OT: Wheel tracking - how accurate does it have to be?

[Dave W]

Of course. I'm under stress.

[Rob Morley]

Indeed - if you want to check your car is running straight you need to drive along the middle of the road, straddling the centre line.

[harry]

If tracking is done properly, the rear wheels are taken into account as well. On some cars the rear wheels can be adjusted also. If the car has been "kerbed" the geometry in the vertical plane can be upset too.

Worn suspension joints can cause uneven wear.

Excessive play on wheel bearings

[The Natural Philosopher]

Would you believe me if I did?

I fail to see your purpose in posting since you dont trust anything anyone says.

Perhaps if I said I worked as a guardian journalist you would believe me.

[Andrew]

Does anyone who runs a garage, do a complementary wheel tracking as part of a service ?. Unless you have a specialist car, or one that had 4-wheel steering, it is unheard of.

If you have a tyre wearing unevenly, then a rare number of garages might mention it on the srvice bill and suggest an alignment check (at extra cost). Most of the time it will be a metalastic bush in the suspension that has failed, and they should have noticed this when it was up on the ramp anyway.

My neighbour is regularly changing lower front wishbones on small modern cars like astras, corsas, etc where these rubbery joints have just broken apart.

[Andrew]

Bollocks. Usual nonsense from you.

Astras and Corsas and many other makes have torsion bar rear suspension. If the rear wheel is out of alignment, then the car has had an 'off road experience' and something is bent.

[The Natural Philosopher]

small cars froma single manufaqctuirere of cheap nasty cars

and many other makes

like?

have torsion bar rear

Corsa has coils

If the rear wheel is out of alignment, then the car

Bollocks from you as usual.

If its independent rear trailing half beam then chances are there is a link as well. Its hard to ensure algnment on a single canyilever.

[Dave W]

Correction - I don't trust YOU. Calling your bluff, how much extra wear would I encounter (as a percentage of normal) if the toe adjustment was say 10 minutes of arc outside the manufacturer's limits?

[The Natural Philosopher]

That rather depends on how many miles you ran the tyre and on what surface. And under what loading. And how hard you cornered and braked.

[harry]

Rear wheel drive cars have "Toe in" Front wheel drive cars have "Toe Out"

When they are running, the wheels are then parallel.

Also, Ackerman principle applies.

[harry]

You're not clever are you?

[T i m]

(Talking about the tracking on the front wheels there).

Ideally. However, if a FWD car is say going up a steep hill under heavy throttle the chances are the front wheels will be experiencing more toe-in than under 'normal' conditions because of all the soft bushings in the suspension.

Not typically adjustable and no more relevant to 'tracking' (when tested / set with the wheels in a straight line) as a diff would be.

Cheers, T i m

[T i m]

On Sat, 25 May 2019 13:21:16 +0100, The Natural Philosopher [e-mail] wrote: <snip>

Irrelevant, other than trying to gain you some wriggle room.

Many and not for others to prove but for you to disprove. [1]

Yes, to provide the actual suspension but both trailing links are joined by a substantial torsional section and so for the *tracking* of the rear wheels (the point of the conversation) to be out, 'something would have to be bent'.

Fact in this case as it happens.

Is that some sort of smart Scottish suspension?

Cheers, T i m

[1] A lorry squashed our Astra against the kerb (whilst parked, at night) and that bent the rear axle / trailing arms.

A mate lost the back end of his Fiesta though some muddy road works and sideswiping the kerb bent the rear axle / trailing arms.

[Dave Liquorice]

It is when there is no adjustment on the rears and has suffered an accident or "off road experience". There's far more to wheel alignment than just simple toe in/out relative to front wheels only. That also needs to be "inline" with the toe in/out "direction" of the rears as well, then there are castor angles. Any or all of which could be out after a car has suffered a whack.

[The Natural Philosopher]

and all of which is either preset or adjustable.

Or both. Shimming suspension pickup points is standard practice

[Martin Brown]

A third to a half of a degree is roughly when it becomes worth adjusting

- especially if you have expensive (eg runflat) tyres.

I had a problem with uneven wear fairly recently. The tracking on one rear wheel was out by about half a degree. Pressures were all spot on. The nasty thing was the wear was hidden on the inside edge of the tyre.

It was only really visible with the car up on a ramp.

[Dave W]

Some evidence at last! Your wear on one edge is typical of toe misalignment, and your experience of half a degree being noticable implies that my disbelief was perhaps unjustified. Half a degree is 30 seconds - in my front tyre they adjusted it by 20 seconds, however I did not see any edge wear.

[polygonum_on_google]

Bit of a shame that we haven't seen at least wheel alignment detectors built-in to newer cars. Might be a challenge to design... but I'm not suggesting automatic adjustment. Yet.

[Fredxx]

You can get these a lot cheaper than this Amazon price:

It gives a very good indication of toe in/out.

[David]

From where, please?