MA-010 - Blueprinting a car for the World Championships - Part 1

I like to start with the heart of the car. The most important part of building an AWD is building one that will last a full modified race. The gear differentials work great, but one small tangle and you are history. That is why starting with good quality ball differentials is the only way to go.

Courtesy or RC Atomic in Hong Kong, I got my hands on a couple of their new T.A.R. differentials. These diffs are almost up to par with Kyosho as far as quality from the package, but still leave FAR too much to be desired.

This is disassembled T.A.R. diff. Take all metallic parts off and soak them with something like denatured alcohol to cut the grease. For plastic, a toothbrush, a little 409 and some warm water should do the trick.

To get smooth action and better slippage control, it is a great idea to sand down your diff plates. Something in the 1200-1500 grit is best.

Once all 4 have been sanded and cleaned, we re-install the plate on the out drive. Make sure you take some lube and apply it to the recently sanded side of the ring. After you are done, set the outdrive aside.

To get smooth diff action, ceramic is the only way to go. We are using Reflex's new 2mm carbon ceramic diff balls.

Lightly coat them in some diff lube, notice the slight haze on the balls.

Install the cleaned out spur gear, the center bearing, the spacer and the diff balls back on the out drive that you previously set aside.

Do the second diff plate and outdrive as you did the first one and slide it over the screw.

Get some good, high quality black grease, you will use this on the cleaned out thrust bearing.

Don't be scared, be generous with the thrust bearing.

Re-install the thrust bearing (washer, lubed bearing, washer), folowed by the o-ring and finally the nut.

Slide the rest of the outdrive and secure it with the o-ring once again.

For the rear diff you want to adjust it to the point where you can no longer make the spur gear skip when holding it and turning both rear tires at the same time (forward, as to check for diff slippage). No more, no less.

The front is up for grabs. We use this as a last resort tuning aid. Loosen it to get more initial steering and more push coming out of the corners, tighten it to receive more initial push and better braking as well as better exit steering and less stability coming out of a corner.

Cristian likes it tight because he uses a lot of brakes. Jacob and Joe like it loose because they like to coast a lot and drive off power. Both styles are fast...

Once finished, you can test your diffs for fitment. Typically the front can be installed without the use of washers.

n the rear we usually use 1 or 2 washers to bring the diff closer to the spur, and then once broken in we use another washer to keep it from skipping.

A good spur gear is very necessary, especially since we are building our car in 98mm spec. This is the best and most consistent handling AWD platform. The 94mm, we have found to suffer under mid-to high grip conditions, so we opt to not run this configuration any longer.

So for that, we chose the Atomic 98mm spurs. We typically ONLY use the 29 tooth.

Next is the extension system. PN Makes a great kit that does not require extension blocks, but in all honesty, it does not work as well as the stock Kyosho plastic gearbox. The tolerances are slightly off and this causes suspension friction as well as mis-fitment of the upper decks and diffs.

The best extension system available is the 3Racing plastic version. It is light-weight, very precise and nearly undetectable on the chassis.

Make sure that the extension lines up well, once it is set square, you can use superglue to secure it to the chassis.

Good, strong knuckles are CRUCIAL!!! A lot of people like using the Kyosho plastic ones, but far too many times I have seen people not finish a race because of one. And remember what is the most important part of building a good AWD... ...making it last the race!!!

We chose PN Racing knuckles in 1.75 deg for the rear end of our cars. These enable for even tire wear at the rear when running Kyosho Semi-Wide Tires. They also enable us the option of using PN's new damper caps in the suspension, something we are not exactly convinced with yet...

Next we go to the Universals. Please get rid of the Kyosho plastic units. No matter what people say, they don't last. Many times you can't realize that one of the plastic ones is slipping and your car will act like crap.

Here, we use 3Racing's Heavy duty steel units. These are identical to the Kyoshos in terms of axle, so you can replace them with Kyosho ones if you want a little better fitting axle. The shaft being Steel allows the universal to wear much less and withstand bending much more.

Make sure you push the axle and bearing all the way in, otherwise you will be left with an unseated bearing.

You can now move to the rear end and install the suspension. We use PN V2 AWD Green Springs for our stock set-up, with 0.8mm of preload at the top. No spacers under the knuckle in the rear.

Here's a side view. Notice how the extension is nearly undetectable! Also notice how there is no screws in the front of the gear box. This is done to prevent the diff bearings from getting squeezed too tight inside and causing friction, it will also allow a little bit more chassis flex for better handling.

In the front, our standard set-up spring is the PN V3 AWD black spring. This is slightly softer than the whites that come with the V2's if I'm not wrong.

We use the Kyosho stock knuckle up travel limiters under the knuckle. For Pre-Load, we use enough shims so that the spring sits without any pre-laod at all, but no slack as well.

On top of the Kyosho gear covers, you can drill small holes in order to adjust your diff to the tension of your liking.

Alright, so that's it for part 1. Next time maybe we will cover tires and adjustment of off-sets and degrees, as well as how we got to those numbers.