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Strut bump stop 31336776390 is a polyurethane suspension cushion manufactured in China by Bonpora and exported worldwide under factory-direct terms. The part carries Bonpora reference 4110226 and corresponds to OE number 31336776390, a front suspension reference catalogued for BMW applications. This page describes the role of the bump stop inside a strut assembly, presents the complete technical data for the reference, and summarises the wholesale, OEM, packaging and warranty conditions offered by the moulding factory. Distributors, importers and workshop groups can use the details to prepare an accurate first inquiry and reduce the number of clarification rounds before a purchase order is placed.
The strut bump stop - also called a jounce bumper, bump stopper or auxiliary spring - is the progressive elastomer element fitted on the piston rod of a MacPherson strut. It works during the final stage of suspension travel: when a wheel drops into a pothole, crosses a sharp ridge or the vehicle carries a heavier load than usual, the coil spring alone cannot absorb the remaining stroke and the bump stop compresses progressively to cushion the impact. A serviceable stop therefore protects the damper from metal-to-metal bottoming, reduces the shock loads transferred into the body structure, and slows wear on the strut top mount and adjacent chassis joints. Once the stop is permanently flattened, split or crumbled, ride comfort at full compression drops sharply and damper life shortens noticeably, which is why professional workshops treat the stop as a routine service part rather than an accessory.
On the front axle the bump stop slides over the damper rod between the top mount and the dust boot; on many platforms it is moulded together with the dust cover as a single unit. The 31336776390 reference follows the original geometry with a compact, low-profile body: a 17 mm bore seats over the strut rod, the 60 mm outer diameter forms the contact face inside the strut housing, and the 16 mm free height sets the point where the cushion engages. This flat ring-shaped profile is typical of designs where the stop works as a short-stroke end-of-travel cushion rather than a tall progressive spring, so buyers converting between related references should confirm all three dimensions against the removed part instead of judging by shape alone.
Polyurethane bump stops deteriorate 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 once the strut is dismantled for service. Because the part sits 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 stop is a low-cost safeguard against a damper damaged by repeated bottoming, and replacing stops in pairs on the same axle keeps the left and right sides of the suspension balanced.
The published parameters for Bonpora reference 4110226 are summarised in the table below.
| Parameter | Value |
|---|---|
| Product Name | Strut Bump Stop |
| OE Number | 31336776390 |
| Bonpora Nos | 4110226 |
| Fitment | BMW |
| Size | Φ17 × Φ60 × 16 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 |
In the BMW parts numbering scheme, the leading group 31 33 belongs to the front axle section of the catalogue, which covers suspension and spring-strut components, and the remaining digits identify the individual part and its revision level. References inside this group are used for front suspension cushions and related parts, while the exact vehicle applications can differ between model years and markets. Because BMW groups contain many visually similar variants that differ in bore, diameter and free height, the complete number printed or moulded on the original part remains the decisive identification detail. If the markings on a removed sample have worn away, send the three measurements together with any partial markings so the correct reference can be verified before an order is scheduled.
Many professional buyers source suspension elastomer parts not by vehicle model but by part type and measurements - for example a strut bump stop with a 17 mm bore and a 60 mm outer diameter, or a low-profile polyurethane cushion with a free height close to 16 mm. Specification-based sourcing suits bump stops well because the three dimensions largely determine whether a replacement will seat and engage correctly. Measure the inner diameter, outer diameter and free height of the removed component, note the material and Shore hardness if a datasheet is available, and compare the values against catalogue data. The polyurethane bump stop catalogue lists references with their dimensions and OE numbers, so a spec-based cross-check takes only minutes before an inquiry is sent.
OE-number sourcing remains the most dependable route for imported replacement parts, because part numbers are specific while vehicle descriptions are often ambiguous across markets. The following workflow keeps an inquiry efficient and lowers the risk of mismatched stock.
Provide the full OE number together with the inner diameter, outer diameter and free height of the old part. For this reference the expected values are approximately 17 mm, 60 mm and 16 mm. When all three agree, the stop will seat on the rod and engage at the intended point of the suspension travel.
Micro-cellular polyurethane is the prevailing material for current-generation bump stops thanks to its progressive compression curve and low permanent set. Buyers converting from an original rubber stop may notice a slightly firmer feel in the final stage of travel; sharing the Shore hardness and free height of a reference sample allows the factory to match the formulation to the application instead of relying on appearance.
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.
Factory-direct purchasing removes intermediary margins and gives buyers visibility over the factors that decide batch consistency: tooling condition, material batching and process parameters. Bonpora moulds the shock absorber parts range in-house, from rubber and polyurethane compounding through to finished-component testing, so dimension reports can be produced per batch and mould maintenance is scheduled internally rather than outsourced. Direct 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 importers building a BMW 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 4110226 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 accompanies 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 31336776390 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 reference is catalogued for BMW front suspension applications, and the 31 33 group in the BMW numbering scheme relates to front axle components. Fitment should be verified against the complete OE number on the original part or through a parts-catalogue lookup before ordering, since applications can differ between model years and markets.
Measure the inner diameter, outer diameter and free height. For this reference the approximate values are 17 mm, 60 mm and 16 mm. Significant deviations usually indicate a different variant, so the OE number should be re-checked before an order is placed.
Polyurethane offers a progressive compression curve, lower permanent set and better resistance to the cracking and powdering that affect rubber parts exposed to ozone and road chemicals. The firmer final-stage feel is generally mild, and matching the Shore hardness to a reference sample keeps the ride character close to the original.
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.
