When you build your car, make sure there’s enough clearance between the wheels and the body that the wheels can freely spin. If you tighten the axles too much, your wheels won’t be able to spin without making contact with both the car body and the axle hub.
Don’t make those wheels too loose, though. If there’s too much of a gap between the car body and your wheels, the wheel will slide back and forth along the axle as the car rolls down the track. This will make it hard for the car to roll straight.
The easiest way to get the right wheel clearance is to make a wheel gauge. Take the lid from a margarin tub and cut a business card sized piece from it. In the narrow end of the car, cut a slit that’s about a quarter inch long and just a little wider than your axles.
When you install your wheels, put the axle in the car body and then set the gauge between the wheel and the car body with the slit around the axle. Tighten your axle until your wheel is tight against the gauge and then pull the gauge out. Your wheel will now have an optimal gap.
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2 comments so far ↓
Bruce Edney // May 21, 2007 at 12:12 pm
My experience is that more wheel clearance is better! I found early on in my tests on my own 39ft track that the maxium possible clearance is best. I set the heads of my axels to max width allowable of 2.75″ and the car body to minimum of 1.75″. Think of it this way - with more room to move laterally there is more time the wheel is not touching the axel head or the car body, therefore less time for slowing forces at either extreme. I have demonstrated this many many times on my track and with several cars. I suppose results may be different on other tracks and with different car wheel alignments but my results clearly favor more clearance!
Adam Kalsey // May 21, 2007 at 8:37 pm
The farther out your axles are, the harder it’s going to be to align the wheels. Unless you’ve got a lot of experience, patience, and time, you’ll end up with better-aligned wheels if you keep the clearance tight.
Additionally, by pushing the wheels out to their limits, you run a greater risk of the wheels becoming mis-aligned during the race. Bumps against the wheels and axles will put more torque on the axles than if the axles are shorter.
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