VW up! Skoda Citigo Seat Mii Front Strut Bump Stop OE 1S0412303 | PU

Front Strut Bump Stop OE 1S0412303 for the VW up!, Skoda Citigo and Seat Mii

OE 1S0412303 is the front suspension bump stop used across the Volkswagen Group NSF small-car platform, shared by the VW up!, the Skoda Citigo and the Seat Mii. The part sits on the piston rod of each front strut and cushions the final phase of compression travel. Bonpora supplies this buffer as No 4110004, moulded in polyurethane to the drawing size of 16 mm hole, 50.4 mm outer diameter and 63.2 mm free height, for distributors, suspension kit assemblers and aftermarket brands.

What the Bump Stop Does inside the Front Strut

In the McPherson front axle of the up!, Citigo and Mii, the damper travel ends inside the strut tube. The bump stop, sometimes listed as a strut bumper or jounce buffer, is pushed onto the piston rod and works as a progressive cushion. When the wheel hits a pothole or a speed bump, the polyurethane body compresses and slows the last centimetres of travel, so the damper seal and the top mount are protected from metal-to-metal impact.

When the buffer ages, it loses height and starts to crumble. Drivers notice a knocking noise over rough roads, harsher bottoming-out at the front axle and, in some cases, uneven tyre wear. Replacing a worn bump stop during damper service is therefore routine workshop practice, and many repair kits pair the buffer with a new dust boot. Related shock absorber parts are listed in the same programme.

Key Specifications of Bonpora No 4110004

Dimensions follow the factory drawing: the 16 mm centre hole slides over the damper rod, the 50.4 mm outer diameter matches the strut tube clearance, and the 63.2 mm free height corresponds to the 63 mm catalog thickness of the OE reference. Tolerances are checked on a sampling basis before shipment, and a dimensional inspection report can be requested together with the quotation.

Vehicle Applications across the NSF Platform

The NSF platform, also described as the New Small Family, was produced in Bratislava from 2011 and covers three sister models: the VW up!, the Skoda Citigo and the Seat Mii. All three use the same McPherson front axle, which is why one buffer number serves the whole group. Catalogues attach the part to specific suspension PR codes, for example G01 for many Mii and Citigo variants, so the vehicle data label or a damper catalogue check remains part of normal ordering discipline.

Catalogues also list the load up! panel van, the move up! and cross up! trim lines and the up! GTI inside this coverage window. Electric variants such as the e-up!, Citigo-e iV and Mii electric appear in separate catalogue sections, so buyers should confirm each electric job by VIN or damper number instead of assuming coverage. Trade listings occasionally group the reference under Audi and Volkswagen headings, while public aftermarket catalogues assign it to the three NSF brands.

1S0412303 and 1S0412303A Are Different Heights

The closest neighbour in this number family is 1S0412303A, and the two buffers look almost identical in photographs. Catalogue data nevertheless shows a clear difference: the base part measures about 63 mm in free height, while the A-suffix variant is listed at 53 mm. The ten millimetre gap reflects a different damper and suspension setup inside the same platform, and the two references are crossed to different aftermarket numbers.

Because the error is easy to make from a photo alone, the practical rule is to confirm the full OE number and the height together before releasing a purchase order. The same discipline applies to quotes built from generic listings that show only a rough shape. A wrong-height buffer either blocks damper travel or leaves the strut unprotected, so this double check costs little and prevents the most common mix-up in the family.

Cross-Reference Numbers for Global Sourcing

The OE reference is crossed widely in the independent aftermarket, which makes single-number sourcing practical for distributors. The table below lists frequently requested equivalents from European catalogue brands. Kit references that combine two buffers with dust boots are handled in the next section, because their quotation logic differs from single-piece supply.

Availability varies by region, so it is worth confirming two or three cross numbers for each customer market. Buyers in Europe usually start from the febi, SACHS and SKF references, while buyers in other regions more often match the KYB or Bendix listings before comparing factory quotations.

Why Polyurethane for This Application

The OE buffer and the leading aftermarket versions are specified in microcellular polyurethane rather than natural rubber. For a city car that spends its life on uneven streets, the material choice affects how the buffer survives repeated full-compression events. The polyurethane bump stop programme covers this family together with other VW, BMW and Toyota references.

Polyurethane is not presented here as a universal upgrade. In this specific application the material matches the OE specification, and its lower compression set keeps the working height stable through the service life. For fleets operating in hot and dusty regions, the slower ageing of PU is usually the decisive argument, while the slightly higher unit price is recovered through fewer warranty comebacks.

Buffer, Dust Boot and Kit: Keep Quotations Separate

Several catalogue entries around this OE number are kits, not single buffers. The GSP 5402422PK reference and the SKF VKDP 33348 T set each contain two buffers and two protective bellows, and trade kits such as ZT033 pair the buffer with the dust cover reference 357413175A. A kit therefore prices two corners of the front axle, while Bonpora No 4110004 prices one buffer.

Quoting a kit number against a single-piece requirement, or the reverse, distorts the comparison immediately. The practical approach is to state quantity, content and packing for each line item, then let the customer decide whether to buy complete kits or refill buffers only. Both routes can be served from the same production tooling, and mixed pallets are possible inside one container.

Wear Symptoms and Replacement Practice

Buffers fail gradually, so the symptoms are easy to overlook: reduced free height, surface powdering, cracks along the outer wall and hard flattened sections where the material has taken a permanent set. Workshops often discover the condition during damper replacement, when the old buffer comes off the rod in fragments and the strut shows contact marks at the bottom of its travel.

Because the part is fitted on both sides of the front axle, replacement in pairs keeps the two corners responding equally, and the required quantity per vehicle is two. During the same service the dust boots should be inspected, since a torn boot lets grit reach the buffer surface and shortens its working life. Chassis and suspension parts for the NSF platform are grouped in one programme for mixed-container orders.

How Buyers Search and Verify This Part

Purchase enquiries for this family arrive through several different search routes, and each route ends at the same OE anchor. The four patterns below cover the majority of trade enquiries received for this reference.

Part type plus size

Searches such as front strut bump stop 63 mm VW up! or Citigo front spring buffer 50.4 mm land on drawings where the height and diameter can be compared directly with the specification table above. This route works well for buyers who hold a used sample but no readable number, because two dimensions are enough to separate the base part from the A-suffix variant.

Part type plus OEM number

Queries like 1S0412303 bump stop manufacturer or febi 38366 equivalent supplier are the fastest route for B2B buyers, because the OE and cross numbers identify the part without photographs. Bonpora answers these enquiries with the drawing, material data and packing details in a single reply, so the comparison between factories stays on measurable facts.

Vehicle model plus part

Buyers working from licence plates or VIN lists search for Skoda Citigo front bump stop or Seat Mii strut bumper. The result should always be narrowed by the PR code or the damper reference, because the NSF platform uses several damper setups across its production life and the platform ran under three brand names at the same time.

Custom and private label

Enquiries that start from a drawing, a hardness target or an existing sample are handled through the custom route. The custom parts programme covers material selection, tooling and neutral or branded packaging for buyers building their own range of suspension buffers.

Custom and OEM Service for B2B Orders

Bonpora produces suspension buffers in China with OEM and custom design support, covering material formulation, drawing-based tooling and private-label packaging. Standard supply is neutral export packing with a 15-30 day delivery window and a 1 year warranty period. Sample requests, dimensional reports and mixed loading plans for container orders are arranged by the export team before contract. To receive a quotation for No 4110004 or a custom version of the 1S0412303 buffer, send the quantity, destination port and packing preference, and the reply will include unit pricing at the requested order tiers.

Frequently Asked Questions

Which vehicles does the 1S0412303 bump stop fit?

It fits the front axle of the VW up!, the Skoda Citigo and the Seat Mii, the three models of the Volkswagen Group NSF small-car platform produced from 2011. Catalogues attach the part to specific suspension PR codes, so the vehicle data label or a damper catalogue remains the final check before an order is released.

Is 1S0412303 the same part as 1S0412303A?

No. Both references describe front axle buffers for the same platform, but catalogues list the base part at about 63 mm height and the A-suffix variant at 53 mm. They cross to different aftermarket numbers, for example febi 38366 against febi 38388, so the two should not be interchanged on the basis of a photograph.

How many pieces does one vehicle need?

The front axle carries one buffer on each strut, so the required quantity per vehicle is two. Workshops normally replace both sides together to keep the axle response equal, and many combine the job with new dust boots while the struts are already open.

What material does Bonpora use for No 4110004?

The buffer is moulded in polyurethane, matching the material specification of the OE part and of leading aftermarket references such as febi 38366. Polyurethane keeps its working height longer than conventional rubber and resists powdering in hot climates.

Does Bonpora support OEM projects and custom designs?

Yes. The factory offers OEM and custom design support, including drawing-based tooling, material adjustment and private-label or neutral export packaging. Buyers can request samples and dimensional inspection reports before confirming a production order.