Technical Rear wheel bearings

[dapedza]

Hi folks, I’m new to this fabulous forum which is great resource.
After much drama, I got an overhauled 126 box fitted to my 500. It’s great as it has synchro, which means the whole family can now drive it. Whilst test driving I picked up a slight rumble from the rear right, so thought the wheel bearings needed investigation. Ripped out the old oil seals and knocked out the bearings using a copper drift. I noticed there were two circlips between the oil seals and bearings. I wrongly assumed they were left over from the destroyed oil seals.
Put it all back together with new bearings and seals. It’s sweet now and the slight rumble has gone.
I didn’t use the circlips. I now discover they should be in there. What do they do? Does it matter? Thanks!

 

[fiat500]

I would strip that down again. The circlips locate and secure the bearing assembly within the hub. Without them, I think that it's just the friction-fit that is keeping the sub-axle in position. If the bearings decide to move it will put a strain on the driveshaft and differential.

Even if the more serious consequences don't arise (the worst of which could be quite dangerous), it's likely that the bearings will fail quite quickly as things are at present.

The assembly of the rear wheel bearings has quite specific instructions; did you adjust to get the correct turning-torque of the bearings?

 

[dapedza]

I would strip that down again. The circlips locate and secure the bearing assembly within the hub. Without them, I think that it's just the friction-fit that is keeping the sub-axle in position. If the bearings decide to move it will put a strain on the driveshaft and differential.

Even if the more serious consequences don't arise (the worst of which could be quite dangerous), it's likely that the bearings will fail quite quickly as things are at present.

The assembly of the rear wheel bearings has quite specific instructions; did you adjust to get the correct turning-torque of the bearings?

Thanks for that. Yes, I set the bearings up carefully as per the directions. You’re probably correct, will have to strip it down to be safe. Thing that I don’t understand is both bearings butt up against the step inside the hub. So they can’t move ‘inwards’. If one bearing shell was to move ‘outwards’ it would be impossible, as it would have to take the other bearing with it. That would not be possible, as the whole assembly is torqued up together, and it would necessitate taking the other bearing over the step in the hub. Also, I didn’t notice a recess in the hub for the circlip. It was just sitting there and slid out easily.

 

[fiat500]

Thanks for that. Yes, I set the bearings up carefully as per the directions. You’re probably correct, will have to strip it down to be safe. Thing that I don’t understand is both bearings butt up against the step inside the hub. So they can’t move ‘inwards’. If one bearing shell was to move ‘outwards’ it would be impossible, as it would have to take the other bearing with it. That would not be possible, as the whole assembly is torqued up together, and it would necessitate taking the other bearing over the step in the hub. Also, I didn’t notice a recess in the hub for the circlip. It was just sitting there and slid out easily.

I assume that the step is to the outside? There must be some method that stops the axle-shaft assembly from moving laterally. That does mean it can't be as dangerous as I thought. It's ages since I did my bearings, but there must be access to fit and remove them from the inner end?
I wasn't aware that the bearings float within the hub, but if the circlips are actually snap-rings, with no location groove in the hub, then it looks like they are used for alignment or perhaps to space the bearings from the seals.
When you tighten against the collapsible spacer, the dimension between the bearings is unpredictable, so I can see that there can't be a fixed location for a ciclip groove. I'll look for my images of when I did the job and see if that reminds me more accurately.


Thinking about it

 

[dapedza]

I wouldn’t go as far as to say the bearings float in the hub, but the combination of the inner step plus the torqued axle shaft should stop any lateral movement. Happily the ‘crushable’ spacer is now part of ancient history. It now has a standard spacer between the bearings. I’ll do the opposite side bearings next week. I’ll be intrigued to see if there is a groove for the circlip, but I honestly didn’t see one!