Editing Chassis development (section)

==Castor==
[[Image:Chassis_development_castor.png|frame|left]]
This one is a little more difficult
to explain.. You will
have to look at the wheel
from the side. The hub is
behind the wheel and if you
look at it, you will see that
there's an angle between
the top and bottom connection
of the wishbones. This angle is called Castor.
Castor is controlled by shims at the connection
points of the upper front wishbone.

If the castor angle is too small, the car will feel
very unstable at high speeds and will react very
nervously on any steering action. If the castor angle
is too big, the tyres will wear very quickly and you
will lose grip in corners. The reason for this is that
castor (on the front wheels) will produce camber as
soon as you turn the wheels. Finding the right balance
is key again.

I can hear you thinking now: ‘The workshop I’m
visiting has a very expensive test setup to do these
alignments. How could I possibly do that on my
garage floor?’ The good news is - you can! The bad
news is… it’ll take you some time to get there. If
you are serious about this, you could bring your car
to this workshop to try a new setting you’ve figured
out, but in the end, it would cost quite some money.
An optimal setup for a nice, warm, dry track is different
to that for the cold, wet roads at home, so
you might end up queuing at the workshop every
week.

So it’s time to make a decision here. Are you going
to try a handful of general setups during a season?
You might opt for the workshop.
If you would like to end up making your own setup
per different track or according to weather, you
could start investing in your own equipment. You
could look at companies like
www.longacreracing.com who are selling quite
interesting low-budget solutions for Geometry
modifications. If you search on the Internet, you
will also find other companies, and also descriptions
of doing a setup yourself using small ropes.

There’s one thing which is important to understand
before you start. The floor you are doing the
setup on needs to be level and you must put some
weight in the driver’s seat (preferably something
that matches your own).

One more thing: say you’ve added a shim in the
front suspension. You’ve lifted the car, removed the
wheel, done the shimming and built it all together
again. After doing that you should check what
you’ve done, but you shouldn’t just measure again
after lowering the car! Roll it forward and roll it
back again! The suspension needs to settle, and
you do that while rolling the car back and forth.

Your car came out of the factory with what you’d
call a general setup. Depending on what you want
to achieve, there are a couple of different setups
that you can use as a starting point to find your
own. Lotus has released quite a few setups for the
Elise, Exige and 340R. You can choose one of these
as a starting point and start modifying from there.
If you’re doing your own Geo for the first time, I’d
advise you to take it step by step: e.g. first do the
Toe-in / Toe-out until you’re satisfied with the
behaviour. Next step could be the camber, etc.

It’s winter - a good time to start understanding all
of this and preparing yourself for a new season.
Once you’re able to do your own Geo, I’ll start nagging
you about bump steer settings and springs
and dampers.

This artice, written by Yvo Tuk, is taken from issue 2 of the Lotus Enthusiast, the magazine for SELOC Members.

[[Category:Chassis]]