Scrub line and air suspension

[chrisjam]

Hi

I'm building a 1956 chevy pickup and want to run air suspension.

1. When I'm calculating the scrub line it is done at the ride height or is it calculated when an air bag is deflated in the same corner?

2. Is the vehicle body considered when looking at scrub line?

Cheers Chris

[Leon]

An air-bag system fitted to a low volume vehicle must be
designed and manufactured in such a way that:
(a) effective bump-stops similar to those expected in a spring
and shock-absorber combination are incorporated within the
system that are either:
(i) separate units mounted externally from the air-bag;
or
(ii) incorporated internally within the air-bag;
and
(b) in the event of a failure of all or any part of the system,
bump-stops will prevent the vehicle from being able to be
driven at a ride-height below the specified minimum safe
setting.

and

(g) not have any components mounted lower than that specified
for steering system scrub-line geometry in 7.37 ‘Chapter 7 -
Steering Systems’.

When talking about scrub line, the wording is
No solid, steering, suspension or locating member should hang below [the scrub line]

We would measure scrub line at normal ride height, not at a combination of flat tyre, and flat airbag at the same time. No, we don't consider parts of the body connecting to the ground in the case of a flat tyre, so long as you're not compromising your suspension or steering.

Just in case you haven't already, if you're looking at airbag stuff, please do get yourself a copy of the Hobby Car Technical Manual