Mostly fronts. The difference for me has been where the Jaco wheels may bend a tab shape in a hard hit, the CRC cracks. Sometimes all the way from inside to outside. I also broke two rears. One I am not sure exactly how it happened as I didn't notice it till I brought the car in after a race, and the other sheared off the 2 aluminum screws brushing next to a board on the straight. Half of the wheel was attached to the wheel and the other half passed the car. These were my first two pairs of CRC's, but I have seen similar failures from some others that tried them at our track. I've not ever broken a Jaco rear wheel in the 2+ years I've used them. Our LHS ordered the CRC's as tehy aren't able to get the Jaco's at the moment. Something to do with a fire at one of the facilities involved in making the wheels? Were wondering if Jaco will have to replace the molds if this is true. Might mean the bearing issue gets fixed . . .? I do love how the bearings fit in the CRC front wheels!