There are plenty of motors in the market today.  From the reliable Tamiya series and the Auldey Champs to the AC Power motor.  Choosing a motor is very delicate as it is what will make or break a car.  The most essential consideration should be "USE" -meaning what kind of track are you going to race on - TECHNICAL or SPEED.

If you are going for a technical track you can use the Tamiya ATOMIC TUNED motor at the most to avoid the car from flying off the track.  For tracks with many uphills, use the TORQUE TUNED and compensate with gearing to keep up with the others.  In technical races, the trick is to qualify for the next round by making your car stick to the track.  Another guys car may be faster at the onset, but surely will have greater chances of flying of the track and being disqualified.

If you are a speed addict and love racing fence cars or trikes, the best motors are those sold by AC.  The ULTRA Dash and Mach Dash of Tamiya may also do for intermediate racers.  But these motors will be no match for rewound scratch built ones that have bearings and stronger magnets.

Motor choice depends on the type of track you wish to run or race on.  Here are some data on Tamiya Motors.
 

Photo	Name	RPM	Torque	Comment	Power Consumed	RPM with Load
	TORQUE TUNED MOTOR	13,600 RPM	14.5 g-cm.	Good for uphills and curves. Tech motor	1200 mA	12000 RPM
	REV TUNED MOTOR	17,600 RPM	10 g-cm.	Good top speed for tech straights. Tech motor	1500 mA	14300 RPM
	ATOMIC TUNED MOTOR	15,700 RPM	10 g-cm.	Best for super technical courses.	1300 mA	15700 RPM
	PLASMA DASH MOTOR	29,000 RPM	20 g-cm.	Raw power for speed tracks.	4100 mA	25000 RPM
	MACH DASH MOTOR	23,400 RPM	15 g-cm.	Faster than a Hyper dash. Speed Motor	1900 mA	20,800 RPM
	ULTRA DASH MOTOR	29,000 RPM	20 g-cm.	Good climbing motor. Speed with uphills	4000 mA	24,000 RPM
	JET DASH MOTOR	23,000 RPM	22 g-cm.	High top speed with high torque.  Speed motor	4000 mA	28,000 RPM

 

Motor Tuning and care

Once you've bought a Motor, make sure to fine-tune and care for it.

Fine-tuning means breaking in the motor before racing it.  I use 1 1600 AA cell to run the motor without any load until the battery runs out.  I find this to be sufficient enough to make the carbon brushes sit well on the commutator.  After which I run the motor without any pinion on 2 600 AA cells for 10 minutes before I finally race them.  Breaking in and tuning the motor ensures less scratches on the commutator and therefore, a longer life and faster run.

After racing, I usually spray the motor with an anti-static fluid to clean it. Some people spray WD 40 but I prefer LUBE IT UP as it is less oily.

Lastly, if you are a frequent racer and know the tracks where you race well vis-a-vis you car performance, it would be cheaper in the long run to buy 2 or 3 of the same kind of motor as it may save you a little money and at the same time prevent too much stress building up on just one motor.

These are the life blood of a mini 4wd! I prefer using the SANYO Twicell 1600's and the Radio Shack 1500 mAh's as both brands are NICKEL METAL HYDRIDE.  Although these batteries are on the expensive side and takes more time to charge, they are rechargeable and do not store MEMORIES unlike their Nickel Cadmium cousins.  As time passes, Nimh's as they are more popularly known, outlasts the NiCads.

Battery Care

Battery matching is also essential to get the most juice out (more power and longer run time) of them.  Discharge rates of each single cell must be the same to that of its partner to ensure that both batteries are dishing out the same amount of power.  Just imagine being in a race and one battery discharges faster than the other, the second or third heat of your car will be generally slower if your batteries are unmatched!  Try getting a Tekin Charger or a Novak charger to help you monitor your batteries.

After races, discharging is a must if you are running on NiCads as they will store unwanted Memory.  Use a flashlight if you don't have a discharger, but as soon as the light comes off, stop discharging to avoid damaging the cells.

At about 50 uses, cycle your batteries by charging them once and slowly discharging them.  At this point you will definitely need to match them again.

Typical examples are hair strands that collect in wheel wells and axles.  Dust in gears that act like sand paper during continued high speed use thereby destroying gear meshing.

Gears

Do not over grease your gears. Instead before a race, dip all your gears in WD 40 or a similar brand of lubricant.  The oil will stick to the gears thereby lessening the need for greasing.

Bearings

Dip your bearings in the lubricant as well after spraying with anti-static spray.  Binded gears will heat up the plastic and loosen its hold.  Worse, it may even break the bearing wells.

Dirt is the enemy of an efficient racing machine.  The more dirt, the less performance from the motor or the batteries.

Shaving off parts from your stock kit is part of the modification process.  Sometimes placing hop-up parts or changing bodies require this process.  Here are some tips and photos.

Body

Lighten the body first by boring holes and creating "windows".  Using the tip of a heated Philips Screw Driver will do the trick for some holes. This will definitely decrease weight.

Using the finest sand paper, sand the outer body (do not perform on Lexan) to thin the plastic a little.  Concentrate on thick areas as these were the areas where plastic was poured in during the molding process.  DO NOT SAND OFF THE LOGOs or TRADEMARKS most specially if they are Tamiya.  Some race marshalls are very particular on this during all tamiya races.

Gears

Lighten the gears by boring holes into them, usually 4 holes will be enough.

Chassis

DO NOT touch the chassis as it may become weakened unless you are planning to reinforce it with FRP. Check the pictures out.
 

 
3 Photos show lightening as well as strengthening.  The bottom battery plate of the VS chassis on the upper left has been replaced to accommodate a side switch assembly.  The sides of the same car have been reinforced with front x chassis FRP mounts to avoid Flexing to keep all four tires on the track.  The X Chassis on the upper right and right features a double chassis set-up to avoid flexing as well and lowering the center of gravity.  I am not going to show you how it's done so you can experiment.  Race legal only for open races!

Gear ratio determines the speed and performance of a certain car for a certain track.  It is the benchmark for speed or torque, therefore, motor choice is reliant on this particular topic.

While scanning through the different web sites and pages, I found some charts that may be useful to you in helping determine the gear ratio suited to your Tracks and car set-up.  Enjoy!!

 
 
 

Gear Ratio	Color	Acceleration	Speed	Climbing
3.5:1	Light Blue and Yellow	Worst	Top	Bad
4:1	Black and Flesh	Worst	Best	Worst
4.2:1	Red and Flesh	Average	Average	Average
5:1	Blue and Green	Best	Worst	Best
6.4:1		Fast	Worse than Worst	Top

The Chart will explain the other charts and illustrations in the most simplest way.

Your tires are another crucial factor in achieving a stable running modified vehicle.  Again the tire choice depends on the set-up - Technical or Speed.

Large Diameter wheels are usually used for Speed while Small Diameter wheels are used for Technical races.

There are basically 4 types of tires. These are known as the following:

1) Stock rubber tires and Rubber low bounce tires;
2) Sponge Tires;
3) Semi Pneumatic tires; and,
4) Reston tires.

 

For cleaning rubber tires, use sand paper or an eraser.  Just rub the sand paper or the eraser on the rubber to remove oil and dirt.  This will restore traction.

For Sponge and Reston tires, use Scotch tape.  Run the tires over an inverted piece of scotch tape to remove dirt and loose pieces of sponge.  This action will also increase traction most specially when done before a race.

For Semi Pneumatic tires, use an eraser.  Dab lightly until the rubber becomes dull.  DO NOT use sand paper as it will slowly thin the rubber.  Also make sure that the tires are in their proper grooves to ensure balance.

Check the chart in the Gear Ratio section to ensure that the proper wheel is used for the right gears in order to avoid taxing your motors or batteries.

Remember this, wider and lower tires and wheels add to the stability of the kit but also creates DRAG.  Narrow and Larger tires and wheels increases speed but decreases road contact, hence it is more unstable.

Normal Wheel vs One Way Wheel

Normal: The speed of the wheels at both sides of a car is the same. This is good for the straights, however the outer wheel tends to be dragged during cornering and this may slow your car down.

One Way: The outer wheel rotates faster than the inner wheel does. Ensures smooth cornering and is preferred for technical courses with many curves.

Rollers are a must when racing on walled circuits. They help your car negotiate corners smoothly. Key points in using rollers is their size, location and angle.

Handling Settings by Roller Size

Same size: Standard setting. Front and rear rollers have the same diameter. This makes your car easier to run straight since rollers are lined parallel when they contact a wall. Also minimizes power loss.
 

Smaller in front: Rear roller diameter is bigger than that of front roller. This makes your car run along with a wall. Gives stability during cornering, but creates power loss.

Remember, Double Ball Race Rollers are counted as one piece during official Tamiya races.  They are best located at the front rather than the rear.  However, if you have cash to spend you can use them in the rear as well.

Some parts of this section were lifted from the Tamiya America Website, Tips Section.