Technical Tightening rear hub bearings

[fiat500]

I am already contributing to two threads that have involved this topic but I am keen to get some extra input from knowledgeable contributors who have done this job.
I think I can be sure that the hubs are correctly re-assembled with new seals bearings and that "resilient spacer".
Too resilient is my feeling. The ones that came out were correctly barrelled having been under tightening strain.
I seem not to be the first person to find that the new ones need seemingly excessive tightening and are still not collapsing as intended under load. I am unable to eliminate the free play on the axle and am reaching the highest torque on my 1/2" drive wrench
Do I just keep tightening or have I missed something?
There is already a useful thread with a link to a non Fiat video which shows the principle of this.

https://www.fiatforum.com/500-classic/324250-rear-wheel-bearings.html

 

[Toshi 975]

I gave up trying to compress that spacer after I pulled the car off the ramps trying to get enough force on the wrench. There is no way you will do it with a standard wrench unless you can get a large extension on it to get more leverage. A mechanic mate told me that you need a torque converter wrench . He has one that gives a 4:1 increase in the applied force.

 

[fiat500]

Just as I thought. I need to sleep on this one a big longer. .

 

[fiat500]

Persistence, patience and the knowledge that others have faced similar issues helped to get the job done as follows:

*

1. Got hold of a 1/2" drive air-tool socket with just the six flats for better grip. I have broken (irony obvious)t two breaker bars in the past so instead used my old torque wrench set to maximum.

2 Chocked the car front and rear and with all wheels on the ground and handbrake tight I used strength and dexterity to achieve maybe 1/32 of a turn at a time on the big nut. Each time I jacked up the car, off with the handbrakea and checked for play at the rim. After about 20 stages of this the play started to reduce quite quickly and the tightening became slightly easier. This is because the spacer between the bearings is becoming compressed as intended and even more caution is needed.

3. With play apparently gone, the car was jacked up, wheels and brake drum removed and the old Haynes rotational test with a weight carried out. *The hub turned just a touch too easily which was put right when the castle nut was nipped up a touch to make it align with one of the two holes in the shaft.

*

So this very simple job seems quite hard work and it is possible I could have nursed the old bearings by just tightening the nut. Relieved it's done though and will post a pic of the preload procedure tomorrow.

 

[fiat500]

Photo to show the weight being suspended from the hub at 4.3" from the centreline.
BRA_9548 by peterthompson, on Flickr
Immediately afterwards it slowly pulls the hub round. A slight nip of the rear nut to align holes achieves just the right preload.
BRA_9549 by peterthompson, on Flickr

 

[Donny 500L]

Used a 1/2 " breaker bar with a 30 inch 1 1/2" pipe for leverage. Finally got it correct.

 

[Luxe]

How much weight was used?

 

[fiat500]

How much weight was used?

It's a 1lb weight.

 

[Luxe]

Ok,


So I have been mulling this one over. I understand setting the pre-load for the bearing if the shaft is pulled or the bearings themselves have been removed or disturbed, but if all that remains in place and only the flexible coupler is swapped, is there really a need to do the whole pre-load game? Shouldn't I be able to just torque the castellated nut to the torque spec specified earlier in the thread?

 

[fiat500]

I think the simple answer is that you could just stick the new coupling on, tighten the big nut until starts to tighten and then go a bit more until the split-pin holes align. Ideally you would also carry out that rotational check.
the real problem is if you tighten too far so the turning is too stiff. To do it properly you then need to dismantle and replace the crushable spacer at least.
If you've had no problems I would just do the first thing described. Because the big nut has already done its work when the bearings were first fitted, you shouldnt need to tighten much further once the nut makes contact; it's not going to need the ten foot bar treatment.

 

[Luxe]

What is the size of the castellated nut. Have to get a bigger spanner.

 

[Luxe]

It is a 31 or 32mm thinking.

 

[fiat500]

It is a 31 or 32mm thinking.

32mm.....worth getting one of those black, air-tool quality ones. It's also useful to take off the crankshaft pulley nut.

 

[Luxe]

I am glad I changed the flexible joints. One looks to have been installed backwards with all the rubber dissolving, bubble gummed outward, and greasy on the nut side with the bearing side dry rotted.

 

[Chrismunn]

I am about to tighten the rear wheel bearing assembly and I am trying to identify the correct socket size before attacking this, a 5/8 Whitworth socket is a bit sloppy and I do not want to round over the edges of the nut. Can someone help me with the correct metric socket size for this please?

 

[Chrismunn]

Not so sure if it is 31mm, 32 seems to be too big? Conversion charts are saying about 28 mm but that does not seem to be correct....

 

[fiat500]

Not so sure if it is 31mm, 32 seems to be too big? Conversion charts are saying about 28 mm but that does not seem to be correct....

The standard ones on the 500 which have spilt-pins are 32mm. Apparently there are later, self-locking nuts which look to be a significantly smaller, across-the-flats size.

 

[Chrismunn]

I can confirm it is 27 mm!

 

[fiat500]

Have fun with it.

 

[Chrismunn]

Done!

I have been delaying this for far too long , worried about how to lock up the shell while torquing the axle assembly. Then it came to me...simple and effective. Done in less than an hour. Now time to slide in the engine.