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MG MGB Technical - Smiling tie rod angles

I just finished rebuilding the front suspension in my 68 B. Everything seems to function well on the road, but I noticed that the tie rods slope upward, from the rack to the steering arms. At first I thought I got the steering arms switched around, but as the tie rod end shafts fit into a taper in the steering rod, its not likely I would have made that mistake. Did I just not notice this upward angle before or did I screw something up in the rebuild? My 57 A seems to be straight across from end to end.

Bill
Bill Boorse

They should be horizontal when the car is sitting normally loaded. That way you don't get bump-steer, ie the tendency for a bump to throw the steering one way or the other. If your tie rods go up at the outside end, it looks as though your car is lower than before. Did you fit shorter springs?

Mike
Mike Howlett

Is it possible that you got the steering arms reversed such that the tie rod is not seating properly. The steering arms are sided (L & R).
Just a thought.
Frank

Mike,
That's what I thought. I'm using stock springs and, if anything, the cars sits just slightly higher than before.

Frank,
I'm beginning to think that's what I did. The steering arms have a tapered hole that mates up to the threaded shaft on the tie rod end. If they're reversed the shaft shouldn't fit properly, so I didn't think I could get them reversed without noticing. But obviously I got them on the wrong sides.

Bill
Bill Boorse

If the steering arms are on the wrong sides, the tie rod ball joint will have to enter from the bottom to get into the taper, whereas it should be on top of the arm. Should be obvious.

Mike
Mike Howlett

Mike,
Thats the problem, it's not obvious, at least not on my car. Both tie rod ends entered from the top and seated smoothly in the steering arms. Yet when its all assembled the arms appear to be incorrect.
I won't have an opportunity to remove them for several days, but I'll let you guys know what I find. Thanks for your help.

Bill
Bill Boorse

Bill,
Just wanted to apologize for not paying more attention to your original post and seeing that you had already considered what I was suggesting. Hope that is all it is and its gets everything straightened out.
Frank
Frank

Frank,
Thanks. I don't mind any suggestions. I just have to get around to taking a closer look at my assembly to see what I did wrong. This is what I get for rushing at the end of the job. I started out with the intentions of just replacing the rubber A-arm bushings and it snowballed into a full, front end rebuild. The tie rod ends were one of the last things to go on and I probably wasn't paying attention. Some day I'll learn.
Bill
Bill Boorse

This may be irrelevant, but I remember reading that one should not tighten the suspension arm bushings without having placed the weight of the car on the system. Might the added torsion of the bushings tightened while on jacks account for such a mis-positioning?
Doug
D Sjostrom

Doug,
Thanks for the suggestion, but I did wait until the car was back on the ground before tightening the nuts on the suspension arms.
Bill
Bill Boorse

Bill; I don't think anything is wrong. My 68 GT has the track rods pointing up from the rack. On my 74 roadster the rods are parallel to the floor. I looked at some spare swivel pins with arms and tried to install a new tie rod end both ways through the steering arm eye, I could not get the nut on when trying to install the pin through ehe narrow side of the eye.

Track rods pointing up will not introduce bump steer. Bump steer is caused during suspension travel when the apparent length of the tie rod changes too much in relation to the upper and lower control arms causing a toe out or toe in error during suspension compression or rebound.

Clifton

Clifton Gordon

Bill,
My '66 has slightly lowered springs and a good bit of positive dihedral in the tie rods. Just as Clifton says, no bump steer.
David
David

Clifton
If the arms point up when static, they will effectively shorten on bump (so toe-ing in), and extend on rebound, (so toe-ing out). That's why statically they should be close to horizontal which gives minimum variation.
Dave
Dave Wellings

Dave,
The upper and lower a frames also effectively shorten on bump and the change in their effective lengths should keep the tie rod and a-frames in parallel arcs and prevent toe in/out changes. This web site link explains bump steer and how the alignment between the the upper and lower a-frames must have the correct relationship to each other throughout total suspension travel. The static position of the tie rod should not
affect this relationship unless other changes have been made to the suspension.
http://www.longacreracing.com/articles/art.asp?ARTID=13#Q1

Clifton
Clifton Gordon

Clifton
An interesting read. But..... I'm convinced that the original design was that the track rods would be horizontal static. I'll have a look this weekend, as I have 2 B's with original set ups.
Dave
Dave Wellings

Dave, Your assumption is probably correct. I just checked my 68 GT ride height and it is 14", the track rods are pointing up. I put a jack under the cross member and jacked until the track rods were horizontal (approximate, I didn't use a level, just eyeballed them). I measured the ride height with the jack in place and it was 14 1/2". I have the OE springs and I suspect they may have dropped. On later North American chrome bumper cars, around 72, the ride height was increased to meet some bumper height standards and the springs were the only suspension component that was changed. My guess is the track rods on those cars were not horizontal. They are on my 74 but it also has older springs

I also observed the lower a-frames on the 68 are horizontal and they are pointing down on the 74. The shock lever which is the top a-frame isn't parallel to the lower a-frame and the track rods aren't parallel to either a-frame plus they are located between the the upper and lower a-frames.

If the track rods are horizontal in the static position we have to consider that when the suspension goes into bump the effective length of the track rods will decrease. As the suspension bumps the the a-frames will also have their effective length changed, their effective length equals true length only when they are horizontal, in all other positions the effective length will decrease.

The point I was trying to make is that the track rods, upper and lower a-frames have to work together to control bump steer. If there is no bump steer it shouldn't make any difference if the track rod isn't horizontal even though the original disign was to have them horizontal. All that said, when I'm looking for a lot of work I plan to remove the springs from one of my MGB's and check the bump steer. I have a gauge I made to check the bump steer on my son's Legends race car.

Cheers, have a good weekend.
Clifton
Clifton Gordon

Clifton
I've just been in the garage. On the 74 V8 the damper arms and lower arms are very very slightly pointing down towards the wheels. It's so slight that I had to use a mini spirit level to be sure. The track control arms are very very slightly inclined towards the wheel.
On the 80GT it's much the same but interestingly slightly more angle both with the suspension arms and the track control arms - a combination of crossmember and relative rack mounting positions.
Two quick anecdotes - years ago I had a midget which displayed a serious swerve-power on/power off. Tried the usual back axle etc and after a few months of head scratching traced it to the nearside steering arm, which had been bent in a kerbing incident. It was only fractionally out, but boy did it make a difference.
Second thing - in the UK it's been common practice with the Metro to lower the suspension by letting gas out of the hydrogas units. Lowering one inch is sufficient to destroy the geometry so that even with a retrack, the inside edges of the tyres scrub off in no time. Bottom line - many lowered or tired B's have wishbones which point upwards. I don't think this gives optimum geometry, and I guess we've all driven or had B's which feel dodgy at the front. Maybe this has a lot to do with it.
Have a good weekend too!!
Dave
Dave Wellings

All,

Just back from a brief holiday at the beach (too cold yet for my taste), and I took another look at my front end. The tie rod ends are definitely installed correctly; it would be almost impossible to get them in the steering arms upsidedown. After reading the recent posts above, it seems right that there would be no bump steer if the tie rods are parallel to the wishbones. But I didn't read them until after I came in from the garage, so I don't know how things line up. When I go home tonight I'll check.

Bill
Bill Boorse

This thread was discussed between 25/05/2004 and 01/06/2004

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