Technical Rear Hub Lock Nuts

[criceo]

I'm striping my car's suspension, and I'm confused about the castled nut on the rear of the hub. The manual says it's a 17mm nut, and FDRicambi sells an 18mm nut. However, the nut on the passenger rear of my car is much larger, around 23mm. The Haynes manual shows a folding plate that goes around this nut, but I don't see it on mine. Am I not understanding something here?

Also, the Haynes manual says that the coupling boot that slides over the splined end of the axle and that bolts into the hub coupling sleeve should only have three bolts, but mine has four.

 

[fiat500]

I'm striping my car's suspension, and I'm confused about the castled nut on the rear of the hub. The manual says it's a 17mm nut, and FDRicambi sells an 18mm nut. However, the nut on the passenger rear of my car is much larger, around 23mm. The Haynes manual shows a folding plate that goes around this nut, but I don't see it on mine. Am I not understanding something here?

Also, the Haynes manual says that the coupling boot that slides over the splined end of the axle and that bolts into the hub coupling sleeve should only have three bolts, but mine has four.

You're correct in that it's much larger, and might even be 32mm. I think the plate is more of a load spreader rather than lockwasher.
It's only the early cars that have three bolts....four is more regular.

 

[the hobbler]

You're correct in that it's much larger, and might even be 32mm. I think the plate is more of a load spreader rather than lockwasher.
It's only the early cars that have three bolts....four is more regular.

Hi Cricero; Peter (Fair 500) is quite correct in stating that only the early 500s had a 3-bolt coupling at the rear---all the later ones had a 25mm drive-shaft and a 4-bolt coupling. The early 500s had "castellated" rear stub-axle nuts (to hold the rubber/alloy coupling onto the stub-axle) whereas the later cars all had "deformable-edge" nuts, of either 31 or 32mm (I can't remember off-hand which size they are).These nuts have to be done up very tight as there is a deformable spacer between the 2 bearings. I have been advised (by an Abarth expert) that if only the rubber/alloy coupling is replaced, the deformable spacer does NOT have to be replaced, but if the bearings are renewed than the spacer MUST be replaced. As Peter also quite correctly pointed out, the "4-armed plate" that goes between the nut and the coupling is less of a 'lock-washer'.and more of a load-spreader---it is not fitted on the later 500s.

 

[criceo]

Thanks for the advice. I'll be sure to get a spacer. I think the bearing set from FDRicambi probably comes with said spacer, but I'll double check.

 

[fiat500]

Hi Cricero; Peter (Fair 500) is quite correct in stating that only the early 500s had a 3-bolt coupling at the rear---all the later ones had a 25mm drive-shaft and a 4-bolt coupling. The early 500s had "castellated" rear stub-axle nuts (to hold the rubber/alloy coupling onto the stub-axle) whereas the later cars all had "deformable-edge" nuts, of either 31 or 32mm (I can't remember off-hand which size they are).These nuts have to be done up very tight as there is a deformable spacer between the 2 bearings. I have been advised (by an Abarth expert) that if only the rubber/alloy coupling is replaced, the deformable spacer does NOT have to be replaced, but if the bearings are renewed than the spacer MUST be replaced. As Peter also quite correctly pointed out, the "4-armed plate" that goes between the nut and the coupling is less of a 'lock-washer'.and more of a load-spreader---it is not fitted on the later 500s.

Thank you for rubber-stamping my reply.
A slight correction; not all Fiat 500s will have 25mm driveshafts. It may have been the case on very late production, but even in 1969, mine was deovered with 19mm shafts with the four bolts.