I picked up a D3.5 17.5 on here a while back. Havent run it yet but tore it down tonight to clean it all up before racing with it this weekend. I noticed it does not have any shims on the rear rotor shaft. Is that normal? Or do all brushless motors need at least some sort of shim on the back side of the rotor (that goes into the endbell bearing).

Hi,

I don't have a D3.5, yet, but for most motors:

- assemble w/o shims;

- spin by hand and press arm each direction, one direction after each spin, and get an idea of how much shimming is needed (or measure with calipers) on each end;

- re-assemble and repeat until it has little to no sideways movement through the bearings.

Even non-slotted (less notchiness, do I understand that terminology correctly?) motors will resolve and center the rotor as it spins.

If it seems properly held in the magnetic gap, but feels a little marbly when you rotate it, try one less very thin shim or replace a thicker one with a thinner one until the marbly grumbly feel goes away.

If that "bumpiness" doesn't go away after proper shimming, you might need to replace a bearing.

Gene

xj .. it all depends on how much play the rotor has in motor can.. it should have about 1mm of play max..