There's a lotta neat engineering in the ND wheel hubs..

I finally tore apart the wheel hub assembly to figure out the exact failure mode after smacking a curb in the ice a few months ago.  In addition to bending an arm or two, it also toasted the bearings, I'm guessing a ball or two has a flat spot.

That's not the point of this post, though..

I was surprised to see the ABS tone ring on these this is solid! 

The ring itself is magnetic, and that's what the reluctor/hall effect a sensor is picking up:

The other neat thing is that they appear to friction weld the front and rear hub assembly:

That's a really cool manufacturing idea... Perfect preload every time.

There's no point here, I just thought it was cool and hadn't seen anything like it before.

The ND is full of all sorts of clever stuff. I didn't know that about the hubs.

I've been meaning to chop up an old hub bearing to see what's in there and how it's held together.  When you think of the weight and leverage on those, it's amazing they work as well as they do, I guess just good materials and precision.  And then, three or four bolts holding on when there's four or five out at the wheel.

I'd guess the tone ring has a series of small magnets to create the pulses. The wheel bearing in a Suzuki SX4 use a similar setup for the tone ring (black disc in bearing in photo)

I only figured it out because a previous owner used a bearing from the Bezos site that had the wrong number of magnets in them triggering the ABS light and disabling the awd. 

In reply to No Time :

Wow, that's a heckuva diagnosis.  Nice job!

Yeah, I'm assuming that it's an alternating +- pattern, but I lost our magnetic viewing paper.. I'll confirm when the replacement gets here.

In reply to WonkoTheSane :

I lucked out and have a scanner that could view all 4 wheel speed sensors at the same time. I was expecting to see one working intermittently , but ended up seeing one was always different than the other three. 

I replace the one that was off with an SKF and everything was back to normal. 

Update, my (replacement) magnetic viewing film arrived..

Check out the resolution!

In reply to WonkoTheSane :

That makes most tone rings seem course, actually I guess they are in comparison. 

I love this kind of information! I've been trying to gather information on the nd front suspension. It seems like a perfect front for swapping into other stuff, just like the NA/NB stuff, but more aluminum, bolt in hubs, and a flipped lower ball joint.

No Time said:

In reply to WonkoTheSane :

That makes most tone rings seem course, actually I guess they are in comparison. 

Not as much as you might think. I run the rally computer in the Targa Miata off a 1994 Miata ABS tone ring. It sends 44 pulses per wheel revolution, which is equivalent to 1 pulse for every 41mm ( 1 5/8") of distance traveled. I'd say this ND one is approximately twice as fine.

Here's the cut down version, the resolution of my WRC-spec Coralba rally computer is "only" 10 cm.

In reply to Keith Tanner :

I didn't think about it in terms of distance traveled, but now that you've put it in terms of distance, it is pretty impressive (even at 10cm).

I only thought about it in terms of distance traveled because that's what I was trying to achieve. 

Here's another way to look at it. The old 44 tooth wheel had a tooth every 8.2 degrees. The ND one is going to be about every 4. Even 8 degrees isn't much.

Or, if we look at it relative to time - a 1995 Miata wheel is rotating at 916 rpm at 60 mph. With 44 teeth, that's over 40 KHz.

If I'm counting right, that ND tone ring seems to have 100 teeth. It's probably something like 101 so it can be a prime for an obscure engineering reason, but that's an 86 KHz signal at 60 mph. Or one pulse every 3/4".

Also, I need some magnetic viewing film.

In reply to WonkoTheSane :

TIL that magnetic viewing film exists.