New to latex tubes. Installed my first one yesterday. It seemed to lose pressure quickly. To verify, put a pump head with dial indicator on the wheel and let it sit. Lost 15 lbs of pressure (from 100 to 85) in ten hours. (Did a control test on a wheel with a butyl tube first, and did not lose any pressure.)

I know that latex is somewhat porous and some loss of pressure over time is expected. However, this seems excessive. Is it?

"Ain't no shortcuts to the Opry."

The Artist formally known as Leegoocrap
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Really? Wow, that could be a problem. Between close of transition, wave start and my bike times, I could have that kind of loss in a long course race. I don't understand how latex is feasible if this is correct.

"Ain't no shortcuts to the Opry."
I got told about 1 psi per hour in the pressure range / volume typical of road tyres.

I found that the addition of a bit of stans sealant slows the loss considerably.

WD :-)
As wd said, add some sealant and pump them up a slight bit higher in transition the morning of.

The Artist formally known as Leegoocrap
My Blog - http://leegoocrap.blogspot.com
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Tri3 wrote:
Between close of transition, wave start and my bike times, I could have that kind of loss in a long course race. I don't understand how latex is feasible if this is correct.
It is simple to adjust for... For argument's sake, lets say you lose 1 PSI/hour. So, when you pump up the tires before the race, simply add 1 PSI for every hour you expect from that point in time until you start your bike. Then, if it is a long course, assume you will lose 5 PSI. So, add another 2.5 PSI to average your target PSI.

At race time, you will average your target PSI and be within Â±2.5 of your target. That is not too shabby. And, it is inconsequential, given that latex is faster than butyl.

If you enter a race where you cannot pump your tires race morning, then I would use butyl. But that would be stupid of the RD to disallow racers from tuning their tire pressure for the morning conditions.
OK. Thanks, all. Just wasn't sure what to expect. While I can pump pressure a bit higher to compensate, I can't use sealant. That's because these are race wheels that will only get used every couple of months. I've been told that sealant is incompatible with infrequent use of that nature.

"Ain't no shortcuts to the Opry."
Tri3 wrote:
I can't use sealant. That's because these are race wheels that will only get used every couple of months. I've been told that sealant is incompatible with infrequent use of that nature.
Ditto the sealant. I don't use it and don't mind pumping up my tires every time I ride. I want to avoid the nasty.
Not true on the sealant front - I ran tubulars for years that had latex tubes in them on wheels I only rode a few times a year in races and made sure to ALWAYS run sealnat in them. It depends on the type of sealant you use more than anything, but not reason you cant also put that in clinchers with latex tubes - its the same thing. You want something that doesnt dry quickly like stans or slime. As long as the tire valve remains sealed then air wont get in and harden the sealant for at least 6-12 months. I typically would replace the tubular at the start of each season just to keep fresh, but tires/tubes were fine still with the sealant. You could just add some more at that point.
What sealant do you use?

"Ain't no shortcuts to the Opry."
Take a look through these articles:

http://www.slowtwitch.com/...t_-_Part_1_4147.html

http://www.slowtwitch.com/Products/Things_that_Roll/Tires/Sealant_Test_-_Part_2_4155.html

I like to pretreat tubes with Slime Tube because it has the longest drying time up to 2 years. I'm probably not gonna use any tube for that long. During races I will carry Effetto Mariposa Caffelatex, which is basically like Pitstop, but has a longer valve tube that makes it ideal for disc wheels. Hutchinson FastAir is another good one for on the road punctures. Only massive sidewall cuts or blowouts cant be fixed with this combination of pre-treated tubes and on-the-spot sealant/CO2.
exxxviii wrote:
Tri3 wrote:
Between close of transition, wave start and my bike times, I could have that kind of loss in a long course race. I don't understand how latex is feasible if this is correct.

It is simple to adjust for... For argument's sake, lets say you lose 1 PSI/hour. So, when you pump up the tires before the race, simply add 1 PSI for every hour you expect from that point in time until you start your bike. Then, if it is a long course, assume you will lose 5 PSI. So, add another 2.5 PSI to average your target PSI.

At race time, you will average your target PSI and be within Â±2.5 of your target. That is not too shabby. And, it is inconsequential, given that latex is faster than butyl.

Unless the tires are sitting out in the hot sun. In which case the opposite happens and the pressure increases. Be careful over inflating.

-------------------
Timtek wrote:
Unless the tires are sitting out in the hot sun. In which case the opposite happens and the pressure increases. Be careful over inflating.
Sound advice. Though, the sun is rarely hot at 0600 on race morning. :)
Tri3 wrote:
New to latex tubes. Installed my first one yesterday. It seemed to lose pressure quickly. To verify, put a pump head with dial indicator on the wheel and let it sit. Lost 15 lbs of pressure (from 100 to 85) in ten hours. (Did a control test on a wheel with a butyl tube first, and did not lose any pressure.)

I know that latex is somewhat porous and some loss of pressure over time is expected. However, this seems excessive. Is it?

Yes, that sounds excessive. Typical is at most half that rate. I would suspect other leaks in your test setup (i.e. pump head or gauge connection)

http://bikeblather.blogspot.com/
That's why I did a control on the wheel with a butyl tube. I didn't get any drop over time on that wheel with the same pump.

"Ain't no shortcuts to the Opry."
I am not quiet sure, wether I just get stories confused or whatever, but I am pretty sure Latex doesn't hold Co2 well, thats why there is such a loss in pressure.
I also think Lionel Sanders once was using a Latex tube, flatted, used his co2 cartridge and before the bike ride ends it was flat again...because of the Co2
Correct me if i am wrong or get things mixed up here, but i am pretty sure it was that way.
So probably test your tube with a Co2 before using it on a long distance 5h ride :D

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The leak down is brand specific as well. I've found that the thin Race Vredesteins leak down about twice as fast as the thicker Vittorias.

Hugh

Genetics load the gun, lifestyle pulls the trigger.
Stromlinie wrote:
So probably test your tube with a Co2 before using it on a long distance 5h ride :D
I would not carry latex as replacement tube. Carry butyl for emergency replacement because:
1. Higher probability of successful roadside replacement during a race
2. Holds C02 better

Yes, that's right. I plan on butyl for training and spares.

"Ain't no shortcuts to the Opry."
haven't used latex tubes before, but am considering them this season. read something about them not being good to use with carbon clinchers (due to heating issues) - is this outdated thinking?
SBRmd wrote:
haven't used latex tubes before, but am considering them this season. read something about them not being good to use with carbon clinchers (due to heating issues) - is this outdated thinking?

I would not blame the tubes but carbon clinchers do not like being ridden by those that ride their brakes a lot on long descents.

I live where its pretty flat and 6 years of riding carbon clinchers with latex tubes and zero issues.
Put sealant in. I only lose 3-4 psi a day with sealant in.
So...we know that latex is better than butyl (RR-wise). But is latex + sealant better than latex without sealant? Not being snarky here, just want to know if anyone has tested latex + sealant vs latex without sealant vs butyl. Says a guy who raced on his training bike today because it was raining and my fancy-pants carbon wheels can barely stop in the dry - no stopping in the wet. So I raced on a 20 year old CAAD3 without aero bars/clipons using my training tires with butyl tubes. And it felt just like that. I was missing my QR and carbon wheels every minute of the bike...
giorgitd wrote:
So...we know that latex is better than butyl (RR-wise). But is latex + sealant better than latex without sealant? Not being snarky here, just want to know if anyone has tested latex + sealant vs latex without sealant vs butyl. Says a guy who raced on his training bike today because it was raining and my fancy-pants carbon wheels can barely stop in the dry - no stopping in the wet. So I raced on a 20 year old CAAD3 without aero bars/clipons using my training tires with butyl tubes. And it felt just like that. I was missing my QR and carbon wheels every minute of the bike...

I think some people have tested it and found no measurable difference between latex and latex+sealant. I am sure if you put in enough sealant, you could get a difference, but the small amount needed to coat the inside is not enough to affect RR.