Tubulars not holding air

[zed]

I haven't raced in a few months and just inflated my race wheels for a race this week, but both front and rear aren't holding air. Fully deflating after a hour. They were definitely not flat when I last used them. They're Vittoria Corsa tubs which I think have latex tubes? I suppose it could be faulty valves? Can I just chuck more sealant in, in case they have got a small hole?

[SydneyRider]

Hello Zed, I think it is more likely that the tubes have both perished, given they are flat in an hour. It would be unusual if both valves had failed. How old are the tubulars?

[CmdrBiggles]

I haven't raced in a few months and just inflated my race wheels for a race this week, but both front and rear aren't holding air. Fully deflating after a hour. They were definitely not flat when I last used them. They're Vittoria Corsa tubs which I think have latex tubes? I suppose it could be faulty valves? Can I just chuck more sealant in, in case they have got a small hole?

Latex is inherently porous and will not hold air for as long as rubber. The chief advantage of latex is weight saving over and secondary to durability and longevity. Back in my road racing days in the 1980s, after the ride / race the tyres were fully deflated and the bikes hung up to keep wait off the deflated tyres. Generally speaking, none of today's modern road bikes (ultralight clincher tyres) should be bearing weight when stored / not riding.

Replacement is the surest option, along with the above changes to how the bike is stored. Another is sealant, at the expense of added weight. If sealant is not preventing any loss of air, the "toobies" should be ditched.

[open roader]

I concur. It's happened to me a few times.

Alas the latex inner tubes will have perished to the point where they are no longer serviceable and possibly burst on the roll.

It happens - time to replace but I'd never suggest it's a good reason to give tubulars the flick for ......something else.

BTW I had an acquaintance who once successfully replaced the inner with a Michelin latex tube by unstitching and re-stitching / glueing the carcass by hand but it took him countless hours and the result only lasted another few hundred km before the stitching came out of shape and the tyre warped.

[Thoglette]

This is the downside of latex. I've had to toss perfectly good (but machine made) tyres due to leaving the tyres folded too long #facepalm.

...the stitching came out of shape and the tyre warped.

My re-sewing sucks too

Rather than open up the entire tyre, it is possible to splice latex tubes, according to Sheldon Brown and Jobst Brandt.

...Overlap the tube ends so the free end goes about one cm inside the end with the stem. With the tube overlapped, use a toothpick to wipe Pastali rim cement into the interface. The reason this MUST be done in place is that the solvent will curl the rubber into an unmanageable mess if you try this in free space. Carefully glue the entire circumference and press the joint together by pressing the tube flat in opposing directions. Wait a minute and then gently inflate to check the results. More glue can be inserted if necessary if you do not wait too long.

I've not tried it myself and it's still a pile of pharting about (and requires having spare latex tubes lying around). And of course it only works with repairable tyres, not (most) machine made ones.

Oh, there is one other option: Stans or some other tubeless sealant. I've used sealant to "patch" a punctured tubular and can confirm that it will stop it leaking. I'm not sure I'd do that to a $$$ race tyre but you can certainly save a cheapie this way.

[Duck!]

Sealant in latex tubes can be counterproductive.... It's good if the tyres are kept inflated - as noted in previous posts, latex is porous and will lose air much more rapidly than butyl rubber - but if they're allowed to go flat, the sealant will glue the sides of the tube together, and when reinflated can tear the tube, causing punctures that are nearly impossible to fix unless you have the skills to unpick & resew tubs.

[Thoglette]

Sealant in latex tubes can be counterproductive....

Sorry, I should have been clearer: I have put sealant in punctured, conventional tubes.

For a failing latex tubby this’d might be a last gasp form of “ghetto tubeless” as the sealant would mostly be sealing the tyre rather than the tube.

Replacing the tube would be better but good luck finding someone able and willing to give it a go.

All of which is a trade off between skills, time and money (inc. insurance premiums). And then there’s access to raw materials (thread and the various glues). I’m sure mine will have dried out!