I think "I'm going slightly mad" after going through this thread!
Let's see what others have to say about motor springs:
Green : Medium Good for general use
Red : Medium / Heavy Good for general use
Medium / Heavy Good for Touring on a very large track
Purple : Heavy Great for hard working motors like Touring & 4wd Truck
Silver : Extra Heavy Great for hard working motors like Touring & 4wd Truck
Alter the powerband and characteristics of your motor by changing your motor spring tension. Try a little stiffer spring for more torque and a little softer for more RPM.
Team Associated / Reedy
Simply put, harder spring pressure increases friction and slows down the commutator. In general, the less tension placed on the brush, the more RPM (top speed). The more tension, the more torque (faster acceleration). Spring tension is measured by ounce rate. The lower ounce rate generates less pressure than a higher ounce rate. Choose a lower ounce rate for slightly more RPM, and a higher rate for more torque. However, harder pressure will hasten commutator wear.
Our Touring Car line of motors include winds from 7 to 12 turns, singles and doubles, using the base tear downs. Our double winds feature a Variance Split Wound armature, combined with smaller than average wire gauges these motors generate the quickest Spool-Up times possible, and provide the most torque coming off the coroners, exactly what’s need for Touring Car racing here in the Unites States. These motors are tuned with an aggressive motor setup, featuring High Silver Brushes, Heavy Springs and Advanced Timing for maximum performance through out a 5 minute run…
The more arcing between the brush and the commutator, the more spring tension is needed to counteract that arcing. Factors that cause the motor to arc more and therefore more needed tension are: excessive timing, low winds, out-of-round commutator, heavy loads (tall gears, heavy cars, lots of traction), motors with electrical problems, etc.
It's always better to "over-spring" than "under-spring".
Ok, that's all I could find in a few minutes of online search. I allways thought that the heavier the car, the heavier the motor springs to increase punch. Now, after reading this thread, it doesn't make sense anymore. Are the above motor tuners wrong? They all seem to claim that heavysprings=torque, light=rpm