LocostUSA.com

cool another spec miata racer locost builder -- make sure you take into account servicing your car (I do ot see how you will be able to remove/install the PPF after the car is build -- I had to leave 2" to get it in and out)

The PPF is tucked in there pretty tight but it does come out pretty easy once you get the right combination, drop the rear differential and move it back slightly and the PPF pulls free from the transmission or lift and pull the engine forward. Of course, this is early in the build. Sure would hate to have to take any more out of the passenger side width. I've got 17" of width now for the seat.

Started building my rear lower control arms. I've really been struggling with a design. This is Option 1 and I have Option 2 ready to fab if I change my mind.

nice jig...

Mocked up rear lower A-Arm. Upper will be a little more difficult due to the offset of the upper mount.

Just bought a few items from a friend that was thinning out a garage. Griffin dual core radiator with fan. Perfect size for the car and the inlet/outlets are exactly in the right place for the Miata engine. 2 steering wheels, one is a Momo. All in great shape...Total cost $100.

To make the upper A-arm for the rear, I started with cutting the original arm to reuse the connection to the upright.

wow! nice craftsmanship.. i realy hope i can work like that..

After some serious consideration, I decided to re-do the lower a-arm in the rear. The 14mm spherical rod ends at the upright just did not have as tight of a fit in the threaded tube as I would have liked. I even tried 2 different manufacture's taps and neither had a tight enough fit on the threads. Snugging up the jam nut locks it in but I decided to take another approach and reuse the original sleeves with bushings.

It's interesting that you can't get a tight enough fit with the heim joints outboard, but reusing the same heim joints inboard you can?

Good observation. The spherical rod end used at the upright is 14 mm due to the 14mm bolt used on the Miata upright. Since I could not find 14mm tube ends, I had to tap a 1" x 0.25" wall tube which is a little to large in diameter for the 14mm threads so I do not get as good of a fit as needed on the threads. On the new a-arms, I am using 5/8" x 1/2" rod ends with purchased threaded tube ends so the fit perfect.

Oh, I see, it looked as if you'd just swapped ends with the heim joints.

A friend of mine just brought over what appears to be 8 brand new, aluminum threaded small body pro shocks. He also has a bunch of springs but only brought over 1 for my trial fit. Problem is we do not know what the valving is. He is trying to find the dyno sheets. I'm not sure what he wants for these but they are perfect for the car. The spring is a 10" 200 lb/in which should be in the range of what I need for the rear. These shocks with the small diameter spring fits perfect in the rear and clears everything.

I really hate redoing anything but I figure I should deal with it now or pay for it later. I was never too happy about the squareness of the rear upper A-arms. My original jig was not set up the best so the right and left arms did not turn out as mirror images. Plus, one was not exactly square. Therefore, I decided to remake a jig and pay a lot for attention to alignment and not use the spherical rods ends for the mockup. Using the rod ends in the previous jig allowed for some amount of angular rotation so the tube ends can end up not being perpendicular to the bolt, of which is not a real problem but one that buged me too much to leave. My new jig allowed me to easily align the fixed points. Plus, it was real easy to make right and left side A-arms by offset holes in the angle.

Well...I've not been able to do much with the build. I finally got the rear A-arms fitted and I am real pleased. Now for the front. I've made the lower control arms so that the Miata spindals and steering rack will not interfer with the lower arm front tube. These have been positioned and tack welded. I aligned the front with the rear. I was quite pleased at how square everything ended up. Front and rear track width is stock Miata. I've got the front LCA positioned but I am having a difficult time deciding exactly how to positon the upper control arm mounts. I made 1 upper control arm and now I am staring at the assembly trying to figure the best way to locate the mounts and tubes on the frame. Any suggestions would be appreciated. I also would like to add some anti-dive angle to the UCA. I was considering 4 degrees but welcome comments. Do you even need this on the Locost since the engine sets further back from the front wheels than a typical car. The Miata I believe has 4 degrees.

Interested in your build as I am using the Miata Suspension as well. I like how you have done the rear suspension and as I have not got that far will store your ideas along with a few others. I feel however you have dropped the ball with the front lower in that the square tube does not look nice at all. I feel that the front in particular has to look as good as it is functional, because it is out there for all to see. We are able to use an oval tube which really looks the part but unfortunately I can't find a photo of my mock up one on the computer and the real ones are in the process of being made. I was able to get the ball joint mounted high enough so that the tie rod cleared the tube and the arm could be made in the traditional A form.
Bruce