Track rod ends

[Readit]

I was going to start a new thread entitled DON'T TRY THIS AT HOME!!! but then I thought NO these LECkies are not wimps they are GODS, or so it says on the profiles.
Anyway I spoke to a very nice man at Jaymar Autoparts who rang Quinton Hazell to confirm that part No QR3167S fitted an Elan M100. The man from QH could NOT confirm this however the very nice man from Jaymar sold me the bits, bade me farewall and "see you tomorrow" (don't know why?).

Back home with 5 minutes to spare I decided to tackle the job. Now for the TECHNICAL BIT.
The QH part is not the same as the Lotus part but it does fit. The QH part is both 6mm longer and 6mm higher (see photos) The good news is that the threads and the taper are similar.
TOOLS REQUIRED Large hammer, very large hammer, contents of Mactool van and a Local Kwikfit depot

DSCN0776.JPG

DSCN0778.JPG

6mm may not sound much but it requires moving the lock nut back along a rusty thread subjected to nearly 20 years of salt spray and Lotus mechanics with specialist tools (large hammers)
Do not bother buying a ball joint cracker, as I did, because by the time you have moved the rusty nut on top of the ball, the taper will be loose , a sharp hacksaw blade to saw through the nut will be a better investment.Grease all the threads well before re-assembling making sure to move the lock nut 6mm back on the thread. The extra 6mm in height may also affect the tracking so the first trip after re-assembly should be to your local Kwikfit or similar to have the tracking checked.

Now the good news ,both sides only took about 4 hours to complete but the ball joints cost £7.49 + VAT instead of £66 + VAT from a Lotus dealer in Devon.

GOOD LUCK to all you DIY LECkies

[bobbrown]

If you move the position of the track rod it will effect bump steer, not sure if 6mm has much effect though.
Bump steer for those who do not know is the change of steering angle as the wheel goes up or down.
I have a feeling, if the grey matter is working correctly, that you do not have to move the position very much to induce or increase bump steer.

[GeoffSmith]

Bummer. Well spotted Readit and sound advice about checking the geometry. As Bob says, it has got to affect the dynamics of the setup to some degree, so I've updated the Wiki.

[Freelander]

I recently completed the replacement of both tie rod ends using the part nos referenced. The difference in horizontal length is not a problem as it is accomodated in the tracking adjustment. I did not measure the difference in vertical height but I would anticipate that would be due to wear. I agree that full tracking (and laser alignment) is an important check and should be carried out by a reputable garage.

[bobbrown]

I think I remember how this all comes together now.
It is to do with the relationship of the lower wishbone or tca for Mcpherson strut suspension and the rack position
I think the two should be parallel such that as the wheel moves up or down the the rod between the steering rack and the track rod end follows the same arc. If you move the position of the track rod end up or down you change the angles not by much but enough to cause the wheels to turn slightly.
In really bad cases you go over a bump and you end up heading for the hedge, I am not saying 6mm will cause this to happen just that it is something to be aware of.

[bobbrown]

I recently completed the replacement of both tie rod ends using the part nos referenced. The difference in horizontal length is not a problem as it is accomodated in the tracking adjustment. I did not measure the difference in vertical height but I would anticipate that would be due to wear. I agree that full tracking (and laser alignment) is an important check and should be carried out by a reputable garage.

Full tracking (and laser alignment) will not show up bump steer
Now I can remember how to check it, you have first to remove the spring!
The with the wheel in the straight ahead position and the wheel at full droop move the wheel upwards and see how much the wheel moves in or out, as if steering lock is being applied when in fact it is not.

[RayD]

When someone gets chance it would be a good idea to check if the angle of the taper is the same... rather than similar.

If they are different they want disregarding altogether.

On the picture they look different although it might be the angle of the shot.

Ray

[DeeAitch]

On the earlier Elans bump steer was very critical. It was adjusted by shims under the rack. Real important thing was to get the rack height correct and equal on both sides.
If the heights are not equal then the car will drift to one side as the track rod effectively gets longer (or shorter as the case may be) on one side compared to the other at various points in the suspension travel.
My +2 goes left on the brow of a hill and right in a dip Only a bit mind. Must get it sorted
Bob is correct, you need to remove the spring and move the suspension through various points in its travel, checking toe as you go, to make sure it is equal equal both sides.

[bobbrown]

It is not quite a case of being equal both sides although it needs to be the same both sides, if only one wheel goes up as if going over a bump on one side of the road then the tracking is changed on just the one wheel, the car will feel like some sort of steering input has been applied.

Interesting to note you comment about shims and the early racks, but it goes to show how little you need to be out with these things.

[GeoffSmith]

I've done an overlay of the two in the Wiki. The good news is that the threads and taper correspond well, however the minimum diameter at the top of the taper appears to be some way out! The Vauxhall QH3167S appears to be a wider diameter so would not engage fully (which is not good) and could give twice the 6mm offset that Readit suggests.

It's all arcs in three dimensions and far too much for me to comprehend and take in, but my gut feeling would be that if the geometry is set up correctly, then the error will be comparatively small (but compared to what, I do not know) under normal driving conditions but will become larger towards the limits as Dave reports (Dave, when you say 'earlier Elan' I presume the shims are used in the prehistoric Elan and not the M100?) which could isn't good as you want things to be predictable if things get near the edge.

Personally, I've got a bad feeling about this and we could do with getting the OEMs measured so we've got a baseline to work to. Readit, please don't bin the old one! If you haven't got access to a vernier gauge etc., whereabouts are you and is anyone close enough to do some accurate measurements?

[RayD]

If I’m not mistaken...You might be reading too much into this.

This is a simplistic view but it might help anyone struggling with the concept.

Looking at the car from the front... the wheels move in an arc on the suspension, and the track rod moves in an arc on the inner ball joint behind the gaiter.

From new, the suspension arc, and the track rod arc, are on the same plane and regardless of whether the wheel is up, down or anywhere in between, the track rod end will follow it without any unwanted steering action.

Looking at the sketch where the steering rack (in red) is too low... you can see how it would pull the wheel (in black) IN at the top and push it OUT at the bottom as the wheel moves up and down.

With regard to the 6mm difference in the QH track rod end... it doesn’t have any effect on bump steer. It just changes the shape of the track rod. The track rod could be any shape. It could look like part of a wrought iron gate as long as it starts and ends at the right place.

You can see how, as Dave mentions, the rack needs to be exactly positioned. Any movement, however small, from where it should be would have a “bump steer” effect.

The main thing, I think, is to make sure the track rod end has the right angle of taper, otherwise it will seemingly go on, tighten up, but only have a point contact.

Ray

BS1.jpg

BS2.jpg

[bobbrown]

My understanding of this is that if the track rod end was a rose joint, which OK its not but this still applies.
To adjust the bump steer you move the position of the rose joint relative to the steering arm either up or down by shimming the rose joint.
If the track rod end sits 6mm higher then this has the same effect of moving the pivot position.

So the QH track rod will effect the bump steer by how much I do not know as it would need to be measured to see.

[bobbrown]

I think this shows what bump steer is about

Bumpsteering.jpg

[RayD]

If the track rod end sits 6mm higher then this has the same effect of moving the pivot position.

So the QH track rod will effect the bump steer by how much I do not know as it would need to be measured to see.

Bob,

if I never move out of this chair...I took out the following paragraph before posting...

(Before anyone pulls me up...I do realise by moving the track rod end ball joint away from the hub it might make a thousandth of an inch difference... two things, I’m trying to keep it simple and I don’t know how the tapers match up... the ball joint might be in the same place for all I know.)

It followed the word, place. I removed it because I thought it was un-neccesary and sounded a bit sarcastic.

Ray

[GeoffSmith]

With reference to Bob's pictures, I think that you're effectively moving the centre of the outer track rod joint by ~1cm. Given the distance between the upper and lower ball joints is only ~30cm, I still think the difference is going to be significant.

I understand the track rod and top / bottom links describe arcs but I'm having difficulty comprehending the arcs in three dimensions i.e. the complication brought about by the angle of the wheels.

[bobbrown]

I've just run the front suspension through an Auto Cad drawing using approx dimensions taken off a front suspension setup I have e.g hub and wish bones and as I did all the measurements with a tape I do not supose it was that accurate but give us an idea of what is happening

This shows that if you move the track rod end pivot down/up 6mm then at 50mm of wheel travel the tracking change over stock is 1.1mm.

[DeeAitch]

Dave, when you say 'earlier Elan' I presume the shims are used in the prehistoric Elan and not the M100?

Yes
Sorry, by early Elan I meant the type 26/36 (Sometimes refered to as 'Baby' Elan) and type 50 (+2)
I always thought the shims were there to get over any tolerance issues with the rack platforms - they are quite basic - and it is important that both track rods sit at the same angle, static at least
I don't think the M100 has shims.

The way I think of this is to imagine a clock with two pointers the same length. The centre is the rack balljoint and the outer pointer ends = the track rod end.
Now if both rods are set statically at say 2 & 10 o'clock all is well - assuming the numpty at quick 5hit sets the toe right.
Moving them both up or down (I'm talking about both moving in equal ammounts here, as happens on the crest of a rise or in a dip, not in isolation which throws in all sorts of complication ) changes the horizontal length from the tip to the centre by the same ammount.
However if one is set at 2 o'clock and the other at 8 o'clock statically then moving both up by for example 1 hour, will give a longer length on the left = toe in, and a shorter length on the right = toe out, = bump steer.
Can't imagine it being a problem but I do think it best to change both sides at the same time.
Incidentally when I removed mine recently to change a wheel bearing the taper just dropped out with a light tap. First time ever for me, suggesting the taper tolerances might be crap Or someone has fitted a the wrong Track rod end in the past

[RayD]

I don’t know why I got involved with this... I hardly know anything about bump steer...

The things I may be able to help with are these...

... if the track rod end was a rose joint...To adjust the bump steer you move the position of the rose joint relative to the steering arm either up or down by shimming the rose joint.

The effect of raising a rose joint up on the steering arm is so tiny that the packing being used would not qualify to be called shimming...as Bob later says; lifting it 6mm only moves the arc out 1.1mm. Putting 50thou of shimming under a rose joint on the steering arm would do nothing. (see Fig 1)

The QH track rod end might not move it up at all, and if it did its the tracking that needs addressing. The 1.1mm Bob refers to is 1.1mm’s worth of toe in, not 1.1mm's worth of extra bump steer.

With reference to Bob's pictures, I think that you're effectively moving the centre of the outer track rod joint by ~1cm. Given the distance between the upper and lower ball joints is only ~30cm, I still think the difference is going to be significant.

I don’t think the pictures can’t be scaled. They’ve been put together to highlight bump steer. Everything is slightly exaggerated to get the point over...the radius of the track rod for instance. (See Fig 2)

It appears the diagram is of a competition car with the wheels moving vertically up and down at the expense of an amount of built in bump steer. Whereas on a road car they would be moving more in an arc. (I realise there’s a similar arrangement on road cars but not to the same extent)

Ray

[bobbrown]

heres a pic of a bump steer kit and there's even one for the Elise http://www.eliseparts.com/shop/index.ph ... cts_id=315

bumpsteer.jpg

Ok the term shim may not have been the best wording if you want the other way then spacer if you prefer.

I do not think the simple drawing works very well as the fact is there are two unequal length wish bones which control the position of the wheel and the outer steering tie rod is a different length again,this makes it all quite complex to draw as you can not take a simple view of two arcs!!!!!

Let's not forget the track rod end pivot point is the ball not the tapered bit if that what is shown in the previous posts drawing.

pulled from the internet along with the above picture
"Definition of bumpsteer:
Bump-steer is a change in toe* angle caused by the suspension moving up or down. Bump-steer is built into the geometry of the suspension and steering system, and has nothing to do with turning the steering wheel. The effect of bump-steer is for the wheel to toe-in or toe-out when the suspension moves up or down. This toe change or "steering" occurs any time the suspension moves, whether it is from body roll, brake-dive, or hitting a bump in the road. Bump steer is undesirable because the suspension is steering the car instead of the driver.

Cause of bumpsteer:
The front wheels do not move directly straight up or down when the car hits a bump. Instead, the wheel follows an arc, or curving path, that pushes the wheel slightly inward (towards the centerline of the car) or outward (away from the car) in response to vertical wheel movement. The outer tie-rod (which connects the steering rack to the wheel) also moves in-and-out in an arc as it moves up and down. If the rate which the outer tie-rod arcs in or out does not match the rate the wheel moves in or out, the wheel will be turned by the tie-rod. This is bumpsteer. The center point of the arc traveled by the wheel (known as the instant-center) is controlled by the location and angle of the moving suspension links. This point moves as the ride height changes. In contrast, the arc of the outer tie-rod is controlled by the position of the steering rack, which is fixed. In order to eliminate bumpsteer, both the length and the center point of the two arcs must be the same. However, since the instant center moves with ride height, bumpsteer cannot be eliminated throughout the entire range of suspension travel. Therefore suspension designers concentrate on minimizing bumpsteer within the range of movement closest to factory ride height. Changing the ride height or other suspension components may move the suspension outside this narrow "optimized" window.

To fix a bumpsteer problem, you need to alter the height of outer tie-rod relative to the steering rack. Small changes in this relationship can be made with offset rack bushings. Making big changes requires adjustable tie-rod ends, also known as a bumpsteer kit. * Toe: Toe-in or Toe-out describes the alignment of the front wheels relative to each other, the same way you would describe your feet. For example, toe-in means they are closer together at the front than the rear"

[RayD]

Ok the term shim may not have been the best wording if you want the other way then spacer if you prefer.

Sorry about that Bob, I thought you actually meant shimming...a small amount...otherwise I wouldn’t have mentioned it.

I do not think the simple drawing works very well ... you cannot take a simple view of two arcs!!!!!

At work I used to use a piece of chalk to make a sketch while explaining to people what needed to be done. At home I tend to do the same with my lad, only with pen and paper. All this time I've thought it helped get the point over but you are probably right...

Let's not forget the track rod end pivot point is the ball not the tapered bit if that what is shown in the previous posts drawing.

I had the ball in mind: If anyone wants to understand the difference between having the ball close to the steering arm - when it almost works as one with the track rod – or further away as shown in the bump steer kit picture... A good starting point would be to imagine a bit of delayed action as the spindle goes over and the track rod stays where it is, as the wheel tries to induce bump steer...the problem might be, it causes a similar delay when you move the steering wheel.

Cause of bumpsteer:
The front wheels do not move directly straight up or down when the car hits a bump. Instead, the wheel follows an arc, or curving path, that pushes the wheel slightly inward (towards the centerline of the car) or outward (away from the car) in response to vertical wheel movement. The outer tie-rod (which connects the steering rack to the wheel) also moves in-and-out in an arc as it moves up and down. If the rate which the outer tie-rod arcs in or out does not match the rate the wheel moves in or out, the wheel will be turned by the tie-rod. This is bumpsteer.

This is an excellent description...Is there any difference between this and the way I tried to explain it? If you start reading from the top you'll find I was explaining it for the first time in simple terms for the benefit of people who were having difficulty getting to grips with it. It's not as though I wrote mine to contradict someone else.

I try not to quote from the internet, I realise it’s a bit risky speaking off the top but it would just be my luck to pick someone who was talking a load of rubbish.

There’ll always be bits missing from anyone’s explanation on here. It doesn’t necessarily make it wrong, it just makes it incomplete, and there’s nothing to stop someone continuing the story and adding the missing bits. Most people would welcome it.

I'll nevertheless have a rethink about the way I’m doing things.

When I said I didn’t know anything about 'bump steer' I was being serious. It’s only crossed my mind once or twice since I started driving. I hadn’t heard the phrase 'bump steer kit' until now.

Ray