Rockwell / Quality 10K Electric Brake Hub Drum Kit – #99 Spindle – 4.88" Pilot
Part Number: 99865-1PAB-KIT
This hub drum kit is engineered specifically for Rockwell American / Quality 10,000-lb trailer axles using the #99 spindle. It is not a generic 10K assembly. Every component in this kit is dictated by spindle geometry, bearing stack, seal land diameter, and drum depth unique to Rockwell-pattern axles.
Why This Kit Exists
Rockwell and Quality 10K axles follow a different design lineage than modern Dexter 10K and 12K running gear. While capacities may appear similar on paper, the physical dimensions are not interchangeable. This kit exists to correctly service trailers built around the #99 spindle standard, which has remained dimensionally consistent for decades.
#99 Spindle Geometry (The Anchor)
The #99 spindle defines the entire assembly. If these measurements match your axle, this kit is the correct solution:
| Inner Bearing Journal | 2.00" diameter |
| Outer Bearing Journal | 1.75" diameter |
| Seal Land Diameter | 2.75" |
These dimensions immediately exclude Dexter 10K short spindles, Dexter 12K / 15K spindles, and Lippert LCI 10K variants. If your spindle measures differently, this kit is not compatible.
Bearing Stack (Non-Negotiable)
The bearing pairing in this kit is a long-established Rockwell standard:
| Inner Bearing | 28580 (2.00" ID) |
| Outer Bearing | 25580 (1.75" ID) |
If your axle uses these bearings, the spindle family is confirmed.
Drum Dimensions & Braking Capacity
The drum supplied in this kit measures 12-1/4" × 3-1/2". This width is critical for heat dissipation under sustained braking loads and is characteristic of Rockwell 10K electric brake systems.
- 12-1/4" diameter matches Rockwell brake shoe geometry
- 3-1/2" width supports true 10K braking loads
- Not interchangeable with 3" or 3-3/8" drums
4.88" Pilot Bore (Hub Family Identifier)
The 4.88" pilot bore places this hub squarely in the Rockwell / Quality 10K family. Smaller pilots indicate lighter assemblies, while larger pilots move into 12K+ designs.
Oil Bath Configuration
This is an oil bath hub assembly by design — not a grease conversion.
| Seal Size | 2.75" × 3.779" (OB27377 / 91030) |
| Oil Cap Assembly | 3.75" cap with O-ring and plug |
What’s Included
- 12-1/4" × 3-1/2" electric brake hub drum
- Inner bearing: 28580
- Outer bearing: 25580
- Oil seal: 2.75" × 3.779"
- 3.75" oil cap with O-ring and center plug
- 8 × 5/8" swivel lug nuts
How to Validate Fitment
- Measure inner bearing journal: must be 2.00"
- Measure outer bearing journal: must be 1.75"
- Measure seal land: must be 2.75"
- Confirm 8-lug wheel with ~4.88" pilot
If all four checkpoints match, this kit is not just compatible — it is correct.