Depending on the application, we generally satr with the same brush/spring combination that we've found to be most successful for that particular motor, then tweak a bit from there.
No, that's not what I'm saying at all. My point is that if you start with a motor that has been properly and fully blueprinted, (balanced, hoods aligned, etc
that from there on out the racer is left with just simple comm cutting and rebrushing. Arms still remain balanced, hoods still remain aligned,etc; from rebuild to rebuild.
Basically, once you have the all the components of the motor blueprinted and maximized, they remain that way...they will just need the basic rebuild to return to their maximum performance.
As I posted above to Hyper1, I agree and disagree with parts of your post. If you just rebuild one of our motors, (cut comm, replace brushes with what it came with, break in properly) you will return the motor back to the performance it was when it was new...and performance will generally increase as the comm size decreases, to an extent.
Our numbers (CE Turbo Dyno 45) are directly related to what you will see on the track. A Fantom/RSR flywheel dyno will not. With our dyno numbers, if you see an increase of watts, you absolutely will see an increase in performance on the track.
The key is to buy a motor that has been balanced/blueprinted/tuned fully, by a reputable company, using a proven dyno. I can absolutley see how a racer could get a bad taste in their mouths if they bought a "tuned/pro" version motor from a company who either uses the an inaccurate dyno or doesn't tune them at all, just "tunes" the dyno printout.
All tuning processes and tuners are not alike.
Hope this helps...