Q: Bushing Materials — Pros. and Cons.
I have heard a lot of debate for what type of body bushings to use. Can anyone give me a definative answer?
A: Bushing Materials– Pros and Cons.
NVH – Stands for Noise, Vibration, and Harmonics. Typicall things an engineer wishes to limit in a car design. Something a racer isn’t too worried about.
Rubber: Measured in durometer units, they can vary in hardness. Most stock bushings are fairly soft and are a compromise to offer reasonable handling but keep the ride relatively smooth. Remember that the factory had to sell these cars to both speed enthusiats as well as buyers who would be troubled by a harsh ride or NVH.The Ford Mustang especially was criticized for it’s harsh ride, and Pontiac sought to improve on that. The WS6 cars of later years (including the present) use a harder durometer rubber bushing to limit deflection.
The downside of rubber is that it decays and wears out. This is accelerated when the car is pushed very hard as in road racing or heavy drag racing.
Polyurethane: A relatively inexpensive upgrade that limits deflection. Users typically see an increase in NVH, but is acceptable to those more interested in performance driving. This is a synthetic material recently introduced into automobiles. Some of the big names in aftermarket suspension designers use this such as Saleen (Mustangs), SLP, Kenny Brown, Hochkiss, etc. Since deflection is the enemy of precise handling, limiting it is a good thing.
The downside of polyurethane is that it is very prone to squeaking, and sometimes bind. The squeaking can be eliminated or at least limited by modifying the bushing shells to accept a grease fitting and lubing them regularly. Another bad aspect of polyurethane is cold flow. It seems that after a period of time, especially under hard use, the bushing material may deform, slowly flowing like a liquid, ultimately needing replacement. Increased harsness can be expected. I put them in a 1970 El Camino, and it is noticable. Because it is much heavier than my Firebird, the weight of the car offsets the stiffer ride. I’ve also got them in the front of my 1986 Mustang GT ragtop. I find the ride quite acceptable. But that car also has a 6 point roll cage, subframe connectors, and Koni shocks/struts. On rough roads with potholes, it isn’t very fun. But that isn’t very often either. Maybe if I lived in New Jersey…
Steel/nylon or aluminum/nylon (Duralum): Absolutely a sure fire way to get rid of deflection. Companies such as Global West, VSE, and others tout this as the best choice for slot car like handling. Some of my road racing pals use these as well as heim joints in the suspension. These are usually dedicated race cars, but not always.
The downside is increased NVH. I know that Glen says it was either not increased, or at least tolerable. But I suggest to anyone considering these to try and get a ride in a car already equipped. You may like what it does for your car, but it will come at a price measured in increased NVH. Some can live with it and be very happy with the results. Others cannot.
What did I choose formy Firebird? Stock replacement rubber (TRW). My car is a convertible that had a lot of squeaks and rattles that I hoped to eliminate when I rebuilt it. I decided that I could live with the deflection in trade for a nicer ride. I’ve got other cars I can turn to when it comes to burning up the twisties.
You have to decide what you want to get out of your car, and what you are willing to trade off. Once you know that, the choices may become more clear.
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Content last modified: January 20, 2014 at 9:48 pm