TCR Guides: About Tires

About Tires
by Terry “Stumpy” Stone

One of the most important parts of any race car, in any scale, is the tires.  No matter how much horsepower or how good the chassis is or the aerodynamics, it is the tires which are the interface with the track surface.  And the area they meet the track is known as the “contact patch.”  Even with the widest tires race cars can use, this connection ot the track is incredibly small.  For model race cars in HO scale it is tiny!

Therefore, the tires are very important to traction and handling.  In most cases the wider and softer the tires, the better the traction.  In real racing cars going to too soft a rubber compound in the tires also makes them wear out faster.

On the other hand, narrow hard tires lack traction.  I worked with a vintage racing association, and one of the problems was finding the correct size tires with “live” rubber.  The older cars had used what is today some odd sizes and new tires are often not available.  Until the officials called a halt to it, some guys were running on tires that were hard, cracked, and dangerous.

In slotless racing, which is for all practical purposes “vintage” racing since these cars have been out of production for twenty or more years, we face similar problems.  Many original tires are in bad shape.  Storage of model cars in an attic, where temperatures can get quite high, dries and bakes the miniature tires to the point that they tend to crumble.  They are often also hard enough to make traction almost non-existent.

I’ve seen guys try all sorts of tire cleaning and softening things over the years and they generally don’t work on very old tires.  In fact some products actually accelerate the deterioration of the tires!  The best bet is new tires, not much of a problem for most slot cars, but new rubber can be a challenge for slotless cars.  

Currently, Slot Car Central carries new or NOS (New-Old Stock) tires for the popular slotless cars such as Tyco TCR and Command Control, Aurora Speedsteer, and even Ideal TCR cars.  Obviously new tires are best, but the NOS tires are stored in far better conditions than most hot attics or damp basements and remain viable. 

If you can’t find front tires, automotive or plumbing rubber “O-rings” of the appropriate size work on the front wheels.  They feature pliable “live” rubber and the small “contact patch” and low roll resistance allows the cars to be slightly faster.   And due to the unique needs of cars that steer using narrow front tires, they work pretty well.

Rear tires for Tyco TCR and Aurora Speedsteer cars can use Auto World X-Traction rear tires, they are direct replacement.  There are also various brands of silicone tires available for these cars, as well as many different sizes that can be used for other brands of slotless cars.

New tires or old, rubber or silicone, the best way to clean them is to get a roll of blue painter’s tape, roll the tape into a loop sticky side out, and place it on a flat surface.  To clean the tires just roll the cars along the tape and watch the dirt stick to the tape!  The cream colored “regular” masking tape is often sticky enough to pull the tires away from the rims slightly and therefore stretch the tires.  Eventually this will make them loose on the wheels.  Heavier adhesive can also transfer to the tires, making them pick up more dirt. Duct tape is even worse.

With slot cars you generally clean the rear tires for traction and the front tires only need to roll and keep the front of the chassis off the ground.  But slotless cars use all four tires.  The fronts must be clean to steer the car and the rears to drive it forward.  Don’t sand the tires to clean them.  This wears them MUCH too fast and you run the risk of sanding them “out of round” so they bounce on the track much like real car tires that are not balanced.

Use of “stickier” silicone tires, creates a new problem.  The rear tires are sometimes too “sticky” and the front tires can’t grip as much to steer the car properly.  In real racing this is called having a “push” where the front tire slide and make the car’s turning radius much wider.   Clean the front tires but not the rears to equalize the traction somewhat.

Another tire trick is to use the rear tire diameter to adjust the car’s gearing.  While optional gears are often available for radio control cars and larger scale slot cars, this isn’t common in HO.  However, you can hunt around for taller, larger diameter tires, as long as they fit under the body.   A larger diameter tire allows the car to have a higher top speed and less roll resistance, but it also slightly decreases acceleration.  This is good for tracks with long straights and fewer curves.

Tires of smaller diameter “re-gear” the car for quicker acceleration and let the chassis ride closer to the track for better handling.  (You can sand the tires down to a smaller diameter.)   The downside is that roll resistance is increased and top speed is lower, tires wear out quicker, and allow the chassis to drag on the track.  Smaller tires work best on tracks with short straights and many curves where acceleration is more important.

Tires are a very important part of your race cars.  Take care of them.