Spec Racer Ford --- Lower Control Arm Failures

Updated: December 16, 1998

There have been quite a number of SRF left rear lower control arm (LCA) failures recently. This problem is due to the flexing at the bend in the lower control arm on the left side of the car.

Due to the number of LCA failures, SCCA Enterprises started delivering a new design, but from early reports, it seems that the new LCA design is less reliable than the old design.

old_new_lca.jpg (5739 bytes)

Here is a close-up photo of the "old" design gusset:

lca_old.jpg (11912 bytes)

And here is a photo of the "new" design gusset:

lca-new.jpg (9524 bytes)

In the old design, the gusset was thicker and the weld extended all the way around the gusset. In contrast the new design has a thinner gusset and is not welded at the ends of the gusset.

Here is a picture of the LCA that failed at Firebird in Kim Knapp's car:

lca_kim_1.jpg (12131 bytes)

On Kim's LCA, you can see some rust in the center of the crack, near the weld. It appears that the crack had been developing for some time. Kim thought that this particular LCA had been on the car for at least 10 weekends, maybe more.

After Kim's LCA failed, Ray LaRue took a good look at all of our cars, and found that the LCA on my car was also cracking. I have no recollection of exactly how old that LCA may be, but it probably has in excess of 20 weekends on it.

I had the LCA replaced it with the old style, which seems to me to be the better of the present choices. Here's a photo of the LCA crack that was developing on my car:

lca_rjs_1.jpg (11258 bytes)

Note that in both cases, the crack began at the edge of the weld.

Inspect your LCA carefully. If you find the crack before it completely breaks, it only costs the price of the LCA... but if you wait until it breaks, the cost may be lot higher.

Richard Shelquist
Longmont, Colorado