Can someone explain the advantages / disadvantages of running 5/16" wheel studs instead of 1/4" wheel studs? I would think that the 5/16" studs would be stronger. Thanks.
Most hubs these days come with tapped holes for 1/4 and 5/16 studs. You get more clamping power with the fine thread than the course. Unless they're new, I've never seen any course thread hubs unless they were drilled and re-tapped. I always run the 5/16, especially on the laydown enduro stuff because you are going over 100mph, and I just feel better with a wheel stud that has a little more meat on it.
None ! If your wheels have 1/4 holes dont be concerned not that big of a difference fine thead is the way to go
If its no big deal...

Then why the option? Also, why would anyone drill out their wheels? That seems like a labor overkill and easy to screw-up?

My point is, if its an option on most new hubs these days, there must be a good reason. Right?
Depending on which association you run, and also which series within that association, 5/16" studs are mandated. I have personally seen 1/4" studs on the RF break on a high bank asphalt oval. Not at the right time either. They are mandated in the WKA National Road Racing Series also. We haven't used the 1/4" for over 20 years.

Do you guys torque the wheel studs on? To what torque? Everything has a torque value, wheel studs included.

Dave E.
Here-in lies the problem...... Those who run the nuts up with a cordless tool and the torque is unknown.

That's where they get into trouble. They use an impact gun on them and they will stretch, then they will break, usually at the worse time, like when it has a bunch of side load in the corner.
I run 1/4 with the quick start ends on them with no issues. My buddy runs 5/16 on his and if he needs a rim at the track he has to drill it so no swapping a loaner in. Not a big issue but something to plan for if you choose the larger stud.
I machined some wheel nuts that have a flange on them to use 5/16 rims. If the wheel has a 5/16 hole, then you can run it on a 1/4 stud.
Ok, I'm about to sound stupid, but... Isn't the "load" on the hub and the studs and nuts are just there to keep the wheel from sliding off the hub (lateral forces only)? Look when you mount your wheels on the hub for the wheel to rest on the hub. I wouldn't trust three studs to support the weight no matter if they were 1/4", 5/16", or 3/8". I'm no engineer, so correct me if I'm wrong on where the load is on the hub.

At the same time, I don't think the 5/16" is a bad idea. I have always run 1/4" but not because I chose it, just because that's what all my karts and wheels have been set up for when I bought them. One advantage to the 5/16" studs is to get the 1/2" nuts so you can use the 1/2" socket for wheel nuts and weight bolts/nuts. I could see it being beneficial to get the gear hub to 1/2" nuts also so you wouldn't need as many different socket sizes for adjustments.

The impact warning is good. If you are putting a nut on with it just run it until it clicks a couple times and quit. Any more and you are pulling the stud apart by the threads, so you'll either ruin the threads or the stud itself. A weakened stud will fail at the worst possible time.
I bet you there is more load on those three little studs and nuts you would care to know. They would transmit the load to the hub from the wheel.
Metal is very strong when installed correctly... I.E. not over torqued. I counted up the threads one time on the 6 bolts that hold an H60 helicopters main gearbox. I come up with 24 total threads holding 22,000 pounds in the air? Think about the load on them in a hard bank at 130 knots?
Has to be some load on the studs.. don't believe it try to run with just 2 nuts... it wont make it but a couple laps