BGM gearbox shoulder rings are manufactured with high precision. They are hardened and plane-parallel ground to an accuracy of a hundredth of a millimetre. Thus they correspond exactly to the specified dimensions. Quality assurance guarantees a maximum deviation of only four hundredths of a millimetre undersize. This makes BGM discs much more precise than Piaggio shoulder rings.

WOFÜR
shoulder rings are used to compensate for the axial play between the gang wheels. The spacing of the gear wheels is essential for a cleanly working shift. The closer the clearance is chosen, the less the gears can slip sideways. The gear change becomes more precise because the shift paddle engages exactly in the middle of the gear wheel and does not push it away. It is therefore worthwhile to measure the gearbox precisely.

WIEVIEL
The play specified by Piaggio is 0.15-0.40mm. It is determined with a feeler gauge between gear wheel and shoulder ring.

thick (2.0-2.5mm original with only one nose) suitable for Vespa Largeframe from 1952-1984
thin (0.9-1,4mm with four noses) suitable for Vespa Smallframe and Vespa Largeframe from 1984 onwards (main shaft with two shoulder rings/sea rings)

OLDIES
The thick version of the shoulder rings for Largeframe Vespas before 1984 has not been available from Piaggio for quite some time. Thanks to bgm PRO, the matching shoulder rings in the range of 2mm to 2.50mm are now finally available again for these transmissions.
As a deviation from the original, they have, like the more stable Vespa PX Lusso version, 4 lugs for locking. The knock off of the single nose is therefore no longer possible in the new design.

TIP: The exact determination of the play between the gearwheels is only possible with a feeler gauge (see accessories). Do not forget a new BGM Pro shifting cross and the gear oil.

Vespa Gearbox & Transmission*