Questions about the Metro balljoints have appeared in the Facebook page several times now, but the problem with FB is that the answers disappear into the mists of time.
So to avoid having to keep repeating the same answer again and again I thought that I should deposit the information here so that I can provide a link to it in the future.
As most Midas Gold owners will know, the balljoints were uprated on the Mk2 -post 84- Metro, an upgrade that appears to have come in with the Metro Turbo at the end of 1983.
The Rover Metro/100 had a different front upright design with the lower balljoint being changed to one fitted to the lower wishbone. However, it used the same upper balljoint as the Mk2.
The Mk1 - Pre-84- Metro had the same size taper fitting on the balljoint as the Mini, with the small end being around 12.7mm (1/2" ?) in diameter.
20200227_155133 by Alistair Courtney, on Flickr
These are the part numbers that I know of:
Mk1 1980-84
Rover – GSJ189, GSJ207, GSJ268, FAM9220
Borg & Beck BBJ5150
FAI – SS170
FIRSTLINE – FBJ5150
QSJ1059S
The Mk2 -post 84- had a thicker taper fitting, with the small end being around 14mm in diameter.
20200227_154830 by Alistair Courtney, on Flickr
MK2 1984-1990 + Rover Metro/100 1990-97 Upper balljoint
Rover – GSJ257, GSJ 269, NAM5308, RBG000020
Borg & Beck BBJ5151
FIRSTLINE – FBJ5151
QSJ1060
These are the part numbers that I am aware of. If any Midas owner has used balljoints from other OEM part brands then please post them below.
One question that shouldn't really be asked is can I use a post-84 balljoint with a pre-83 arm, or vice-versa. The front upright was unchanged so either type of balljoint could be fitted.
In the case of the later balljoint in the earlier arm, the taper will go into the hole about halfway and you will only have a few threads showing. I would hope that would be enough to put anyone off the idea.
I have come across a car where an earlier balljoint had been fitted to a later arm. In this case, the end of the taper stood out by around 4mm and the giveaway was that three washers had been used to allow the nut to pull the taper up tight into the arm. Even then the taper was not a tight fit and it wasn't necessary to use a splitter to separate the balljoint from the arm.
Another part of the question is how can you tell which you have fitted to your car, without dismantling the front suspension first?
The answer may be that you can't, at least not without taking one of the nuts off a balljoint to see if you can measure the end of the taper - see diameters above.
The upper and lower arms obviously had the different taper sizes machined into the ends to match the different balljoints, so they would have had different part numbers. However, the foundry numbers which were cast onto the arms were unchanged, i.e. the foundry was producing the same blank arm forging pre- and post-84, the difference only came when they machined the taper.
The lower arms also had a raised date stamp, which was formed in the recess of the arm. You may be lucky enough to find that this has survived the ravages of time, but the chances are that it has been eroded by rust and may no longer be legible.
So really the best answer is to use a balljoint splitter, take them apart and measure them.
Another word of caution - it is not unknown for Midas Golds to have a mixture of pre- and post-84 balljoints, where perhaps the owner had replaced damaged upper, or lower arms, during the build. This isn't ideal, but as long as the balljoints are in good condition and the tapers are correct for the arms then it shouldn't be an issue. I've only ever heard of balljoints failing due to wear in the ball and never due to a breakage in the taper.