I looked at the 1940 thread and it seems to me that the 1940/10 might have been undergeared at 13/44. In anycase, whether undergeared or not, I'm not sure that I follow with the overdoing it logic.
If you go with a larger motor, you may have a problem putting a proper load on it. I know that there are some running the 1521 in their trucks, but I don't know that they are doing so in a racing environment. Racing is a grueling test of RC equipment and problems that don't manifest themselves during bash sessions, become readily apparent during or after a race.
I believe that going with the right equipment is better than going with more than you need. I'd say, go with the 1515.
Well, I started with a 15/44 gearing and it got hot way too quick. This 13/44 setup worked great in my sessions at the track up until the race. I think the big thing was that the track was dampened down for traction and therefore put much more strain on the motor than I had ever had before. The dry dirt is much more forgiving, you know?
I have no problem going with the 1515, but I just want to make sure that it can handle that kind of race situation. If spending a little more on the 1521 will avoid this problem, I'm there. That's what I'm trying to figure out.
So I've heard a couple of opinions, but I would really like to know why I should or shouldn't go with the 1515 vs the 1521. Can anyone tell me what the big difference is between the two besides the physical size? I've been on the Neu website, but it doesn't tell me the difference in power, efficiency or any of that info.
Do any of you have a little more detailed info on the two motors? Thanks.