Rubber-Bumper MGB: A Sensible Choice

The rubber-bumper MGB has been given a bum rap for too long. Our opinion? They make excellent, practical drivers.

When the rubber-bumper MGB was introduced in September 1974, many considered it to be an unworthy addition to the British sports car stable. The classic chrome accents were gone, the handling was affected by the elevated ride height and the performance was diminished.

But take notice: These cars make excellent daily drivers. Plus, they can be easily modified for enhanced performance and handling. They can even be converted back to classic chrome-bumper appearance. These attributes make these newer MGBs versatile and a good value, quite worthy of ownership today.

Kelvin Dodd, technical expert with Moss Motors, owns two rubber-bumper MGBs (’78 and ’80), and says they have advantages often overlooked. “The rubber bumpers offer great protection in parking lots and when you get hit, making it a safer daily driver,” he says.

The 1977-’80 MGB dashboard went back to a classic look, featuring round gauges and central warning lights.

Dodd adds that the raised ride height makes the car easier to get in and out of, and prevents scraping over traffic bumps. And the heavier weight makes for a smoother ride, especially over longer distances. However, lowering the car an inch makes it look and handle better while maintaining the benefits of comfort and practicality, he adds. Plus the rubber-bumper cars use a body shell derived from the MGB GT V8, making engine swaps easier.

Model Issues
Detractors of the rubber-bumper MGB tend to center on a few issues. Fortunately, all of them can be resolved.

For one, handling was affected by the raised suspension and the heavier rubber bumpers, two measures designed to meet Department of Transportation safety requirements. Also, in 1975 and ’76, the front sway bar was removed for cost purposes.

Performance and acceleration were hindered by smog and emissions requirements. A catalytic converter was added, while a single Zenith-Stromberg carburetor replaced the twin SU carbs in 1975.
By the mid-‘70s the car was obsolete. “It was a boulevard cruiser, not a sports car,” Dodd admits. “But people liked it because it was a cute convertible with retro looks. Since the tooling was paid off and it was still selling, British Leyland continued to make it.” At that point the company poured its efforts into the TR7 as their new, modern design sports car.

For classic looks, lower the ride height with a suspension kit and add Moss’ chrome bumper conversion kit.

First Fixes
The first priority on a stock rubber-bumper MGB is to lower the ride height an inch to the original GT V8 specs, Dodd explains. Thanks to a different crossmember, the MGB GT V8 sat three-quarters of an inch higher than the chrome-bumper MGB roadsters.

The Moss suspension lowering kit uses a one-inch lowered spring with higher spring rate that stiffens the front suspension to reduce body roll. The rear is also lowered an inch and the rebound straps are changed out.

“This is the most cost effective way to drop the car, and it provides better handling with good ride quality,” explains Dodd. He adds that it’s a good compromise on ride height as it looks better, yet maintains safety and practicality.

For those who yearn for the classic look of chrome bumpers, Moss sells conversion kits that include all the parts necessary to install chrome bumpers on the later shell. “Underneath a rubber-bumper model is a chrome-bumper car that was chopped up by the factory to meet government regulations,” Dodd says. “We just give you the bits to put it back the way it was originally designed.”

For max performance and speed, go for the supercharger, free-flowing header and high-boost kit.

Must-Do Performance Mod
The best possible modification to improve performance and acceleration requires increasing the engine’s breathing: After removing the single Zenith-Stromberg carburetor log-type exhaust manifold, catalytic converter and air pump, bolt on a Moss supercharger and inexpensive free-flowing header. Adding a high-boost kit allows the supercharger to make the most of its potential, Dodd stresses.

“It’s about $4,000 for the equipment, but it will double the horsepower and make the car go like a rocket ship,” he adds. “There has never been anything that makes such a difference to the way the car drives. Even the handling is improved because now there is enough torque to throw the car into corners and power out again.”

Taking It Further
Without going to a supercharger, horsepower gains are still possible. A dual-carb conversion is easily accomplished, while the intake manifold and entire exhaust system from the earlier MGB can be added. This conversion yields an extra five to 15 horsepower.

Moss’ popular five-speed transmission conversion kit reduces noise and vibration at speed. To make the car more dependable, Moss offers both Crane and Pertronix electronic ignition kits to replace the Lucas electronic ignition that typically fails after a few years.

More modifications to enhance handling include adding the missing anti-sway bars to 1975 and ’76 models. Moss offers a tube shock conversion kit for the front and rear lever shocks. Improved bushings are also available.

The ultimate handling solution is the Five-Link Rear Suspension Kit that replaces the leaf springs and lever arm damper setup with modern parallel trailing arms and coil-over gas shock absorbers. This conversion increases control, comfort and safety.

With better handling and speed, upgrading brakes is a good idea. For the best in braking, Moss offers a kit for installing the latest generation of Wilwood alloy brake calipers. Performance pads, cross-drilled and slotted rotors, and stainless steel flexible line kits enhance stopping ability.

There are plenty of styling options. For example, choose among a number of steering wheels or upgrade original vinyl seats to leather. Moss offers wire wheel conversion kits; the new wire wheels are available in either painted or chrome finish. Minilite wheels are a perfect fit and come in a few price ranges.

Buying Advice
“If I was buying a rubber-bumper MGB, I’d get a 1977-’80 model,” advises Dodd, as these cars have a V8’s cooling system, front and rear anti-sway bars and updated dash. “I think the ’77-’80 dash is the nicest of the three MGB dashboards because it has round gauges, a larger speedometer and tachometer, and a cluster of warning lights in a logical, central location,” he explains. “I like the classic look of the steel dash cars, but the later dash is more user friendly for hard driving.”

For those preferring to keep things stock, Dodd recommends the 1979-’80 Limited Edition model. “They’re pretty cars and they have more presence,” he says. “They came only in black, and the flat black front spoiler blends nicely with the bumper and body. Plus it seems to lower the front end of the car so it doesn’t look as high. The silver side stripes give the sides more definition.”

The 1979-80 Limited Edition model added the alloy wheels, side stripes and front spoiler.

The LE also received wider alloy wheels fitted with lower-profile tires—the package looks and handles very well. In fact, Dodd recommends the 5.5-inch wide LE wheels with 185-70 tires for all rubber-bumper MGBs. These wheels, and all the MGB LE parts, are available through Moss.

When it comes to the MG world, the value of a specific car has little to do with originality. Instead, it depends on the car’s performance and condition. So why not modify it to better suit your taste?

Popular Replacement Parts
190-808 – Borg & Beck Clutch Kit
180-737 – Brake Master Cylinder Assembly
182-171 – Brake Rotor, front
434-045 – Water Pump
459-675 – Radiator
264-408 – Major Suspension Kit, front
457-275 – Front Fender, LH
457-250 – Hood (steel)
457-155 – Rocker Panel
641-600 – Front Seat Cover Set, black vinyl
242-655 – Convertible Top by Robbins, black vinyl

Insider’s Info:
• The term rubber-bumper cars is misleading. The bumpers are actually polyurethane plastic with steel inserts.
• British Leyland’s first attempt at meeting the DOT’s 5 mph crash tests appeared in early 1974: two large rubber blocks added to each end of the car.
• Rust is the enemy of the MGB’s monocoque body design. Check the dogleg between the door and rear wheel, the front and rear door pillars, the rocker panels and the points where the rear suspension fastens to the body shell.
• In 1975, the car produced 62.5 bhp at 5500 rpm, and 86 lb.-ft. of torque at 3000 rpm. Curb weight was 2,287 pounds.
• The MGB got some nice upgrades starting in 1977: front and rear anti-roll bars, larger radiator, upgraded alternator, updated dashboard and a zip-out rear window.
• There’s a fantastic network of enthusiasts. Check out the MG 2009 Convention organized by the North American MGB Register in Breckenridge, Colorado, June 24-28: mg2009.com.
• The last MGB left the Abingdon factory on October 22, 1980.
• Original condition rubber-bumper MGBs are still found for $5000 or less. The nicest ones in the world can fetch the high-teens.

By Kathleen M. Mangan