On 2 Jul 2010 at 17:09, Matthew Milkevitch wrote:
> When I jacked up one side, I noticed that the wheel "tucked in"
> rather dramatically... Is this normal...or is this the classic
> sign of a sagging rear spring?
I hate to tell you this, Matthew, but that is completely normal. It
is doing exactly what it should do. You can worry if you want to but
it won't do any good. :-) Not that worrying ever does any good
anyway.
The Spitfire rear suspension uses swing axles. The axle moves up and
down through the suspension travel by pivoting at the u-joint at the
differential end. The axle is a solid shaft and the wheel is always
perpendicular to the axle, so as the axle drops down the wheel's
angle changes along with it.
The reason the axle hit the frame when you jacked up the car is
because there is nothing to prevent it from doing so. The spring is
meant to hold the car up, which actually means pushing the wheel and
the car body away from each other. In other words, it pushes the
spring down and the car up. When the tire sits on the ground the
wheel pushes upward on the spring, and spring pushes the car up off
the wheel. But when the car is lifted up by a jack the spring won't
hold the wheel up, and in fact the spring is still pushing it down so
it goes as far down as it can go.
As for the sagging rear, that happens when the spring doesn't push
the wheel and body apart hard enough. You wouldn't notice one way or
the other when you jack the car up.
--
Jim Muller
jimmuller@rcn.com
'80 Spitfire, '70 GT6+
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