Good question Dick,
Toe change, or more correctly "bump steer" is something that designers spend
a lot of time trying to get just right. The ideal situation would of course
appear to have no bump steer, but in the real world everything in steering
and suspension design is a compromise.
Many things affect bump steer and these include
Rack centerline position, rack length, tie rod center position, A arm
lengths, A arm angles, camber change, swivel pin angles etc etc.
Change one and everything else is affected.
For example one of the considerations is as follows.
In some cases you want to have a changing bump steer to compensate for the
decreased slip of a tire when the load on it increases when a bump is
encountered in a turn. If you end up with an increase in steering angle when
the suspension on the outside of a turn compresses you can experience
substantial momentary oversteer, never a good thing.
But wait....there's more....as they say...
When I see a Acura with shortened springs bobbling along on the bump stops I
just cringe!!!
To illustrate just how sensitive this all is, when setting up the front end
on AHX12 I found that raising or lowering the steering rack as little as
0.010" made a measurable change to the bump steer.
There is a picture here of the crude jig we developed for measuring bump
steer. http://www.acmefluid.com.au/larry/ahx12-1.html
Michael Salter
http://www.netbug.net/blogmichael/?p=445
-----Original Message-----
From: healeys-bounces@autox.team.net [mailto:healeys-bounces@autox.team.net]
On Behalf Of Dick Matson
Sent: Friday, June 26, 2009 11:43 AM
To: AustinHealey List
Subject: [Healeys] Fw: BJ8 Tractability
And BTW , , , and I'm a perpetual student I guess , , , why is it
that
toe-in changes as the front end weights and unweights. Meaning , , ,
tow
in is set with the car at rest. Right ? But lift the car some from that
position - like with a jack - and there is a (measurable) change in toe-in.
To me that would mean that toe-in is changing as you drive.
Dick Matson / Bj8
_______________________________________________
Support Team.Net http://www.team.net/donate.html
Healeys@autox.team.net
http://autox.team.net/mailman/listinfo/healeys
http://www.team.net/archive
|