Overview
The Baer Brakes 4302438B is an SS4 Plus rear brake system kit built around a 4-piston S4 caliper and a 13 inch, 2-piece slotted, drilled, zinc-plated rotor. It is made for rear ends with a GM small pattern 10/12 bolt bearing-on-axle flange and flush mount bearing housing ends, on a 5×4.75/5×5.00 wheel bolt pattern.
Bearing on axle (BOA) means the wheel bearing sits on the axle shaft, so the rear flange has to match the kit. The Baer backing plate serves as the caliper mount and also houses a 1-piece park brake shoe assembly. Rotors come pre-assembled with NAS high grade stainless hardware, and stainless braided hoses and hardware are included.
Key features
- 2-piece, 4-piston S4 caliper manufactured in Phoenix, Arizona
- CNC machined from U.S.-sourced forged or billet aluminum
- Powder coated black finish
- Hard anodized aluminum pistons with stainless steel abutments and noise suppression clips
- Dual seals for dust, weather and pressure
- 2-piece slotted, drilled, zinc-plated rotor with billet aluminum hat
- Backing plate that carries the 1-piece park brake shoe assembly
- Stainless braided hoses and hardware included
Matching a BOA rear end
Bearing on axle designs put the wheel bearing directly on the axle shaft, so the flange, axle shaft and brake mounting surfaces all have to line up before a rear brake kit can go on. Before buying, identify the axle housing and compare its flange pattern with the kit’s stated pattern. Small differences in flange design or bolt spacing can stop a backing plate from seating correctly, so it is worth checking rather than assuming a match.
A 13 inch rotor changes the clearance around the hub, so wheel choice matters. Confirm that the wheel’s backspacing and brake clearance work with the caliper body. Rear brake work often calls for new brake hoses or a fresh park brake adjustment, and rotors and pads are commonly replaced in the same job.
- Verify the axle is a bearing-on-axle design before ordering
- Check the wheel’s backspacing against the caliper body
- Inspect axle seals while the hub is open
- Replace pads and rotors together for even braking
Specifications
| Brand | Baer Brakes |
|---|---|
| Part number | 4302438B |
| UPC | 844165049579 |
| Sold as | Kit |
| Caliper | S4, 4-piston, fixed, black |
| Axle | Rear |
| Axle flange | GM small pattern 10/12 bolt, flush mount bearing |
| Wheel bolt pattern | 5×4.75/5×5.00 |
| Lug count | 5 lug |
| Rotor outside diameter | 13.0 inch |
| Rotor construction | Vented, 2-piece, slotted, drilled, zinc plated |
| Rotor thickness | 0.81 |
| Pad type | DR1-C (FMSI DR1-C) |
| Min wheel diameter | 17.0 inch |
| Hose material | Steel braided |
| Park brake | Included (1-piece shoe assembly) |
| Park brake cables | Not included |
| Template | S135H |
| Emission code | 6 |
| Country of origin | USA |
Vehicle fitment
The kit is designed for rear ends with a GM small pattern 10/12 bolt BOA flange and a 5×4.75/5×5.00 bolt pattern, so the rear end must match both to take this kit. Confirm fit for your vehicle’s year, model and trim before ordering.
Measure your axle flange and bolt pattern and match them to the specifications before buying.
Installation notes
The backing plate doubles as the caliper mount and carries the park brake shoe, so the flange must match before any parts are fitted. Baer advises comparing the S135H template with your chosen wheel, since the 13 inch rotor fits most wheels 17 inch or larger. Have a qualified brake technician handle the install.
What’s included
The kit includes the S4 4-piston caliper, the 13 inch 2-piece rotors pre-assembled with NAS high grade stainless hardware, the backing plate with 1-piece park brake shoe assembly, and stainless braided hoses with hardware.
Not included: park brake cables.
