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In this testing session I tried 2 sets of tires. The first set of tires had foam cut from a large piece of stock foam. Then I glued the foam onto the custom aluminum rims that my father machined. Then I trued down the diameter of the foam from 4.5 inch to 3.5 inches. The second set of tires are based on the stock foam tires that come in the OFNA Ultra GTP kit. The only thing I did was true down the diameter from 4 inches to 3.5 inches. Then I modified the center of the rim to accept the 1/10th scale clamp style hub.
I first tested the aluminum tires. I ran these tires for about 5 passes. After each pass I would check the diameter of the tire. It was apparent that the foam I used for the aluminum rims was wearing out very fast. Sunny said that as the X2 passed by, he could see tire dust billowing from the sides of the car. Within 5 runs the tire diameter went from 3.5" to about 3.25". The minimum diameter I can run is about 3.25" before the chassis starts to hit the ground. These tires worked very well and held together for a pass with a max speed of about 70 mph. The problem that I am seeing is that on that 70 mph pass, I was using 100% throttle. With 30 V at a KV of 480 that is an rpm of 14440. That should be a speed of 110mph. There is obviously serious wheel spin.
The second set started out very well. But after I made more passes and increasing throttle, the tires exploded. The same thing happened as with the first set, I was giving the X2 full throttle and the tires were spinning at a much higher rate than what the car was traveling.
It looks like I am going to put the X2 on standby for now. I am going to concentrate on the X3 for the International Speed Competition in October. I am working on getting a 12s battery setup. The X3 has been performing very well and I am going to be shooting for 100mph on the 12s setup. Check back for details on the X3.