@nimbuzz I've just posted an update to the
AMP-to-Circuit Stadium Truck racer conversion
To answer your questions:
1.) I'm a mid-pack finisher with my TLR 22 3.0 (racing against drivers with years of experience and loads of practice time on the track) but tend to come in last place with the Circuit in the truck class (again racing against better, more experienced drivers and better, more expensive cars).
2.) Overall I've found the Circuit/AMP to be very difficult to race on an indoor carpet/astro track. Traction is critical and the rear-motor design of the ECX 2WD cars makes the front end VERY light and understeer (pushing in corners) makes getting a good, consistent line a constant struggle. Especially with a torque-y 13.5T motor, any significant application of the throttle lifts almost all weight from the front end and the wheels may as well be on ice for all the traction they seem to have! Last summer I took my Boost (virtually the same chassis as the AMP and Circuit) on an outdoor dirt track and it performed much more predictably. With the right tires, I think the Circuit would also do quite well in the dirt (since a rear-weight bias is key for traction).
3.) The surface at the closest indoor track is "astroturf." It's that weird super-short grassy stuff you've probably seen bordering pools. Jumps are made of wood and covered with the astro. (I've also raced on Ozite carpet- it's a knap-free, no-static gray carpet. Sadly that track closed last summer.)
4.) For the Circuit, I'd recommend you check out the thread I created where I detail the conversion build (see the first line in this post). In a nutshell: Shorty Turnigy 4800 mAh 90C pack with 5mm bullets; Hobbywing Justock XR10 ESC and Justock 3650 13.5T sensored brushless motor; Schumacher Minispikes and Schumacher soft inserts on ECX Circuit wheels. Previously Schumacher Stagger Rib (F) and Minipin (R) with AKA red inserts on JConcepts T4 wheels (these have too much offset for the ECX Circuit and AMP and rub the steering link rod ends.)
