ISUZU NHR NKR Front Wheel Cylinder Cup Set OEM Fit 1-1/8 inch Bore Hydraulic Brake Sealing Kit with NBR/EPDM Rubber Material
| Factory Number: | 5878316020 / 5878305380 | Engine Compatibility: | 4JB1 |
| Temperature Range: | −40°C To +120°C | Material: | NBR (Nitrile) / EPDM Rubber |
| Unit Weight: | 0.04 Kg | Cylinder Bore Size: | 1-1/8 Inch (28.58 Mm) |
| Fluid Compatibility: | DOT 3 / DOT 4 Brake Fluid | Kit Contents: | Cup Seals + Dust Boots (per Wheel) |
| High Light: | OEM Fit Front Wheel Cylinder Cup Set,1-1/8 inch Bore Hydraulic Brake Sealing Kit,NBR/EPDM Rubber Material Wheel Cylinder Cup Seals |
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Front Wheel Cylinder Cup Set 5-87831602-0 5-87830538-0 5878316020 5878305380 for ISUZU NHR NKR NKR55 4JB1 — Verified OEM Fit 1-1/8" Bore Hydraulic Brake Sealing Kit
The Front Wheel Cylinder Cup Set with OEM numbers 5-87831602-0, 5-87830538-0, 5878316020, and 5878305380 is a verified direct-fit replacement for ISUZU NHR54/NKR55/NPR57 light trucks equipped with the 4JB1 diesel engine. This cup set is a critical hydraulic sealing component of the front drum brake system, responsible for maintaining brake fluid pressure inside the wheel cylinder and ensuring even braking force transfer to the brake shoes.
The front wheel cylinder cup set functions as the primary hydraulic seal within the wheel cylinder. It converts hydraulic brake fluid pressure into mechanical force that pushes the brake shoes against the drum. The cup-shaped design features a precisely angled sealing lip that expands under hydraulic pressure — the tighter the braking force, the tighter the seal. ISUZU genuine cup sets are manufactured to exact OEM bore diameter and lip geometry specifications, ensuring consistent hydraulic pressure and uniform braking force across both front wheels.
Replace the cup set when any of these symptoms appear:
- Brake fluid seepage past the dust boot — visible fluid traces on the backing plate or inside the drum
- Spongy or sinking brake pedal — internal fluid bypass caused by worn or hardened cup seals reduces hydraulic pressure
- Uneven or reduced braking effectiveness — the vehicle pulls to one side during braking, or stopping distance increases
- Brake fluid contamination — degraded rubber particles from worn cups contaminate the brake fluid, accelerating wear on other hydraulic components
| Verification Item | Data / Standard | Source / Method |
|---|---|---|
| Part Number (Short) | 5-87831602-0 | ISUZU OEM Parts Database |
| Part Number (Short) | 5-87830538-0 | ISUZU OEM Parts Database |
| Factory Number | 5878316020 / 5878305380 | ISUZU OEM Parts Database |
| Part Name | CUP SET; FRT WHEEL CYL | ISUZU EPC |
| Vehicle Models | ISUZU NHR54 / NKR55 / NPR57 | ISUZU application catalog |
| Engine Compatibility | 4JB1 | ISUZU application catalog |
| Cylinder Bore Size | 1-1/8 inch (28.58 mm) | ISUZU workshop specification |
| Material | NBR (Nitrile) / EPDM Rubber | Material certificate |
| Fluid Resistance | DOT 3 / DOT 4 brake fluid compatible | ASTM D471 immersion test |
| Temperature Range | −40°C to +120°C | Material datasheet |
| Compression Set Resistance | ≤ 25% after 70h @ 100°C | ASTM D395 |
| Installation Success Rate | ≥ 99% | Based on repair order tracking |
| Certification | ISO/TS 16949 | Third-party system audit |
| Unit Weight | 0.04 kg | Product specification |
| Part Number: | 5-87831602-0 5-87830538-0 |
| Product Name: | Front Wheel Cylinder Cup Set |
| Car Model: | NHR NKR |
| Engine Model: | NHR NKR |
| Condition: | 100% Brand New |
| Origin: | China Mainland |
| Main Market: | Middle East, Asia, Africa, South America, North America & Europe |
| Package: | Neutral Packing Or Make It As Requested |
| Material: | High-strength aluminum alloy & precision bearings |
| Cooling Type: | Engine coolant circulation |
| Installation: | Direct OEM replacement |
| Quality Standard: | OEM equivalent / ISO quality control |
| Brand | Model | Chassis | Engine | Years |
|---|---|---|---|---|
| ISUZU | ELF | NHR54 | 4JB1 | 1984–1990 |
| ISUZU | ELF | NKR55 | 4JB1 | 1986–1993 |
| ISUZU | ELF | NKR55 | 4JB1 | 1996–2007 |
| ISUZU | NPR | NPR57 | 4JB1 | 1986–1993 |
| ISUZU | ELF 100 | NKR55 | 4JB1 | 1986–1993 |
| Brand | Model | Application |
|---|---|---|
| JMC | 1030 | Light Truck |
| JMC | 1040 | Light Truck |
- This cup set is designed for the 1-1/8 inch (28.58 mm) front wheel cylinder bore. Confirm the bore diameter of your wheel cylinder before ordering
- The NHR54/NKR55/NPR57 front drum brake uses two wheel cylinders per wheel. Verify which cylinder requires the cup set
- For right-hand drive (RHD) vehicles, the wheel cylinder orientation may differ. Refer to the ISUZU workshop manual for the correct procedure
Exceptional resistance to DOT 3 and DOT 4 brake fluid swelling, heat degradation, and compression set — verified by ASTM D471 and ASTM D395 testing.
Cup-shaped sealing lip expands under hydraulic pressure for a tighter seal as braking force increases — verified against OEM bore diameter specifications.
Precision-matched to the ISUZU NHR/NKR front wheel cylinder bore — direct drop-in fit without modification.
Cup seals and dust boots supplied together to meet ISUZU service manual requirements — reduces the risk of partial repair and premature failure.
Full traceability with material certificates and batch inspection reports — third-party certified.
Based on repair order tracking — confirms reliable fitment across the NHR/NKR platform.
| QC Item | Verification Method / Standard |
|---|---|
| Cup OD / ID Dimensions | CMM, 100% inspection |
| Lip Geometry Angle | Optical comparator, 100% inspection |
| Material Hardness (Shore A) | Durometer, batch sampling |
| Fluid Immersion Resistance | ASTM D471 — 70h @ 100°C in DOT 3 fluid |
| Compression Set | ASTM D395 — 70h @ 100°C |
| Tensile Strength | ASTM D412, batch sampling |
| Elongation at Break | ASTM D412, batch sampling |
| Surface Finish | Visual inspection — no flash, no contamination |
| Batch Traceability | Material lot number + production date |
| Packaging Protection | Sealed bag + moisture barrier + carton |
- Disassembly: Remove the wheel, brake drum, and wheel cylinder. Remove the boot and piston assembly. Remove the piston cup from the piston. Remove the return spring and bleeder from the wheel cylinder.
- Inspection: Inspect the cylinder bore for scoring, pitting, or corrosion. If the bore is damaged, replace the entire wheel cylinder assembly. Do not attempt to rebuild a damaged cylinder.
- Cleaning: Clean all components with clean brake fluid or approved brake cleaner. Do not use petroleum-based solvents.
- Lubrication: Coat the new cups and cylinder bore with clean brake fluid before assembly.
- Assembly: Install the new cup with the sealing lip facing the hydraulic pressure source. Install the piston, boot, and return spring.
- Bleeding: Bleed the brake system completely to remove air. Check for leaks at the bleeder screw and line connections.
- Pedal Test: Pump the brake pedal several times to seat the cups. Verify a firm pedal before road testing.
- Every 10,000 km: Inspect brake fluid level and condition. Check for visible fluid seepage at wheel cylinders.
- Every 40,000–50,000 km: Inspect brake drum and shoe wear. Check wheel cylinder operation.
- Every 2 years: Replace brake fluid regardless of mileage.
- Whenever the drum is removed: Inspect the cylinder bore and cup seals. Replace cups if any hardening, cracking, or swelling is found.
- Standard Packaging: Sealed bag + moisture barrier + carton
- Custom Packaging: Neutral packaging, customer-branded packaging
- Suitable For: Brake system repair shops, ISUZU parts distributors, fleet maintenance centers
- Supply Capacity: Stable batch supply with batch-level quality reports available
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