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The VW Golf Mk4 generation and its saloon derivative, the Bora, still run in large numbers across Europe, Latin America, the Middle East, and Asia. As this vehicle population ages, the elastomer components around the rear suspension are among the first parts to deteriorate. Bonpora supplies a replacement rear strut bump stop for this vehicle family under Bonpora No. 4110030, matching OE number 1J0512131B, molded in polyurethane with dimensions of Φ14.8 × Φ58 × 129.5 mm. This page is written for importers, auto parts distributors, and suspension workshops that source Volkswagen components by OEM number and need a dependable factory channel for suspension buffers.
The bump stop, listed in Volkswagen parts books together with the rear shock absorber dust cover, slides onto the piston rod of the rear damper and cushions the final stage of compression travel before metal can strike metal. When the buffer is cracked, torn, or crushed flat, the rear axle bottoms out on hard impacts, ride comfort deteriorates, and the damper seal and internal valve parts wear faster. Workshops therefore replace the bump stop together with the shock absorber or dust cover during rear axle service. Related suspension components can be found in our shock absorber parts catalog.
Buyers who match parts by size or by OE number can check the parameters of Bonpora No. 4110030 in the table below. The bore of about 14.8 mm slides over the damper piston rod, the body diameter of 58 mm carries the compression load, and the free height of 129.5 mm corresponds to the original buffer fitted on the rear axle of the Golf Mk4 generation and related models.
| Item | Specification |
|---|---|
| Product Name | Strut Bump Stop (rear axle) |
| OE Number | 1J0512131B |
| Bonpora No. | 4110030 |
| Fitment | VW Golf Mk4, Bora, New Beetle, rear axle |
| Size | Φ14.8 × Φ58 × 129.5 mm |
| Material | Polyurethane |
| Country of Origin | China |
| Warranty | 1 Year |
| Delivery Time | 15–30 Days |
| Packaging | Neutral Export Packaging |
| Custom Service | OEM and Custom Design Support |
When a rear wheel meets a deep pothole or a speed bump at speed, suspension travel can approach its mechanical limit. The bump stop engages in this final stage and compresses progressively, absorbing impact energy before the damper reaches full compression. The micro-cellular polyurethane body stiffens gradually instead of transmitting a sudden jolt to the chassis, which protects the damper internals, the top mounts, and the surrounding body structure.
Original catalogs list this reference for vehicles with standard suspension. Models ordered with the factory sport chassis, which sits roughly 20 mm lower, use a shorter companion buffer with a different part number. Distributors and workshops should therefore confirm the chassis version of the customer vehicle before quoting, either from the vehicle identification plate or from the old part removed from the car.
Reference 1J0512131B is cataloged for the rear axle, with one buffer per side on the left and right dampers. The reference belongs to the Volkswagen Group A4 platform generation, so a single buffer covers several best selling nameplates of the late 1990s and early 2000s. The main applications are summarized below.
The core applications are the Golf Mk4 built from 1998 to 2006, the Bora saloon and wagon built from 1999 to 2005 and sold as the Jetta in many markets, and the New Beetle built from 1998 to 2010. These models sold in very large volumes, and substantial numbers still operate as daily drivers, taxi vehicles, and fleet cars in export markets. Catalogs note that special high performance versions, such as the Golf R32 with its dedicated rear damper setup, are excluded, so confirm the exact model before shipping.
Because the Audi A3 of the 8L generation, the SEAT Leon and Toledo of the 1M generation, and the first generation Skoda Octavia share this platform architecture, several aftermarket cross-reference lists extend the 1J0512131B family to these nameplates for the rear axle. Suspension variants can differ between brands, markets, and model years, so verify the VIN or the number printed on the old part before quoting these applications.
| Vehicle Model | Platform Code | Production Years | Axle | Notes |
|---|---|---|---|---|
| VW Golf IV (Mk4) | 1J | 1998–2006 | Rear | Standard suspension |
| VW Bora / Jetta Mk4 | 1J | 1999–2005 | Rear | Saloon and wagon |
| VW New Beetle | 9C | 1998–2010 | Rear | Standard suspension |
| Audi A3 | 8L | 1997–2003 | Rear | Listed in cross-reference catalogs |
| SEAT Leon / Toledo | 1M | 1998–2006 | Rear | Verify by VIN or old part |
| Skoda Octavia I | 1U | 1996–2010 | Rear | Verify by VIN or old part |
Bonpora molds this buffer in micro-cellular polyurethane rather than conventional rubber. For wholesale buyers, the material offers three practical benefits. First, resistance to ozone, heat, and aging is higher than that of typical rubber compounds, which matters on vehicles that remain parked outdoors for long periods. Second, density is stable from batch to batch, so the compression curve remains consistent. Third, polyurethane keeps a smooth molded surface that resists splitting during installation and storage. Our complete range of molded buffers is available in the polyurethane bump stops category.
Polyurethane performs well across temperature extremes. In hot export markets the material stays stable under high underbody temperatures, while in northern climates it remains flexible at low temperatures where some rubber buffers harden and crack. This wide operating window is one reason polyurethane buffers have become a common choice for aftermarket suspension programs.
Distributors who resell buffers under their own brands depend on repeatable quality. Compression testing on samples from every batch keeps the stiffness curve within the agreed range, and dimensional inspection with calipers and height gauges confirms that the bore, body diameter, and free height stay within tolerance. Sampling follows AQL practice, and inspection records can be shared with customers on request.
A worn buffer announces itself through clear symptoms. Drivers report a harsh knocking sound from the rear axle when entering potholes or crossing speed bumps, because the damper reaches full compression without the elastic cushion in place. On inspection, the old buffer shows surface cracks, powder residue, or a permanent compression set that has flattened the original height.
Workshops normally inspect the bump stops whenever rear dampers or dust cover kits are replaced, and they replace the buffers in pairs to keep the axle balanced. Polyurethane buffers slide onto the damper rod by hand pressure in most cases, so fitting time is short and does not require special tools.
Bonpora produces suspension buffers for importers, wholesalers, and brand owners worldwide, and the company supports both catalogue supply and engineered custom projects.
Send the OE reference 1J0512131B, or the Bonpora number 4110030, to the sales team, ideally together with the chassis version and the required quantity. Quote any format variant that appears in the parts book, such as 1J0 512 131 B. The team confirms the drawing dimensions, quotes on FOB or CIF terms, and provides samples for inspection when required. Mixed orders that combine this buffer with other bump stops, dust covers, and suspension components are welcome.
Beyond catalogue items, Bonpora provides OEM and custom design support for polyurethane buffers. If your market requires a different hardness, an adjusted geometry, a reinforced mounting seat, or private brand packaging, the engineering team can develop the part from a sample or a drawing. The standard procedure covers mold design, sample confirmation, a dimensional report, and batch production after approval.
Each bump stop is packed in a poly bag and boxed in neutral export packaging, so the goods can be resold under your own brand without conflict. Standard production time is 15 to 30 days depending on order quantity, and the warranty period is one year under normal service conditions. Palletized loading is available for container orders, and stock references can usually leave the factory earlier than full production runs when urgent replenishment is needed.
The buffer fits the rear axle of the VW Golf Mk4, Bora, and New Beetle on standard suspension, and several cross-reference catalogs extend the family to the Audi A3 8L, SEAT Leon and Toledo 1M, and Skoda Octavia 1U. Confirm the chassis version and the old part number before ordering.
No. Original catalogs assign this reference to standard suspension only. Vehicles with the factory sport chassis, which sits about 20 mm lower, require a shorter companion buffer with a different reference, so identify the chassis version first.
The 1J0512131 family includes variants such as 1J0512131B and 1J0512131C that look similar but differ in height and in the suspension variants they serve. Compare the free height and the bore of the removed part with the specification table above, or send the old part number to the sales team for confirmation.
Bonpora offers a one year warranty under normal service conditions, a production and delivery window of 15 to 30 days, and neutral export packaging for resale under your own brand. Quotations are available on FOB or CIF terms, and sample pieces can be arranged before bulk orders.
If you source Volkswagen suspension buffers by OEM number, Bonpora can supply the 1J0512131B rear strut bump stop from stock or from scheduled production. Contact the sales team through the contact information page to receive a quotation, drawings, and sample arrangements for Bonpora No. 4110030.
