At 09:32 PM 11/6/03 -0800, Ron King wrote:
>I seem to recall a recent thread regarding rear leaf spring replacements
>either ending up raising or lowering the car. As this is my next area of
>restoration/repair can I get some feedback?
When the rear of the car sits too low it can bottom out the suspension on
bumps or potholes and can extricate your exhaust system while traversing a
speed bump. This is the problem which most often starts this quest.
When the leaf springs make your car sit too high in the back, it can
quickly run out of travel on the rebound straps with quick cornering and
moderate body roll. As soon as a rebound strap goes taught it will lift
the inside rear wheel, placing all of the rear weight of your car on one
wheel. With the excess weight on the one wheel, that tire looses grip
efficiency, and the tail end of the car will swing wide rather quickly and
without notice. This represents a severe case of oversteer, where you may
find yourself quickly steering the other direction to keep the front wheels
tracking the right direction down the road. Sideways is not the quickest
way around a turn. God forbid you should panic and fully lift the throttle
about that time, as the car may well swap ends and leave you wondering
where the road went.
Increasing the length of the rebound strap may help some, but if you run
out of travel on the shock absorber you end up with the same problem
anyway. The only good solution is to keep the ride height down to
something near the original specs. Unfortunately a lot of new leaf springs
in recent years have been manufactured with too much arch, leaving the car
sitting too high. New rear springs I installed on my MGA in 1997 were too
high like this. They screwed up the handling so bad that they didn't make
it through the summer before they were recycled to the nearest swap
meet. The original issue parts were restored and renistalled, and are
still on the car today, 45 years after the factory knew best.
I have no idea who supplies leaf springs of the correct height today, but I
still hear a lot of bad stories about new ones being too high.
A couple of our local club members got it right about a year ago when
repairing a broken spring on their BGT. They decided to upgrade to
additional load capacity at the same time, so they took the problem to a
local spring shop. They determined the ride height desired with unloaded
condition, including the loaded arch height of the spring. Then they
considered the load they wanted to carry, divided by the allowable settling
distance, which gave the required spring rate. These two numbers were
given to the local spring shop along with the old worn and broken
springs. The shop shortly returned refurbished springs with an extra leaf
and the correct loaded ride height. All is well that ends well. The whole
story is here: http://www.chicagolandmgclub.com/driveline/1002/jasw.html
Barney Gaylord
1958 MGA with an attitude
http://MGAguru.com
|