Axles and wheels, fast then slow
I spent the night testing cars trying to find something to run for the Before & After series. doesn't matter what I do, my cars don't seem fast. I ran into a new problem last night. I don't remember the car but I had a set of wheels on it that were spinning really good. Sitting at the workbench in the shop, by hand, they seemed good anyways. I took them to the track and the car was really slow. I ran it twice against my fastest car. I spun the wheels again by hand and three were great but one of the rear wheels now hardly spun. Nothing like it had spun 5 minutes early. The more I play with these things, the more I get frustrated. Has this ever happened to anyone else?
Discussion
Probably an obvious thing, but I find when I see the car that "appears" to be fast thanks to good wheel spinning and then craps out on the track, it's because the wheels/axle is rubbing against something. Even just a little will slow it all down.
I was always grinding out the wheel well to allow clearance. Not sure if you're making your axles stationary or letting them run free...fixing your axles with JB or glue might eliminate something so you can find the bigger problem.
From your description and as is noted - sounds like wheel rub.
If you can move your axles side to side try centering them again and see if it frees up the sticky wheel.
There is often a piece of flashing still in the hole on the outside of the wheel from the mold process. You cant really see it unless you move the wheel back away from the axle end. Trim it with an exacto knife as you can.
The axle may also have a burr that is binding the wheel when it runs out to the end. Are you testing on the bench with the axle pointing up on the test wheel or down for the test wheel. I do both tests on each wheel.
Hogging out the wheel wells for clearance or locating the axle to the bottom of the chassis can fix wheel to fender rub.
One of my cars for the bare metal series had this problem and nothing I have tried has fixed it. As soon as it spun to the end of the axle - it was like the brakes came on!
Is there a bump on any of the wheels from the injection mold?
If you let us know what car you are testing - we can maybe provide some other ideals.
yup, been there and built slow cars...when I build I try to start with a fast car, even if I'm just stealing the axles. I also look for a set of axles that have limited wheel run out, or less wobbly the better. testing againt a known fast car is a great start.