sbyrne

I developed a knocking sound from the right front corner during our autocross this past Sunday. Just put the car ('84 - steel control arms) in the air and removed the front wheels for inspection, and found the control arm bushing - at the crossmember - destroyed. These bushings (Weltmiester polyurethane) are less than a year old and have only been driven 1000 or so miles and 8 autocrosses. The rear flange of the bushing has been cut off by rearward motion of the control arm, allowing the arm and crossmember to make contact during bumpy left hand turns. Should I just get new ones and assume bad luck? Is there a better alternative (Delrin?)?

M758

Yep,
I had the same exact issue and I went through 3-4 of them before Karl at racers edge made some delrins for me. Delrin bushing cost more, but have lasted 4 years without issue. The delrins are used at the crossmember and you can use the welts at the caster block.

TNT25169

If you read about the weltmeister ones, some websites have described them as "restoration" bushings as opposed to "race" which is not something you would expect from weltmeister. I believe the paragon-products web-site says this and in the end, you're better off using the stock Porsche bushings or aftermarket ones (delrin or monoball depending on your budget).

sillbeer

I also have the weltmeister "reds" but I don't track the car. Am I alright then?

TNT25169

You should be. From what I understand they are meant to be used just as the factory ones are but I think they are a little softer. For daily use you shouldn't have any problems.

sbyrne

Just ordered the Delrin pieces from Jason at Paragon. He tells me that this was a common enough problem that the stopped selling the Welt bushings. My Perf Prod catalog does state that the Welts are not to be used for a-x or racing, so i guess they're right! Problem appears to be the shape of the control arm - there's no flange at the bushing interface to distribute the load, so the arm cuts right through the bushing.

M758

Yep,
The red welts are fine for aluminum arm cars as the control arm does not have a sharp edge to it like the steel arms. For street or light autocross use (street tires) you are probably fine on welt reds. I would repeated tear up the the pass side bushing at my local race track. It came from hard braking from 100+ mph when running on race tires and race pads. You just don't put that kind of load in the car on the street. For a while I ran a stock 83 944 on street tires in autocross on the old welt black bushings. Never had an issue, but the street tires and street pads meant I was never really hard on the brakes.

I do have to say that the stock rubber bushings are not any better. They don't get torn up due their design, but the just allow the control arm to slide over the bushing and still rub the crossmember. The delrins seem strong enough to stand up to anything I throw at them.