Did you ever imagine that there was a real risk, when you pumped up your road tubeless setup to your tire’s max PSI, that you could delaminate your carbon rim? Well, ENVE explains how an imperfect (and quite common) tubeless setup can actually pressurize the internal cavity of your rim, exposing it to high internal pressures that rims, especially lightweight carbon rims, were never designed to handle. So they made these unique little Pressure Relief Valve Nuts as a simple, low-cost solution to safeguard your wheels.

And not just their wheels, they’ll work on any brand rims. Because the problem is. It specific to their rims. Actually, it’s not a problem with any brands’ rims per se, it’s all about the set up.

Why would you need to release pressure?

The general thinking behind ENVE’s Pressure Relief Valve Nut is that any failure in the tubeless setup of your rim can allow air pressure to build up in the inner chamber of the rim. That will happen if there is an imperfect seal between the rim bed & tubeless rim tape, like if a tight tire scrapes the tape off the rim shoulder (or you use tape too narrow for your rim). Basically any damage the tape while installing a tire can allow air to pass through. An imperfect seal between the rubber gasket end of the tubeless valve stem & the valve hole can have the same result, and those holes are often just poked into the tape with the valve itself.

Our first thought would be that if there isn’t a good seal with the tire-to-tape or the valve-to-rim, your tubeless setup wouldn’t hold air anyway. I’ve experienced this more than once.

ENVE Pressure Relief Valve Stem Nut prevent accidental damage to lightweight carbon road tubeless rims & wheels c. ENVE

But since many carbon rims have an especially tight connection between nipple & rim, and often no other opening in the rim (some rims have drain holes that would probably alleviate the issue), if pressure escapes from the tire through the rim bed, it can become trapped inside the rim. Then when you pump that new road tubeless tire to its maximum pressure over 100psi, the rim can become internally pressurized at that same pressure. And ENVE says that is something rim producers have not designed their products to withstand.

Why is this coming to light now?

ENVE Pressure Relief Valve Stem Nut prevent accidental damage to lightweight carbon road tubeless rims & wheels

First, at tubeless mountain bike tire pressures, the potential pressure inside a rim was relatively low and unlikely to cause any damage. But now as more road riders adopt tubeless, and more DIY setups are installed, there just is greater risk of pressurizing rims. And since we all keep demanding lighter road tubeless rims, especially in deeper carbon wheels, rim producers have been pushing the envelope of the material. ENVE even says that most standard weep holes drilled in the side of road rims aren’t big enough to let air out quickly enough, and can still result in dangerous internal pressures.

So when you expose a lightweight rim to high internal pressures that it wasn’t designed to handle, you open up the possibility of delaminating the carbon structure of the rim. In extreme cases, you can separate the rim sidewall from the tire bed (many carbon rims are to some degree molded in multiple parts) or even create internal damage not visible from the outside while still weakening the rim.

What is ENVE’s solution?

ENVE Pressure Relief Valve Stem Nut prevent accidental damage to lightweight carbon road tubeless rims & wheels

Looking to solve the problem, Enve developed a safer tubeless valve and locknut that ditches the O-ring & airtight seal we are used to. Four fluted openings in the inner threads of the nut provide additional air gaps around the valve stem so air can escape the rim cavity if there is a problem with your tubeless setup. It may sound like the problem is air leaking around your valve, but tightening the valve down will still allow the air to escape, which is a sign you may need to redo your tubeless tape.

The product is a simple $5 (each) fluted alloy valve nut. ENVE recommends it for all of their top-end SES carbon tubeless wheelsets, and it can protect pretty much any lightweight road tubeless wheelset from any other manufacturer, too. It’s hard to argue with spending ten bucks to safeguard your multi-thousand dollar wheelset.

ENVE.com

28 COMMENTS

  1. Seems like you could simply remove the o-ring from your valve nut for free. Assuming this is actually a real problem

  2. I know the tire issue that Enve has made news about, and now a blow-off valve so your rims don’t explode, aren’t Enve specific but them bringing all this out in a week or so really turns me off Enve specifically.

    If wheels can’t handle certain tires or tubeless setups they aren’t worth a penny to me.

    I know the chances of either happening are low but there are wheels out there that have nearly zero chance of either happening.

    • My Enve AR rims are the easiest to seal up tubeless of any rim I’ve used (HED, Pacentis, Bontrager, Mavic). Solution makes sense to me…

  3. Enve says the weep holes aren’t big enough to let the air out fast enough, um, ok? Please explain how the 1/16ish inch diameter weep hole in my Bontrager wheels is smaller and slower for air escape than 4 tiny flutes cut in the nut. I know they are bigger than the threads are tall, but those threads will still slow the air down considerably and I would imagine that any tire sealant which managed to escape into the rim with the air will instantly clog that back up. I understand the goal, and this is a very legitimate engineering solution, just look at the cut threads of a garden sprayer for proof, but I can’t see this being better than the weep holes, IF your rim has them.

    • I had the exact same problem (I’ll upload the video of it actually exploding) even though I had set up multiple sets of tubeless road rims (enve and others) and not had one even leak. After returning the rim for warranty as it made a horrible cracking noise apron reinflation after changing a tire, I was told that the rim was fine and the cracking noise was nothing to worry about….. it then blew itself to bits in my hands….

  4. One thing I love about bicycling, and this site in particular, is how upbeat people are. This is a simple, inexpensive solution to an admittedly low-probability, but high-consequence problem, who could complain about that? Especially with the obvious solution of not buying it if you don’t believe it’s a real problem or worth $10 of insurance. Who could complain about that? Bicyclists, that’s who.

    I mean, if you already have carbon wheels, that you’re running tubeless, is a $10 nut that would prevent your wheel from exploding, and the inevitable crash worth it?
    Seems reasonable to me, at least as much as carbon rims. But do you hear me not complaining?

    • There is one in the Slowtwitch Forum. A 80mm depth Enve rim if I remember correctly. The explosion and thread actually started not long before Enve announced these nuts, so the timing is interesting. This is a pretty simple product, but I’m unsure if they could have developed these quite so quickly as to have that thread kick off the process..

  5. There are a lot of brands out there that have a small hole in the side of the rim for drainage that also act as an equalization hole as well. So while the issue had been known since the days of exploding Spinergy Rev-X’s back in the 90’s, only some of the wheel designers factor this in. Hopefully this product helps the consumer negate the lack of proper design on the rim makers side.

    • Hi Bre, Much respect on your frame building. I’ve seen the holes you reference on both aluminum and carbon rims, and was always under the impression that they were weep holes, intended to allow water that worked it’s way down through the spoke holes. I agree with you that water would be much slower to escape than air, due to its viscosity, but I don’t think it would be entering the rim cavity at anywhere near the rate that the air would either, and certainly wouldn’t be achieving this sort of pressurized condition. One is a film of water being slowly drawn down through largely obstructed spoke and valve holes, the other is highly pressurized air suddenly escaping through a hole/s of much greater size. In other words, I am not sure that weep holes, of the typically 1-2mm size, would negate this issue. Having said that, this valve nuts sure don’t seem like they allow a lot of airflow either, so if Enve has really done their homework, and these nuts are sufficient, then maybe you are right.

  6. So the problem here is due to well fitting internal nipples (and seats) that Enve use which apart from being a completle PITA from a maintenance/servicing point of view they can mask a leak in a tubeless setup and lead to a blow out…

  7. If a drain hole is big enough to drain liquids, it’s big enough to let air out fast enough. Drain holes are always bigger than those tiny grooves in their presta nut.

  8. The slowtwitch thread upstream is an interesting read. I build a lot of wheels, and had no idea that ENVE specified using their tubeless tape. I’ve always found the ENVE tubeless tape to be absurdly too wide for a given rim. The internal depth of say their SES7.8s is something like 19mm, and the tubeless tape they shipped me I think was 30-32mm. It goes essentially all the way up to the bead hook. I had a hell of a time getting any tires mounted. Talking to the people at ENVE, I was told something to the effect of “yeah some of the time you’ve gotta use narrower tape.” So I used some tape that was about 22-24mm wide or so and have had better luck.

    I guess I have to call a bunch of people with ENVE wheels and tell them a couple of things:
    1) you can’t use fast tires because ENVE will saw through them and you’ll die.
    2) If you’re using some of the tires that ENVEs won’t saw through, gotta use tubeless tape that’s too big for the rim, otherwise they’ll explode and you’ll die.

    This also concerns me with respect to a lot of wheels I’ve seen that have seemingly incompletely attached brake tracks that ENVE says is fine. If that area is compromised and this pressurization problem creeps in, then it could be really bad.

  9. I just blew up a Reynolds rim this way last week. I didn’t understand what happened until I saw this article. Seems like you need a double case of bad luck for it to happen…. and I did. Happened at about 90psi.

  10. If there are “air outlet” holes at the valve, then these will act as “water inlet” holes. So, with an inlet path for water, the rim will fill with some water and there is no drain hole (that is why an air outlet path was needed). The solution is to provide a drain hole, but then there is no need for the “water inlet” hole at the valve as the drain hole will relieve air pressure.

  11. I’ve actually had an Enve SES 7.8 rim (the 8) blow out.
    It’s catastrophic, loud.
    Then it’s really sad.
    Rim bed stays in place, the sidewall sheath gets blown off.
    They should ship with these.

  12. Here is a video of my 80mm enve rim from a set of 7.8s on enves carbon hubs that were returned for warranty after hearing a trribble cracking noise after fitting a new tire to a rim that had been taped and running fine for months. I was told the rim was fine and the cracking noise was nothing to worry about. So after getting the wheels back from warranty and ENVE’s assurance the wheel was fine this happened. BOOM!

COMMENT HERE: (For best results, log in through Wordpress or your social media account. Anonymous/fake email comments may be unapproved or deleted. ALL first-time commenter's posts are held for moderation. Check our Comment Policy for full details.)

This site uses Akismet to reduce spam. Learn how your comment data is processed.