What is the difference between 1/2 or 1/2-20 lug nuts?

Question

My stock rims used 1/2 open ended lug nuts. I then replaced the rims with aftermarket rims that have almost an oval bolt hole shape so the tire shop said I needed 1/2-20 lug nuts that were close ended. Now I ordered some 22inch universal bolt pattern rims..can I use the same 1/2 -20 lug nuts? or do i use the stock half inch lug nuts ? whats the difference anyway?

Answer 1

Use whichever one seats into the taper of the rim properly as if it doesn't seat correctly they can come loose and you could lose a wheel.

The 1/2-20 designation has nothing to do with the taper where the nut touches the rim it is simply a standard thread type.  1/2 means the bolt is 1/2 inch in diameter and -20 means the bolt has 20 threads per inch of length.

Answer 2

The 1/2 -20 measurement is only part of what you'll have to consider to get the right lug nuts for your car. That only ensures that your lug nuts will fit onto the studs you already have, which are not being changed.

The other part you need to consider is the part of the nut that touches the wheel. Most aftermarket (Aluminum) wheels use an oval hole where the studs go through. This oval hole then has a depression cast into the surface, so that an oval washer can be placed into it, which will have a hole at one end of the oval.

That way, by flipping the washer end to end, you can fit the wheel to 2 different (hence "universal") bolt patterns. These washers are flat, so the lug nut you need will have a shoulder where it clamps down, instead of a tapered seat like most factory wheels.

The fact that the end of the nut is closed is mostly just for looks, although they do also keep water out, which helps to keep the nuts from rusting onto the studs, which can make them hard to take off later.

If you already had aftermarket rims on your car before, you can probably use those same lug nuts again on your new rims. Unless the rim is thicker or thinner than your old ones, in which case you may need a different shank length. (the part that goes into the hole, that you can't see when it's all put together)