Wall thickness for rear suspension link


Hi all, soon I'll be at the stage of making rear suspensions, so I started to consider how to dimension the various parts. I see around that weld-in 5/8" threaded insert are mainly offered for 1" x 0.058" and 1 1/4" x 0.120" tubes. From a rough calculation, 4130 tubes 1" x 0.058" should be enough to use in a track racing car (no road usage). The main advantage would be in saving weight (they are more than 2x lighter than the 0.120 ones) and in case of crash the link deformation would better absorb some energy before transfering it to the chassis.

I see only few references to similar wall thickness usage, mainly from Russ Noble in this thread https://www.gt40s.com/threads/scratchbuilt-kiwi-40-goes-racing.30372/page-5#post-316956

How much safe or unsafe would this choice be? Does anyone know the original GT40 specs for these components?


Howard Jones

Look here:


You have a choice of 1 X .083, 1 X .065, or 1 X .058 if you use a 5/8 X18 rod end. I would use the heavier wall .083 for the bottom A Arm and the .058 on the top links and the front upper A Arm. The lower A Arms are the most loaded suspension part on the car. They are subjected to the full bump load unlike the top that's simply follows the lower and locates the top of the upright.

I agree that the .120 is over kill.

Ian Anderson

Lifetime Supporter