Wow that pretty bad, looks like your car has mostly survived in tact though which is fortunate.

My first questions aren't to do with how smooth they move, but rather:
When you rebuilt the hubs, what ball joints did you instal, how much were they, or where did they come from?
Secondly, did you work out the preload for the joints without grease, then go back and pack it in?
Did you use a torque wrench and a new spring washer when they were fitted to the car?

A photo of the broken joint will reveal whats gone wrong. I'm wondering if the taper was mismatched slightly between the joints and the new control arms you got.

All good questions. And a bit more info...

I'l get a picture up tomorrow, but the swivel pin sheared clean off right at the opening of the cup. I was turning slightly left, on a super smooth surface (car park) driving about 4km/hr, and it was the inside wheel that failed. I'd like to believe I got a bad joint. The joint was purchased from Lindsay at Mini's Plus. He said it isn't "genuine", but it's the only ones he ever uses and has had plenty of success with them.

I did all the shim packing/testing fully greased, and in the case of the bottom ones, with the spring installed. I always torqued to spec and tested "tightness". And yes, I torqued the ball joint cup to 75ft/lb, and the swivel pin-to-arm bolts were torqued to 40ft/lb with new washers, springs, nuts and shims.

The upper arms were existing, but the lower control arms were brand new adjustable heavy duty type from MiniSpares. The taper seems normal, though today when I separated all 4 ball joints they certainly came out of the drivers side easier than the (broken) passenger side.

I've now rebuilt both hubs, and though I claimed earlier that it seemed "chunky" - I put that same piece of 4" tube on it and it actually moved quite freely, with not much force. I removed one small shim from both top joints to tighten them up a touch, though I can still easily move them both around with my fingers. I will constantly be checking for any wheel movement to indicate a loose joint.

So with all of that new info, it seems to be that I was simply unlucky with a bad joint. How often does this happen? I am quite curious about your comment with the taper on the arms - is there a way to identify or fix this? How often does this happen?

Thanks Harley.

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1998 Rover Mk VII
2001 Honda CBR 929RR (street)
2014 BMW S1000RR (track)

Here's how my comments fit into what you'e just said:

1. I always use genuine ball joints, because even though it's rare, aftermarket ones have been made / seen in the past without a small grease groove in the spherical seat which causes them to run dry, some have also had incorrect or no hardening applied, causing failure at speed.
Probably not the problem, but there's always the possibility.

2. Shim packing and testing should be done dry, with the spring removed. When it's ready for final assembly, the threads on the nuts want to be on the cleaner side than greasy (in engineering, greased fasteners are supposed to have the tightening torque reduced so that they aren't over tightened).

3. If the two tapers don't match 100%, the locking doesn't happen and movement between the two is possible which on a highly stressed part can lead to failure. Never seen mismatched tapers myself, but I check the feel of it with aftermarket parts. They should also be assembled clean and dry, with no burrs on any edges that may have happened from a previous removal.

On the note of new lock washers under the ball joint nuts - I've had one kit contain washers that peeled out when the nut was tightened - if this happens and its not noticed at the time, the joint may be free to move.

Have you got a photo of the failed joint?

sounds like you got one set of the very poor charge of parts that was around not that long ago. if you search around you will find some failures around the world. at first no one thought of weak material and blamed the installer.
they where also sold by retailers claiming they only sell quality parts over here in Germany.

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Rover 214 atm ....

As Harley said, the bottom ones should be shimmed with the spring removed. Once you put the spring back in they are near impossible to move around. Yours might have been done up too loose?

Did you lap in the new joints with grinding paste?

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The thing that gets me is it broke at such a low speed. Those 12x5 rover wheels have standard offset so theres nearly no scrub radius to add extra load onto the joint.....kinds leads me to thinking that the joint was pried off by having restricted angular movement (mechanically, ie. something stuck in there) for some reason.

Yep lapped them in quite good with fine valve paste. Then soaked the whole lot in metho being sure to remove any leftover. But I really doubt too loose is the problem. When I assembled them, it was very impossible to move with your fingers, and took a touch of effort with a 4" tube attached. Now, the remaining lower joint is still a bit stiff, but add the 4" pipe and it moves rather nicely.

I'll get a decent picture going tonight. As for Harley's suggestion about doing them dry - they definitely have been put together (over and over and over) all greasy. On final assembly I give the whole outside and all threads a decent wiping with a microfibre, just to ensure there isn't any grit. This will clean away the bulk of grease, but is by no means "dry".

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1998 Rover Mk VII
2001 Honda CBR 929RR (street)
2014 BMW S1000RR (track)

I think KLAS will be on the money with it being a faulty pin. Probably be a machining fault, like a knife edge instead of a radius at the edge of the ball.

Yeah, I don't know if that's good or bad news. It means I have to re-do the whole job a third time to feel safe. (Since I bought all 4 joints at the same time, and even the new ones that I've just received from Karcraft are likely the same manufacturer.)

Ugh.

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1998 Rover Mk VII
2001 Honda CBR 929RR (street)
2014 BMW S1000RR (track)

Just for any people interested, here's a pic of a new genuine ball joint:





The joint seated in the cup moves very smoothly, like its been partially or fully lapped in by the manufacturer.
You can also see the groove down the side for letting air / grease out to lubricate the running surface.

For a size reference - its Ø11.7mm through the neck at the smallest part.

over here GSJ1152 is no longer available. sometimes some NOS showes up.
and the successor 8G4197EVA is not better than the non-genuine. even comes with the wrong locktabs, the non-genuine with the correct ones

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Rover 214 atm ....

Well, here's some photos of the carnage. After a thorough inspection I can't find any fault (other than the obvious).

The seat has it's grease groove and hole, and is smooth and nice. The swivel pin mating surfaces are smooth top and bottom, has the flat spot for grease, and the taper doesn't show any irregular wear or damage. The cup is smooth and clean, I can't find any signs of something being stuck in there, inside or out. (Those hairlines inside on the pic are grease from my lackluster cleaning effort) All threads appear new.

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1998 Rover Mk VII
2001 Honda CBR 929RR (street)
2014 BMW S1000RR (track)

And here it is carefully balanced to see how it looked when it was still one piece. The profile looks close enough for horseshoes...

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1998 Rover Mk VII
2001 Honda CBR 929RR (street)
2014 BMW S1000RR (track)

Pretty clean break - fatigue failure - I'd say either manufacturing defect (like wrong heat treat), or poor material quality.
Probably just bad luck.

I'm thinking I'll design my own heavy-duty ones and get them made myself though for future use if I see another thread like this!

i would be very interested, if you make and sell them. no company over here was interested at all to make some

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Rover 214 atm ....