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Strut bump stop 357412303F is a polyurethane suspension cushion produced by Bonpora, a Chinese manufacturer of rubber and polyurethane chassis components, as a replacement part for Volkswagen vehicles. The part carries Bonpora reference 4110031 and is supplied in wholesale quantities to parts distributors, importers and workshop groups worldwide. This page explains the role of the bump stop inside the strut assembly, presents the published technical data for the 357412303F reference, and describes how professional buyers source it by OE number or by specification, together with the OEM, packaging and warranty terms offered by the factory.
The strut bump stop - also called a jounce bumper, bump stopper or auxiliary spring - is the progressive elastomer element fitted around the piston rod of a MacPherson strut. It engages during the final stage of suspension travel: when a wheel drops into a pothole, crosses a sharp ridge or the vehicle carries a heavy load, the coil spring alone cannot absorb the remaining stroke and the bump stop compresses to cushion the impact. Without a serviceable stop, the damper bottoms out metal to metal, sending sharp shocks into the body structure and accelerating wear on the strut, its top mount and adjacent components.
On the front axle the bump stop slides over the damper rod between the top mount and the dust boot, and on some platforms it is moulded together with the dust cover as a single unit. The 357412303F reference follows the original geometry: an 18 mm bore seats on the strut rod, the 49.9 mm outer diameter defines the contact face inside the housing, and the 85 mm free height sets the point at which the progressive section engages. The comparatively tall 85 mm body is characteristic of this platform generation, so buyers converting from a shorter stop should confirm the height before ordering rather than judging by appearance alone.
Polyurethane bump stops degrade gradually rather than suddenly. Typical workshop indicators include knocking or thudding from the suspension over sharp impacts, a noticeably harsher ride at full compression, and visible cracking, powdering or permanent flattening when the strut is dismantled for service. Because the part is hidden inside the assembly, most workshops inspect or renew it whenever a strut, top mount or dust boot is already being replaced. Fitting a new bump stop is a low-cost safeguard compared with the cost of a damper damaged by repeated bottoming, and replacing stops in pairs on the same axle keeps handling balanced between left and right sides.
The published parameters for Bonpora reference 4110031 are listed below.
| Parameter | Value |
|---|---|
| Product Name | Strut Bump Stop |
| OE Number | 357412303F |
| Bonpora Nos | 4110031 |
| Fitment | Volkswagen |
| Size | Φ18 × Φ49.9 × 85 mm |
| Material | Polyurethane (micro-cellular) |
| Country of Origin | China |
| Warranty | 1 year |
| Delivery Time | 15-30 days |
| Packaging | Neutral export packaging |
| Custom Service | OEM & custom design support |
The 357 prefix belongs to the numbering scheme Volkswagen applied to one of its medium platform generations, and references in this series are commonly associated with Passat model lines of that era. Because the same chassis family was assembled under different brand and market names, and because components were revised during the production run, Bonpora recommends confirming fitment with the complete OE number printed or moulded on the original part, or through a parts-catalogue lookup, before placing an order. If the number on the sample differs in a prefix or suffix, send it together with the three measurements so the engineering team can check whether the reference matches or whether an equivalent should be quoted.
Many buyers search suspension elastomer parts not by vehicle model but by part type and measurements - for example a strut bump stop with an 18 mm bore and a 49.9 mm outer diameter, or a polyurethane stop of a specific free height. Specification-based sourcing works well for bump stops because the three dimensions largely determine whether a part will seat and engage correctly. Measure the inner diameter, outer diameter and free height of the removed component, note the material, and compare the values with the catalogue data. The polyurethane bump stop catalogue lists references with their dimensions and OE numbers, so a spec-based cross-check is straightforward before an inquiry is sent.
OE-number sourcing remains the most reliable route for imported replacement parts, because part numbers are specific while vehicle descriptions are not. The following workflow keeps an inquiry efficient and lowers the risk of mismatched stock.
Provide the full OE number together with inner diameter, outer diameter and free height of the old part. For this reference the expected values are approximately 18 mm, 49.9 mm and 85 mm. When all three agree, the stop will seat on the rod and engage at the intended point of the travel.
Micro-cellular polyurethane is the prevailing material for current-generation bump stops because it offers a progressive compression curve and low permanent set. Buyers converting from an original rubber stop may notice a slightly different stiffness feel; sharing the Shore hardness and free height of a reference sample allows the factory to tune the formulation to the application.
For first-time cooperation, dimensional inspection and material verification on samples are the most practical risk controls. Bonpora supports sample approval ahead of batch production, and volume supply runs under IATF 16949-based process control, so inspection records can accompany shipment documents when required.
Purchasing bump stops directly from the moulding factory rather than through trading intermediaries gives buyers visibility over the factors that decide batch consistency: tooling condition, material batching and process parameters. Bonpora manufactures the shock absorber parts range in-house, from rubber and polyurethane compounding through to finished-component testing, which means dimension reports can be produced per batch and mould maintenance is scheduled internally. Direct factory supply also simplifies commercial matters for wholesale buyers: volume pricing by order quantity, repeat-order scheduling against stock levels, and neutral export packaging that leaves goods unbranded for re-packing under the distributor label. For distributors building a Volkswagen suspension programme across several OE references, one factory covering multiple part families reduces the number of suppliers to qualify and audit.
Beyond catalogue references, the factory develops bump stops and related custom parts from customer drawings, 3D data or physical samples. A typical project covers dimension confirmation, material formulation, hardness matching, pilot moulding and sample approval before mass production begins. Custom service also extends to colour, branding and packaging, which suits importers establishing their own ranges as well as fleet programmes that require batch documentation with every delivery.
Standard shipments use neutral export packaging labelled with the Bonpora number 4110031 for traceability, leaving the goods unbranded for distributor re-packing at destination. Delivery time is 15-30 days depending on order quantity and the production schedule, and a 1-year warranty applies to manufacturing defects. Batch traceability information is provided with each shipment, so any delivery can be matched back to production records if a quality question arises during the warranty period.
To obtain wholesale pricing for the 357412303F strut bump stop, send the OE number, target quantity and destination port through the contact form on this site. A standard quotation includes unit pricing by volume break, packaging specification and the earliest available production slot, so total landed cost can be compared rather than unit price alone.
The 357 prefix is commonly associated with Volkswagen Passat model lines of the corresponding platform generation. Because components were revised during production, fitment should be verified against the complete OE number on the original part or through a parts-catalogue lookup before ordering.
Measure inner diameter, outer diameter and free height. For this reference the approximate values are 18 mm, 49.9 mm and 85 mm. Significant deviations usually indicate a different variant, so the OE number should be re-checked before an order is placed.
Yes. OEM and custom design support covers product dimensions, material and hardness, and also colour and branding options on the packaging. Standard shipments remain neutral and unbranded unless custom packaging has been agreed in advance.
A 1-year warranty applies to manufacturing defects, and standard delivery time is 15-30 days after order confirmation, depending on quantity and production schedule. Custom projects may need additional time for sample approval before mass production.
