Building your own SLA front suspension takes a lot of skill. Measuring, cutting and welding are all needed, but they must follow the planning and calculation. One problem I have is that suspension geometry involves a lot of math, particularly trigonometry. Most of my attention in trigonometry class was given to the rather buxom blond next to whom I sat. Her curves were far more captivating than the angles being taught.
Thankfully, double A-arm suspensions are very common in racing and there are resources available to racers that do all that uninteresting math. Plus, I have another aid – Dan Durusky. Dan has graciously volunteered to be the official geek of the Mongrel suspension project and run the numbers for me. Dan is an engineer who is thinking about turning his hobby into a career. With his professional training and drive, I think he can do it and do it well. The V8Mongrel suspension project will hopefully give Dan some experience.
I was also fortunate enough to have Jon Rathbone and Brad Thompson spend some more time in the garage helping me line things up. While the final position will be determined by the combination of careful measurement and calculations, I find that I have a much better time understanding what needs to be done if I can see the problems. Moving a full wheel end assembly isn’t a one man job, so thanks again to Jon and Brad for putting in some sweat on the project.
Dan and I will be selecting the software to use shortly, and will share the output here. In the meantime, Dan has hit me up with a bunch of questions that I will attempt to answer. Hopefully this will set the backdrop for readers to know exactly where we are and where we intend to go. Dan asked:
What do you have already?
Here is a picture of most of what I have.
That is hub, spindle, lower control arm steering arm and upper control arm. On the white stand, you can see part of the upper control arm mount.
Where are our variables?
Variables are as follows.
- Small changes in lower control arm inner mount horizontal and vertical mounting point, approximately ± 2″.
- Location of upper control arm mount with only restriction being the engine and existing frame horns.
- Choice of short or long upper control arms, length variation to be reported. More available inexpensively if needed.
- Two settings for the lower control arm balljoint on the spindle, high and low.
- Complete control over length and chassis mounting location of the strut rod.
One of the main challenges will be fitting the wheels. The plan is to run a zero offset 10″ wide, 15″ diameter steel wheel due to their low cost, availability and capacity for large tires.
Using the existing lower control arm mount and eyeballing everything else, here is a view of the wheel end assembly, a rotor and wheel. Plenty of clearance for travel.
Unfortunately, the clearance is less encouraging when looking from the outside of the car. This will likely be a balancing act in terms of moving everything further inboard and maintaining decent steering angle for a small turn radius.
Up next, more questions from Dan and some better measurements so we can really get started.