Conversion to 9 inch front & rear
- for 8-inch vintage Vespas
The main advantage of 9-inch technology is the smaller cross-section of the tyres: less heavy, rotating (tyre) mass sits on the outside of the light alloy rim. In addition, the lower tyre cross-section is less likely to roll sideways and swerve. The 9-inch tyres guide the wheel much more stably and precisely than a 3.50 8-inch balloon tyre.
An additional advantage is the option of converting to the large 150 mm diameter brakes that have proved their worth up to the last PX series. The braking performance is therefore absolutely sufficient, even for the most powerful tuning engines of wideframe and largeframe vintage bikes, such as VNA, VBA and -B.
Last but not least, the look changes significantly towards the design of the GS150-like, often so-called "star rims".
The following wheels are originally fitted to Vespa vintage bikes:
3.50 - 8" | Vespa 98/125 V1-15, V30-33, VU, VM, VN, VNA, Hoffmann, VNB, ACMA, 150 VL, VB, VBA, VBB (SIP rim type 8301) |
3.50 - 9" | ACMA Vespa GL 150, built 1956-58 (SIP rim type 8019) |
3.50 - 10" | Vespa 150 GS VS1-VS5 (SIP rim type 8018) |
The larger rims are compatible with vehicles that have smaller wheels. This means, for example, that the 10" rims of the GS can be fitted to both the 9" ACMA GL and 8" vintage models (see above).
Combinable brakes for different rims
8-inch rims (sheet metal rims and SIP type 8301) require small Brake Drum with an inner diameter of 125-127 mm.
Recommendation: SIP Performance Brake Drum, high-precision CNC-machined from free-cutting steel. They offer smooth braking, good modulation and high braking power. In VBB style: item no. 23208610(front) and item no. 23208261(rear). In SeiGiorni style: item no. 23208600(front) and item no. 23208260(rear).
Note: 8-inch sheet metal rims are not always standardised. There are reproductions and contemporary aftermarket rims that do not always fit all Brake Drum models. Partly on models such as Motovespa and Vespa Augsburg - exact origin and construction time are often difficult to narrow down.
9-inch original rims (sheet metal rims) of the ACMA GL150 also require small Brake Drum with an inner diameter of 125-127 mm, as with 8-inch rims.
9-inch SIP rims (aluminium, tubeless, type 8019) for the ACMA GL150 can be combined with 9-inch 150 mm Brake Drum SIP Performance.
Recommendation: SIP Performance 9-inch Brake Drum 150 mm, high-precision CNC-machined from free-cutting steel, suitable for front and rear.
10-inch original GS 150rims and 10-inch SIP rims for the GS 150 (aluminium, tubeless, type 8018) can also be combined with 150 mm Brake Drum.
Recommendation: SIP Performance 10-inch Brake Drum for Vespa GS 150, high-precision CNC-machined from free-cutting steel, suitable for front and rear.
The SIP Performance 9-inch Brake Drum can also be combined with the GS 150 rims (SIP type 8018).
Which rim size fits best?
9-inch Rim SIP 8019 for ACMA GL 150 / Conversion rim from 8 to 9 inches:
Suitable for Models Vespa 98/125 V1-15, V30-33, VU, VM, VN, VNA, Hoffmann, VNB, ACMA, 150 VL, VB, VBA, VBB.
The conversion from 8 to 9 inches is characterised by the fact that the larger rim diameter is compensated for by a lower tyre cross-section. A 3.00-9" Tyre corresponds to a 3.50-8" Tyre in terms of overall height.
Advantages:
Gearbox ratio does not change and does not need to be adjusted.
Speedometer ratio does not change, which is one of the reasons why it was possible to obtain an ABE (general operating licence) for German road traffic.
Maintaining the distance between the front wheel and the Legshield
With other tyre sizes offered by SIP, such as 2.75-9" and 3.50-9", the appearance and transmission ratio of the vehicle can be individually adapted.
An ABE for the conversion is included with every Rim type 8019 and is also available for download on the article page in the webshop. It fits the Brake Drum 23208710 or smaller drums.
10-inch Rim SIP for Vespa GS 150 / Conversion rim from 8 to 10 inches:
Suitable for the Vespa 150 GS (VS1-VS5) as well as for Vespa models such as 98/125 V1-15, V30-33, VU, VM, VN, VNA, Hoffmann, VNB, ACMA, 150 VL, VB, VBA, VBB.
The 10-inch Rim of the Vespa GS is visually similar to the 9-inch Rim of the ACMA GL, which allows an attractive mixed installation, e.g. 9-inch front and 10-inch rear(8018 + 8019). When converting from 8 to 10 inches, however, the length of the Steering Column may not be sufficient in the event of emergency braking and the front wheel may collide with the mudguard and Legshield. 10-inch Vespas such as the VGL, German T4 and 150 GS were fitted ex works with a Fork that has a longer lower tube section (similar to GL/Sprint/Rally). The rear wheel can easily be converted to 10 inches, whereby the drive ratio can be significantly longer depending on the tyre dimensions.
The drive ratio can be adjusted if necessary with suitable Clutch Gear Cogs or primary ratios.
Suitable Brake Drum: SIP part no. 23208700 and 23208710. The smaller 127 mm Brake Drum can also be combined, but offer no advantages from a braking point of view.
Recommended Rim Replacement Parts
For mounting SIP rims in sizes 8, 9 and 10 inches, it is best to use four Nord-Lock washers with a wide contact surface. These washers offer optimum protection against loosening wheel nuts.
It is particularly important that the wheel nuts and the studs of the Drum Brake Seating overlap sufficiently. Please also refer to the enclosed Mounting Instruction for the Rim to ensure correct and safe installation.
SIP has longer studs in M8 and M10 threaded versions for you. Complete new Drum Brake Seating are also available.
We strongly advise against using the original aluminium bronze rim nuts. These nuts were fitted to early Vespas ex works and are not comparable to steel nuts in terms of material strength. You can recognise them by the pale gold-coloured material if you scratch the surface lightly. The surface is originally nickel-plated. SIP offers you steel nuts with a nickel-plated surface that is true to the original; this gives you the original look and reliable mechanical strength values at the same time.
Recommended brake Replacement Parts
For a reliable brake system, it is always advisable to take good care of the linkage and mechanics. This includes SIP Performance cables and unworn Brake Cams. High-quality pads are also a must: our Performance or Premium Brake Shoes are both powerful and reliable. Professionals use the "Brake Pads Hex" milling tool to fit newBrakePads and ensure that the shoes make full contact with the drum and achieve a strong braking effect.
The following are required for the conversion from 127 mm to 150 mm Brake Drum FRONT:
GL/Sprint/Rally frontDust Cover
BrakeShoes GL/Sprint/Rally
Brake Cam front GL/Sprint/Rally
For the conversion from 127 mm to 150 mm Brake Drum REAR are required:
DustCover GS150 rear (Wideframe)
BrakeShoes GL/Sprint/Rally
Rear Brake Cam GS150 if necessary
Bolt Brake Shoes rear
If no longer available, also remember the Spring for the Brake Shoes, the Omega Clips and some assembly paste for optimum installation.
Which Tyre fits best?
The SIP Classic 9" Tyres offer a classic profile and still allow sporty performance.
If you are converting an 8" Vespa and want to be on the safe side, order the 3.00-9" size. This combination should be accepted by the TÜV without any problems, as the appropriate ABE is enclosed with the rims.
According to the ABE, owners of an ACMA GL are also permitted to fit 3.50-9" Tyres.
The 2.75-9" Tyres are actually the original size of older Vespa 50 Models, but can also be fitted to Large and Wideframes. This size can be useful, e.g. for visual reasons or to shorten the gear ratio.
There are around 1001 different Speedometer Drive Gears available for the Vespa models mentioned, so that a correct speedometer display is possible for many different rolling circumferences. However, this is much more convenient and accurate with our electronic Rev Counters/Tachometers for Large and Wideframe Models (item no. 50002600, 50002700, 50002100, 50000730). This allows the rolling circumference to be set with millimetre precision.
PX Engine in a classic car
Of course, our classic car rims can also be adapted here. The Drum Brake Seating with "toothing: coarse" fits on the Driveshafts of the newer Vespa models and even on PX Lusso gearboxes. The SIP Drum Brake Seating with long and robust M10 Studs is the ideal choice for most conversions. All the rims mentioned here in the blog can be driven with it:
The SIP 8" Rim requires the Dust Cover 78483000
The SIP 9" and 10" Rims, in conjunction with the 127 mm Brake Drum, also require the Dust Cover 78483000.
The SIP 9" and 10" Rims, in conjunction with the 150 mm Brake Drum, require the Dust Cover 78482100.
If the smaller 127 mm Brake Drum of the 8" oldtimers is sufficient, you can also use the SIP complete kit and combine it with one of the above-mentioned Rims.
