The XCR isn't available in the 18" size that is ideal for MX. I have been running the DWT MX V4 rears and the MX V3 fronts lately and have been really happy with them. FYI the knobs on the red compound soft tires are like squeezing a gummy bear between your fingers. They grip on anything, but won't last you very long. I recommend the blue medium compound if you want to get some life out of them.