Volkswagen Strut Bump Stop 1K0412303H: OEM and Custom Polyurethane Replacement Parts from China Factory

Between 2003 and the late 2010s, the Volkswagen Group built tens of millions of compact cars on the shared PQ35 architecture, from the Golf V and the Touran to the Octavia II and the Jetta. The front suspension of these vehicles uses a MacPherson strut, and inside every strut sits a polyurethane buffer that controls the final stage of compression travel. Bonpora supplies the front axle replacement under Bonpora No. 4110022, matching OE number 1K0412303H, molded in micro-cellular polyurethane with a bore of 23 mm, an outer diameter of 50.4 mm, and a free height of 91.1 mm. This page is written for importers, parts distributors, and suspension workshops that source VW Group parts by OEM number.

In the Volkswagen parts book, 1K0412303H appears as the suspension strut bumper of the front axle, fitted on both left and right sides. The buffer slides over the piston rod of the front damper and cushions the last millimeters of compression before the strut housing can strike the top mount. When the buffer cracks, tears, or collapses with age, the front axle bottoms out on potholes, ride comfort drops under load, and dust and water reach the damper rod, which shortens the service life of the shock absorber seal. Workshops therefore replace the bump stop together with the damper or the dust cover during front axle service. Related suspension components can be found in our shock absorber parts catalog.

What Is the 1K0412303H Strut Bump Stop?

Function in the Front Axle

A strut bump stop, also called a jounce bumper or suspension buffer, is a progressive compression element that engages only during the last part of suspension travel. Under normal driving the coil spring carries the load and the buffer does not work. When the wheel drops into a deep pothole or a heavily loaded vehicle crosses a speed bump, the spring reaches its limit and the damper rod would hit the top mount without protection. The polyurethane buffer compresses progressively, absorbs the impact energy, and returns to shape after the load is released. This protects the damper, the top mount, and the body structure from harsh metallic impacts.

Height Variants and Related Suffixes

The 1K0412303 buffer family includes several height variants that correspond to different suspension setups. The H suffix covered on this page corresponds to a buffer of about 90 mm free height, the standard value for most Golf V, Golf VI, Jetta, Touran, and Passat B6 front struts. The F suffix corresponds to a shorter 55 mm buffer used with sport suspension, while the M and AA suffixes belong to the rear axle of the same platform. Because the suffix changes the height and the application, buyers should always confirm the full OE number or measure the old buffer before ordering.

Technical Specifications of Bonpora No. 4110022

The table below lists the parameters of the Bonpora replacement. Buyers who order by size can use the bore, outer diameter, and free height as the reference values, and buyers who order by OE number can match 1K0412303H directly.

Vehicle Applications of OE 1K0412303H

OE 1K0412303H covers the front axle of the compact families that the Volkswagen Group built on the PQ35 architecture from 2003 onward. Independent catalogs list the applications below, and North American dealer systems additionally reference the same buffer for the Jetta sedan family and the front axle of the Atlas. Because buffer heights differ inside the same platform depending on model year and suspension equipment, buyers should confirm the fitment against the VIN or the full OE number before ordering.

The buffer is installed on both sides of the front axle, so a complete front axle service requires two units. Rear axle buffers for the same vehicles carry the numbers 1K0412303M or 1K0412303AA.

OE Number Cross-Reference for 1K0412303H

Purchasers usually start from one of three entry points: the full VW OE number 1K0412303H, its superseded predecessor 1K0412303E, or the internal numbers of aftermarket brands that list the same application. Independent suppliers market this application under their own numbering systems, so one physical part can carry a dozen commercial references. The reliable verification method is to compare three data points: the axle position (front), the free height of about 90 to 91 mm, and the mounting bore of about 23 mm. Bonpora ships buffers that match the OE geometry, and our engineering team can check an unknown sample against the OE drawing on request.

Symptoms of a Worn Front Strut Bump Stop

Polyurethane buffers age gradually, and the symptoms appear long before the driver notices a hard metallic knock. Workshops and parts sellers can use the following signs to identify vehicles that need new front buffers:

• Knocking over potholes: a dull impact sound from the front axle when the wheel drops into holes.
• Harsher ride under load: worn buffers no longer absorb the remaining travel when the vehicle sits lower under cargo.
• Visible cracks or powder: during damper replacement, the old buffer often shows surface cracks, tears, or a crumbled lower section.
• Collapsing height: a buffer that has taken a permanent set measures shorter than 91 mm at rest.
• Early damper seal wear: impact energy transfers directly to the damper rod and top mount, shortening the life of the strut assembly.

Why Polyurethane Instead of Rubber

Original buffers of this generation are produced from micro-cellular polyurethane foam, and Bonpora keeps the same material class for the replacement. Compared with conventional rubber, polyurethane offers a more stable compression curve over temperature changes, better resistance to ozone and road salt, and a lower permanent set after repeated impacts. The foam structure allows a soft initial response and a progressive rise in stiffness. For distributors, the practical benefit is a lower return rate, because polyurethane parts resist the cracking and powdering that end the life of a rubber buffer. The full range of molded buffers can be reviewed in the polyurethane bump stops section.

OEM and Custom Strut Bump Stop Manufacturing

Production Based on Drawings or Samples

Bonpora is a manufacturer of polyurethane suspension buffers. Besides the standard program that covers OE numbers for European, Asian, and American vehicles, the factory supports OEM production for brand owners and wholesale distributors. Customers can send a technical drawing, a physical sample, or simply the required height, outer diameter, and bore. The engineering team then selects the foam density and the compression characteristic to match the behavior of the original part. Existing molds cover several hundred references, and tooling for a new custom buffer is quoted separately after drawing review.

Branding, Packaging, and Private Label

The standard condition is neutral export packaging with the Bonpora article number on the label. For distributors with their own brand, the factory prints customer labels and carton marks from an agreed artwork, and it can pack the buffers as single parts or as complete strut service kits with dust covers. This private label service is used by importers in Europe, South America, the Middle East, and Southeast Asia.

Quality Control, Warranty and Delivery

Each production batch passes dimensional checks on height, bore, and outer diameter, hardness verification, and a visual inspection of the foam surface before packing. Parts are packed in polybags and export cartons, and palletized shipments are prepared for full container orders. The standard lead time is 15 to 30 days depending on order quantity and mold availability. Samples for fitment verification are available before bulk production, and the article carries a 1 year warranty against material and manufacturing defects.

FAQ About the 1K0412303H Strut Bump Stop

Which vehicles does OE 1K0412303H fit?

It fits the front axle of the VW Group compact models built on the PQ35 platform, including VW Golf V and VI, Golf Plus, Jetta and Sagitar, Touran, Passat B6 Variant, Caddy III, SEAT Leon, SKODA Octavia II, and SKODA Yeti, plus the front axle of the North American Atlas. Always verify the full OE number or the height of the old part against the specifications on this page.

What is the difference between 1K0412303H and 1K0412303E?

Both numbers describe the same 90 mm front axle buffer, and catalogs list 1K0412303E as the earlier reference that was superseded by the H version. Parts books show the H number on current applications, so the two references can be treated as interchangeable for the listed vehicles.

How do I tell whether I need the 90 mm or the 55 mm front buffer?

The H and E versions measure about 90 to 91 mm in free height and serve standard suspension, while the F version measures about 55 mm and serves sport suspension. Measure the free height of the old buffer or read the suffix on the OE number before ordering.

Can you produce custom polyurethane buffers with my brand?

Yes. Bonpora supports OEM and custom design service. Send the drawing, the OE number, or a sample together with the required height and hardness, and the factory will quote tooling and unit price. Neutral export packaging is standard, and private label packaging with customer artwork is available for bulk orders.

Request a Quote for Bonpora No. 4110022

Distributors, wholesalers, and suspension workshops that need the front axle buffer 1K0412303H in volume can request a quotation with the Bonpora number, the OE reference, or a sample. The sales team answers inquiries about pricing, packaging, lead time, and custom development, and engineering support is available for cross-reference checks of related buffer numbers. Please visit our contact page to send an inquiry and request a formal offer.