ok so i am building my first wheel and its a reari have done sumthing wrong with the way i have laced the spokes as the non drive side leading spokes are to long and the traling ones are to short. what have i done wrong and how can i fix it, i will put up sum pics as soon a my camra is charged. i am useing a shimano exage FH-HG50 hub with a Rigida chrina and this was the spoke calculator i used http://lenni.info/edd/, i also rounded the spoke up to the nearest mm.
If it's the problem I think it is, you need to move all the spokes on one side of the wheel by one position. Note how the holes in one side of the hub are offset from the holes in the other side, with me so far?
Now, as a reference point, look at the first driveside spoke to the right of the valve hole, we'll call it the Boss Spoke. Now look at the non-driveside spoke just to the left of the Boss Spoke, which is normally next to the valve hole. Since this spoke is 'behind' the Boss Spoke, its hub hole should also be 'behind' the hole that the Boss Spoke is. I think you've got it ahead rather than behind. So unlace the non-driveside and redo it.