48 replies to this topic

[MRA]

As most abrasives are rock based anyway, the abrasive in toothpaste is no different, it is just finer, it would need a lot of work to lap them in using it though.... lapping in paste is not expensive, just get fine, don't ever bother to use course simply too much and will cause damage instead

[Gulfclubby]

All rock is not equal. Most toothpastes, unless they utilize some modern silica based compound, use some sort of calciumcarbonate as abrasive. That's got a hardness of around 3, whereas hardened steel will be around 7. My best guess is that the abrasive stuff in lapping paste is corundum based, which is somewhere around 8-9. Definitely a good advise to get the right stuff in the first place:)

[JustSteve]

I used a drill,,,,, if i did them by hand I'd still be doing them 6 months later! (that was minispares non--genuine ones)



i did it really slow and kept stopping to let it cool down etc.

I'm happy, they move almost perfectly and I don't see any reason for me to have caused any harm.

[MRA]

Yes you may have done, however the "heat" is local overheating which can easily exceed the tempering and hardening temperature.. so the surface of your ball joints will almost certainly have soft spots where the heat treatment has fundamentally been annealed

[MRA]

All rock is not equal. Most toothpastes, unless they utilize some modern silica based compound, use some sort of calciumcarbonate as abrasive. That's got a hardness of around 3, whereas hardened steel will be around 7. My best guess is that the abrasive stuff in lapping paste is corundum based, which is somewhere around 8-9. Definitely a good advise to get the right stuff in the first place:)

calciumcarbonate .... that's a mouth full

However even water will wear something down if left for long enough..... water jet cutting is a little different as it has grit added to the flow, and yes most valve lapping pastes used to be corundum grit, haven't bought any for some time but a modern material is what most call diamond paste, or cubic boron nitride....

[JustSteve]

Yes you may have done, however the "heat" is local overheating which can easily exceed the tempering and hardening temperature.. so the surface of your ball joints will almost certainly have soft spots where the heat treatment has fundamentally been annealed

ahhh, I get your point now!

think I'l spend 6 months doing them by hand next time then haha. Thanks MRA-mini's, I guess you really do learn something new every day.

[MRA]

I certainly try to

[jaydee]

I've always lapped 'em in, I use a pillar drill on the lowest speed and NEVER had problems. It's how the works minis ball joints where prepared. Like most things if done correctly...............

Second this one.
I use a drill at the lowest speed, a fine valve grinding paste mixed with high temp grease, and spend a bit of time to make them near to perfection.

All the non lapped balljoints i've ever fitted where in quite bad conditions and pitted when inspected after a few thousands miles.

No garage will lap balljoints because the modern type come already lapped in and assembled, and, unless they are really classic-car experienced, lapping balljoints will sound stupid to them.

[robtheplod]

I did them today, spent 4 hours on the bottom and one on the top - first time I've done ball joints. One is stiffer than the other but there is no play in them which I think is the main thing??

Out of interest, what is considered dangerous, definate no-no with ball joints, just so i can be sure i havent done it!!!!

I use Colegate - seemed ok!!

[MRA]

Lol.... hop eyou used one of those tablets to show up all th enasty bits

Definate no-no's... are notchiness, too tight or too loose, you should be able to move the pin with a short spanner over the end.

Smoothness of movement is very important

[robtheplod]

you should be able to move the pin with a short spanner over the end.

not sure i get you here - is it that it should be difficult to move by hand?? the upper one is not loose (no play), but is noticeably looser than the other one ... if there is no play is it ok - it does not 'flop' about - difficult to describe!!

[MRA]

Yes and of course like all things subject to the person with the spanner a body builder type and a not so body builder type will have different forces that they can apply to the spanner....

as long as it is smooth and not loose and doesn't flop about then you are heading in the right direction..

[Nu2mini]

Just wondering what is the collective wisdom with regards to re-shimming the joints. Does it pose any dangers, presuming you can re-establish a good joint. I'm also assuming it removes any need to lap as the joint will have made its own mate. I do realise this is subject to a close visual inspection of both the ball and cup

[MRA]

Yes it does pose issues.....

1) Due to the amount of wear over the years, it will be almost impossible to re lap in a ball joint.
2) They wear into an oval pattern.
3) This oval pattern if disturbed will create a situation where the joint is either very loose at some points and very tight at other points, now the loose points will cause the issues that you are "attempting to adjust to remove" and the tight "spots" will cause a very dangerous situation where the joint can be moved into an area of fatigue stress failure

In other words is your life worth the £20 for a pair of ball joints that if fitted correctly will last for years

Ask how many Mini owners have had sudden failures with ball joints... and within reason I would almost gaurantee that they where adjusted within the last 3 months prior to failure, depending on useage of the car of course.

[ryan22_lgm]

we done all 4 on mine yesterday. Used the drill on a slow speed adding more paste as we went. made sure one of us held the drill and the other held a pair of grippers to make sure it didnt tighten up and heat up.
what a difference it makes to the handling! feels so smooth now like a brand new car! is this the lapping or have my ball joints always been rubbish lol!
The cups were all loose on the old ones and the pins moved easily :s it passed MOT like this a month ago!