Features
Chassis - At first glace, the TC4's chassis looks nearly identical to that of its predecessor. Most competitive TC3 drivers had used a Dremel tool to remove some of the material along the centerline of the chassis to re-position the battery pack closer to the center of the car, so the TC4 comes with the battery positioned as close to the center as possible. Also on the old car, the motor mount was molded into the chassis, and some drivers reported that area becoming malformed due to the excessive heat and stress associated with modified racing. The TC4 features an alloy motor mount and clamp assembly that helps to dissipate this heat and keep it away from the chassis. With these changes, the TC4's molded plastic chassis is also more space efficient, leading to a narrower design. Finally, a series of cooling ducts are fashioned into the bottom of the plate, allowing an optional motor cooling scoop and fan assembly to be installed. Although the scoop doesn't come standard with the car, it's the first thing of its kind that we've ever seen, and should really help get some airflow across the motor.

Suspension - Like the chassis, the TC4's suspension remains largely unchanged from the TC3, but the few small differences can make a big impact. First and foremost, the shock towers have been redesigned, and the camber links have been moved to the chassis braces instead. This use of vertical ball studs allows the car's roll center to be more accurately adjusted at both the front and rear, which is a valuable and easily adjustable tuning aid. The four aluminum threaded-body shocks are carried over from the old car, although they now mount to the arms via a ball stud. The biggest change, though, is also one of the most innovative we've seen: the car's front and rear anti-roll bars, although not included, attach to the suspension arms via a captured pivot ball that makes adjusting the bars a snap.
The arms themselves are held on hinge pins that fit inside small plastic bushings inside the suspension mounts, and unlike the TC3, the kit includes enough spacers to achieve just about any anti-dive, anti-squat or roll center setting right out of the box. The caster blocks and rear hubs are very similar to the old car, although their hinge pins are now captured via a single button-head screw at each end, rather than the old set screw, which is a huge improvement. If I had a dollar for every one of those TC3 blocks that I had seen stripped out...I'd have at least a few bucks.

Drive Train - The TC4's shaft-driven design is no surprise, since it is carried over directly from the TC3. The spur gear standoffs are anchored to the chassis via two screws at the bottom rather than "pinched" by two screws at the top, which helps to keep it free and, in my opinion, makes it easier to work on. That area of the car had a tendency to get bound up on the TC3, and the TC4 addresses the problem well. The shaft itself has been redesigned for durability as well, although I doubt many people will realize it. The differentials are identical to the TC3, and the car comes with new oversized MIP CVDs that should hold up well.

Steering - One of the few areas of the car that received a complete overhaul was the steering system. The old swing rack is gone, replaced instead with a system that looks like a cross between a swing rack and a dual bellcrank design, very similar to what is on the Nitro TC3. Ackerman can be fully adjusted by adding washers under the ball studs on the rack, or by using an alternate steering link mounting location on the steering knuckles.

Body, Tires, and Wheels - Like many race-oriented kits on the market, the TC3 forgoes a body with the kit, although any standard 190mm touring body will fit. White dish wheels are included, along with foam inserts and a set of Associated's treaded touring tires.

Instructions - The TC4's manual is clear and concise, and I had absolutely no trouble assembling the kit. The only annoyance, if there was one, had to be the need to use a Dremel tool to remove material from all four of the chassis braces to allow proper clearance for the diff outdrives. This was outlined in a supplemental instruction page, but is still something that could throw a novice for a loop; I never like to see a vehicle's instructions tell the builder to modify the kit's parts.

Testing
Ever since I've moved out to California, I really haven't had any time for club racing, although I've been telling people for months that I would start getting back to the track on a regular basis. This car was enough to jump start my habit again, as I packed up my gear and headed to SoCal Raceway in Huntington Beach, California. Collin, being the crazy Mini Cooper-driving rebel that he is, suggested that I run modified with him, so I dropped a 9-turn single into the car and got my wallet ready to buy the replacement parts that I figured I'd need shortly. A new car, a surface I'd never raced on, me being rusty having not driven for months, and the Pro Mod class at one of the most competitive tracks in the nation. What could be more fun?

Acceleration - The only real thing limiting the TC4's acceleration was traction, and as soon as my new tires were scrubbed into the track surface, the car was a bona fide rocket. The car launched quickly and in a straight line, and there was no hint of drag in the drive train whatsoever. In other words, it was everything I remembered about racing a TC3, which is a very good thing.
Rating: 10

Top Speed - Once again, the car was fast, especially with the Reedy 9-turn lighting a fire under it. It can be hard to judge a kit car's speed capabilities, but I look at it from a "was it as fast as it should have been" perspective, and the TC4 certainly was. If you're looking for a fast car, you can't go wrong here.
Rating: 10

Braking - I put a few runs on the car with the included differential before I added a one-way, and that meant I had to rely heavily on the brakes. The braking was solid, although it was a bit temperamental on SoCal's banked surface. From medium speeds in the infield I had no problems, but bringing the car from straightaway speeds to a full stop usually resulted in it getting a bit unsettled.
Rating: 9

Low-Speed Handling - The only real problem I had with driving the TC4 was solving a huge (and I mean huge) push in the infield. With the stock setup, the car simply would not turn. This isn't really a fair assessment, though, since the track I was racing at heavily favored cars with a one-way differential in the front, so like any befuddled racer would, I walked over to the counter and dropped $60 on a one-way. Once I put it in, it was like a totally different car, and the low-speed handling was much better, although it still didn't have as much steering as I would have liked. A few of Associated's engineers were at the track, and helped me make a few adjustments, and the car continued to get better throughout the night. Still, it always felt like there was something more out there, and I couldn't quite find it. I would surmise that on the right track, this wouldn't be an issue, but for this test I found it lacking.
Rating: 8

High-Speed Handling - One of the things that I absolutely loved about the TC3 was how stable it felt at high speeds in comparison to some other cars I've driven. The TC4 seems to retain some, but not all of this stability. It felt rock solid at times, but somewhat twitchy at others. SoCal's track is built around a high-banked concrete oval, which lets the cars carry some serious speed as they cruise around the perimeter and into the infield, and the TC4 handled these sections well. Overall, the handling was good, but there was room to grow. Optional suspension mounts and caster blocks would have improved things, but parts were still scarce at the time of the test (this won't be the case for long). One of the TC4's biggest challenges is that no matter how hard we try to avoid it, we can't help but compare it to the TC3s that we've been driving for years. In this area, my TC3 was markedly better.
Rating: 8

Rough-Track Handling - Other than the very outside ring of the track, SoCal's surface is very smooth, with no more than a handful of tiny rough spots. I didn't notice any ill effects on the car from these areas, but I don't think it was the most comprehensive test of the car's suspension. Most tracks that the TC4 will see are going to be relatively smooth, and I have no doubts about the ability of its suspension to handle them.
Rating: 9

Tuning - The biggest improvements over the TC3, in my opinion, come in the TC4's tuning options and ease of adjustment. Out of the box, everything but caster and rear toe-in can be adjusted, and most of the adjustments are easy to make. Dealing with the shims under the suspension blocks can be cumbersome at times, but the benefits are many, and the tuning chart that is included with the TC4's manual is a real help. Add in the adjustable anti-roll bars and the vertical ball studs, and I can't think of anything else that a car would need. Some people complained about the TC3's tunability, and the TC4 solves those problems and then some.
Rating: 10

Damage - Remember when I said that I'd never driven this track before? It sure showed in my first couple runs! I had things down by the time the actual racing rolled around, but there was one casualty in the process. During one of my practice sessions, the car drifted down on the banked front straightaway and launched off a corner dot, getting enough air to send it all the way into the outside retaining wall in such spectacular fashion that Associated's Tony Phalen, who was driving next to me at the time, managed to fall off the drivers' stand laughing. Tony hooked me up with a new rear hub and I was back rolling again, and despite a few more bumps and crashes, the car held together very well structurally.
I did have two major concerns, though, that related more to wear than to damage. Most drivers who choose to run mod with the TC4 (and the TC3 before it) upgrade to aluminum or steel diff outdrives, and I had to do so as well, as the car's plastic diff gave out after a few runs with my low-wind motor. Additionally, there was excessive play in the suspension, a problem that can be solved with shims, but still something that the TC3 never suffered from.
Rating: 8

Conclusion
With all of its success, the TC3 is a tough act to follow, and it's obvious that Associated has put a great deal of thought and effort into the TC4. Despite the similarities, the amount of engineering that has gone into the finer points of this car is obvious, and any racer will appreciate those tiny details that make the car easier to work on, adjust and repair. It's difficult to say that Associated has hit a home run with the car, but they've come close. Once you factor in the price, which places it below nearly every other competition-level touring car on the market, it is hard to not give the car a long, hard look. Plus, we all have to keep in mind that we are comparing a brand-new base version car to the Factory Team TC3 that we're used to. I found myself drawing comparisons to the TC3 all the time, and I surmise that most will do the same. With a ton of factory support and a strong race team working with the car, there's no doubt in my mind that the TC4 will enjoy just as much success as its predecessor, and if you're in the market for a new touring car, the TC4 should be on your list.