Rear Strut Brace, Part the First
In October of last year, a friend of mine at work, Jon, mentioned to me a project he’s been wanting to do to his car. He has a wonderful Mazdaspeed 3, which is still under warranty, which is why his wife won’t let him do this little project. So he suggested that I do it. I work in the manufacturing shop of Gable Signs, and we have there several 20 ft .75″ diameter steel poles which were ordered for a project that was finished long ago. These poles are the leftover material and not likely to be used anytime soon. Jon’s suggestion was that I create a set of strut braces out of these poles, especially since there was some scrap .125″ steel sheet being tossed for recycling. I found out that I could purchase one pole for $20 and get what I needed of the sheet steel for free. $20 for a set of strut braces that would otherwise cost me in the realm of $300 sounded like a good deal to me.
A quick overview on exactly what a strut brace is: the wheels on your car are attached to a suspension system (this is what keeps the car off the ground and held up by the wheels). That suspension system attaches to the body of the car in the engine bay (under the hood) and on either side of the trunk (at least, in a sedan/coupe/hatchback they do; SUVs and vans/minivans are a little different in the back). Where the struts attach to the car has a surprising amount of flex when going around turns, resulting in poor transfer of weight from one side of the car to the other, reducing traction and handling performance. A strut brace simply reduces or eliminates that flex, increasing handling. This makes the car safer, as it stays in better control under emergency maneuvering, and more fun to drive, as it handles better overall. In my setup, the strut brace in the front attaches directly to the struts, the brace in the back will attach to the body as near to the struts as I can make them. I can’t access the struts directly without cutting huge holes in the side of my trunk, and I’m not willing to do that.
I made the front strut brace last November. It is completed and in the car, though it is only primed and it is beginning to rust ever so slightly. I bought paint, it’s actually engine enamel, but it just got too cold to do. At that point I decided to hold off on the rear brace because I didn’t feel like getting it figured out in the cold as well.
But now it is July, so I’m making the rear braces. I began by measuring the necessary dimensions in my trunk. I have a pair of 12″ subwoofers in my trunk, and they go slightly higher than the ideal mounting point for the brace, so I have to make the brace go over the subs, and under the rear speakers, but mount just lower than that level on either side. Since I’m now working in the Router Dept, I used a computer and generated a template with all the correct dimensions. I cut it out, and it fits perfectly. I’m using this template for when I make the actual brace.
The brace is the white piece taped to my toolbox. It goes horizontally in the trunk. It is the exact dimension I need, and I will use it to match the placement of the bends in the brace. Now that I have a template at the correct size, I simply need to cut two pieces of the pole (a single 20 ft pole is more than enough to provide all the material I need for both braces, I will have about 4 ft left over) at 56″, 3″ or so longer than I need. The brace is going to be two parallel poles with 3 spacers in between, all welded together. This will be very rigid.
I also need a way to get the brace in and out of the car without any special tools. Because my spare tire is under the floor of my trunk, and I have the subwoofers in the trunk, the addition of this brace essentially makes it impossible for me to actually get to my spare tire. Because this isn’t a racing car, I need to be able to get to the spare. So I created brackets consisting of two 1/8″ steel plates. One plate has two #10 bolts welded to it that protrude into the trunk and 2 #10 bolts that hold it to the inside of the trunk. The other plate has matching slots for the bolts and will be welded to the brace. There are two sets of these plates, one for each side of the brace. This way, I can leave the mounting plates attached to the inside of the trunk, and leave a wrench in the back for getting the brace in and out as needed. The first picture below is the assembled brace, the second the disassembled brace. As always, there are more pictures in my Flickr stream than in this post.
Now that my brackets are made (you’re seeing one, but I made two!) I just need to cut the main poles and the .75″ spacers.
The spacers and the poles are cut! Tomorrow, I have to grind the spacers to an even length, and then it’s time to break out the oxy-acetylene torch! To bend the poles, I simply heat the pole until it is bright, bend it, and repeat as necessary until I achieve the proper angle. Until next time!
