> [...] a 72 MGBGT with a
> 68 engine and overdrive, new front end bushings and brakes. It is an
> interesting shade of turquoise, which I rather like, but then I painted my
> bugeye leaf green. He says it runs extremely well, but suddenly lifting
> off the gas causes the rear to wiggle; he thinks one side of the rear axle
> is shifting on a spring. The first question of the day is: is this a
> common problem, and if so, what is the cause/cure?
I doubt that's the cause of the problem, but it's easy to check for.
Stick a 9/16" deep socket on the nuts that hold the U-bolts on the
axle-spring interface and see if they're tight. They should be,
and even if they're not, there's a peg in the middle of the spring
that hooks up to the axle pad so there isn't much chance of motion
on a stock B rear end.
What usually causes the sensation of wobble in the back is the slackness
of the bushings and spring mounting pads. These can be replaced with
either new rubber bushings (for comfort) or with Nylatron (for taut
performance with a little more roughness). You'll need a press to get
the bushing out of (and back into) the front spring eye, but the rest
of them are hand-tool jobs. And you don't need to worry about spring
compressors on a B (or any other leaf-sprung car, if memory serves).
I left the axle centered on my big floor jack while I replaced the spring
pads and rear bushings one side at a time.
Just doing the bushings should be cheap, take about an hour, and make
at least 75% of the difference. The front bushings are another story,
also cheap but require pressing to remove and reinstall. I've got new
ones but haven't put them in yet; they're pretty sturdy but will
eventually perish as will all rubber parts. Maybe this winter.
If he still has a little wobble from the back end, it might be worn
dampers, or for that matter dampers low on fluid. Put in new shock
oil first, cleaning off the filler hole on the top of the shock before
trying to add fluid. It's best to have the car jostled slowly up and
down while adding fluid, as this works the piston and helps bleed the
shocks. And if that doesn't work, then it's time to look into broken
leaves inside one of the springs, or possibly even front (yes, front)
suspension alignment. (Remind your friend that when he hops off the
gas, the weight settles back down on the front, and if there's bump
steer at that end it'll make the back end wobble.)
So to recap:
- Check the spring bolts for tightness
- Replace the bushings and spring pads
- Fill the shock absorbers with new oil
- Then start looking for more serious problems
Also, as much as I love MGBs, they *are* antiques in the design
department, and while Enever and Thornley did marvels with the
geometry, spring rates, and damping, it is your basic Hotchkiss-
drive solid axle car, and there's always going to be more rear-end
tramp and wobble in it than in a modern IRS. That's no excuse for
not doing what one can to make it right; it's more along the lines
of reasonable versus unreasonable expectations...
--Scott
> It seems a reasonable candidate for a running restoration. The tops of
> the front wings have been bondoed in the usual place; the inner fenders
> appear sound in the engine compartment. There is a significant rust hole
> in each rear sill (dogleg) just in front of the rear wheels, and bubbles
> in the outer sills (the originals) beneath the doors. Through the hole in
> the outer sill just in front of the rear wheels, I can see that each inner
> sill has a corresponding 2" to 3" hole in it. The front rear spring
> mounts and the metal surrounding them appear very sound, as does the floor
> (Tim saw the car with the carpets out). The jacking points seem sound.
> The door gaps appear fine, with no indication anything is sagging or
> misaligned. The second question for the day is: given the additional
> strength provided by the hard top, would it be reasonable and safe (if not
> necessarily admirable) to weld heavy gauge patches in the rear of the
> inner sills to tide the car over a few years (always assuming that sound
> metal can be found to weld to)?
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