

This part is optional, but on the racecar, it is a must. Effectively, the wheel hub and bearing are swapped, and you are free to install the wheel and go about your day. But as you can see in the picture below, the lug nut engagement is less than ideal due to the shorter wheel studs on the replacement hubs. Compounded by the aftermarket wheels.

The shorter wheel studs on the replacement front wheel hub caused less than optimal engagement of the lug nuts.
I wasn’t too happy with the lug nut engagement with the new wheel hubs.

In my case, I swapped the wheel studs from the old hub over to the new. To do this, use a small mallet and tap the studs out of the old hub. Then, one at a time tap the shorter studs out of the new hub. When one was removed, I would slide the longer stud in its place. A stack of washers is then placed over the stud. The lug nut along with an impact gun are then used to snug the stud in place. It’s a quick and easy process and by doing the removal/replacement one at a time on the new hub, I was able to leave the rotor in place during the changeover.

Long wheel studs next to the short wheels studs from the new wheel hub for the NA Mazda Miata MX-5
Quite a dramatic difference in the long vs. short wheel studs.
One removed wheel stud from the front miata hub to install longer wheel studs.
Replacing one stud at a time allowed the rotor and brake caliper to remain in place.
Stack of washers and the lug nut are used to seat the long wheel studs on the Mazda Miata.
A stack of washers is used while the lug nut is tightened on the newly inserted wheel stud. This seats the wheel stud. (With a deep enough socket and open lug nuts, the washers aren’t necessary.)

Conclusion

There you have it. How to replace the front wheel studs on a Mazda Miata. With a few practical solutions thrown in for my case. This one was so easy I performed the work with the car on the trailer in about 15 minutes. And it ran perfect the next weekend at Nashville Superspeedway.

By Chris Simmons

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