I've had very good luck with the Trinty locked 17.5t I have them in my son's B4 and B44, and he loves them. Plenty of power even without the CHEAT mode. We run an indoor carpet off-road with jumps track, on Friday's and a hard packed clay indoor on Sats. And he has enough power to clear the triples on the clay track. And as reference of size, this indoor clay track also runs E-scale buggies. I guess I would call it a 1/9th scale track. Not really a true 1/8th scale, but bigger than a 1/10th scale track too.