Other than the valve & spoke holes😁
My new arc rims have a small hole in each side on the sidewall.

Hole!

Any ideas why?

Pressure equalisation for when you’re getting full on rad air, init.

Arcs you say? It’s so you can get a slide hammer in to bend them back into shape..

On a more helpful note, mine have this, I presumed it was to prevent some sort of of pressure imbalance between the two sealed chambers when run tubeless, so there wasn’t anything stopping the tape sealing

It’s there to slowly let mud in so your wheels get heavier and heavier, and in 5 years time when you upgrade them to the same rims with different stickers on you find they’re much lighter and better.

Or maybe something to do with welding if they are welded rims? (why not put this hole in a location that would have a spoke hole I’m not sure.)

Are they recesses (rather than holes) and are the rims also designed for rim braking? If yes and yes they might be brake track wear indicators.

It’s a drain/vent hole for the chamber between the spoke holes and rim bed, I think.

In any case, don’t worry about it. Mine have the same.

Water drain hole – presumably it is right next to the rim bed, so when the wheel is in motion water will be forced out.

Pinned rims have this ability by design; I’m not sure why don’t all welded rims have this hole, maybe to avoid questions from customers.

My Shimano road wheels have a single hole halfway down the rim wall. I assumed some kind of pressure relief feature.

I added such a hole to my LB rims so the water could drain out.

My DT Swiss road wheels have no hole and rear had filled with water, felt odd riding it.

Why would there be a pressure imbalance between the two ‘chambers’? Firstly if running tubeless your rim tape would be sealing the main chamber, and secondly the spoke nipples wont be making an airtight seal so plenty of opportunity for any air pressure imbalance to release.

I can only think it is for drainage but I have no idea how water would get into the wheel…maybe via the spoke nipples. It’s positioned to the outside so moisture/water would be centrifuged out of the hole. Or it could be something to do with the manufacture of the rims, a locating feature or something like that …maybe they’re heat treated after extrusion but before spoke and valve hole drilling so need a vent hole or two. Or to ensure the anodizing gets inside the cavities to anodize the internal surfaces. Who knows. Chuffing good rims in my experience though. Ignore the haters…if you searched the forum long enough you’d find examples where someone has broken or buckled just about every rim out there, so no rim is bullet proof. If they can withstand my clumsy clattering through rock gardens and mis-judged heavy landings onto flat off jumps then they’re robust enough.

they are tubeless tape indicators, mine indicated that i should have put more time and effort in when taping the rim as sealant p1$$ed out of said holes

i dont know but maybe the holes are drilled after its welded together? so it would be vent hole

They are tubeless tape indicators, mine indicated that i should have put more time and effort in when taping the rim as sealant p1$$ed out of said hole

That’s how I found them. Pumped up the front tyre on my new bike and there was a hissing sound. The tape had lifted at one of the valve holes.

Gah, how do you do the quote thing on here?

Water drain holes. I had some deep V rims that filled with water seemingly easily but held it in rather well.

Yep, very useful for identifying problems with tape sealing or valve seating. If there is a leak, a wiggle of the valve will usually tell you if it is a leak from the valve seat. If not… then it’s the tape. Easier to identify than when the air is coming from numerous spoke holes.

Rim worm obvs.

It’ll look like Swiss cheese in a few years.

Get it treated.