Bob's Resource Website (2007)

Delrin Bushings

I've been questoned about my stance on Delrin bushings and it isn't a positive one!

I know these have been installed on a street car, however, I don't have any experience driving a Studebaker using them. Other vehicles, yes!

My views and experience are rooted, in an association I have with track racing. If all the roads in the USA were as smooth as a cherubs butt, Delrins would probably be a good bet. Delrin bushings are used extensively on dedicated race cars that have minimal use (mileage), limited driving, generally good pavement. In this arena, where you have thousands of vendors for various parts, none (read NONE) of them will recommend Delrin for street use. This could be to head off any complaints from over eager purchasers, wanting their street cars to feel like their club racer and being sorry for it later.

With Delrin bushings, in a passenger car, the only shock buffering is coming from your tires. On an average road surface, the frame of a Studebaker will be considerably hammered, by having Delrin in the suspension. This can't be a good thing, given the difference in technology of building a Studebaker vs the technology of building a car they are designed for; ie, a rigid unibody with computer designed, compound curve metal stampings, assembled as a multi-weld platform with added high strength bonding adhesives. The flexiness of the Stude frame may be a help here though. A comment on the Lark steering endplay is a case in point. Without the rubber bushings absorbing road shock or countering looseness, vibration from excess clearances, will only beat the clearances larger and fairly quickly.

The Stude frame already has a reputation for cracking, right on top of the spring pocket. The regular production frame was never modified for this, they just issued a Service Bulletin on how to repair it,when it happens. The Avanti, with 60% of the weight on the front wheels is a prime candidate for 'hurt'.

If you have Delrins in your daily driver and don't frequently check the tightness of your frame and suspension mounting bolts, you could be in for an unpleasant surprise. Even the slightest compromise of a torque spec, can lead to a bolt hole elongating with movement. The Stude torque spec on lower inner pin bolts (Avanti) is 60-65 ft/lbs. Right now, I'd hop out to the garage and give them a check.. Loose? replace them with grade 8 (or higher) bolts, big washers and toplock nuts, then increase the torque to 90#. Then, too, there are the main crossmember rivets....
What do you do with these?

The 1951-52 suspension (Solid upper inners), later used in the R3 Avanti, may ride fine and seem adequate, but was only in production for 2 years, and replaced with what, rubber bushings! This was during an era when the average mileage per year of driving was only, say 5000 miles at most. So there must be a story here somewhere..

Bottom line is, everyone does what they see fit, depending on the depth of their education and strength of their logic. If your car is a toy and driven infrequently, you can probably go a long time without any problems. If you've done more than 3-4K a year, and haven't yet, then start looking closely underneath.

As previously stated, in my opinion, polyurethane would be a better material. In the absence of that, I'd opt to redo the standard rubber bushings with NEW reproduction parts from our vendors.

R3 steel upper inners are made of the same alloy as the outer trunnions and require grease fittings. They're the same shafts that were used on the early 50's cars.

All of the Delrin bushings I've seen, have no metal sleeves. They are cut from a billet, drilled and turned down on a lathe. The bushings are much more dense, like soft aluminum, with memory. They require a grease fitting and actually ride/twist on the pin. Delrin does not deflect in a hard turn and will definitely wear out if not lubricated. It does contribute toward very precise steering and quicker cornering control, however shock buffering is nil and road noise and vibration are transmitted right through the frame.
It would be pretty bad driving with these, even if you had a minimal tire balance problem. Due to their harshness, NO professional driver recommends them for normal street use, only for hard core racing.

Given the frame thickness or lack of it in a Studebaker, Delrin bushings will be, notably instrumental in beating your car to death. Aren't we owners, at least in SDC, working under the premise of "keep then running" or has it changed to "Let's use them up"..

I don't know why our vendors sell them, other than, they're very cheap to produce, compared to the manufacturing cost of polyurethane.

Poly-Urethane bushings do not degrade, are a bit denser than rubber parts and afford a more rigid ride, but do have a fair amount of shock buffering. These are a decent replacement, but none of our vendors choose to have them manufactured.

Jan 2010
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