I recently came to be repossessed by a British car, 73 MGB/GT
Does this mean your new owners didn't keep up with their payments on
you, or is this more like Linda Blair than Emilio Estevez? :-)
Question is how do I know when it is time to rebuild/replace bushings
and the like on the front end ?? All the rubber "looks" bad. (cracked
and disentigrating) All pointers and information will be appreciated.
Sounds like it's time to rebuild and replace bushings. Here are some
things to look for on a B front end:
- Cracked and disintegrating rubber. The B has rubber bushings at
the outer end of the upper A-arms and at the inner end of the lower
A-arms. These you can do with hand tools and a good floor jack.
- Off-center bolt for the trunnion at the bottom of the kingpin.
This is a common problem on older Bs, because the kingpin bushing
is supposed to be lubricated. It often isn't, which means the
bolt seizes inside the bushing. When that happens, all the
movement of the suspension is carried by the A-arm instead of
by the bolt and bushing. This cuts through the bolt and wears
out the A-arm. You'll probably need to have this done in a shop,
unless you've got a hydraulic press and a fairly precise reamer.
- Kingpin bushings. There are (I think) three bushings that keep
the kingpin and the stub axle assembly moving freely. These also
require a press to get the old ones out and a reamer to get the
new ones to fit. It's a couple hours' bench work for a shop.
When I've done front ends, I usually remove the lower A-arm,
kingpin, and stub axle assembly and take it to the shop.
- Leaking shock absorbers. The Armstrong lever dampers last a long
time, but eventually they can wear out. The seals inside them will
fail, causing them to lose fluid. Look around the holes in the
shock body, where the shaft of the A-arm goes through, for evidence
of leakage.
When you replace the bushings, there are three different options.
Stock. The original rubber bushings will offer the highest level of
ride comfort, which as any MG owner will tell you is still pretty low.
They deflect, which absorbs some of the small-amplitude vibrations you
get from the road surface. In hard cornering these bushings will let
the suspension move in unintended directions, though. If you're planning
to modify the suspension for better handling, you'll probably want to
pick one of the other options. There are six stock rubber bushings,
two where the upper A-arm mounts to the kingpin and two at each inner
mount of the lower A-arm.
V8 bushings. These use a rubber-steel composition, with a steel sleeve
that goes over the spindle to which the inner end of the lower A-arm
mounts. (There is no V8-style bushing for the upper A-arm.) These
last longer, wear better, provide somewhat improved handling, and are
fairly cheap. You will need to make sure that the shaft on the spindle
is clean and round before installing these. I've got them on the B now,
on the driver's side anyway (that's the side that was so badly worn
that the bolt was way off-center).
Nylatron. Nylatron is the trade name for a variety of nylon that is
impregnated with molybdenum disulfide. The principle is that the nylon
allows virtually no deflection, and the molybdenum disulfide acts as
a friction reducer. Motion is far less restricted in the intended axis
of rotation, and far more restricted in any unintended axis. I've put
these on the rear of my MGB, and I'm quite pleased; they locate the
rear axle nicely, and the B is stiff and jiffly enough that I haven't
noticed it being any worse with the nylatron bushings. These are also
available for the front of the car; I'll be putting them in over the
winter, while I clean up and restore the whole front suspension.
How to dismantle the suspension:
Raise the car and place it on jackstands, then remove the road wheels.
Remove the brake caliper from the stub axle and support it somewhere on
the chassis; do NOT let it hang by the brake line. There is a lock tab
on the two bolts that hold the caliper on; knock them back with a hammer
and a large screwdriver or chisel.
Disconnect the anti-sway-bar mounting link. You can disconnect it
from either the top (where it connects to the bar) or the bottom (where
it connects to the lower A-arm). The latter will save you a step
later when you're stripping the A-arm pieces.
Disconnect the steering linkage. The easiest way is to remove the
steering arm from the rear of the stub axle; it's also held on with
a lock tab. You can also remove the tie rod ends, but that requires
a ball-joint separator and requires realigning the steering when
you get the car back together. The rest of this job does not disturb
the steering alignment, and no other part of the stock suspension is
adjustable.
Place a jack under the outboard end of the lower A-arm and provide
a very small amount of tension (that is, raise the outer end about 1/4"
or so). Remove the nut from the top of the kingpin; it might be
castellated and held on with a cotter pin. I think it takes a 13/16"
socket but it's been two years since I've done this.
When the nut comes off, SLOWLY use the jack to lower the A-arm. The
spring tension will press the A-arm down and force the kingpin out of
the upper trunnion. Go slowly; there is a lot of force in the spring.
As the top of the kingpin clears the lower edge of the trunnion, take
care to support the brake and stub axle so that it doesn't fall free.
Continue to lower the A-arm carefully till the spring rattles in its
mountings. That means that the spring is not under compression, and
you can proceed a little more rapidly to remove the spring.
Once the spring is out, I found it easier to remove the spindle from
the chassis crossmember, then to take the A-arm pieces off the spindle
and also off the lower spring plate. (The lower A-arm is two thick
pieces of metal shaped like a staple in cross-section; they bolt to a
spring mounting plate in the center and to the A-arm link.) You'll
need to clean the spindle in any case to fit the new bushings on it,
so you might as well take it out of the car now. Note that two of
the bolts that hold the spindle to the crossmember drop down through
the chassis, and two rise up through the spindle. Unless you're doing
the car one side at a time, make a note of which way they go through.
(I seem to remember it making a difference in reassembly, that only
one way would work due to the way that the chassis did or didn't
interfere with the bolt heads and the nuts, not to mention where you
can fit the wrench.)
>From this point, disassemble what you can in your garage and then
take what you must to a shop for machine work. This would be a great
time to rebuild the front brakes, replace the hoses, or do other
work at that end of the car (steering boots, for instance, or putting
in a stiffer front anti-roll bar, or repacking the front wheel bearings).
The upper trunnion has a blind bolt -- that is, the bolt that goes
through the upper trunnion has a round head with a flat cut into it.
The flat lines up with a boss in the trunnion to keep it from
turning when you tighten or loosen it. Since the rebuild kit comes
with a new bolt, you probably don't need to worry much about getting
the old one out in good condition, but it will help save it if you
keep a nut on the end of the bolt so that you don't mushroom the tip
and bend the threads. Once the bolt comes out, you can remove the
trunnion and its bushings.
While it's all apart, take advantage of this time to clean up all the
pieces you'll be reusing, as well as the chassis and wheel wells. If
you have access to a recirculating parts washer, that's great for the
bits you can take off the car. If not, use the same stuff that you'll
use on the chassis: brake cleaning spray, Simple Green or Breeze, a
couple of wire brushes (I've got one that looks like a brush for
spreading barbecue sauce that works very well) and lots of rags and
shop-quality paper towels.
Reassembly is pretty straightforward. Do the same trick with the
jack, supporting the lower A-arm while you line up the spring.
When you install the upper trunnion, the new bushings will be a
much tighter fit than the old ones; expect some fiddling to get
them all to line up so that the bolt will go through. A tip:
loosen the support bolt in the middle of the upper A-arm so that
the two halves of the arm can be spread slightly. Be sure to
tighten the support bolt when you're done. It's probably easier
to leave the upper trunnion a little loose as you line up the
kingpin on reassembly, then tighten all the bolts after everything
is in place.
When you reinstall the steering link and the brake caliper, knock
the lock tabs into place against a flat of each bolt so that the
bolts can't vibrate loose. Use a hammer and a large screwdriver
or chisel.
There should be three lubrication points on the outer kingpin and
stub axle. One is on the bottom trunnion, the other two are on
the stub axle itself, where the axle piece slips over the kingpin.
Be sure to give these a thorough squirt with the grease gun before
you finish up, and then give them a squirt every time you change
the oil or have the wheels off. I don't think it's possible to
overdo the lubrication here, as long as you try to wipe up the
old grease as it is forced out of the bushings.
If you have any questions, just ask!
--Scott
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