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MG TD TF 1500 - steering geometry question.

As you can see from the attached picture the tie rods are not parallel (both wheels pointed straight ahead). Is this a peculiarity of LHD or could the steering arms be of different lengths? I've measured them and they are the same if not very close in length. There doesn't appear to be any damage to the frame that would cause one side to be longer or shorter than the other. I note that Moss sells RH and LH steering arms (although currently NA). That's why I'm wondering if there is a reason the tie rods are not parallel due to different steering arms.

Tim
TD12524


TW Burchfield

Its to do with the Ackermann angle. When turning the inner wheel needs a tighter radius.
Dave H
Dave Hill

Not sure I understand. You ask if the steering arms could be different lengths, then you say you measured them and they're the same.

I don't see the problem from your photos. The steering arms look the same to me. The tie rods seem to be coming off the steering rack at different angles, but that's probably just from slightly different camera angles.
S Maas

Dave, I'll research the Ackermannn angle, thanks

S Mass, actually I said the same or not much different. Because of the location of the steering arms it is difficult to get an exact measurement. The right tie rod is definitely not on the same plane as the left one. The photos show a correct relationship between the angle of each tie rod.

Tim
TW Burchfield

If your boots are in the right place on the track rods then you have them at different lengths.
You need turn one in and one out until they are the same length. You must then set the tracking which can only be done with the full weight on the suspension. Then you will need to adjust one in one out to align the steering wheel straight ahead.
Odd lengths give weird steering and wreck tyres.
Ray TF 2884
Ray Lee raybar2(at) tiscalidotcodotuk

Ray, thanks. But even with the toe in set correctly the right tie rod is not parallel to the left one (tires pointing straight ahead. If you look closely at the photo you will see the ball joint on the right is closer to the outside wheel rim than the one on the left.

Tim
TW Burchfield

Tim,
The rods are not in line with each other, they are angled forward. See Fig K1, page K2 in the WSM, it shows it clearly.
The arm difference seems minimal, you can still get the correct toe in with the arms the wrong length. That they are the same length from the rack ball to the track rod end is critical to the geometry. If they are not the same, the Ackermann geometry is out and the wheels will turn in different angles for the same rack movement.
Ray
Ray Lee raybar2(at) tiscalidotcodotuk

I think you mean that the right tie rod is angled forward at the outer end, while the left is nearly 90 degrees to the centerline. If that is the case, need to accurately measure the steering arms. I think you can use just a regular straight edge ruler and measure from the surface of the spindle/stub axle housing to the center point of the arm. Also, what is the actual distance from some point to the wheel rim- compare both sided. Those should be the same. R and L are different due to a keyway difference I think. They will not be parallel to the ground w/o full weight on them as noted above. MGA arms have a different part number but I think they fit- if off quite a lot above, perhaps an A arm on one side? George
George Butz

George you are correct and that's what I meant to say. The right tie rod is angled out to the front of the car while the left is perpendicular to the center line of the car. Based on what those above have said it looks like the right steering arm is too long. Although I hate to do it looks like a tear down is in order. Thanks you everyone for your help.

Ray, thanks. Perhaps the steering arm on the right is not fully seated into the upright. I didn't take them apart and didn't notice anything different before disassembly. I hate redos.

Tim
TD12524
TW Burchfield

Tim,

Don't hate redo's! They teach you more than simple assembly? By now you may even have researched the Ackermann principle.

Properly done redo's boost knowledge and confidence in your car's and your own abilities.
Willem van der Veer

Willem, when I was a little kid I asked my dad, an auto mechanic, how he knew so much about cars. He said it was because he had made every mistake you can make working on a car. I never forgot that.

Tim
TW Burchfield

I once had a bent tie rod on the TF, which needed some adjustment to get the right toe-in. The car drove fine, until the bent tie-rod broke.....

David
DavePro

Dave, the tie rods are new as is the steering rack. I've never driven the car so I don't know if the angled tie rod (right side) would adversely affect the steering or not.

Tim
TW Burchfield

Tim,
check that the woodruff key on the arm has entered the keyway. If it has missed it you would see a slight gap where the taper fits the upright as it is held off by the key.
If you remove the arm and take out the key you can then trial fit and see if it goes in deeper.
Ray TF 2884
Ray Lee raybar2(at) tiscalidotcodotuk

Thanks Ray, much appreciated.

Tim
TW Burchfield

I think your problem might be that the left steering arm, tie rod at 90 deg, is a T type unit, but the right steering arm, tie rod angled forward, is an MGA unit. The MGA used 15" wheels, but the early cars had 10" drum brakes, so the steering arms were slightly longer. My TD has MGA front suspension with drum brakes, and both tie rods angle forward, although any steering left or right means the tie rods move more in line. The MGA had the steering rack moved forward, but steering left or right means the tie rods angle back. In both cases the Ackerman principle still holds over most of the left or right lock. A previous owner may have fitted the wrong unit, not realising it was different, but if so, you should correct the error.
R A WILSON

Perhaps you should also check that you have 9" brakes on both sides. 10" means MGA.
R A WILSON

RA, thanks for the tip. I will certainly check out the items you mention.

Regards

Tim
TW Burchfield

This may help. The T type measurement will be about half an inch less.
(Constable, Turner and Leonardo have nothing to worry about)


R A WILSON

Crudely measuring with a ruler, the above dimension on my TD is 5.75" or 146mm. I don't think 4mm would cause your angle, or even 1/2" as noted in above diagram. Distance from rim to bulge of arm just less than 0.75" also. Check the cross member steering box mount. A local TD had an accident and one side is sort of smashed back. Just curious- have you measured your frame and points for squareness? Diagrams in back of factory manual. George
George Butz

This may be more help.


R A WILSON

Forgot to say, the half inch is just an estimate, because T types had 9" drums and the early MGA had 10" drums.
R A WILSON

Just checked TD and TF.
124mm, approximately 4.5" face to centre of the TRE nut.
Just under 0.5" shorter than an MGA arm.
At full lock the RH wheel will be seriously out of alignment. In normal use the car will not feel wrong but it will wreck tyres.
Ray TF 2884
Ray Lee raybar2(at) tiscalidotcodotuk

RA, after converting your measurements to "American" your measurement is very close to mine. I come up with 6" + or - a 16th. It is certainly possible that in 55 years the steering arm could have been changed. But regardless of the measurements the two steering arms are the same length so something else must be going on.

George, I will recheck my frame measurements. I initially checked the location of the a two leading frame members (bumper attachment locations), shock locations and steering gear placement. They were equal on each side. I will examine the steering rack location much more closely.

Ray, Reassuring about the handling but disconcerting about the tire wear. I was going to finish the car and address the steering geometry once I had a chance to drive the car. But your comment on tire wear causes me to address the problem sooner.

Thank you gentlemen, you comments have been most helpful. If/when I discover the reason for the misalignment i will report back.

Tim
TD12524
TW Burchfield

The more I look the more I think it is photographic parallax error.
Any chance of a photo from directly above of both wheels together. Stepladder or hovercam :-)
Ray
Ray Lee raybar2(at) tiscalidotcodotuk

124mm is closer to 4.9", but as it seems likely that the car has MGA steering arms both sides, a high level 'both-side' photo would help. If proven, the Ackerman principle will hold (as I already mentioned).
Drum inner diameter ?? - although more work to measure.
R A WILSON

Ray, it's the correct angle. It looks the same with the naked eye from many angles. I wish I could photoshop it straight :-)

Tim
TW Burchfield

OK, as most suggested the right steering arm is longer (by about 1/4") than the left. After checking many other front end measurements I resorted to a set of calipers for the steering arm. The the tape measure was difficult to get consistent readings. Hard for me to believe 1/4" would produce that much of an angle but seeing is believing. Now to find the correct steering arm (without selling the silver to pay for it).

Thanks to every one who commented.

Tim
TW Burchfield

Sorry - I thought you had established the two arms were the same. Anyway, does the left one measure 124mm to the joint centre line, confirming it to be a T type arm. Then a request on this BBS thread system may, hopefully, produce results.
R A WILSON

This thread was discussed between 25/04/2016 and 29/04/2016

MG TD TF 1500 index

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