I think you're overthinking the moment, I think mine could be anywhere from 20% to 50% on any given day.

I like the new Silca latex tubes with aluminum stem. They lose significantly less pressure than older tubes. These are really just rebranded Vittoria tubes and it looks like recently they (Vittoria) changed something in the tube material which makes them hold on to air better. I shipped my bike to IMAZ last year and the tires still had about 60-70psi in them after 10 days in transit.

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What's your CdA?

It will vary between brands and even potentially tube batches; then if you use different tyres, that could affect it slightly too.

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29 years and counting

As far as the air loss goes, I would think that as long as you have sealant in there an extender issue wouldn't be a problem. If the extenders were really improperly installed the leak-down would be huge.

Josh Portner talked about this. Vittoria started adding Graphene to the tubes and the air loss has dropped.

Not sure if there is a correlation here, but I use Vittoria latex tubes. When I ran 23mm tires I used the smaller 18-23mm tube and those lost air like crazy over a few hours (would go from 90 to 50 overnight). But then I switched to 25mm tires and now run the Vittorias still, but the 25-28mm size and those hold air reasonably well. (They go from 80 to 70 overnight)

My non-scientific, casual observation is that I lose about 1 PSI per hour with latex tubes. Air loss is not linear, of course, but this has been consistent for me when I have pre-pumed my tires at night to about 90 PSI, and then re-pumped them in the morning, about 12 hours later, for my ride.

Yes, that seems excessive air loss to me.

Seems high, but don't sweat it. Sort it out after the race.

Pump them to 75 right before the race and you'll be absolutely fine.


After, pull out the tube, remove the stem and extenders, reinstall with 2 layers of teflon tape on the threads. Trip excess width so that it doesn't flap around and get in the way.

How are you measuring the pressure loss?

I'm measuring it by pumping it up and then looking at the gauge when I attach the pump the next morning before adding any air. There is always some loss when attaching the pump.

How much air goes into the pump's hose?

Easiest way to test this is to pump up your tires, remove the chuck, then reattach it. Every pump is going to be slightly different based on the volume of air the hose can hold, as well as how cleanly the chuck can be applied to the valve head without any other leakage besides pressurizing the hose.

Sorry, I knew the answer to my question. I just wanted others to think about it.

I think the additional stretching of the tube has a lot to do with this.

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Andy Tetmeyer (I work at HED)

Josh Poertner mentioned recently on a podcast that Vittoria has apparently started adding Graphene to their latex tube material (Vittoria supplies the Silca tubes) and this supposedly has reduced the air diffusion rate through the material...so, in this case it could be partially attributed to "old vs. new"...

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http://bikeblather.blogspot.com/

That depends on the temperature and pressure doesn't it Dr Boyle?

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"They know f_ck-all over at Slowtwitch"
- Lionel Sanders

And inside diameter and length.

Makes sense to me

I looked at a pair of my race wheels which were pumped up 13 days ago. They have the new tubes. They are just about fully pumped

Don’t want to hijack the thread, but on the subject of latex tubes what’s the life expectancy? I have a wrapped in box set that are over 10 years old, are they still and good?

Probably.

The two things that kill latex are UV and ozone. Assuming they are boxed and not in a high ozone area (rare) they should be fine.

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ECMGN Therapy Silicon Valley:
Depression, Neurocognitive problems, Dementias (Testing and Evaluation), Trauma and PTSD, Traumatic Brain Injury (TBI)

A simple soap/water spray or even a water dunk will tell you the answer to this very quickly

Can you tell us more about the ozone issue? Ozone where I live (CO) has been absolutely awful this summer. Multiple ozone alerts every week.

Latex tube failed within about 10 seconds at my last race with no puncture to the tire. My thought was that I pulled too hard on the tube when I unhooked the bike pump- my pump tends to hang on to my valve a bit. But your post makes me think that maybe something else is going on.

It is a fact Jack that Latex tubes lose pressure overnight. As far as lasting, I have had "aged" 20 year old tubulars that the cotton was shot but the tube still held air. I sort of forgot about the tires I was keeping for later.

Jacob, I am guessing you messed up something in the valve stem with a catastrophic failure you had. I don't think a month or two of ozone alerts will kill a tube, but hanging one up for a year in the sunlight and open air probably will. If you keep the tubes in a box, seal them in a sandwich bagged put them in a drawer or closet, that will keep the air/light exposure down a lot.

It is all plus and minus on tubes longevity, easy care and rolling resistance. If your racing is very important to you dealing with the problems of super fast and light equipment is just a part of the process. Now that FMB and Dugast are making 28s and 32s in their Roubaix tires, they sure are a pleasure to ride on long road rides.