Woohoo, a question on the 12th thread to which I can confidently reply as the expert!

Caps for a 12th are pretty much unobtainable. I know, I've been trying for 2 years. You can occasionally find some old caps on ebay, but that is the extent of it. I wrote to Bob Stormer, and even he couldn't help me. There is a company that advertises 12th caps but when you press them for a price and minimum order they stop responding.

Anyway, back to how to get the car to work. How clean the surface is, is important. Even when you think the surface is clean its probably still a little dusty, unless it has had a lot of running. The smoother the surface too, the more difficult it will be to get the car to work.

You want to use a Japanese foam because these have the highest rubber content. I'm using Speedminds. Find the softest possible foam for the rear. Currently I'm using Speedmind 30 shores. Rub in as much Banana Boat sunscreen as you can find, bake the sunscreen into the tyre with wrap-around tyre warmers at about 50-60 degrees Celsius.

For the front Speedmind 35 shore, or 32 shore when the grip comes up are a good start. Do not sauce the fronts at all.

Now, you will still have really low rear grip, so you'll want to dial in some mechanical grip. I'm using an Associated RC12R5.1, which has a side shock. 20 wt oil is as heavy as you want to get in the side shock. You won't want to use a harder side spring than silver. Green sometimes works better. The centre shock you'll also want to run soft, I suggest 20 to 25 wt, with no stiffer than a blue centre spring. Now, because the rear is so soft, you have to run the front a little softer too. 0.018" front springs are what you need, then run as much caster as the chassis allows. I'm running around 6*, with the active caster at 10*.

Use a high downforce body. Run a diffuser if you can find one. I've also toyed with using a motor fan to suck the car to the ground a bit. It works if your surface is smooth enough. There is nothing in the rules to stop you doing this. Tape up any other holes in the bottom of the chassis.

Now, if the surface is at all dusty, then the tyres will pick up the dust, and your grip will be reduced though the night. You will either have to take a skim off the rear tyres between runs, or have a new set available to swap to after each run. Beware of any chalk used on the surface, it will kill your grip in 2 laps.

Hope this helps.