E30 M3 ABS Sensor Rings

E30 M3 ABS Sensor Rings

The factory E30 M3 front wheel bearings (# 31-21-2-225-362) continue to increase in price and are not always readily available. A few years back, there was a 6-8 month period when they were on backorder from the manufacturer (SKF).

In order to provide product to E30 M3 owners who needed front bearings during this period, I manufactured my own ABS sensor rings. The M3 rings are made to be used with front E28 5 series bearings (a heavier model and presumably a stronger bearing...all 5 series, including the M5, use the same part).

Bearings are available for sale separately or installed on new E28 bearing assemblies (no labor charge or the ring conversion).

1. The E28 sensor ring is 96 teeth, the E30 M3 ring is 48 teeth. A factory wheel bearing sensor ring (mfg = SKF) was sent to a metallurgist for analysis so we could use construct the new pieces of the same material and hardness. The factory rings, when analyzed under a comparator at the machine shop, were shown to be cut poorly... SKF's tooling for this piece is apparently showing its age. Here is the stock SKF ring (an E28 piece, right) next to an Ultimate Garage sensor ring (left). Note the height difference. I also had the new rings plated for surface protection and aesthetics.

2. Removing the factory rings from the stock E28 wheel bearings.

3. Special press attachment ensures the Ultimate Garage sensor ring is pressed onto the E28 bearing evenly. If not done properly, the ring may be damaged which could affect fit and sensor readings.

4. A 2.5mm thick washer is placed atop the bearing as a "stop-limit" . If the thicker E30 M3 ring is pressed all the way to the seat on the bearing, it may not align properly (when the bearing is installed on the car) with the ABS sensor.

5. Pressing the sensor ring onto the E28 bearing. Travel will stop when the press plate hits the washer (shown above).

6. Close-up photos of the new M3 sensor ring on the E28 bearing.

7. A pair of new bearings ready to install on an E30 M3.