I race with a 90mm and a disc. I carry a spare tube with a stem that will fit the disc, and a removable valve. I also have an extender and valve tool. So if I flat on the disc it's a simple tube replacement. If I flat on the 90, I must remove the valve and install the extender. Removing the valve core and installing the extender will not take long at all, maybe a minute, probably less.

If I get two flats, that's just bad luck and wait for assistance. I'm not carrying two tubes that's for sure.

I'd leave the valve extender attached to my front wheel, and carry 2 extra tubes with standard sized valve stems. Then, if you flat on the front, just swap the extender from the flat tube to the new tube. If the rear disc wheel flats, just change it.

This is basically what I do. But my front is latex with removable core so I have my spare fitted with my removable extender so if I need to change the disc I just unscrew the extender and am good to go.

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The LBS's chief mechanic told me to skip the spare tubes on race day for Vitorria Pit Stop. I have Zipp 808's.

808 front and rear disc.


Butyl tube (or tubes depending on the race) with valve core open, teflon tape and external valve extender. Easy to remove valve extender for a rear flat, ready to go for front.

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Suffer Well.

I had this setup (rear was a disc cover... but same basic situation). I selected one tube which had a stem size that was optimal for the rear wheel disc cover. I prepped the tube with thread tape and had a valve extension already in place to be ready for the front. If I flatted with the rear I would just have used and Allen wrench and backed off the valve extender.

While I never had to use it, I did help another rider who flatted a second time and needed the tube. So I removed the valve extender and gave him the tube. That would have sucked if I then flatted in the final 10 miles... but it didn't happen.

Anyway, that seemed to be the best setup at the time for me.

Though Pit Stop works well, and almost always seals to some degree, it *does* work like road tubeless tires re-sealing, which means that it's not atypical for the pressure to drop as low as ~40 PSI before it effectively reseals and completely stops leaking. Generally OK for limping home. But if that happens in the first 10 miles of an IM leg, I'd certainly prefer to spend the extra time to get back up to proper pessure. At very low pressure you'd be stressing out on every dump possibly causing a pinch flat. And turns.

I used Pit Stop when I raced tubulars, but with clinchers you might as well bring a tube, just in case.

How about inflate/seal with Pit Stop, then top it off with CO2 to get back to race pressure?

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I only have one instance, personally, of using Pit Stop. But if it works like road tubeless sealant (which I do use), then increasing pressure can re-break the seal. In my experience road sealant generally seems to often struggle with pressures over around 60PSI. This may be one of the reasons why tubeless is nearly ubiquitous in mountain, but still niche in road.

I think Pit Stop is great as a first-line of defense. It can get you back in the race in under a minute, without removing the wheel. I'd just prefer a tube and CO2 stashed somewhere as insurance against the catastrophic, unless you really have no extra room for it. But taping a CO2 and lightweight tube to your can of Pit Stop shouldn't add too much.

I ride a disc and either a 404 or 808, I carry four tubes in anything longer then Olympic distance.

I race with a 60 front and a disc, both clinchers, with latex tubes. I usually carry 2 conti super lights for spares, one with an extender attached pre teflon taped. I use removable cores. I have had double flats during a race and now like 2 spares for anything half distance and up. Years ago I rode tubulars and tried pitstop. It sealed the puncture but tire pressure was very low, I tried to inflate with a mini pump and the sealant failed. I have not tried it again.

This is one reason I love my 60/ 60 combo with a disc cover. A spare tube with an 80 mm stem works perfect on either wheel and my training wheels.

If I did need two different valve stem lengths I would go with the shorter length plus external extender.

Hi

I have Zipp 606's and in a race I just carry foam tyre canister, think it's called "Pit Stop"

Paul

90 front, disc rear. I use 36mm threaded tubes which work for the disc cutout, and the topeak extender that screws on for the front. It has a knurled stem thingy that grabs the existing valve head so you can open and close it from the top of the extender and don't need to piss about with removable cores.

Keep the extender on the front. Carry a single butyl tube with PTFE wrapped around the threads. Reuse existing extender if I have to, takes literally seconds to swap onto new tube. Only bother for 70.3 and longer anyway.

Thanks everyone for the feedback provided!