The Steel DM is quite a unique chassis on CarX as it has the potential to wheelie. I believe it is due to three factors: Decent power to weight ratio, short wheelbase and wide variety of suspension tuning options and limits. This guide should help you tune your car and master the technique of wheelies. I wrote this guide because of the amount of people online asking how to setup their car like mine, so here goes.

Note: This has only been tested to work correctly on the Steel DM Ultimate Setup

The most important factor is that the rear tires have as much grip as possible. To do this, lower the tire pressure and increase the width and grip as much as possible.

When it comes to the front there are two valid options. Firstly, you could repeat the same process from the rear to get it as grippy as possible. This is my preferred method as the car can handle very aggressively and achieve manic 360's.
The second method (as advised Kopala by and Demonhog) is to narrow the tires, increase the tire pressure and lower the grip. This setup tends to be a little bouncier and can initiate wheelies easier. The vehicle also tends to track straighter with the drawback being a weaker turning ability.
As for wheel base offset you can pretty much dictate that yourself. A wider stance will decrease the chance of a roll-over, but I have found that the chance is pretty low to begin with.

In order to wheelie you need the front end to be soft and bouncy and the rear to be stiff to act as a pivot point. It also helps to raise the suspension as high as possible for more travel.

This one is pretty simple, max everything out.

Braking is key to initiate a wheelie so max out the braking torque.

In this case a short gear ratio works best. This allows you to do wheelies in third gear without spinning the tires and losing grip. It also allows for extending the wheelie to 4th gear without a large gap in between gears.

So you've got the tune set and now it's time to get those front tires off the ground. I've found that getting up to around 4000 rpm in third gear is a good starting point. Make sure the tires have gripped up and start to get into a pattern of full throttle, then full brakes. Rock the car forwards and backwards and use your soft suspension to slowly work it up.
I use a keyboard and have noticed that my whole body rocks forward and back in my chair, like rowing a boat. Rhythem is key. (I must look pretty stupid but I cant't help it) Keep doing this until your in a wheelie and try to hold it. Depending on what you want to achieve you can either hold it for a few seconds or continue to bounce it up and down, resulting in a longer stretch of wheelies. It is also possible to tranission into 4th once you've been bouncing off the rev limiter. It can look pretty rediculous but that's the point. Have fun and enjoy your new tune.

Edit: With the new update most of this is unnecesary to initiate a wheelie as using first gear and launching works perfectly. The throttle-brake pattern still works to get back into a wheelie at speed.

Thank you for taking the time to read through this guide, I hope it helps you and you get some fun out of it.

It can take some practice but if you are still having trouble leave a comment and I will try to get back to you.