Control Arm Bushings with Fitting Position Front for 1978 MG MGB MK IV

Control arm bushings sit where the arm meets the chassis, letting it swing as the suspension travels while holding the wheel in the position your MG MGB alignment set.

They are the most commonly replaced bushing on any vehicle, and the one most often ordered incorrectly, because a single arm usually takes two different bushings that look similar in a photograph.

The Forward and Rearward MG MGB Control Arm Bushings Are Not the Same Part

Open a parts diagram for almost any lower arm and you will find two inner pivots with separate part numbers.

The forward one sits closer to the front of the vehicle and handles lateral location, keeping the wheel where it belongs as the arm is loaded sideways through a corner. It is usually smaller, firmer and simpler in construction.

The rearward one is built differently on purpose, because it takes the fore and aft hit every time you hit a pothole or brake hard, so manufacturers make it considerably softer and often much larger, with voids moulded into it so the material can deform in one direction while resisting movement in another.

Ordering the wrong one of that pair is the single most common mistake made with control arm bushings. A control arm bushing diagram for your MG MGB is worth two minutes before you commit to anything, particularly on a car where both arms are listed under similar part numbers.

Add upper and lower, then front and rear of the vehicle, and the full description gets long. A front control arm bushing and a rear control arm bushing are entirely separate components, and an upper control arm bushing rarely interchanges with a lower control arm bushing on the same car.

Why the Rearward MG MGB Control Arm Bushing Usually Fails First

Given the choice, put your money on the rearward position.

That bushing is deliberately the softest thing holding your front suspension, because it has to absorb impact harshness before it reaches the cabin. Soft material under repeated heavy load degrades faster than firm material under light load, which is exactly the situation here.

It is also the one taking braking energy. Every stop pushes the wheel backward and that force lands on this bushing, tens of thousands of times a year on a daily driver.

The forward bushing often outlasts the vehicle, while the rearward one wears out, splits, and in plenty of cases has collapsed entirely while the one twelve inches away still looks serviceable.

That is worth knowing when a shop quotes both, because replacing both together is usually correct on labor grounds even when only one has failed.

Hydraulic MG MGB Control Arm Bushings and Why They Leak

Plenty of modern vehicles use fluid filled bushings in the rearward position, and they fail differently to anything else on the vehicle.

Inside a hydraulic bushing are sealed chambers of fluid connected by a small passage. Under a sharp impact the fluid is forced through that passage, which damps the movement in a way solid rubber cannot, so the ride is quieter and more comfortable than the geometry alone would allow.

The problem is that anything sealed eventually is not. The rubber perishes, the seal fails, the fluid weeps out, and what remains is a soft rubber bushing with a hollow void inside it. At that point the bushing is worse than the solid item it replaced, because it has the compliance of neither.

The visible sign is fluid residue or staining on the arm and around the mounting point, which people frequently mistake for a leaking shock or an oil drip. If a rearward control arm bushing has oily residue around it, that is a bushing that has failed rather than one that has been contaminated from above.

Replacement with a solid polyurethane bushing removes that failure mode completely, at the cost of a small amount of impact absorption.

Symptoms of Bad MG MGB Control Arm Bushings

• A dull clunk or thud from the front over expansion joints, potholes and driveways
• A single knock as you take up drive, shift, or release the brake at a stop
• Steering that needs constant small corrections to track straight
• Pulling to one side under braking
• Shudder or vibration through the wheel when braking from speed
• Tire wear on the inside edge that returns after every alignment
• An alignment that will not hold spec between services
• Fluid residue or staining around the rearward bushing on a hydraulic design

Control arm bushing noise has a specific character worth learning, because it saves chasing the wrong part. It is a dull thud rather than a metallic rattle, it shows up at low speed over sharp edges, and braking makes it worse. Sway bar links produce a lighter, faster rattle. A ball joint knocks when the wheel is turned under load rather than when the suspension simply moves.

Signs of Bad MG MGB Control Arm Bushings You Can See

Bad control arm bushing symptoms are one thing, and what the part looks like is another. Both are worth checking before you order a replacement.

Rubber bushings are bonded to a metal outer sleeve. As the rubber ages that bond breaks down, so look for a visible gap between rubber and sleeve, cracking radiating across the exposed face, or material squeezed out past the housing edge.

A broken control arm bushing is usually unmistakable once the wheel is off, with the arm sitting visibly off center in its mount or the rubber missing entirely on one side.

A worn control arm bushing that still looks presentable is the harder case. Lever the arm against its mounting point and watch the bushing rather than the arm. Any shift at the bushing itself means it is finished, whatever the surface looks like.

Good vs bad control arm bushings comes down to that test more than appearance, because a bushing can look tired and still hold, or look reasonable and have nothing left.

How Long Can You Drive Your MG MGB With Bad Control Arm Bushings

Early wear is not particularly urgent, because you will lose steering precision and wear tires faster than you should, and you can schedule the repair rather than rushing it.

Advanced wear changes the picture entirely, since an arm moving at its mounts means the alignment shifts under load, so the vehicle is least predictable under braking and cornering. Worse, the movement starts damaging things around it, working the ball joint harder and eventually wearing the mounting eye out of round, which turns a bushing job into an arm replacement.

A bushing that has collapsed or gone missing should be dealt with straight away rather than at the next service.

MG MGB Control Arm Bushing Replacement Cost

Control arm bushing replacement cost is almost entirely labor, and the parts are a small fraction of any quote you receive.

The arm has to come off the vehicle, the old bushing has to be pressed out, the new one pressed in square, and the assembly refitted and torqued. Add an alignment on the end, which is mandatory rather than optional after this work.

Because access is the cost, doing both bushings on an arm together costs barely more than doing one, and doing both sides at the same visit saves an entire second teardown. Lower control arm bushing replacement cost quoted per position looks high in isolation and reasonable when you see what it includes.

Three things explain most of the variation between shop quotes: how many positions are being replaced, whether the arms come off or the bushings are being done in situ where the design allows, and whether the alignment is bundled or billed separately.

Press-In MG MGB Bushings and Bolt-Through Designs

How the bushing is retained decides whether this is a home job or a shop job.

Press-in bushings are an interference fit in the arm eye and need a hydraulic press with a control arm bushing tool of the correct diameter. Improvised drifts and sockets damage the eye, and a damaged eye means a new arm. There are removal tools designed to work in situ on some applications, though the results depend heavily on the vehicle.

Bolt-through and two-piece polyurethane designs go in without pressing at all, which is one of the practical advantages of a polyurethane control arm bushing kit on applications where it is offered. The old rubber is cut or burned out, the eye is cleaned up, and the new bushing halves go in by hand.

Whichever you have, inspect the eye before fitting anything. A bore worn out of round will not retain a new bushing, and finding that out at the press rather than after the car is back together saves considerable time.

Install every sleeve and crush tube supplied, grease polyurethane on assembly with a silicone or PTFE based product rather than a lithium or petroleum one, and tighten the through bolts with the vehicle sitting on its wheels rather than hanging on a lift. A bushing clamped at full droop is permanently twisted at normal ride height, and more new bushings die that way than from any other cause.

Find Control Arm Bushings for Your MG MGB

Control arm bushings are the biggest line in the Nolathane polyurethane bushings selection. If the arm is bent or the ball joint is worn out, a complete control arm kit is the better repair.

Select your MG MGB to see every control arm bushing position listed for it, including forward and rearward inner positions and upper and lower arms where the design uses both. Every Nolathane component is backed by our warranty, a fitment guarantee and 60 day returns.