I thought it might :-) It sound sounds like an interesting subject that
I've neglected for too long, but how do you find out about the geometry
of one's vehicle? For the near future, I'll be mostly interested in my
old Fiesta, and missus' V40.
I used a piece of rope pulled from around the back wheels last time I
changed the track rod ends, but it seems a bit hit-and-miss, hence the
question. I decided years ago to decline the offer of having them
checked whenever I have a tyre changed, because I've never seen any
evidence that they actually do anything other than charge you a few
On Sun, 20 Aug 2017 13:51:03 +0100, Dan S. MacAbre wrote:
Yeah, they charge you a couple of quid for checking the tyres for uneven
wear patterns which might indicate the tracking needs adjusting; I'll bet
they never check it if they can see for themselves what your old tyres
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But isn't the idea of having the right amount of toe in (assuming that
is the best result all round) a function of if the vehicle is front or
RWD (as mentioned elsewhere)?
So, if it's a RWD then the toe in will reduce as the vehicle goes
faster and the frictions (tyre drag / bearings / air resistance etc)
will cause the toe in to minimise, ending up with parallel at the
Whereas a FWD car will cause the wheels to toe in more as the speeds
increase (ignoring acceleration loads etc) and hence why you might
start with them toe'd out at rest?
I'm guessing if you replace all the suspension bushes with harder ones
you wouldn't have to compensate to the tracking changing so much?
So, even if 'some' toe-in is is considered 'good' for most vehicles,
too much could knock your tyres out in short order. ;-( 
Cheers, T i m
 The Mrs managed to reverse slice the Kitcar into a parked (on the
other side of the road, facing the 'wrong' way) Daimler Sovereign and
the kitcar came to an abrupt halt as our OSR wheel rim caught the NSR
wheel hub of the Daimler. The inertia of the car, engine, gearbox and
prop shaft going backwards was countered by the back axle going
forwards (on the OS) and unbeknown to me at the time, wrapping the
rear axle around the prop shaft etc, bending the rear axle tube
I replaced all the obviously damaged bits (OSR shackles, damper,
anti-roll bar) and straightened the dent in the rim and we continued
driving it. About 1500 miles later the (M&S) rear tyres were nearly
bald and the wear pattern was that of toe in? I took it to QF who said
they couldn't measure the tracking on what was the rear of a MkII
Escort so I asked them if I could use their gear myself, they let me
(and I did). ;-)
It showed there was just under 1.5 deg toe in (as I suspected) and a
replacement axle tube was found and fitted, along with a new pair of
tyres, which perished long before they wore out (again). ;-)
So, 'even' 1.5 degree of toe in on something that should be nearer
parallel (?) had a major impact on the tyre wear.
1.5 degrees is 10 times the amount a fiesta would have on the front.
Too much of anything is bad. On the average car I just use a slip gauge
and set it to parallel or very slight toe in, never gives any trouble.
Big stuff with expensive tyres I get the tracking set with a local place
I trust with a laser 4 wheel tracking set up.
Yeah, maybe I shouldn't have used 'even' here but I was thinking 'most
people' would consider 1.5 deg on something as big / dynamic as a car
wheel to still be a 'small number'? ;-)
Often (depending on who is determining the baseline). ;-)
And that was sort of my thought. eg. If you set some toe in on
something that might traditionally be set toe out, could you end up
with an error that might not be 'good'?
So, OOI, if you replaced *any* of the suspension / steering
components, do you routinely check the tracking? I ask because we
recently replaced the NSF lower arm on our daughters Corsa C (the big
/ rear bush had rusted out) and didn't check the tracking? ;-(
Cheers, T i m
Yes, any steering suspension part changed needs at least a quick
tracking check after (hence the side slip gauge I use) In the absence
of a check : if the steering wheel is still centred when driving in a
straight line. it is a pretty good guide.
There is a very big difference between degrees and mm toe-in.
Many Fiestas have 0 - 0.2 degrees toe-in.
On a 195/65R15 tyre 2mm toe-in is 0.18 degrees.
1.5 degrees is 8.7mm. That would easily destroy a tyre.
the mm difference is taken at hub height, from the wheel rim. If you
have made yourself a measuring bar, it is good practice to measure to
the same point on the wheel rim: ie: move the car forward half a wheel
turn before taking the second measurement (this eliminates any anomaly
caused by a damaged wheel rim. Never measure to the tyre, they vary too
So you have to do this from the inside I'm guessing (with the tyre
fitted in any case)?
No, quite, I'd put a straight edge across the outside of the wheel
with spacers between the edge and the rim if the tyre was wider than
As long as you measured both front and back track at the outside
diameter of the tyre you could at least measure for parallel (I'm
thinking trailers here really) but I'm guessing you couldn't use mm
difference unless you did so at some set radius (or did the calcs
etc)? eg, 2mm at a 400 mm radius would be the same as 1mm at an 200 mm
radius (that you may not be able to measure directly)?
Cheers, T i m
Measuring to the outside is easiest.
Long straight edges on the wheel rim is fine, then measure two points on
the straight edges that are equal distances apart to the points on the
wheel rims (so about 14 inches apart and starting a set distance from
Just to be sure ... I get the straight edges against the two rims and
measuring between them front and back but are you just measuring for
the difference between the two, no matter what arbitrary radius you
chose to take the measurements at? Wouldn't that number be bigger the
greater the measurement radius so what number would you use ... or
would you just convert that into an angle in any case?
Cheers, T i m
The distance you are measuring is the difference in distance between the
rims at the front of the wheel and at the back.
If you have nothing between the wheels then this is easy. However you
will have loads of junk in the way.
All a tracking gauge does is to measure the distance between the rims,
either the inside edges or the outside edges. Making your own tracking
gauge is not too hard, basically a long U shape that can reach the wheel
rim on one side, on the other you can just have a fixed upright, measure
from the upright to the rim at the back, note the measurement and
remeasure to the the front of the rim, the difference is the toe -in (out)
Using straightedges they need to extend beyond the front of the car to
be convenient to measure between. The two measurements should be taken
at the same distance apart as the points that the edges touch the
wheels. Take one measurement from the other and you have your toe in
(or out) Remember which is the bigger measurement so you know if it is
showing in or out.
set the edges up on the floor to prove this to yourself.
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