Butler Cobra with Mustang II IFS

[RallySnake]

Hey Guys,

I have to speak up here for a minute in defense of the MGB suspension. Sure the kingpins are old technology, but is that a bad thing?

I remember vividly the first time I drove a new MGB in 1969. The steering was amazingly precise and direct. Ron Butler has built a lot of race cars and if he didn't have a lot of faith in the MG front end he would have changed it when he took over the production from Steve Arntz.

Things do wear out, though. I had a similar problem to Tom's. After years of driving, the car wandered a lot and was all over the place when I braked hard. I pulled the body off and started trying to "bumpsteer" the car. I worked on the steering angles for hours before I leaned against the brake caliper and the upper a-am moved forward 1/2 inch! The lever shock bushings were completely worn out. I bought some second hand shocks and took them apart to remove the levers and pistons. Then, I drilled and tapped them to install grease fittings on both sides of the horizontal shaft. I bought the hard "racing-type" polyurethane bushings for the outer pivot points and also for the lower arms.

The lower arms were a problem themselves. The bolt holes (under the kingpin) had worn down more than a quarter inch from their original position. I bought new ones from Moss for less than $20.

I then started checking the bump steer and it was very near perfect without any adjustment. I did change the castor angle. Brett Butler (Ron's son) suggested this. With the MGB suspension bolted to the Arntz chassis, the angle is about 6 degrees. This makes the car run VERY straight on the freeway, but VERY hard to turn while parking. I used spacers under the front mounts to reduce the angle to 3 degrees.

After putting the car back together, the transformation was amazing! The car tracked straight and true even at really high speeds. I could steer within an inch of an apex. The steering remained straight under hard braking (even though the engine often dies). I do have about a dozen grease fitting to hit a couple of times a year and I am running KYB shocks meant for the rear of an early 'Vette. The kingpins show no wear or play and they are at least 40 years old.

I did replace the calipers with rebuilt ones ('74 Dodge Dart). I had the rotors turned and installed Porterfield pads. Since then, I've probably driven 50,000 hard, fast miles and it's still working great.

Paul