Steel vs Aluminum Side Mount Seat Brackets
Most race seats nowadays are mounted with side mount brackets: the seat has two holes on either side which attach to an L-shaped metal bracket, then the bottom of the bracket somehow bolts to the car. There are several manufacturers of the brackets. Another question is whether to use steel or aluminum brackets. In this post I will go over the difference between steel and aluminum brackets from the same manufacturer.
Planted Seat Brackets
Both steel and aluminum brackets are made by Planted. They have a similar shape, and looking at pictures of either on the Internent won't tell you much about the differences between them.
An obvious difference is cost: steel brackets are $80/pair currently, while aluminum brackets are $100/pair. Aluminum brackets are also lighter, even though they are thicker. At first glance one would be wise to get the aluminum brackets as a reduction in weight is easily worth $20. However, the situation is far from this simple.
Whereas the steel brackets are approximately 3 mm wide, alimunum brackets are 5-6 mm wide. In a small car such as Miata where the driver seat is often positioned as far toward the right as it would go (and my car has had its transmission tunnel hammered for further clearance), these millimeters count.
In my Miata, the brackets are positioned with the bottoms facing each other like this: |_ |. In my Civic, the bottoms are facing away from each other like so: _| |. Using aluminum mounts in the Civic should be possible while maintaining the seat position if the brackets are flipped to be like they are in the Miata, however doing so will forego the ability to move the seat with the brackets back and forth on the car (on the Miata, seat must be removed to remove the bolts holding the brackets to the car).
Both types of brackets have uniform thickness, which means that the aluminum brackets are also 2-3 mm taller. Again, in a small car such as Miata where head to roof clearance is at a premium it the steel brackets are coming out ahead.
Seat Mounting Holes
The seat mounting holes look like they are in the same positions, but they are not. Perhaps the holes are the same vertical distance from bracket base, but because aluminum brackets are thicker there is less space between the bottom hole and the horizontal part of the bracket. The Momo Daytona seat I tried could not be mounted in the lowest holes on the aluminum brackets whereas this was possible on the steel brackets.
Raising the seat a whole mounting position is obviously a huge loss of helmet to roof clearance.
I will continue to use steel brackets for the driver seats, as it is difficult and time consuming enough to put the driver seats exactly where I want them to be. Right now my passenger seats are all bottom mounted, but when I go with side mounted seats I will strongly consider using aluminum mounts as passenger seat position is not as crucial as driver seat position.