Tubeless Air Loss
 

Hey all. Hope you all had a wonderful holiday season. I got my first set of tubeless rims for Christmas (Stands Alpha 400's.) I fit them with Pirelli P Zero Race TLR SL's (28 mm.) Really nice. Rides quicker than the Campy Zondas I had with Conty Grand Sports. Quicker up grades too. But I find that my tubeless tires lose air pretty drastically. Not while I'm riding, but over night. I typically fill my tires every outing (mornings) With the Conty tubes, I wouldn't lose too much air. For instance, I would inflate the rear to about 70 psi. The next morning I might be registering the tire pressure at about 62 psi. With the Pirelli tubeless, I will set the rear at about 76 psi. But the next morning the pressure will be in the low 40's. So my question concerns whether it's normal to see such loss of air pressure so quickly with a tubeless set up? Thanks!

I lose about 5 psi a week with Sahwalbe Pro Ones on Campy Shamals, 700x28 normal running pressure 65 psi. Regular Orange Seal.

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My first thought is that your tape job is not the best. Can you share what your tubeless tape job is like? Also what valves & what tires are you running?

So the wheels came pre-taped from Bicycle Wheel Warehouse. The tape job looked well done. The valves were already installed, so I don't know what type they were. The tires are Pirelli P Zero Race TLR SL's. From the replies I'm getting it appears that the extent of the pressure loss I'm experiencing is not normal, but excessive. Is that a correct observation? Thanks!

I run into the same issue from time to time with Bontrager Pro 37 wheels fitted with the same Pirelli tires, Bontrager Elite 35 wheels fitted with Conti 5000 TR, and Enve wheels fitted with Conti 5000 TR.

I lose about 5PSI per week when not in use too.

Going for a ride as soon as the sealant is added and the tire is inflated is also recommended by many tire manufacturers. It helps create a good seal.

Otherwise, and as others said, it may be your rim tape inside that isn't properly installed. I've seen factory TL rims that had defective installations. Never assume it's good. The air is often lost around the valve area inside the tire.

Air retention is really dependent on tire construction, in particular whether there is an air retaining barrier element, but also things like the amount of rubber on the tread and sidewalls. Highly permeable tires will require liquid sealant to make them airtight, and it can take some work and/or time ensuring the sealant coats and seals the casing. Also, very supple casings can deform quite a lot while riding, particularly at low pressures, which can cause breaks in the sealant layer and allow seepage.

It's hard to know which tires will behave which way, although some say they have a liner and should seal easily. I guess there might be something in the designation, e.g. "tubeless" and "tubeless ready," but I've never been able to figure that one out, and I've been riding road tubeless since '13!

Anyway, make sure there is sufficient sealant in the tire to make a decent pool of liquid, and pull the wheels off so you can give them a spin horizontally to ensure the sealant gets to the sidewalls and bead. Spin them around and shake them a bit to ensure good distribution of sealant.

Things should stabilize after doing that.

Tubeless = Rim is approved for tubeless tires, but not ready. Needs rim tape to be installed before a TL tire can be mounted.
Tubeless ready = Rim already has rim tape installed (TL valves are also usually supplied). A TL tire can be mounted.

Normal? No. Common? Yes.

The whole tubeless thing is really tricky, I think. I watched several videos on how to mounts the tires, even bought a special presta valve attachment for my compressor. But I couldn't get my tire to inflate sufficiently to seat them. Brought them to my LBS and was advised that the valves were loose, among some other tid bits of information. I guess I can bring them back to my LBS if it become a problem.

I was referring only to tire type designation, not rims at all.

Some tubeless tires are simply called "Tubeless" (e.g. Enve), whereas some others are designated "Tubeless Easy"/TLE (e.g. Schwalbe), and yet others as "Tubeless Ready"/TLR. Some make tubeless tires in multiple formats (e.g. IRC).

I think that it was Tubeless tires (capital T) had an air barrier and did not need sealant to be airtight, and that TLR do require sealant, but I don't know if that is an industry standard or brand-by-brand distinction. Also, I don't recall where TLE falls on the air retention side of things, or if that's a brand specific thing or industry standard, either. It has been the case that retailers don't clearly indicate the designation, either, so it can be hard to know what's what. In fact, I gave up and just buy the tires I'm interested in and make sure I have plenty of sealant on hand.

I have five tubeless wheelsets which require taping, but that's rarely ever a problem for me. As they get years old, I've replaced tape, but generally tape is reliable, durable and not prone to failure in my experience.

Oh, another think for the OP to look out for is bent valve pins. Sometimes those can get bent enough that they prevent the captive nut from seating fully, allowing a little air loss periodically, I guess from vibrations allowing the o-ring at the bottom of the core to gap away from movement of the unsecured pin. I dunno exactly; air pressure is what closes the Presta valve, but I do know if you don't tighten down the captive nut on the pin, it can leak air.

That's another potential problem area: the interface of the valve and the rim. Some of the rubber gasket shapes on the valves don't sit nicely with the rim bed, and can be hard to secure tightly to prevent leakage. I generally run valves supplied with the wheels anymore, to avoid that hassle.

Physically tightening down the valve nut-- the one against the rim-- can be a problem spot, too, if it's insufficently snug, which can happen particularly if there's a mismatch between the rim profile and the plastic, under-nut spacer. It might feel snug, but may not be compressing the inner gasket against the rim bed enough to seal.

Losing half your pressure overnight is excessive. I doubt you're losing the air through the tires. I've used the same Pirelli tires and there was nothing unusual about it. Though I have had tires from WTB that leaked a lot through the sidewalls, and this was much worse with Stan's sealant as compared to Orange Seal. I've only used Orange Seal with the Pirellis.

If you can, fill a bathtub with water so it covers the rim and nipples while the wheel is upright. Then rotate it around and see if you can see bubbles. Sidewall leaks will have very small bubbles, like the kind inside a glass full of soda. But you may spot bubbles at the the tire rim interface. Bubbles around the nipple could indicate a leak around the tape or of course the valve. Then there is the valve core itself. Maybe it simply isn't screwed in all the way.

I assume this is happening to both tires. If not, it could also be that you have an actual puncture in the tire. I had one like that that would seem to seal, but clearly wasn't staying sealed. If you can find it, and it is small, then remove the tire and apply a standard inner tube patch to the inside of the tire. If it is large, put in a plug.

Off topic, but likely running 76 PSI is also higher than optimal for you. But that depends on several factors. You might want to checkout a tire pressure calculator. I like this one on the Silca website:
https://silca.cc/pages/sppc-form

Just curious...which sealant are you using?

Stan's...

Mtracer: I actually set the PSI using the Zipp (Sram) calculator.

Apparently that doesn’t matter.

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No, it doesn't. The tires hold air pretty well for my uses. I rode 7.2 quick miles this morning and the pressure held up.

I get this sometimes. Might be worth carefully unsealing the tyres and redoing them to reseat the bead. I then hold the wheel horizontal and twist it around in a kind of figure 8 to get the sealant all along the beads. Maybe placebo but seems to help. Do you have a track pump with a 160psi reservoir to rapidly inflate the tyre?

I love how you Brits always spell "tire" incorrectly;) Just joking! I have an air compressor with a presta valve attachment. I attempted to seat the tires myself, but even with the compressor they wouldn't take sufficient air to allow seating. I could have just toyed with it all to figure things out, but with the holiday madness and all the pressure I've been under I thought it best to have the bike shop guys do it. $20 per tire! But I guess I can take them back to re-seat them.

I run a "ghetto" tubeless setup and initially had some slow leaking. What I found was some micro bubbles escaping along the rim. I rotated/shook the wheels more and it went away. About six months later I had a similar problem after remounting and traced it to a small leak through a spoke hole. More shaking and now fixed. These days I typically go many weeks without adding air.

i'd pour in more sealant, even if that means going over the "suggested" amount. Air it up, let it sit for a few minutes. Let half the psi out, & then inflate it up to about 5 psi from the max limit. See how much it holds over the course of a 24hr period.

I get about 2 days before the psi drops. If it drops sooner, chances are it has been impregnated with debris or/& it's in need of sealant.

Take the wheel off the bike, pump it up and submerse it to see where it's leaking from.

I've noticed that when the sealant gets old, I start seeing microbubbles through the tire. They are very fine bubbles but with so much area, pressure loss is more than usual. Fresh sealant, stops it.

I always inflate before going for a ride so some loss is no big deal. I typically see about 10psi lost in 2-3 days.

check that the valve cores are threaded on and closed all of the way.

I've been using the P-Zero tlr tires for a couple of years with Zipp 303s wheels that are factory taped and BTLOS wheels that don't need any tape. I get no more pressure loss than a tubed setup. I use orange seal endurance sealant.

If tires leak sealant through the side wall, they're crappy tires, like Michelin tubeless. Michelin tires also suffer from excessive bead stretch.