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MG MGB Technical - Steering box help

My 67 B GT. has always had hard steering since I purchased it. It does not return to neutral when you corner, you have to actually bring the wheel back to center. With the wheels off the ground, the system turns smoothly. King pins were replaced in the last 2 years and it did not change the steering.

I have realigned the box and worked on correct spacers under the mounts. This made it a bit easier steering. Have added oil and checked the shims under the top plate.


The car does show some damage on the frame, I was told the PO hit a rock. So, figuring it may be a good idea to have the body shop check the frame to see if it is not slightly up on one side prior to pulling the old unit.

I have a spare rack and pinion unit and was going to install it, but wondered if anyone has good instructions on exactly how to set up the box, including figuring how many shims to put under the plate, what to look for in wear, etc.
BEC Cunha

Not coming back to center sounds like a caster setting problem to me. Have you had a full camber, caster, toe alignment check done?

There could be other problems causing it to be stiff that would not show themselves with the wheels off the ground, simply because the lack of load removes the problem.

As to replacing the rack, I don't think anyone can say how many shims you need. I believe it has to be installed, measured, and adjusted. Some special (though not exotic) tools are used to set it up. That said, there are differences in the arrangement throughout the years and I am not well versed enough to know for your exact model.

Charley
C R Huff

Hi BEC

I agree with Charley. I doubt it is the rack, as it is free when the wheels are off the ground. Have the alignment checked, also your tyre pressures.

Aligning the steering is fully described in various service manuals. One tip that I found very useful is to use two ignition coil rubber boots and two screw driver bits as the alignment tool. Check that the tips of the bits are the correct distance from the centre of the locating grooves on the shafts. To find this distance measure the distance from the centre of the crosspiece of the uni joint to the centre of the locating screw hole.
From memory on my 67 B it was 46.5 mm.

Check this web page for alignment method.

http://www.mgb-stuff.org.uk/suspensiontext.htm#align

Herb
H J Adler

If new king-pins (for what ever reason) didn't change it, then it has to be castor angle, nothing else can 'load up', when the weight is on the wheels compared to up in the air. However it will *always* be freer up in the air as opposed to down on the ground, so maybe your 'up in the air' test is freer, but isn't as free as ours. I can swing mine from lock to lock with the tip of a little finger, and once it starts moving it will run with virtually no pressure at all.

Are you sure it hasn't had a castor reduction kit fitted in the past? The castor action on an MGB is pretty strong usually, to cope with the lower self-centering action of the original cross-ply tyres, which is why the kits have been produced. It's going to be quite difficult to measure 5 to 7 1/4 degrees though.

"use two ignition coil rubber boots and two screw driver bits" now that I *do* like! The distance is interesting. Someone at Moss measured their alignment CB gauge at 44.8mm, I measured my CB roadster UJ at 45mm. I measured my RB V8 at 32/33mm, and that should have the same UJ as 4-cylinder cars, but Moss measured their gauge as 29/30mm.
P Hunt

fwiw - my steering was very stiff and would not self centre after I renewed the bushes in the steering column, even though it felt free when off the ground. It took several thousand miles for the new bushes to settle in. It might be worth lubricating yours - the upper one is easy, but the lower one needs a tiny hole drilled in the outer column so you can squirt WD40 or similar onto the inner column and let it trickle down onto the bush.
Miles Banister

Super information all.

This car came with a different steering column. . Probably from a 1970 MG. Why, I don't know. This is where it gets odd. U.S. cars form 1970 had a collapsable steering column. This shaft was a two piece steering shaft with nylon pins that hold the two shafts together. Yet it clearly had the splines for a 70 or later steering wheel. I came to the conclusion that the assembly was for a right hand drive. I noted that the cover assembly was upside down so the turn signal would be on the left.

I changed this out with an original 67 shaft, steering wheel and tube from a US MGB. It did get new plastic bushings for the shaft and tube. That could be a part of the issue.

My son fabricated the shaft alignment tools in his machine shop. They seemed to work well.

I replaced the whole swivel axles with rebuilt units when I rebuilt the front end rubber. Steering was much the same prior to the rebuild. I was hoping that the swivel/kingpin system was the problem.

Club members helped set up the steering shims under the mounts. A lot of measuring and trying. That made things a bit better.

Shims I was asking about are the ones under the metal cap on the top of the steering box. The one that holds the brass damper down. How do you measure how much pressure the damper should put on the steering pinion?

BEC Cunha

Bruce -
Correct is "just not tight". By the book, put all the pieces in except shims, tighten bolts down until you can "just" pull the rack through the housing. Measure the gap to the cover, add .0005-.003 shims and tighten down. You have to be a little careful on worn racks that it doesn't get tight at extremes of travel where it has not worn.

FRM
FR Millmore

It's interesting that you renewed the column bushes. When I did mine I couldn't see a way of fitting the lower bush without splitting the inner column. I didn't want to do that so I used the thinest saw blade I could find and split the bush instead. That must have reduced the inner diameter a little making it a tad tight to start with even though the tightness was undetectable off the ground. Presumably it eased with wear, and a squirt of thin oil every few weeks helped. It might be worth giving yours a squirt to see if it makes any difference.
Miles Banister

"You have to be a little careful on worn racks that it doesn't get tight at extremes of travel "

That's it, although it happens a lot sooner than at the extremes. My V8 rack is a little worn and playing with shims I could get it where it was free around the straight-ahead but binded (bound?) OK, got stiff, only about 1/4 turn off either way. Didn't leave it there of course, it as horrible.
P Hunt

This thread was discussed between 22/12/2009 and 23/12/2009

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