I have finally properly tested my ktm MX wheels on my '04 wr450 and they work fine. Here is what you need to do to get wheels from pre-'03 ktm exc/mxc 4strokes to work on your WR450. 1. Get the wheels. Can be 18'" rear, 19" rear, or supermoto. I suspect the wheels from LC4 engined bikes won't work due to the drive being on the wrong side, but supposedly they have the same hubs with different discs, so i may be wrong. I have no idea about the two stroke bike wheels. 2. Get the discs. For the rear you need to get a rear disk off of a 950 Adventure model. It is 240mm instead of the required 245, but it works fine. It is also 1mm thicker so if you have brand new brake pads they will drag a bit at first. Zipty supposedly make a 240mm rear brake kit for the ktm hub and will sell just the disc, but i did not go this route. For the front, the ktm has a 260mm disc. Get a caliper relocation bracket for oversize brake rotors for the WR if you want to use the ktm disc, or if you are going supermoto get the appropriate bracket. 3. Machine the spacers. Rear: Both rear spacers need to be reamed out from 20mm to 22mm. The rear spacer on the brake side needs to be faced off 8mm (in my case, you may want to re-measure things) on the outside end, which is the thickness of the big flange, plus a little bit more. Front: the disc-side spacer from your front WR wheel goes on the non-disc side of your front ktm wheel. Use one of the other front ktm spacers on the disc side (They are identical) You need to trim off enough to make the disc line up with the caliper. For me this was 1mm, but my disc was slightly bent. You have a spare spacer, so don't be afraid to use trial and error. 4. Sprocket: This is the same. The heads on my ktm wheel sprocket bolts were a little prouder than the ones on my yam, but clear the swingarm just fine. The sprocket is fine. I think for '04 and later bikes, the bearings got bigger in either the front or the back or both. You can probably still do this mod but may need to make the spacers from scratch. If anybody tries this, let me know how it goes. If any of you 300exc guys do some measurements to confirm/deny that this will work, let us know.