Technical Tightening rear hub bearings
- Thread starter fiat500
- Start date
Currently reading:
Technical Tightening rear hub bearings
For those who don't have the larger size metric sockets, don't forget Imperial sizes (or as our American friends would say Standard sizes).
E.g. 1 -1/16" AF = 26.9875mm
1-1/4" AF = 31.75mm
If you think that these sizes won't fit, bear in mind that a 1-1/4" socket may be slightly larger (especially if well-used i.e. worn) and a 32mm nut might not be the full 32mm...
There's a few other sizes in AF or Whitworth/BSF that are very close to metric, the sizes that are slightly smaller are useful if the nut or bolt is damaged (e.g if the correct size socket/spanner (wrench) has already slipped and slightly 'rounded' the head of the fastener). You could even 'tap'
an old socket onto the fastener without feeling you're abusing good tools.
Not ideal and certainly not technically correct but might get someone out of a bind.
AL.
E.g. 1 -1/16" AF = 26.9875mm
1-1/4" AF = 31.75mm
If you think that these sizes won't fit, bear in mind that a 1-1/4" socket may be slightly larger (especially if well-used i.e. worn) and a 32mm nut might not be the full 32mm...
There's a few other sizes in AF or Whitworth/BSF that are very close to metric, the sizes that are slightly smaller are useful if the nut or bolt is damaged (e.g if the correct size socket/spanner (wrench) has already slipped and slightly 'rounded' the head of the fastener). You could even 'tap'
an old socket onto the fastener without feeling you're abusing good tools.Not ideal and certainly not technically correct but might get someone out of a bind.
AL.
Just to throw another idea into the mix.....
If you have a range of shim washers available you could re-use the old already collapsed collapsible spacer by using a small shim and avoid the aftermarket hard-to-get-to-initially collapse spacer that many here have complained about.
Prior to the introduction of collapsible spacers, a solid spacer would have been made or selected to give the correct bearing pre-load. But this can be very time consuming, often requiring multiple assembly/disassembly operations.
If I'm rebuilding e.g. a rear drive axle, I prefer to use a solid spacer instead of a collapsible spacer, this also avoids possible problems if e.g. an oil seal needs to be subsequently replaced. If I'm re-using the same bearings and pinion shaft, I can simply measure the collapsed collapsible spacer and make a solid spacer of the same length. (this assumes that the original bearing pre-load was correct, which is not always the case....).
Someone (possibly Gordinir8 ?) suggested turning down the waisted section of the collapsible spacer slightly in order to cause it to begin to collapse without having to apply massive torque but not everyone has access to and ability to use a lathe
AL.
Last edited:
Paolo66
Established member
- Joined
- Feb 6, 2013
- Messages
- 1,004
- Points
- 235
I thought about using a fairly stiff spring instead of the spacer. You wouldn’t have to hang off a scaffold pole to tighten it, it would always be applying preload on the bearings even as they wore and bedded in and it would be reusable
the hobbler
Distinguished member
- Joined
- Jul 25, 2012
- Messages
- 4,077
- Points
- 1,013
I have noticed, by buying parts from different suppliers, that there seems to be 2 slightly different patterns of 'collapsible rear spacers'. One version (which seems to have a gold coloured finish) seems to be too thick to collapse as one hopes that it will--the other version, which is more a silver colour, (which I get from "Motobambino" in Carnforth) looks very similar to the original 'factory' spacers, and does (eventually!) collapse. I was always taught that if you fit new bearings AND/OR drive coup[lings that the spacer had to be renewed. I have been advised by an expert (and he is) that when only replacing the coupling, renewal of the spacer is NOT required.
A year ago i was doing the same thing. So to make a really long story short here are the high lights. First of all you can remove the whole hub assembly and do the work at your vice. Now what i was experienced was that new spacers where so hard that i damaged the threads in an attempt to collapse them. My axle shafts had other problems also, so i replaced them with new ones and tried again to collapse the spacers but i had the feeling that even the new threads was about to get damaged too. So i adjusted the length of the spacer with my little lathe up to the point that i had the correct torque. Now i know that not everyone has a lathe at home but that worked for me. I know a guy that he is adjusting the length of those spacers with a simple grinding wheel.
Just be careful not to damage the threads. Also i had a meter long extension on my ratchet in order to be able to tight the nut.
Thomas
thread is here:https://www.fiatforum.com/500-classic/446102-problem-transmition-please-help-5.html
Just be careful not to damage the threads. Also i had a meter long extension on my ratchet in order to be able to tight the nut.
Thomas
thread is here:https://www.fiatforum.com/500-classic/446102-problem-transmition-please-help-5.html
I've been thinking about 'why is there a spacer fitted'?
There isn't one on the front hubs - taper roller bearings, adjust nut to set bearings, lock in place, job done.
The only conclusion I can reach is that it's to clamp the splined coupling firmly to the axle shaft (via the inner bearing, spacer,outer bearing), while still limiting the bearing preload to the correct figure. Without the spacer fitted, the coupling would only be held in place by it's splines, which would wear due to rocking back and forth as the car went from acceleration to deceleration and eventually result in failure.
Similar situation on rear drive axles with a collapsible spacer fitted between the pinion shaft taper-roller bearings, I reckon it's to clamp the driveshaft flange firmly in place while controlling the bearing pre-load and not rely just on the splines to prevent movement between the flange and shaft.
On the other hand there's other situations on cars where something is driven by splines/serrations where the two parts are not clamped firmly together e.g. front wheel drive cv joints to drive shafts.....
Any Powertrain? Engineers care to comment?
AL.
There isn't one on the front hubs - taper roller bearings, adjust nut to set bearings, lock in place, job done.
The only conclusion I can reach is that it's to clamp the splined coupling firmly to the axle shaft (via the inner bearing, spacer,outer bearing), while still limiting the bearing preload to the correct figure. Without the spacer fitted, the coupling would only be held in place by it's splines, which would wear due to rocking back and forth as the car went from acceleration to deceleration and eventually result in failure.
Similar situation on rear drive axles with a collapsible spacer fitted between the pinion shaft taper-roller bearings, I reckon it's to clamp the driveshaft flange firmly in place while controlling the bearing pre-load and not rely just on the splines to prevent movement between the flange and shaft.
On the other hand there's other situations on cars where something is driven by splines/serrations where the two parts are not clamped firmly together e.g. front wheel drive cv joints to drive shafts.....
Any Powertrain? Engineers care to comment?
AL.
Last edited:
OP
OP
In the rear hub, most modern cars that I have encountered use a single component bearing which consists of two sets of opposed ball or in heavy-duty applications (I am told), roller-bearings set in a single outer shell machined with both races. The precision of the assembly and its cartridge format mean that the faces of the inner races bear upon each other and the bearings are pre-loaded by design to the exact clearances which allow them to function optimally.
The Fiat 500 bearings, when correctly assembled and adjusted with a newly compressed spacer function in just the same way...ie. as a single bearing. Without the spacer to evenly transmit all of the torsional forces encountered over undulations and when turning, the point-loading on different parts of the bearing-races would lead to early failure if the car was used frequently in real-world conditions.
Once the challenge of starting the collapse of the spacer has been achieved, in my experience it then progresses to succumb to pressure very rapidly. If it is attempted to re-use it for any reason, the most important factor to bear in mind is that the process of calibrating the force needed to rotate the hub assembly should be carried out again. Simply tightening the hub nut will not be a guarantee that the pre-load is correct. In fact the characteristics of the spacer mean that it would be easy to over-tighten the bearings.
Of course you can skip all this mullarkey and it seems that some people do, but in the mid to long-term you may be storing up problems for the future.
Among other handling issues, incorrectly adjusted rear bearings may also affect the precision of the steering.
This is why I mentioned inserting a shim washer e.g. 0.010", if available, so that an already collapsed collapsible spacer can be re-used and then carefully tightened to collapse the spacer a little more while checking the bearing pre-load. Saves having to go through the ordeal of trying to get a new collapsible spacer to start collapsing, a process that has caused many a lot of anxiety/grief.
Thanks to "the hobbler" for the info re: the 2 types of spacer that are available.
AL.
I have the opposite problem from the rest of this thread, but it doesn't seem worth starting a new thread for. I am having trouble loosening a castellated hub nut. Before I go at it with a breaker bar, I want to confirm that the lefthand side is NOT reverse threaded. Would heating up the nut help or is the tightness all because of torque?
the hobbler
Distinguished member
- Joined
- Jul 25, 2012
- Messages
- 4,077
- Points
- 1,013
On the rear suspension, BOTH stub-axle nuts are normal clockwise to tighten, ANTI-clockwise to loosen. The fact that both nuts tighten clock-wise is what makes tightening the o/s to its correct torque a bit of a pain in the bum.
- Joined
- Sep 27, 2020
- Messages
- 295
- Points
- 138
Hopefully this is not too much of a thread hi-jack, but I'm aware I have this job waiting for me in the not too distant future...
I've done similar bearings before, as the same design is used for pinion bearings on differentials. In some of those cases there was the option to replace the crushable spacer with fixed spacers, with the bearing preload adjusted with shims. With differentials the general belief was that the fixed spacers were ultimately better, but the crushable spacers were cheaper/easier/time saving for the manufacturer so were more common.
Setting up the fixed spacer can be time consuming as it requires the bearing to be assembled and disassembled several times, but there is no need for monster breaker bars or risks of stripped threads from spacers than won't crush, and it also leaves you with a bearing that is serviceable and can also be re-shimmed to account for wear if needs be.
Has anyone tried going for fixed spacers instead with the Fiat rear wheel bearings?
I've done similar bearings before, as the same design is used for pinion bearings on differentials. In some of those cases there was the option to replace the crushable spacer with fixed spacers, with the bearing preload adjusted with shims. With differentials the general belief was that the fixed spacers were ultimately better, but the crushable spacers were cheaper/easier/time saving for the manufacturer so were more common.
Setting up the fixed spacer can be time consuming as it requires the bearing to be assembled and disassembled several times, but there is no need for monster breaker bars or risks of stripped threads from spacers than won't crush, and it also leaves you with a bearing that is serviceable and can also be re-shimmed to account for wear if needs be.
Has anyone tried going for fixed spacers instead with the Fiat rear wheel bearings?
