diy laser steering track adjustment

Hope this isn't too OT - I did think electroncs and/or auto ng but this has a strong element of diy - so here goes.
History After my not-so-local tyre place fitted and balanced some new tyres (good job, no complaints there) they did a free track aligment check and of course it was out. When I asked by how much they said an amazing (to me) 4mm. Given that the old tyre tread wear pattern was even and steering direction rock steady (no wander or drift), I stupidly agreed to them resetting it (with their wonder laser kit). Of course, now the car wanders nicely to the left and I have to keep the steering wheel right-hand down slighty to go straight ahead. Well, just returned from my 4th visit to them to try and correct this and I'm well and truly ******-off!
Searching the web last night there were a couple of article by folk who'd had exactly the same problem outlined above and made their own Heath-Rob settup with excellent results (so they claim). Setup was some wooden planks, paint-tins to act as pedestals and bits of string! (No kidding). One claimed 1/32" accuracy by some devious way of reversing the planks to cancel the error.
Now to the diy bit. I wonder if it may be possible to diy ones own track kit using a laser! At first that sounds expensive, but as a source, I thought a simple laser pointer device (~20) may do the job. A photo detector is easy to rig-up in a lightproof can - connected to as a microammeter to detect peak of laser alignement.
As to the mechanics of it all - I'm still trying to learn what it does exactly. Toe-in concept is easy enough - but as to measureing it it accurately - well, that's not so easy of course. I guess two parallel laser lines down the side of the car is a starting point - maybe some sort of collimator to ensure alignment and mirror or prism to turn the right-angles. Measuring from beam to wheel-rim could simply use a steel rule. (And always wear laser-safe goggles of course).
Well that's as far as I'm taken the idea. Any comments, ideas, etc?
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[snip]

using a laser! At first

laser pointer device

in a lightproof can -

alignement.
Have you considered the Gunson DIY kit? I used it for many years on a Lotus Elan +2 and other cars after problems similar to yours. You do need a good plane surface to do it on. It's quite crude but wheels and tyres aren't that accurately made, either! If you're going to get serious you need to spin the wheel while taking the measurement to even out wheel and tyre inaccuracies. Difficult -- because you also need to keep the hub under normal load, supporting the front of the car.
While I don't think laser accuracy is necessary you may well improve the ease of use of the Gunson kit by adding a laser.
A spot on a scale may be more workable (and simpler) than a photo detector and microammeter. It will have the advantage of giving a measure of the error and an indication of the change in error as adjustment is made.

what it does exactly.

accurately - well,

lines down the side of

collimator to ensure alignment

from beam to wheel-rim

goggles of course).

ideas, etc?
You need to look at the relationship of the front wheels, one to another rather than to the car. The best test of wheel to car is driving -- is the steering wheel in mid position when you're going straight? If not then use trial and error equal and opposite adjustments to the track rod lengths.
A properly adjusted car will pull to the left on normal roads -- as it drifts down the drainage hill built into the road surface. Have you tried driving on a straight road with the centre line aligned with the centre of the car? Opposing traffic permitting, of course!
It is also essential to get caster and camber angles correct. Even if these are not obviously adjustable they may be wrong -- perhaps because of damage or because they are adjustable by the play of bolts in holes.
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What your tyre place conveniently forgot is that first (if you have rack and pinion steering as most have these days) you *must* centralise the rack. If you don't, apart from the steering wheel being squint, the track rod lengths are wrong even if the toe in is right. So when you corner or hit a bump, the suspension and steering geometry is wrong.
Most racks have an inspection hole where you screw in a bolt to locate the *exact* centre. Only then can you adjust the tracking - and it takes several goes to get it right. Which these quick fitters can't afford the time to do. Even if they knew how, which I doubt very much.
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Dave Liquorice wrote:

And the third aligns them all WITH THE STEERING WHEEL IN THE CENTRAL POSITION.

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That's not good enough - it may have been moved at some time. The rack should be centralised, and then the wheel centred to that.
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Who needs lasers! I just adjusted the track to where I could see a discoloration in the threads (inside/outside of rods) - assuming this may be the original setting point. Just a guess but what the heck. Went for a test drive and the thing's back to were it was! No drift/wander, steering wheel centre on straight ahead, turns fine, doesn't pull and self-centers as it used to. Well I learned something there. Beware those "free" tracking places chaps.
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wrote:

discoloration
original
the
straight
learned
hope it doesn't cost you too much in 6 months when you need new tyres
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wrote:

Thanks - but that's cobblers of course. Anyway, better that new tyres in 3 months due to the shops cack-handed efforts. I'll just have to forgo the pulling to the left and the off-centre steering wheel you seem to think is such a good idea. I WILL post a "follow-up" in 6 months and we'll see - ok.
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and
pulling
good
just cos it's driving straight does not meen it is tracking correctly
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On Tue, 12 Aug 2003 22:43:54 UTC, "James Hart"

Interstingly, I had two new tyres fitted last week at Costco. Front tyres wore out aftre about 16000 miles (good going for me).
There were two separate notices in the shop, at the desk; one from the Tyre Manufacturers Association (or some such) and one from Michelin. Both said that the advice is that new tyres are fitted to the REAR, since failure of a rear tyre is more catastrophic steering-wise, and it's harder to keep adhesion on rear wheels...
--
Bob Eager
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On Wed, 13 Aug 2003 01:24:39 +0100, James Hart wrote:

Still using old technology bi-directional tyres then? The newer "rotational" ones do offer noticeably better performance.

On my cars (all FWD) I have never known the back end do anything but religiously follow the front even when the front isn't going in the most desireable direction. B-) The handbrake can just about make the back end slide out but that its hardly normal driving...

That would be my thoughts, on RWD drive car the dynamics are different as you are pushing the car rather than pulling it so there could be case for decent grip on the back but TBH I'd rather be able to steer and/or brake effectively.
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Are those still made? Thought they were a flash in the pan.

You obviously prefer stodgy handling cars. Try a small Peugeot or the new Mini if you want a FWD where you can hang the tail out.
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On Wed, 13 Aug 2003 10:19:21 +0100, Dave Plowman wrote:

Seem to be getting more and more common if you look at tread patterns. Makes sense to me that a tyre designed to work with either rotation isn't going to work quite as well as one fitted and designed to work in only one direction.

What did SWMBO call the Mondeo after her first trip in it, ah yes, like sitting in an arm chair. I'm not a car freak, they are just a mechnical device to get me from A to B in moderate comfort. Provided it can take a 3M lenght of stiff material inside it will do, even better if it could take 8x4 sheets.
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On Wed, 13 Aug 2003 00:26:04 UTC, Dave Plowman

That's basically what they said.
I found the references. One is the British Rubber Manufacturers Association, whose website seems severely broken. The other is Michelin:
http://www.michelin.co.uk/uk/auto/auto_cons_bib_pqr_neuf.jsp
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On 13 Aug 2003 14:33:33 GMT, Bob Eager wrote:

Same here on a Mondeo. Front set last 20 - 30k if I'm lucky. They get replaced or rotated depending on the relative state of the rears. These days it seems to be replace the fronts then next time replace them all.
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It makes no difference which end of the car is driven - the 'best' tyres always go on the back. Nor is this new or arbitrary - when crossplies were common and radials were new, if you mixed them the law required the better gripping radials went on the rear of the car regardless of which wheels were driven.
Rotating tyres to equalise wear is also frowned upon these days by many makers. Tyres develop a wear pattern due to the suspension design, and swapping them round can cause a loss of grip until this wear pattern is established again. Might be ok if it was done every 1000 miles or so.
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wrote:

her
Sorry for joining this thread a bit late.
I have always put quality new tyres on the front of all the Rover cars I have owned (all FWD), due in the main, to a front tyre blow out I had back in my motorcycle days. When it happened, I got the impression that the frame had snapped, until I realised the tyre had blown. :-((
I have been behind a car that had a rear wheel blow out on the motorway. He was doing 70 MPH at the time and there was no evidence that the car was not under control.
If you don't run up over the kerbs and look after your tyres, changing them whenever you suspect that you have hit a bad pothole and have the tracking checked, then all should be OK and you will probably never experience a blow out.
Dave
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It must be unusual. Most cars have *no* adjustment whatsoever for anything in the suspension apart from toe in, so fixing a fault involves replacing worn or damaged components.
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