How Are Your Bushings & Mounts Holding Up?

by Andrea L. Algar
Motorheads Performance

If they haven't had a recent restoration, chances are that most antique and classic cars, whether on the road or just sitting, have body mounts and suspension bushings that are dried, cracked, and falling apart. Don't overlook this important item when maintaining your older car or truck.

When cars were first made, body mounts were just a strip of tanned leather to act as a cushion or isolator between the body and the frame. Body mounts evolved to be made of hard rubber, which were in use for many years. But since the introduction of modern synthetic technologies, body mounts, motor mounts, transmission mounts, and just about all suspension bushings are made of polyurethane. This material outlasts rubber due to its resistence to heat, dry conditions, lubricants, and other chemicals and its high durometer (hardness) value. It also is a self-lubricated (to a point) if only used in compression such as a body mount locations. When used in suspension or rotating component locations, a thin film of silicone grease is applied to increase its wear resistence.  These polyurethane mounts will outlast rubber by 200% and resist compression by a factor of 75%.

Chances are your body mounts have compressed and are no longer doing their job with most 1960's to 1970's muscle cars, whether it be a light bodied Camaro-Firebird, or a heavier GTO-Chevelle. Also, the metal inserts have probably rotted away, causing the body to twist and rack. This can cause windshields to crack, doors to misalign, trunk lids, hoods and fenders seams to open or close irregularly. Any classsic car or vintage truck from the 1940's to 1950's should have had their body mounts replaced already. If not, is is probably critical to do so, and I would recommend that you consider switching from rubber to polyurethane when you do. Note the compression in the old rubber body mounts shown below. The new polyurethane mounts are superior in design and longevity.


Old Chassis Rear Body Mounts (top)
New Polyurethane (bottom)
Project: 1958 DeSoto by Motorheads Performance

Old Chassis Frame Rail Mounts (right)
New Polyurethane (left)
Project: 1958 DeSoto by Motorheads Performance

















Guy Algar explains, "Years ago when I replaced the rear rubber spring bushings on my 1955 Chevy Belair with another set of rubber spring bushings, the rear tires would rub on the inside of the quarter panels in hard turns. When I later switched the rubber bushings to polyurethane, the rear suspension no longer flexed and allowed the tires to rub. I could also feel the difference in handling." Shortly after installing the rear, I changed my tires from bias ply to radial and it improved my handling even more. "When working on customer's vehicles at Motorheads Performance, I always recommend that dried out and rotted suspension components be replaced with high quality polyrethane ones," he says. Many people never think to check the body mounts unless they're doing a body-off restoration. This can be a mistake, because rubber body mounts compress, dry and rot with age. Motor, suspension and transmission mounts tend to be more visible, and are easier to inspect for damage. "I can tell when the body mounts are bad when installing or inspecting headers by looking at the header collector flange. If I have 1/2" to 1" of clearance the body mounts are not badly compressed, but if the flange is hitting the floorboard I know the mounts are in bad shape and need to be replaced immediately," explains Guy.

"Two suppliers of quality polyurethane components that I use at Motorheads Performance are Energy Suspension and Prothane. What I can't get from one, the other will have," Guy states. If you're looking to do a restoration but want to use polyurethane black is the standard color. Red is supplied as an option for those who are not looking for an OEM look. Also available from polyurethane manufacturers are tie rod boots, upper and lower control arm bumpers, sway bar bushings and end link kits. Guy adds the following tip, "Whenever I work on suspension parts, mount brackers, brakes, or whatever, I always use the opportunity to clean things up. If there are signs of rust, I bead blast, prime and paint before reassembling with new polyurethane." 


Upper Control Arm Polyurethane Bushings
Ready for assembly for '69 Firebird
Project by Motorheads Performance 

 

Upper Control Arm

Primed with New Polyurethane

Bushings in place

 

Upper Control Arms with new
Polyurethane Bushings
Ready to Install





The other benefits to using polyurethane over rubber is its ability to firm up your suspension handling characteristics due to the fact that it is harder than rubber and doesn't stretch and give. The design of polyurethane mounts is much improved over OEM designs. For instance, when using it for transmission motor mounts, they have an interlocking metal to hold it in place, giving better strength in high horsepower applications.

As far as body mounts offered in urethane, they come in two densities (or durometers). One is for light body vehicles such as kit cars, some of the smaller trucks and small hot rods or street rods. Another hard set is offered for the heavier body muscle cars and classic cars and vintage or classic pickup trucks. Making the switch to polyurethane will help your restoration last longer, give you a better ride and great peace of mind.

ABOUT THE AUTHOR:
Andrea L. Algar is co-owner of a classic car performance and restoration design shop in Leesville, Texas. Motorheads Performance specializes in repairs, maintenance, performance upgrades and restorative work on cars and trucks from the 1920’s through 1970’s. Her husband Guy L. Algar is a Mechanical Engineer with over 25 years experience. He holds 5 ASE Certifications from the National Institute for Automotive Service Excellence and has been working on old cars and trucks for over 37 years. Together they share their passion for old cars and trucks with other enthusiasts from around the country.