Biker Pete 

I’ve always had threaded valve stems, using a nut to hold it in place and keep out dirt dust etc. The valve stems on the new PTU inner tubes I just got do not have threads. Noob question: is an O-ring the best way to keep dust dirt etc from entering the valve stem hole in the wheel? I had one and put it on - see pics - doesn’t completely seal around the hole because of the curvature in the wheel.

Mad Honk 

Pete,
I think the seal is not quite so necessary since the spokes have gaps as well so some water can get into the rim, which would be my bigger concern. The o-ring idea is a nice one and would keep big bits of material out of the rim. Good on ya! Smiles, MH

FBinNY 

Best not to try to make a seal. And reminding you that the nut never did anyway.

The reason I argue against weather sealing rims is that with a lifetime of wet riding (including complete rim submersion) I've never had an issue with water, which evaporates out as easily it gets in. OTOH if you try to seal, it still won't do a good job keeping water out, and may do a better job keeping it in.

SoSmellyAir

I did not know Zipp wheels were handmade in Indianapolis, USA!? Most CF wheels have a drain hole or two, so I don't think a seal at the Presta valve stem is necessary.

79pmooney

In my mileage-wise 8 trips around the planet I've never attempted to seal valve holes. Granted, always with aluminum rims. Nearly all of those miles were in or around Boston, Ann Arbor, The Bay Area, Seattle and Portland; riding year 'round. Rainfall 38-42" per years in all those cities. Some of my rides have been epic wet. I've ridden through water almost up to the BB. Rain that had the frogs cowering under whatever shelter they could find. I'd a thunk the issue of water in my rims would have raised its ugly head by now - if it mattered.

Oh, I've never done anything to dry my bikes after those ride. Just park them leaning against the shop table. Later or next day I hang them up. (Dirty or salty rides, they get hosed off before coming inside - if the hoses are hooked up and the water on - think freezing winters.)

Now granted, I've never ridden tubeless so there might be issues there I don't know about. My miles are split between clincher and tubular. The deep rides were on clinchers, the frog terrors on tubulars. My pedals have gone underwater on both.

And edit: My current tires are Vittoria tubulars with smooth valve stems. These tires are clearly made to be ridden in all weather yet Vittoria seems to have zero concern about sealing the stem. Their target audience doesn't do aluminum so that suggests that Vittoria is OK with us doing nothing to seal those valve stems.

jolly_codger

I am pretty sure that the O-ring is there to stop the stem from rattling against the rim. On Ride Now's super duper lightweight TPU tube the O-ring is replaced by a grommet-like sticker for miniscule weight savings.
John

Bill Kapaun

Are the nipple holes waterproof?

Camilo

The nut is not to seal the hole. It is to keep the stem from rattling and for some, to keep the stem sticking out when inflating a flat tire. I never use them and actually prefer the smooth stems because it's easier to get a pump chuck on and off.

Crankycrank

Also be gentle when attaching and pumping your air pump with that plastic stem. They are a little more fragile than the brass types found on most tubes.

Biker Pete 

Hey all, thanks for answering this Noob’s question! I’m a fair weather cyclist with this bike so hopefully not much if any ride time in wet conditions. But living near the Gulf in Florida some of the roads are a bit sandy/gritty so I was thinking the O-ring could help with that. Probably just me over-thinking the situation!

curbtender

I always thought the nut was there to help with inflating but maybe I was wrong.

79pmooney

Biker Pete, welcome to the forum! And fun - my user-namesake, my 1979 Peter Mooney wears the name Pete on its top tube. I was riding it one day its second year when I suddenly realized the bike's name. No thought process at my end, It just was. And not Peter of the builder or my brother or my uncle. Just Pete. At the time I didn't know anybody who went by Pete.

Crankycrank

Lots of debate on what the nut is for and if useful or not but for me, I use super lightweight tubes that need to be inflated every 5 or 6 days and get a flat at least once a month so lots of pump head attach/remove action and the nut helps keep the stem from moving up and down resulting in premature tears at the valve base. I like them.

KerryIrons

Agreed. A couple of 100 thousand miles using either non-threaded stem tubes, or threaded stem tubes and NEVER had an issue with "dirt" getting into the wheel. The pressure of the tube against the rim at the valve hole totally seals things. Worrying about this is a COMPLETE over think.

maddog34

i find the "getting the water OUT" part is far more important than thinking you've kept some out in the first place... Case in point: the rubbery accordion Boots on V-brake noodles.. i never install them, and nearly always remove them on tune-up bikes that get cables done.... As i remove them in the wet season (7 months of the year here), Water inevitably drips out of the cable housings... most low end ones turn rock hard and useless within a year or so anyway... And some literally crumble when i move them, which makes removal Way Easy!

the best plan with the Stem nuts is to NOT install them.they Can cause damage too.. I've seen where someone cranks one tight with Pliers to the point of damage.

FBinNY 

To be clear, and address what may be the OP's issue. It's not about water getting into the tire or tube area, which, as pointed out, is near impossible.

It's about water getting into a hollow rim. Still an over think problem, but at least we're overthinking about the same thing.

FWIW Aeons ago some rim makers fitted a brass ferrule at the valve hole, presumably to close the rim there. We don't see that anymore because it was found to be unnecessary.

smd4

The Vittoria latex tubes I use have no threading. No big deal.