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MG Midget and Sprite Technical - Kingpin Shim Query

Hi All,
Mk III midget
MOT due soon , front bearings happily replaced and now just mentally preparing for the worst!

IF there is any kingpin play that the MOT man doesn't like, there have been some threads on this BBS about taking off one of the shims which live directly underneath the top trunnion, which allows the kingpin to be tightened up again. ( I hasten to add that I have regularly slurped grease into all nipples since I took possession.)

Is it " simply" unbolting the top nut, slipping up the trunnion, removing a shim and then putting it all back together again....or am I being childishly naïve?

I would be really grateful for your comments.
cheers colin
colin frowen

Hi Colin, Yes it is that simple and as its free to do its worth a try. But don't expect it to take up worn kingpins in every case. It really just deals with vertical play, but often this is manifested by lateral play, especially in the lower bushing. So reducing vertical play may also fix lateral slack at the same time.

This is the detailed method that I use, and posted on the other thread:

<<<If removing shims then jack both front wheels off the ground and prop the chassis on axle stands. Check that you can twirl the steering fully lock to lock. Then put a jack under the bottom wishbone on the offending side and jack it up to the point that the weight just begins to transfer from the axle stand on that side onto the jack. This will take the tension of the road spring off the kingpin and you can safely undo the castellated nut.

Very gently lower the jack just enough - and no more - to ease the top of the king pin out of the trunnion whilst lifting the damper lever arm as high as it will go. There should be no need to remove the trunnion itself from the damper lever arm. You will find some small shims that sit on the step in the kingpin, just below the threaded section. Try removing one or more shims depending on what you find.

Pump the jack up (I use an hydraulic bottle jack for these sorts of jobs which gives good control)whilst guiding the kingpin back through the phosphor bronze washer and into the trunnion. Pull it up by tightening the castellated nut and nip it tight. Now remove the jack and test for free steering movement and also see if it has improoved the slack. If steering is tight, then you have removed too many shims and you may have to backtrack a bit. Its just trial and error at this stage.

Sounds complicated, but it is safe and easy to do so long as you use a controllable jack firmly placed under the wishbone or better still, inserted up into the lower spring cone. There is no need at all to do anything more to manage the road spring tension than I have described. If others start talking about removing the spring with long bolts etc, etc, then that is all quite unnecessary for this particular "adjustment"!

NB Correct vertical play is NOT achieved by slackening or adjusting the castellated nut, but by the selected shim pack, so that nut does need to be tight.
GuyW

Hi Guy,
Cheers -EXACTLY what I needed to know!!
Many thanks
Colin
colin frowen

What goes round comes round Colin. I have frequently benefited from advice and help from others.
GuyW

I agree that Guy's method is the way to go, except when I tried this on my 1275, I could not get the jack to release all of the tension in the spring. All that happened was that the car got higher, I then had to release the spring using the long bolt method.
Could a previous owner have fitted stronger springs ?

Dave
Dave Barrow

On mine, the last bit of tension is only released as the nut is slakened. You may also need an Attractive Assistant to sit on the wing above where you are working, but it can become a distraction.
GuyW

So, the castellated nut should be quite tight. If it is and the steering is tight, then rather than loosen the nut one space, you need to add shims? With the proper amount of shimming, then tightening the nut should not tighten the steering? Seems like even with proper shimming, if you tighten the nut enough, it will press the shims enough to put a drag on moving the wheels. Is there a torque setting for that nut? Don't think I've ever seen one.
Jack Orkin

don't know if there's a figure in the workshop manual but it should be tightened to about 30 ft-lbs then aligned to the nearest split pin hole if using the correct original castellated nut. If using a replacement nyloc nut then there's far more scope to over-tighten.
David Smith

If the shim pack is correct it would have to be mightily overtightened to crush the steel shims to the point that the steering became tight.

The other thing to watch is that the large phosphor bronze washer/ bearing isn't worn, but also that it is properly seated with no debris behind it.
GuyW

This thread was discussed between 08/03/2016 and 10/03/2016

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