Every wheel builder has their own style, and their own reasons. Some don't even have a reason other than "that is how I've always done it"
I was told two good reasons as to why you should have the trailing spokes (ie, the pulling) one the inside. But this does apply to the rear wheel drive side only. The reverse applies for disc brake non-drive sides.
When you accelerate, the drive side trailing spokes will straighten. If they are on the inside, they will cross on the outside, and them straightening will pull the spokes towards the inside of the wheel. If they are on the outside, they will cross on the inside, and will pull the spokes out of the wheel. Neither of these scenarios are bad per se, but if your rear derailleur is set up poorly, then the 1mm difference could be the difference between a derailleur in the spokes of not. The other reason is also related to whether the gears are set up correctly. If the chain goes too close to the wheel, and drops between the cluster and the spokes (ie, your gears were set up very badly), which spokes are on the outside makes a big difference. If this happens, and you put the power on, what happens will depend on which way the spokes are. If they are trailing inside, pulling the chain will push the chain outside, but if the trailing spokes are on the inside, the chain will dig into the spokes, putting some serious gouging into the spokes and weakening or snapping them.
When I was taught how to build a wheel, I was told those reasons, and for consistancy, I always built them like that. But, then along came disc brakes. Because the forces involved with braking are much stronger than with acceleration, I switched it around for disc wheels (you want the spokes pulled towards the centre of the wheel under braking).
Ringer X said:
I have noticed different wheel lacing on a few of my wheelsets. I have all disc wheels some Mavic some not. The question is about the trail spokes vs. lead spokes. Does it matter where the trail and lead spokes are on the flange of the hub? All are 2x pattern and some have the trail spokes inside flange and some have them outside flange. I read somewhere the drive side should be outside trail,but not sure. I had Jenson build a set recently and it came drive side outside lead? Contradictory to what I read. How about some input. Thanx.