> > |> Bob, if you really want to improve handling dump the rear antisway bar.
> > |> Put a larger one on the front (5/8 inch) and do not put one in the
> > |> rear. According to the latest Moss catalogue, testing has shown that
> > |> rear antisway bars hurt handling on chrome bumpered MGBs.
> >
> > |> You can use the rear bar but you will need to use a real beefy front bar
> > |> & add unsprung wait to all your wheels.
> > |>
> > |> TeriAnn
> >
> Is this discussed in the catalog, or the update or price list? I'm very
> interested because I use a 70 lb tube of sand over the rear axle of my
> 68 B, and this makes it handle like a wallowing pig. I was hoping to
> cure this distasteful behaviour with a rear bar plus a beefier front bar.
> -Jean H
Jeez, where to start?
1. Weight is always your enemy (unless you're building a stock Group 10
slot car...) Get rid of it wherever possible. It has an adverse affect
on every part of the car's performance, except of course for that Cushy
Bargelike Ride we all know and loathe from most products built on this
side of the Pond. Unless required to do so to meet a minimum weight
for a class, to include a piece of safety equipment such as a roll bar,
or to reinforce parts that had been Chapmaned into a dangerous state,
adding weight to a car is almost always The Wrong Thing To Do.
2. There are two kinds of weight in a car, divided by where it fits in
relation to the moving parts of the car's suspension. If it's part
of the car that wobbles when you heave on the fender while it's
parked, that's called SPRUNG WEIGHT because it's riding on the
springs. If the weight belongs to a part of the car that doesn't
wobble when you sit on the fender, it's called UNSPRUNG WEIGHT
because it's between the springs and the ground. Clear examples
of sprung weight would be the engine, the body, and the lump of
protoplasm that's sitting behind the steering wheel. Clear examples
of unsprung weight would be the wheels, the tires, the knock-off
nuts and any pieces of the car that have fallen off since you
shut it down.
3. We know from Point 1 that weight is not your friend. Of the two,
unsprung weight is the worse enemy. Unsprung weight makes it harder
for your suspension to do its real job, which is to keep the wheels
in contact with the pavement. An increase in unsprung weight makes
it harder for the springs to push back on the mass of the tires, and it
makes it harder for those poor overworked lever shocks to damp out
the pendulum-like oscillations of a wheel when you hit a bump.
Weight, you see, not only is attracted to the center of the earth
by gravity, it also carries with it corresponding mass (measured
in slugs) and inertia. The more slugs you have, the more inertia
you have, and therefore the more force you need to apply to turn
the inertia into some other form of energy (in the case of shock
absorbers, it's turned into heat). Adding unsprung weight is
particularly bad on a car with shock absorbers that date from the
days when they made airplanes out of old clothes.
Okay. SO first of all, if the Moss people told you to add sprung weight
to a car, either they've been sucking the LMA too long or they're selling
unsprung weight kits at a special one-time-only low-low price.
Now, adding a rear bar to an MGB is going to do several things, many of
them useful but all of them different from the way the car is now. To
begin with, it's going to confuse your chassis. You see, for 25 years or
so, your MGB has had an anti-roll bar in the front only. When you put
one on the rear, the chassis will think that the end with the anti-roll
bar is supposed to come out of the corner first, and it will attempt to
comply by making the back end of the car precede the front end.
Now, on Bob's autocross car, he probably wants this to a certain extent,
because after he and the chassis reach an understanding, the anti-roll
bar at the back will make the car more "pointable" -- meaning in essence
that the car will have a form of rear-wheel steering. (Actually, all
MGBs do have rear-wheel steering from the factory; adding an anti-roll
bar will change this rear-steer effect quite drastically.)
I'm still not sure why Jean puts 70 lb of sand over her rear axle; I'd
guess it's to make the tires cut through snow. My recommendation is to
buy a "salt car" and keep the MG for sunny days. The only time MGs and
sand should come into contact is when you drive one to the beach.
I'll be happy to talk about what's wrong with the MGB's suspension,
what you can do to make it better, and also what's good about it.
A rear anti-roll bar may in fact be the wrong approach because of
geometry issues, but we can discuss that later.
I just had to a) define unsprung weight and b) get everyone to
realize that Weight Is Not Your Friend.
--Scott "And no comments from anyone who's met me, either" Fisher
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