Conversion to ZIP/ET4 running gear
- at SIP Scootershop
A ZIP SP Steering Column in a classic Vespa is one of the most radical Fork conversions. Recognisable at first glance: the Suspension Arm is mounted on the left side and not on the right. The elaborate conversion is rewarded by more modern Brake Drum designs instead of the classic Vespa shape, a wider front tyre, a large selection of high-end Shock Absorbers and more agile handling thanks to the shortened wheelbase. It is also pleasing that you can find these Steering Columns for little money as used parts and that they are usually already fitted with original Disc Brakes.
Which classic Vespas can be converted to ZIP Fork?
In general, all classic Vespas and Lambrettas can be converted to ZIP forks with more or less effort. Like the conversion forks with PX/PK technology, we have ZIP SP forks for the following Vespa models in our range:
We also stock the Polini Fork, which is specified to fit all models.
The SIP Conversion Steering Columns from the PIAGGIO ZIP SP are adapted for the specified models in terms of length, steerer tube, Steering Lock and steering stop. The attachment of the Mudguard was subject to frequent detail changes in the history of Vespa models and is therefore not plug & play prefabricated to fit each individual model.
All you need for the conversion to ZIP front axle
Brake Drum and Rim
The biggest visible difference between a classic front axle and ZIP-SP is the available Brake Drum and Rim of the newer generation. Whether rim star for split sheet metal rims(SKR, ZIP) or real rims in car design(ET2/ET4/LX), none of them resemble the look of the Vespa Sprint/Rally and PX drums that have been retained for over 30 years.
Today, the rims no longer available from Piaggio are even reproduced (LX and ET2/ET4). And there are also Replacement Parts variants that leave a lot of scope for visual design (PLC star, Polini Rim). SIP now also offers a rim that fits on ZIP Steering Columns with an offset of 30, in the Pordoi design of the modern Vespa GTS.
Rims that are mounted in the centre of the wheel (star rims, like car rims) usually have a 5-hole circle with a diameter of 86 (5 x 86). Ring-shaped Rims that are mounted far outwards (Vespa classic) usually have a 5 x 220 bolt circle.
Brake Calliper
2-piston, 4-piston, axial and radial fitting. Brake Callipers and Brackets for the ZIP SP Steering Column are available in a variety of shapes and from many different manufacturers. CNC-machined, forged and cast, the choice is extremely wide. Please note: There are two very similar standards for the radial Brake Calliper, but they are not interchangeable: a) Hole spacing 82 mm (various suppliers), hole spacing 84 mm (Formula or KTM SX65 brake calliper and Ottopuntouno).
Brake Disc
All Brake Discs for Classic Vespa PX 125-200 E '98/MY/'11/LML Star and ModernET2/ET4/LX/LXV/S/Primavera/Sprint 50-150 ccm fit on the ZIP Wheel Hubs. Technical details are the outer diameter of 200 mm and the internal Seating with 5 Screws and 96 mm centring diameter. Piaggio Washers and those with few, small holes are designed to be very durable. There are also more aggressive designs, e.g. Galfer Wave. Floating Brake Discs promise even more brutal deceleration values.
Shock Absorbers
The design of the "ZIP SP" Fork has remained almost unchanged until 2024. A number of high-quality shock absorbers from the heyday of Scootermatic tuning are still available today, as well as even more modern high-tech Silencers that are compatible with the successor models.
Steering Column
If you are confident enough to adapt a Fork yourself, you can fall back on a used part. The length of the steerer tube in the Vespa frame is adjusted by welding in the MMW Adaptor. The upper part of the Steering Column/Fork is cut off and the MMW Adaptor is welded at the correct height so that the thread and clamping surface for the Handlebar are in the correct position.
Alternatively, POLINI offers a reinforced Fork for the POLINI Cup. The mudguard bracket is screwed on to make it easier to fit different mudguards. The POLINI Fork is supplied without Suspension Arm. To facilitate mounting and dismounting of the original Swing Arm, a kit with Bolts, Bearing, Stoppers and pressing tool is included. With modifications to the Handlebar Support, the Fork can also be fitted to Vespa Models.
Small parts
We offer you absolute luxury and our complete experience with our small parts kits. The Mounting Kits "for SIP Conversion Steering Column PIAGGIO ZIP SP" contain all the necessary parts such as Wheel Hub, Steering Head Bearing Set, Screws, Speedometer Drive Gear to complete your fork conversion.
Suspension Arm/Swing Arms
The original ZIP Fork comes with a pre-pressed Suspension Arm. The POLINI must be fitted with an Axle and Swing Arm. Certain workshop equipment is required to press the original Swing Arm. Replica Swing Arms are usually bolted together in several parts. They are available from various manufacturers, some in the original length and some extended to influence the driving stability.
Wheel Hub
The Wheel Hub connects the Axle to the Rim and Brake Disc. The original parts are still available from PIAGGIO, but tuning forges offer replicas milled from solid material with a more sophisticated design. Thanks to high-precision CNC machining, the concentricity/balance of these parts is perfect and they are often weight-optimised and made of high-strength material.
Rim spider
Traditionally, a Vesparad consists of a Brake Drum and a ring-shaped Rim. The SKR and ZIP Models, in particular, went beyond this principle. Instead of a Brake Drum, star-shaped elements were temporarily inserted to connect the ring rim to the Wheel Hub. In later models, this transitional form was again abandoned and star or spoke rims with a central connection were used.
Customisers of a ZIP SP Steering Column have the whole range to choose from: Whole rims from ET2/ET4, ZIP SP, Polini or SIP.
Rim spiders separately (for ring rims) from PLC, SIP and recently even in the classic look from VMC. There are even one-piece Wheel Hubs and rim spiders, these are the 5-star Wheel Hubs e.g. from SKR and ZIP II SP.
Axle Seating
The Axle Seating is placed on the Axle and holds the Brake Calliper and Shock Absorber in place. The original PIAGGIO Axle Seating is designed for axially mounted Grimeca and Heng-Tong Brake Callipers, as well as the tried and tested SIP 5640 with ABE.
Thanks to AF-Parts, OTTOPUNTOUNO and POLINI, there are also CNC-milled counterparts to which even modern radial Brake Callipers can be bolted.
Which Tyre should I use?
The ZIP SP front axle is designed ex works for a 2.50 inch wide Rim. The standard tyres for this Rim are 100 and 110 mm wide tyres, but 120 and 130 mm tyres are also within the frame. Usual cross-sections are 80 and 90 percent, e.g. 100/80 - 10" tyres (like 3.00 - 10") and 100/90 - 10" tyres (like 3.50 - 10") are predestined.
As a general rule, flatter tyres (low profile) offer greater steering precision but are less able to iron out bumps and vice versa.
Caution: The rolling circumference of your Tyre influences the overall ratio of your drive axle ..
Tyres | Tyre width | Circumference | Per cent |
3.00-10 | 76.2 mm | 1235 mm | -6 % |
3.50-10 | 88.9 mm | 1307 mm | 0 % |
100/80-10 | 100 mm | 1259 mm | -4 % |
100/90-10 | 100 mm | 1319 mm | 1 % |
