Thread: Mismatched Tie Rod Ends and Accidents

Originally Posted by 123rover50

I keep hearing reports of mismatched TRE,s causing fatal accidents but have seen no evidence of such.
Is this anecdotal or an urban myth?
There is still plenty of thread screwed in and as long as the clamps are tight the rod cant unscrew.
If the rod did slowly unscrew there would be a discernable difference in the feel of the steering surely. This would be looked at before it came undone.
There is the same amount of thread engaging with either TRE so it cant just strip.
Am I missing something here?

Didiman.

I haven't heard anything about it, but not everyone does something about their car when it starts to play up, i.e the steering feels terrible!

Are we talking about Series tie rod ends?

If yes, then you are definately missing something, the early Series 1 and series 2/series 2a have threaded shafts with a raised collar for the last 3/4", this collar has a diameter greater than the outside diameter of the thread and therefore when fully threaded tie rod ends are fitted to tie rods for the shouldered ends there is minimal (if any) clamping pressure on the thread.

If you compare the two types of tie rod end, you will observe that the shafts are the same length, but the early type has 3/4" less thread (the length of raised shoulder), and relies in large part by the clamping pressure on the raised shoulder.

If you have an early tie rod, remove the tie rod end and with a right angle scribe check out how little thread is actually inside the rod.

In any case why would you use the wrong tie rod ends when the correct ones are readily available from suppliers who know there is a difference? (Not ones who have reduced the two types to a single pair which will be incorrect for a significant proportion of sales.)

I have no trouble getting the correct tie rod ends from All Four X 4 at Kotara NSW.

BTW, the problems happens not by unscrewing, but by the thread stripping with lateral forces. As for evidence, one of the members of the now defunct series one garage had a mate die because of the problem. ( I guess that is still in the realm of myth. )

it can also happen on poorly maintained fully threaded rods...

if the rods internal corrosion gets bad enough the threads just strip out. Ive seen one actually snap the rod where the rod end was threaded in, Admitedly a much abused vehicle and fortunately due to the overall state of neglect with a very limited speed so the end result was little more than a spilt hay load and some smart assery along the lines of "well that went well, lets not do it again"

My father's IIA once had one TRE strip the threads out of a track rod. Fortunately he was driving slowly, and of course could still steer one wheel, so was able to stop safely on a side street.

IRC though, that it was a S3 track rod and TRE, and the threads stripped due to corrosion, rather than TRE mismatch.

I have found it hard to get good quality IIA TREs, so in the past have machined down an old track rod, to convert a SIII/Defender TRE to a IIA type.

I had a tie rod end pull on my first 2a that sent me off the road,land cruisers pull the ball joint on the track rod,both will leave you with no steering and I would change them if I had either vehicle as a matter of coarse. Pat

As Diana says, it is apparently not a myth, although most failures have probably not led to accidents, let alone fatal ones. If you have a flat surface clamping on a threaded surface, the problem is that the contact area is very small, and consequently the clamping friction is very low. And the slightest movement will free it further. It is unlikely that movement is gradual - on a corrugated road, I would expect movement, once both ends are free, to progress to where failure is likely within a few kilometres, and in most cases the driver would not notice. I suspect the only reason that it is not more common is that a large proportion of the fleet has the TREs firmly locked by rust, regardless of mismatched threads. But this does not seem a very secure way to operate!

You can argue that if only one end is mismatched, as long as the other end stops the tube from rotating, there is no problem. However, this is a doubtful safety factor, as once the end can move, even if only a little, the thread will wear quite rapidly.

As a final comment - in the event of an accident resulting from a failure caused by mismatched threads, any competent insurer would certainly void cover.

John

Its not mismatched threads that seem to be the problem.
The pitch and all match, it appears to be the clamping force of the clamps.
I feel the clamps are there only to stop rotation and the longitudinal clamping force of the clamps would be minimal. This is the function of the threads. So far failures appear to be from rust and corrosion not from the rod unscrewing or stripping sound threads.

Originally Posted by 123rover50

Its not mismatched threads that seem to be the problem.
The pitch and all match, it appears to be the clamping force of the clamps.
I feel the clamps are there only to stop rotation and the longitudinal clamping force of the clamps would be minimal. This is the function of the threads. So far failures appear to be from rust and corrosion not from the rod unscrewing or stripping sound threads.

The tread in the completely threaded and shouldered series TRE are the same, but how much wear will there be in the threads of a 50+ year old vehicle?

I guess the issue becomes, when should you replace tie rods and not just the TRE!