On 24 May 2004 at 18:13, McEwen, Art wrote:
> >> i.e. if the correct toe-in is say 2 degrees, how do I know
> >> one wheel isn't in 1.5 degrees and the other is .5?
> > It's actually not critical at all, this is in effect just
> > centering the steering.
> So it won't affect tire wear if the toe-in isn't even across both
[ My, such a complex set of reference marks. Who quoted whom, I
wonder??? :-) ]
On a TR3 it may not matter, but (for what it's worth) it can make a
minor difference on a Spitfire or GT6. As the steering lock is
increased, the steering geometry becomes non-linear, which is to say
that the amount of steering angle dialed into the road wheel per
input of the steering wheel isn't constant thoughout the turning
range. It really shouldn't be constant anyway; the inner wheel has
to follow a tighter radius than the outer wheel, so it needs to be
angled further inward just a bit. At nearly centered steering
positions, the difference between the wheels is the toe-in. As
steering is increased, the toe-in becomes effectively toe-out, with
the biggest effect at full lock. On the Spitfire/GT6, the effect can
be significant because the steering goes to such an extreme.
Now (to get to the point), when you tighten one tie rod and loosen
the opposite one, you are changing their effective lengths. Suppose
you were to rotate the steering wheel one notch in its splines at the
top of the steering column, and compensate by adjusting both tie rod
ends to re-center the steering wheel. One tie rod would be too long
and the other too short. In most driving you would notice no
difference. But at nearly full lock you'd have a difference between
turning right and left. To one side the toe-in would be slightly
high and to the other side it would be slightly left. The more
steering lock the car will give you, the more difference you will
have between turning one side vs. the other. In theory, neither
would be optimized to the spec that God and Standard/Triumph (or
British-Leyland, okay, just Harry Webster) intended. You might not
ever notice, but perhaps you might.
Is it really enough to matter? I dunno'. Maybe Joe Curry can say.
Various of the published repair manuals will tell you to adjust
alignment by tweaking both left and right tie rods so as to avoid
this possibility. Given that most people also like the aesthetics of
a centered steering wheel and probably work to obtain it (as, I
confess, I too have done), the real warning should be to be careful
not to mis-align the steering wheel on its mounting splines! Lots of
things can contribute to a non-centered steering wheel, e.g. rear
wheel alignment, asymmetrically worn tires, etc. And one can suppose
that S-T didn't really manufacture its steering columns all that
recisely so as to produce absolultely centered wheels with new tires.
Just my $.007 conbtribution.
'80 Spitfire, '70 GT6+