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Volkswagen platforms such as the Golf IV, Bora and New Beetle share a large number of suspension components, and the strut bump stop is one of the smallest parts with an outsized effect on ride comfort and damper life. The 1J0512131 strut bump stop fits on the damper rod inside the rear strut and cushions the final stage of suspension travel. Bonpora manufactures this reference and a wide range of similar bump stops in polyurethane, supplying OE programs, importers and aftermarket brands from production bases in China and Germany. This guide summarises the specifications, fitment, material advantages and sourcing routes for buyers who search by OEM number, by vehicle model, by part type and specification, or by custom design requirement.
A strut bump stop, also called a jounce bumper or auxiliary foam spring, is mounted on the piston rod of a shock absorber or strut. When the suspension compresses beyond its normal travel over potholes, speed bumps or with a heavy load, the bump stop engages and progressively absorbs the last part of the stroke. This prevents metal to metal contact between the strut body and the chassis, protects the internal valves of the damper from overload, and keeps impact noise and harshness at an acceptable level.
The 1J0512131 part number identifies the rear strut bump stop used across Volkswagen platforms of the 1J generation. Because it is a wear related component, workshops replace it together with shock absorbers, dust covers and mounting kits. For distributors and repair chains, stable supply of this reference is a recurring purchasing task. Bonpora therefore keeps the part in serial production with tooling ready for both OE specification and replacement grade, and buyers can browse the full polyurethane bump stop and jounce bumper range on this site.
The table below lists the key parameters of the Bonpora strut bump stop 4110029, which corresponds to OE number 1J0512131.
| Item | Specification |
|---|---|
| Product Name | Strut Bump Stop |
| Bonpora Number | 4110029 |
| OE Reference | 1J0512131 |
| Fitment | Volkswagen |
| Dimensions | Φ14.5 x Φ59.6 x 142.3 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 |
Dimensions follow the standard convention for strut bump stops: the small diameter slides over the damper rod, the larger diameter forms the working body, and the overall length defines the travel cushion. Buyers should confirm the measurements on the removed part or in the vehicle parts catalog before ordering.
OE reference 1J0512131 is associated with the Volkswagen 1J platform family and related A platform models. In practice this covers vehicles such as the Golf IV, Bora and Jetta of that generation, and the New Beetle. The same bumper shape also appears in the catalogs of sister brands that share VW componentry, so a fitment check against the original part is recommended before a bulk purchase.
VW catalogs may list the reference with or without suffix letters, and service versions can differ in length or foam density. The most reliable method is a three way check: the OE number from the parts catalog, the physical dimensions of the old part, and a photo of the mounting position. Bonpora supports this verification and can send samples for confirmation before mass production.
Traditional bump stops rely on NR or SBR rubber foams. Microcellular polyurethane, the material class used by Bonpora, generally offers a finer and more uniform cell structure, which gives a more progressive force stroke curve. In practical terms the cushioning builds up gradually instead of sharply, which supports ride comfort and helps the damper work within its designed range.
Polyurethane also shows advantages in aging behaviour. It resists ozone attack, common road chemicals and repeated compression cycles better than many rubber compounds, so the part keeps its shape and elasticity over a longer service interval. Hardness can be tuned through the formulation, which is valuable for tuning and off road programs where a firmer progressive cushion is requested. These advantages depend on correct material selection and process control, and Bonpora manufactures under an IATF 16949 certified quality system to keep batch consistency stable.
Professional buyers usually start from an OE number such as 1J0512131, then narrow down by size, material and quantity. A clear RFQ contains the OE reference, the dimensions, the required material grade, the annual volume and the packaging requirement. With this information a manufacturer can confirm tooling, quote accurately and prepare samples in a short time.
Bonpora covers the complete shock absorber parts category, including bump stops, dust covers, mountings and related rubber to metal components, so mixed container loading across categories is possible. Buyers who work from vehicle applications rather than OE numbers can send the model, year and axle position instead, and the engineering team will map the request to a current reference.
Beyond serial references, Bonpora develops custom bump stops from drawings, samples or application data. The service covers material hardness adjustment, dimension changes, mounting features, logo printing and packaging design. For new projects the workflow is straightforward: the buyer provides a drawing or a sample, engineering confirms the force stroke requirement, tooling is produced in house, and samples are submitted for approval before mass production.
This custom suspension parts service is used by OE programs, tuning brands and aftermarket packagers who need a specific cushioning curve that standard catalog items do not provide. Tooling cost and lead time depend on part complexity, and the sales team issues a clear quotation after the drawing review.
Each production batch passes incoming material checks, in process dimension control and final inspection of appearance, hardness and compression behaviour. Parts are packed in neutral export packaging with inner bags and cartons suitable for sea and air freight, and buyer branded packaging is available on request. Standard delivery time is 15 to 30 days depending on quantity and production schedule, and every order is covered by a 1 year warranty against material and workmanship defects.
The reference is used on rear struts of the VW 1J platform family, including the Golf IV, Bora and Jetta of that generation and the New Beetle. Because sister models share components, buyers should verify the OE number in the parts catalog and compare the dimensions of the old part before ordering.
Yes. Bonpora supports OEM and custom design, including size changes, hardness adjustment and logo or packaging customisation. Send a drawing or a sample, and the engineering team will confirm the proposal and submit samples for approval.
Standard delivery time is 15 to 30 days after order confirmation, depending on quantity. Goods are packed in neutral export packaging, and buyer branded packaging is available for agreed volumes.
Bonpora provides a 1 year warranty on the strut bump stop against defects in material and workmanship when the part is installed and used as intended. Claims are handled case by case with the sales team.
If you are sourcing the 1J0512131 strut bump stop or planning a custom polyurethane bump stop program, send the OE number, dimensions and target quantity to the Bonpora sales team. A quotation with lead time and packaging options is returned shortly after the specification review.
