Originally Posted by
kiwiazbro
Thanks Corners, seems like something I need to keep trialling until I get it right. My current gearing is 84/23 which seems quite high for the pinion.
I bought the car second hand which had a 12.5 turn motor so assuming by putting the 21.5 in with the same gearing made it a lot slower than it should be with a 215.
Yeah, that gearing is way too low (FDR is too high) for that motor and would be rather slow. Your theoretical top speed with a fresh lipo is 15.5 mph (25 kph). Try 72/36 and see how that goes (should be 28.5 mph (45.8 kph), FDR = 5.2). Watch those motor temps!
Rule of thumb, the lower the motor turns, the higher the FDR. Higher motor turns, use lower FDR. But overall, keep motor temps below 160F (71C). This isn't "exactly" the right thing to do (you should gear for the track), but basically, you keep lowering the FDR (bigger pinions, smaller spurs) until your motor temps start to get too high.
Edit, for some reason I though the B4 had a 2.4:1 transmission, but really has a 2.6:1. My bad. Changed my mind to start trying 72 and 36 and go from there. Here's a chart for you...
FDR -
http://www.arroyoc.com/index.cfm?fus...=Gear&Plot=mid
MPH -
http://www.arroyoc.com/index.cfm?fus...Speed&Plot=mid
KPH -
http://www.arroyoc.com/index.cfm?fus...Speed&Plot=mid
Double Edit: I see you're from one of those countries that doesn't have their flag on the moon, so I included metric units.
