Thread: Project Sebring GT Spyder

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During the initial build, I also fabbed up an adjustable steering rack mount so that I could adjust bump steer. You adjust it by using shims and it adjusts both forward and backwards as well as vertically. The MII front end has some bump steer when stock and as you dial in more caster, the steering arms move higher. This generally makes bump steer worse. At least, that proved very true on my car. I just wasn’t quite prepared for how bad it actually was.





Bump steer adjustment was the last alignment I tackled. At this time, I don’t have an actual bump steer gauge (as in the type that uses a dial indicator), but was able to rig up a laser setup that got me very close. The setup is not my idea. I first saw it on a YouTube video and it looked like it should work. A laser pointer is attached to the hub or wheel pointing forward. A mirror is positioned 5 times the tire radius to reflect the laser almost straight back on itself. A target is fixed on the hub near the laser and marked with a sharpie where the dot falls. The suspension is then jacked through it’s complete travel. Since the laser and target are moving up and down together, the laser dot only moves left or right from the starting point (lower control arm level). If the dot moves away from the centerline of the car, you have toe out. If it moves toward the center, you have toe in. Since the laser travels 10 times the wheel radius to get back to the target, any indicated lateral movement is 10 times what actually happens at the tread.

My rigged up tool consisted of a piece of heavy angle iron drilled to fit over one wheel stud. This formed a shelf that I clamped a heavy cast iron weight that I had laying around. The laser pointer was in a magnetic torpedo level. The target was just a piece of scrap aluminum clamped to a section of scrap angle iron. The mirror was an old Chevy truck door mirror that was stuck back on the shelf. It was sitting on a couple of milk crates. Definitely a bodge, as a Brit would say, but it did work just fine.





I should also add that I wasn’t concerned, at this point, with exact numbers. All I wanted was to get the bump steer acceptable for initial driving. I was just looking for minimal toe change through the entire suspension travel. I have 6 inches of total travel available (3 up and 3 down) with the body off the chassis, but I doubt I can use all of the compression travel. I might be able to use around 2 inches up before the tire hits the fender. I’ll double check that after the body is back on and if it happens, I can add a bump stop to the shock. The shock does stop the suspension in full droop before the upper control arm contacts the frame or the ball joint runs out of angular travel.