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MG Midget and Sprite Technical - Wishbone/stub axle advice

I wonder if someone could give me the wisdom of there advice on the re-assembly of wishbones and stub axles please.

Basically I have the wishbone built up (Frontline bottom link and roll bar bracket) and the stub axle (new king pins, bearings, nipples etc) is it better to assemble the two items on the bench or on the car.

I will not put the hubs on until the stub axle is on the car due to the weight, but can't decide on the build sequence.

Martyn Wilks

I would attach the wishbone to the car first:

1. To make it easier to see and check proper alignment and assembly of the inner suspension bushes.

2. Because the car will then hold the wishbone for you, leaving you with your hands free hold the kingpin in position (one hand), insert the fulcrum pin and screw it in (second hand, and hold the two cork washers in position as you do so (third hand).
GuyW

Bolt in the wishbone
Bolt on the shock
Hang the stub axle assembly from the shock.
Bolt through wishbone and kingpin
Insert spring and spring pan
Jack up under spring pan and bolt it to the wishbone.

That is one of a million ways to do it.
Onno K

Personally, I would attach the wishbone to the car first, then the kingpin to the wishbone.

I don't like the idea of trying to insert the lower pin after the stub-axle has been attached to the shock, and with the coil spring in place.

You need to be sure that the fulcrum pin will fit properly and that isn't easy to do at that stage.
Dave O'Neill 2

Assemble the stub axle and wishbone on the bench.
Check the wishbone and ensure the faces either side of where the kingpin fits are square and that the cork washers fit snugly. Note that the cork washers have different internal diameters to suit each side.
Also before fitting the trunnion pin check that the threaded hole as clear of swarf.
Ensure the metal work on the wishbone is correctly formed. This applies equally to BMH and aftermarket wishbones.
Check the oil seal bearing surface on the stub axle is not rutted and worn.
You can now fit as a unit or disassemble if you find the bulk of the two assemblies unmanageable. My preference is for new poly type bushes they seem easier to fit than the rubber ones.
Assemble in the wishbone.
Get two paint scrapers and copper slip the blades.
Present the wishbone to the chassis and insert a paint scraper between the bush and the chassis on the inside of each bush assembly. Push and the wishbone should glide in on the scrapers. Once in pull away scrapers leaving wishbone in position.
When fitting the inner trunnions take extra care that the special washers are properly engaged in the chassis holes. A small mirror is handy for viewing the back side.
Fit the top trunnion then the spring and spring plate.

You'll get as many answers as there are ways!

I find a homemade wide blade screwdriver is usefull for fitting the trunnion pin.

You may have to trim the cotter pin but ensure it is locked against the trunnion pin.

Alan

Alan Anstead

It is nice to have assistance.
The task at the recent Practical Classics Restoration Show.
Alan

Alan Anstead

Martyn, if you haven't already done so, then drill and tap the blind end of the bottom fulcrum pin bushes to take a second grease nipple so that it has one at both ends. This will considerably prolong the life of the bushes, assuming that you regularly use your grease gun.

And, when you screw in the fulcrum pin back it off by half a turn or so, so that the flat for the cotter pin is central between the two bushes. Check also that the flat on the side of the fulcrum pin is aligned to the cotter pin hole so that the pin goes in properly
GuyW

Re. fitting a second grease nipple to the wishbone pan (fulcrum pin blanking piece).

Am I alone in still questioning the wisdom of fitting a second grease nipple? Although it seems common sense to fit one (and I have done so in the past), I feel sure there is intentional good reason that the OE pans did NOT have a second nipple fitted (that reason not being the small incurred cost).

I think there are three or four problems:
(i) the circular blanking piece is not of sufficient thick gauge steel that it will accept the second nipple's thread;
(ii) The circular blanking piece is not sufficiently welded (around its entire circumference) that will enable it to withstand the pressure from the applied grease gun - in short, the blanking piece pops out!
(iii) there is insufficient surface area to tap a thread for a nipple 'holder' (the type that is used with the OE single nipple);
(iv) With a single nipple, the theory is that (a) the grease travels through the fulcrum pin's central (full length) 'grease path' access hole to reach the far end thread, and (b) the grease finds its way around the near end thread.

I have found that, with a second nipple, (if the blanking piece hasn't popped off), then grease emerges from the second nipple hole.

Does anybody have any thoughts? Cheers . . . .
Andy Hock

Agree Andy, just adding that the end plug is a Welch plug; they are not welded in place, they work similar to a core plug.
David Smith

I must admit to never fitting a second grease nipple although I can see the logic. I do regularly grease the suspension (every 1500 miles)or twice a year at least. To date the front suspension is over 15 years old and when I checked it 4 years ago as part of a rebuild of the car I could not find any significant wear.
Bob Beaumont

Thanks for the comments I can see the merits of all the different ways, I think I'm going to the assembly it on the bench camp at the moment - but Easter is a few days away yet
Martyn Wilks

>David Smith. Thanks, yes 'welch plug'. I see that the Moss parts list call it a 'blanking plug' #51K3424

>Bob Beaumont. Thanks, Bob. I've now just looked at the pair of 'Barry King' wishbones I bought last year. I see that both ends of the fulcrum pin bearings have a threaded portion that will accept the (Moss) 'screwed grease plug' #8G589. Perhaps that is the way to go - but dual grease nipples still presents the problem of two grease trails being forced in two opposing directions, against each other. If you see what I mean.

Andy Hock

I fitted secondary grease nipples on my Sprite some 80,000 miles ago and they accepted the nipples fine, and didn't pop out the welch plugs that they fitted to.

I also grease the front suspension at least every 2000 miles. My belief is that greasing the fulcrum is not principally about lubrication at all. Grease would last far, far longer if it was just for lubrication. But the significant function is to expel road grit etc. which gets into the joint. To achieve this it is advantageous to force clean grease from either end so that old grease (and the contaminants) are flushed out past the cork washers. You get through a lot of grease this way, but its cheap and the stuff expelled gets wiped over various exposed parts of the suspension anyway so it isn't wasted.
GuyW

This thread was discussed between 21/03/2016 and 22/03/2016

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