haha. I see what you're saying...my Z1 frame doesn't have the chainstay yokes welded at the right angle, it renders the frame with a very limited amount of tire clearence. I had the grind down the side plates so it wouldn't rub as bad... But I had 2 Z1 frames, both measured the same reach(about 673, I think my math was way off earlier, it seems I can't subtract well. So it would be a lot more than 10mm off)...you must have measured wrong.