Piaggio 177508 Speedometer Pinion 12 Teeth – Vespa PX 125-200 (1998-2017)

The original Piaggio 177508 pinion is the small helical gear that fits into the front wheel hub of the Vespa PX and drives the speedometer cable. It is the part that strips first when the speedometer stops working: 12 helical teeth, black plastic body, hexagonal cable connection. Product code 177508.

✓ Strengths

• It's the first part to check if the speedometer isn't working – before suspecting the cable or the instrument, remove the pinion: nine times out of ten the teeth will be worn.
• 12-tooth gearing – the correct gearing for the PX speedometer ratio: a pinion with a different number of teeth will show an incorrect speed.
• Hexagonal cable connection – the seat where the end of the speedometer cable enters, without adapters.
• It costs a few euros and can be changed in five minutes – you work from the outside of the hub, without removing the wheel.
• Original catalog spare part – same code as the original equipment part.

✓ Technical Features

✓ Vehicle Compatibility

The list is taken from the official Piaggio spare parts catalog (B2B area). If you have any doubts, send us your scooter's frame number and we will check the correct code.

✓ Who it's perfect for

For those who have a PX with a stuck speedometer or a dancing needle. It's the classic fault that seems serious but only costs a few euros: the pinion is plastic, works inside the hub in contact with water and dust, and over the years the teeth round off until they no longer grip. It's for the Vespa rider who uses their PX every day and wants to get the speedometer working again without taking it to a workshop, and for the restorer who is rebuilding the front wheel and might as well change it while everything is disassembled.

Frequently Asked Questions

My PX speedometer isn't working: is this the part?
In most cases, yes. The pinion is the only plastic component in the chain and works inside the hub, where water and dust get in: it's the first to wear out. Pull it out and look at the teeth: if they are rounded or missing, you've found the fault. If they are intact, check the cable.

Where exactly is it located on the vehicle?
In the front wheel hub, in the seat where the speedometer cable end screws in. It can be removed from the outside without disassembling the wheel: just unscrew the cable nut and pull it out. It's one of the simplest interventions you can do on a PX.

How many teeth does it have and why does it matter?
It has 12 helical teeth. The number of teeth determines the ratio between the wheel's rotations and the cable's rotations, and thus the speed read on the instrument. Installing one with different gearing will cause the speedometer to read higher or lower than the actual speed, even if it mechanically rotates the same.

Does it also fit the PX 200?
Yes. The official Piaggio spare parts catalog assigns this same code to the PX 125 E, PX 150 E, and PX 200 E from the historic catalogs, as well as to the 2011-2017 PX 125 and 150 two-strokes and the PX 125 30 Anni. It's the same front hub on all three displacements.

Do I also need to change the speedometer cable?
Not necessarily. Look at it while you have the pinion in your hand: if the square or hexagonal end of the cable is worn, change that too, otherwise it will quickly wear out the new pinion. If it's intact and the cable slides freely in the sheath, it's fine as is.

Do I need grease for assembly?
Yes, a thin layer. A little grease on the teeth and the seat reduces friction and keeps water out. Don't overdo it: excessive grease collects dust and becomes an abrasive paste. Before screwing the cable back in, manually check that the pinion turns freely.