Sorting out the Bump Steer

Now that the front end is so low I have some bump steer issues to resolve. Bump steer manifests itself when the suspension loads or unloads from a bump in the road. Bump steer often occurs when one lowers (or raises) the front end and the tie rods become misaligned relative to the lower control arm. They need to be parallel or the tie rod will swing on a different arc as the control arm. The shorter or longer arc will cause the wheels to turn while the steering wheel stays still. Bump steer = thrill ride.  

While inspecting my front end I discovered that the shop that installed my drop spindles put the steering arm on the upper set of bolt holes. I assumed this was done because when the steering rod was bolted to the (proper) lower set of holes, the tie rod knuckle would hit the rim or it may have been done because the tie rod looks like its parallel to the lower control arm this way. In any event, this improper installation has caused my suspension to be out of whack.

 

Did My Cheap Wheels Just Get Expensive?

If the tie rod will hit the rim, the simple solution is have less backspace on my rims. The Vision Legend 17x8 wheels have 5.25" of backspace.

 

Other guys 3rd Gen Nova setups it appears a 17x7 rim with 4.5 inches of backspace would clear the tie rod and the outer fender. Unfortunately Vision doesn't make a 17x7 wheel in this style. So to do this I would have to get 4 new rims. Ouch!

3rd Gen 8" Front Rim Sizes

This Super Chevy article shows a 69 Nova with 2" drop spindles using 17x8 w/ 4.75" back space up front (and 17x9 with 5.75 back space out back).

Here's a chart I made to help wrap my head around the rim widths and backspacing and where they sit in relationship to the outside fender and the tie rod end connection to the steering arm.

Modify the Steering Arms?

From the image above it seems that modifying my steering arms will solve my problem. I only need to pickup about 1/4" to get my tie rod clearance. This could be done by shimming the steering arms out with longer bolts and spacers or by heating and bending the steering arms. Then I could shorten the tie rods by 1/4" (4-5 turns) and we are in business. Time to unbolt the front end and do some work.

Move the Steering Arm Down and In

After removing the wheel, caliper and disc I was able to get to the steering arm bolts. I removed the bolts from the upper position on the spindle and installed new 1/2" x 3" grade 8 bolts in the bottom position. Then I added three washers between the steering arm and spindle to give myself the extra 1/4" of clearance. (I also added 1/2" x 2" bolts to the upper position on the spindle. This is basically overkill as it only holds the dust shield on to the spindle.) I test fit the rim by re-installing the disc, caliper and wheel to verify the 5.25" backspacing actually cleared the tire. It's really close but it clears. I've read you should have 1/2 clearance for tire deflection but my tires are low profile and the tie rod is right at the point where the tire meets the rim so deflection wont be an issue.

 

I now have the tie rods on the same plane as the lower control arms and have tie rod clearance off the tire. (Note: Since this picture I replaced the sway bar mounts and shocks and springs with QA1 coil overs.)

This picture above is a little deceptive as the lower control arm does not look parallel to the tie rod. This has to do with the shape of the lower control arm. This setup is in-fact parallel to the plane of the lower control arm pivot and the ball joint.

Home Alignment
I decided to even up the Caster and Camber and used a home alignment setup I built with a Sears digital level. I got it pretty close but my toe was still off. Then I took it to the alignment shop and had them fine tune the finished product. By the looks of it the toe should come in on the left (+0.05 should go to -0.03) and the right out a hair (from -0.06 to -0.03).  That should give me the 1/16" toe in.

 

After this visit the alignment felt good but the steering wheel was no centered so I brought the tie rod in one turn on the left and out one turn on the right and this centered the wheel nicely.