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MG MGA - Steering problem

I have a 1500 1956 WW coupe in for a brake system rebuild. The brakes are now working (with the extra hurdle of an automec kit which has the wrong fittings in the rear axle pipes....).

What is puzzling me is that the steering lock is overshooting on both sides, in that on full lock the rear inner tyre wall is rubbing on the inner wing. There is a clear stripe on both inner wings from this wear, and it can't be good.

The car tracks true and straight. There is no abnormal tyre wear pattern. The tyres are standard 165x15.

What is wrong - how to correct?
dominic clancy

Tie red ends too long causing gross toe out.
Barney Gaylord

The car tracks true and straight. There is no abnormal tyre wear pattern. The tyres are standard 165x15.
dominic clancy

Are the wheels standard MG wires and not repro ? Possible wrong offset and/or rim width
A J Dee

Dominic

The only thing that comes to my mind is along the lines that I think Barney is intimating. A shorter than standard arm that screws into the king pin will increase the turning radius that is giving you this issue. It would also make the whole steering slightly more sensitive. i.e. the wheels will turn more for the equivalent movement of the steering wheel.

I notice that Moss lists 6 different arms. I wonder what their differences are? Or, could the item have been fitted from a Magnette or suchlike over the period of time?

Steve
Steve Gyles

my thought is if the wheel is pointing forward arm length would have no difference as the ball joint would have to take up the slack(screwed on less to the arm)?
If the wire wheel spokes are not offset and rim not too wide then maybe the drop arm is incorrect.
mog

sorry that should be steering arm not drop arm.
mog

Mog

The length of the steering arm into the king pin has nothing whatsoever to do with the tracking - that would be adjusted as normal. It's a simple case of pivots and moment arms from my mathematics at school. For a given movement of the steering rack, say one inch, the end of the steering arm would also move one inch. If the steering arm is 6 inches long the wheel will turn through X degrees. If the steering arm is only 5.5 inches long the wheel will turn through X + y degrees.

Steve
Steve Gyles

The different steering arms do not seem to vary a lot in length, but there are differences.
They can be quite different in shape.
The identification numbers on the arms should be checked.

Mick


M F Anderson

Yes Steve, its not tracking thats the problem, its that the wheel is hitting the car, so from the math ( never my strong point ) the steering arm could be short so overdriving the stub axle. I doubt its wrong though, thats why I mentioned spoke rim offset, with wire wheels there is a part no: MWS show offset on rim and center for mga. http://www.mws.co.uk/site/cms/contentviewarticle.asp?article=663 explains
mog

Mog, I agree it's doubtful, bearing in mind Mick's pictures, but it's worth Dominic taking comparison measurements against his own car to rule it out. That would leave your rim offset or an over-extending steering rack if that's possible (not an expert in that area).

Steve
Steve Gyles

A shorter arm would have the effect of reducing the throw from the steering rack.

I am leaning toward the wrong wheel offset. I am off skiing in Laax for the weekend, so won't have any time to look for any wheel stampings before the owner collects the car on Monday. Then I am off to Borneo for a few weeks of diving, so will have to investigate when the car comes back for an engine out and replace all seals sometime in the autumn. It's dreadful, the Torrey Canyon leaked less oil than this car. The car is really a strange combination of GREAT original body and chassis (no welding at all as far as I can see) but truly truly dreadful mechanics, and everything is thick with oil, wax, and mud. It really needs a steam clean before I do any more, and as I am fed up with the grime after every job, I may well insist on that before touching it again!
dominic clancy

A shorter arm would increase the throw
A J Dee

Dominic

I agree with AJ.

Shorter arm will increase road wheel turn degrees for any given steering wheel movement. Down side it increases the load on the rack, probably transmitting back through the steering wheel in feel, sensitivity.

Steve
Steve Gyles

Just in case others are not following the logic, see schematic. For any given steering rack (steering wheel rotation) movement (x) the wheel angle will vary depending on the steering arm length.

Steve


Steve Gyles

I had this problem with my MGA, but it wasn't the steering that caused it. Somehow the inner wing had come loose. It was an easy fix.
Rutger Booy

Looks like 3 things for Dominic to check:

1. Inner wing outlined by Rutger, but would this be the same on both sides?

2. WW offset outlined by Mog. This could be checked out simply by putting one of your own WW on to see if that cures the problem.

3. Steering arm length. Probably unlikely, but worth measuring against yours.

If it's none of those it would just leave the steering rack?

Steve
Steve Gyles

This thread was discussed between 09/03/2016 and 11/03/2016

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