Latex tube pressure loss

N0bodyOfTheGoat

Decided this morning it was time to put the summer tyres back on the Cube, a pair of 700x28 GP4000S IIs bought and used last summer, along with the pair of Vittoria 25-28mm latex tubes fitted with these tyres last year.

At ~0830, I inflated them to ~95PSI front and ~100PSI rear.

Just thought I'd check the pressures at ~1715, before thinking about getting changed for an early evening ride, to find the front has dropped to ~80PSI and the rear to ~70PSI! :shock:

I was aware of this pressure drop last summer, albeit not to this extent, often inflating to similar ~95/100 front/rear (when I was ~78Kg rather than ~81.5Kg currently) to allow for ~10PSI drop over a ~3-hour ride.

In contrast, I've been using cheapy Valvert 25-32mm butyl tubes with "28mm" GP 4 Seasons (that measure ~29mm wide) at ~90/95PSI since around early November and they barely drop any pressure between bi-weekly checks with the same track pump.

Now "28mm" GP4000S IIs measure ~31mm in the real world... Is this extra volume stretching the Vittoria tubes so they diffuse air even quicker, or is it more likely I have a micro-punctures (didn't need to use levers to install today, but did last year IIRC)?

I guess I could test the diffusion theory by using the 4 Seasons with the latex tubes, but was keen to feel the ~20W (going on https://www.bicyclerollingresistance.com/ ) reduction in rolling resistance... I need all the help I can get after a ~13% drop in my 20mins power after my early March to early May lurgy!

pblakeney

Temperature will have an effect.
#normalforlatex

zefs

It's recommended to change latex tubes after a year as they expand with heat even if they were not used.

OnTheRopes

Why not try Conti Supersonic tubes, lighter than latex and less prone to lose air.

daniel_b

Can't recall the brand I have inside a pair of 4000's, but yes exactly the same experience as you.

sungod

latex tubes lose pressure much faster than butyl, sounds perfectly normal

you can try larger diameter tubes, might slow it a bit, but they'll still lose pressure

N0bodyOfTheGoat

I was used to topping them up before each ride and even during the odd longer 4+ hour rides last summer, but to discover ~30PSI loss on the rear after ~8 hours today seemed a bit crazy.

The Valvert tubes they replaced are ~150g compared to the latex ones being ~75g each, will see how things go over the next few days or so... Beginning to remember getting a bit peeved with this pressure loss last year and contemplating ditching the Vittorias.

david7m

Are you racing? Can you tell the difference between inner tube materials?

chrisw12

When I was riding a lot, I could definitely feel the difference. I’d sometimes change to latex for race days (tt’s). I’d train on the Tt bike and same front wheel so it wasn’t a race day thing.

I used to think the loss of pressure was a good thing for long races. Start on the high side when you’re fresh, then the loss of pressure would give a bit more comfort as the ride went on. On 21mm tyres everything helped

zefs

Shouldn't be 30psi overnight though, I remember mine losing 5-10psi max (Vittoria/Michelin).