"Dave" wrote in message
. ..

[snip]

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.

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.

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?

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.

In article ,
Dave wrote:
Well that's as far as I'm taken the idea. Any comments, ideas, etc?

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.

--
*The colder the X-ray table, the more of your body is required on it *

Dave Plowman London SW 12
RIP Acorn

Dave Liquorice wrote:

On Mon, 11 Aug 2003 17:10:40 +0100, Dave wrote:


returned from my 4th visit to them to try and correct this and I'm
well and truly ******-off!


Well tell them but preferably politely and firmly. Then refuse to
leave (apart from test drives) until they sort it out properly.

From my experience of setting up tracking there are two methods in use
one just "aligns" the front wheels with no relation to the rear the
other aligns the fronts in relation to each other *and* the rears.



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


I had similar "fun" after new rubber and tracking adjustment. Didn't
have to do more than one return visit (withing 30 mins of leaving)
they checked front alignment first that was close enough then got the
full front/rear rig out that was incorrect small adjustment and it's
been fine since. This cars' monocoque chassis is a bit bent after an
front end collision so the book settings won't be right.

The other thing to bear in mind that it's no use doing the tracking
straight after the car has been jacked up and the rubber changed. The
suspension drops completely with the wheels off and won't have settled
back to its running position without being driven.

In article ,
The Natural Philosopher wrote:
And the third aligns them all WITH THE STEERING WHEEL IN THE CENTRAL
POSITION.

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.

--
*All generalizations are false.

Dave Plowman London SW 12
RIP Acorn

"Dave" wrote in message
...
On Tue, 12 Aug 2003 11:23:52 +0100, Dave wrote:

On Mon, 11 Aug 2003 23:06:02 +0100, The Natural Philosopher
wrote:


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.



hope it doesn't cost you too much in 6 months when you need new tyres

"Dave" wrote in message
...
On Tue, 12 Aug 2003 14:04:39 +0100, "Frank"
wrote:


"Dave" wrote in message
.. .
On Tue, 12 Aug 2003 11:23:52 +0100, Dave wrote:

On Mon, 11 Aug 2003 23:06:02 +0100, The Natural Philosopher
wrote:


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.



hope it doesn't cost you too much in 6 months when you need new tyres

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.



just cos it's driving straight does not meen it is tracking correctly

On Tue, 12 Aug 2003 22:43:54 UTC, "James Hart"
wrote:

My sister went to a fast fit type place once and they replaced 1 tyre on her
car. Not only did they put the new one on the back

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
rde at tavi.co.uk
PC Server 325*4; PS/2s 9585, 8595, 9595*2, 8580*3,
P70, PC/AT..

On Wed, 13 Aug 2003 01:24:39 +0100, James Hart wrote:

My mechanic certainly uses the front-to-back method as it was
the way he was trained and he also swaps the wheels left and right
(the wheels are swapped diagonally in effect)

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

The basis of the 'back' argument is that you don't want the back end
getting loose in emergency situations.

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...

The 'front' argument revolves around the front wheels do most of the
braking, all of the steering and all of the traction (FWD only of
course) so they benefit from the better grip.

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.

--
Cheers
Dave. pam is missing e-mail

On Wed, 13 Aug 2003 00:26:04 UTC, Dave Plowman
wrote:

IIRC, the safest handling for a car is understeer - ie on the limit of
adhesion the car will go straight on. Oversteer means it will tend to
spin. So the best gripping tyres should go on the back. No tyre should
ever be allowed to get so worn it's in danger of failing.

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/au...b_pqr_neuf.jsp

--
Bob Eager
rde at tavi.co.uk
PC Server 325*4; PS/2s 9585, 8595, 9595*2, 8580*3,
P70, PC/AT..

In article ,
James Hart wrote:
Did it make any reference to rear wheel drive? I was of the
understanding that new tyres go on the front as the front wheels do the
steering but I've also been told that new tyres go on the driven wheels.
My mechanic certainly uses the front-to-back method as it was the way he
was trained and he also swaps the wheels left and right (the wheels are
swapped diagonally in effect) as well to even out the wear. We've always
replaced tyres as pairs.

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.

--
*Keep honking...I'm reloading.

Dave Plowman London SW 12
RIP Acorn

In article ,
Dave Liquorice wrote:
Still using old technology bi-directional tyres then? The newer
"rotational" ones do offer noticeably better performance.

Are those still made? Thought they were a flash in the pan.

The basis of the 'back' argument is that you don't want the back end
getting loose in emergency situations.

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...

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.

--
*If horrific means to make horrible, does terrific mean to make terrible?

Dave Plowman London SW 12
RIP Acorn

On 13 Aug 2003 14:33:33 GMT, Bob Eager wrote:

Personally, I change all four at the same time because if they have
done 40,000 miles they are probably shot anyway.

Fair enough. I my case, I probably get through tyres at about 2.5
times the rate on the front that I do on tha back (or would do if
the new ones didn't get put on tha back). That's with my last two
cars, anyway; an Astra and a Galaxy.

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.

--
Cheers
Dave. pam is missing e-mail

On Wed, 13 Aug 2003 10:19:21 +0100, Dave Plowman wrote:

Are those still made? Thought they were a flash in the pan.

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.

You obviously prefer stodgy handling cars.

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.

--
Cheers
Dave. pam is missing e-mail

In article ,
Toby wrote:
A full suspension/geometry set up (with more lasers than a nightclub) on
a top-end Subaru Impreza will set you back over £600.

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.

--
*A clear conscience is usually the sign of a bad memory *

Dave Plowman London SW 12
RIP Acorn

"Bob Eager" wrote in message
...
On Tue, 12 Aug 2003 22:43:54 UTC, "James Hart"
wrote:

My sister went to a fast fit type place once and they replaced 1 tyre on
her
car. Not only did they put the new one on the back

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...

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