If you are going to cut the windshield off, then I think your roll bar options get better. I see roll bars routinely for $100. They're always left over drag racing kits, but that will work fine for an autocross car. Measure the width of the interior where the main hoop will sit and then watch FB Marketplace and ask any sellers what the width of their main hoop is. Buy anything that has the right width and the rest is pretty straight forward cutting and welding.
Example: A $50 kit on FB in Ohio.
https://www.facebook.com/marketplace/item/370553907660703/
In reply to DeadSkunk (Warren) :
Thanks for the information. Roll cage/bar construction is pretty far outside my comfort zone.
My big concern right now is the fuel tank just under the rear deck. If I have to remove it to install the roll bar, I am not sure if it makes sense to install it now. The Z3's roll protection is officially "good enough" for most sanctioning bodies. Worst case scenario, my wife takes it down the drag strip at a leisurely pace.
If I need to drop the fuel tank, driveshaft, and exhaust to get the roll bar in place, I may wait until I am ready to do more significant work after the challenge.
In reply to ojannen :
I ran a Miata at the 2017 Challenge. It ran a 14.72 quarter on drag slicks with no roll bar. It wasn't an issue.
My thoughts on the roll bar were intended for prepping it for autocross if you remove the windshield. I've never looked at a Z3 but I'd be surprised if the gas tank had to be removed to put in a roll bar, unless the tank is wider than the frame rails.
Like so....
You could do something similar to this with a pre-bent drag racing roll bar kit. It depends on what you ultimately want to do with the car. If you intend to autocross it understand the class rules and don't do anything for the Challenge that's difficult to undo later.
I am going to list this for sale in the next few days. I had a grand plan for a dedicated autocross car. Life caught up with me and I figured out that I would rather have a car with 3 seatbelts so I can take the little guy on car adventures.
Here is the challenge friendly pricing:
$1522: The car with stock wheels and all season tires and several boxes of parts that I removed but never sold. I ran at the challenge for this amount (+$150 for the second set of wheels). The car still has stock seats, roll bars, side windows with motors, and a dash which should easily hit the recoup max.
$150: 17x8.5 low offset wheels. They look awesome.
$350: 245/45r17 Hoosier A7s mounted on the low offset wheels. They have 40-50 runs on them. One of them has a fairly deep cut from before I fully clearanced the fenders.
$250: Tie rods and left side lower control arm. These parts feel ok for autocross but there is some play in the ball joints. I was planning on swapping them before taking the car to a track day. I have already swapped the right lower control arm.
The car is a set of M Roadster front shock mounts, stiffer springs, and maybe a swaybar away from winning the autocross. It is Florida road legal and can be driven home with some minor tweaks like plugging in the headlights.
In reply to ojannen :
Was great meeting you and the family at the Challenge. Hopefully the replacement is still capable of showing up next year.
