You can't go wrong with either of the CarboTech choices. The AX6 is designed for autocross, it has the most bite when you hammer the brakes. The BobCat 1521 is the full street compound, it has a lower working temp than the AX6's. So that's a little trade off you get for the better bite. What that means is that when its cold, below say 60 degrees or so, the brakes will need to work and heat up in order to reach its optimal stopping potential. I've never found that to be an issue other than driving in very cold rain in cold weather, and with that I just ensure to leave a good safety margin when following people... which you should do anyways since its raining. The 1521s are to produce less dust and less noise than the AX6s, however I never found dust nor noise to of any issue. They don't produce that much dust and the only time they made any noise was when I was bedding them in or hammering on them for quite a long time.
There's a brake thread for the Roadster that has all the part numbers you need for the pads.
As for installation, be sure to purchase the orange CRC brake goo (again in the brake thread) or the shims that go on the pads, if this is miss, the brake pads will rattle in the caliper. Its not a safety issue, but just annoying.
Talks about the goo/shims:
Brake Pads
I ordered my AX6's from THMotorsports which had a competitive price and free shipping:
[Fronts]
Carbotech AX6 Brake Pads LOTUS ELISE
[Rears]
Carbotech AX6 Brake Pads LOTUS ELISE
You can also order them from CarboTech directly and ask for a "forum" discount.
So as for understanding the part numbers, you can verify on CarboTech's website:
Carbotech Performance Brakes: Products-Lotus Brake Pads & Shoes
Goto the Elise section, you'll see the
CT109L listed for the
Front and
CT491L for the
Rear. The brake compound identification is appended to the end. So for the AX6 pad the fronts would be CT109L-
AX6, the front pads using the 1521 compound would be CT109L-
1521 and so on.
Just make sure when your mechanic puts on the CRC goo that he reads the instructions completely. The goo needs to set for some time to become sticky before the brake pads can be installed in the caliper. If the directions are not followed the brakes will rattle.