[DMCForum] steering geometry. was Re: Speak slowly, use small words (On
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[DMCForum] steering geometry. was Re: Speak slowly, use small words (On Topic)



--- In DMCForum@xxxxxxxxxxxxxxx, "cruznmd" <racuti1@xxxx> wrote:
> Someone please explain DeLorean steering geometry to me. I am
> familiar with some terms: Toe, caster and camber.
>
> Due to the wear on the inner edges of my tires, I suspect they are
> pointed like this:   //  \\  (If you're looking at the car head-on)
>
> Instead of: ||   ||  (Ditto)
>
> Which of the above 3 is responsible for this, and is it adjustable
in
> the DeLorean?
>
> My new tie-rod ends will be here soon and I'm going to take it to
the
> alignment joint up the road Friday morning. Before I do, I want to
> know if I have something else that's really wrong.
>
> I have read the tech section of DMC news and a few other places and
> find the explanations lacking.
>
> Thanks,
>
> Rich A.
> #5335

Hi Rich.

Inner edge tire wear would mostly be caused by excessive negative
camber (wheels pointed like this:   //  \\ if you're looking at the
car head-on), like you said earlier, or misaligned wheels, with toe
out(wheels pointing away from each other in front)
You can check camber easily yourself, with only a roofing square
(24"x18" "L" shaped right angle) for tools.

Camber measurement
Simply find a flat level piece of parking lot, and roll the car to a
coasting straight line stop on it.  Don't use the front brakes
stopping, the brake force changes the steering geometry. Place one
edge of the roofing square against the ground pointing away from the
tire, and the other edge against the tire, pointing upwards, away
from the ground.  Avoid the part of the tire that's squished outwards
at the point where the tire touches the ground.  I personally put it
as close to the middle of the wheel as I can, while avoiding the
contact patch bulge.
Look for a gap between the roofing square and the tire. If there's a
big gap at the top part of the tire between the roofing square and
the tire, the camber is excessively negative. 
If there's a big gap at the bottom part of the tire between the
roofing square and the tire, the camber is excessively positive.
If the roofing square touches the tire at the top and bottom of the
rim, the camber is neutral.
Most cars are specified to have neutral, or very slightly negative
camber.  I don't know the Delorean specification.

Since Deloreans don't have adjustable camber, if you find that the
camber is excessively negative, your car has problems, something bent
or broken or worn out.  If your camber is okay, it's very likely
incorrect toe.  That's what my money is on, since it's the only thing
that's really adjustable, and you haven't crashed your car yet, which
suggests that the suspension is still mostly intact.

Toe is a little harder to check yourself, but it can also be done. 

I wouldn't worry about the caster, since it is not adjustable, and is
much less likely to get screwed up from suspension damage than camber

Since people who lower their cars don't complain about this wear
problem, it's likely that ride height doesn't affect this wear, so
springs or shocks are also less likely culprits.

As an aside, the three different parameters, camber, caster, and toe,
all interact.  If more than one is wrong at a time, it gets really
hard to diagnose tire wear.  If you make changes, make small changes
to only one at a time, and assess the effect.

Rick.



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