Having had yet another botched transition from a kerb to the road (and possibly some underinflation) I’ve heard that horrifying thump as the weight of the steel rims and the lock crashed down. Sure enough, I woke up to a flat. Thinking it is just the pinch from the kerb and nothing else, how are my chances of fixing it just by pouring some DocBlue in? It’s a hub, so changing the tube is something I’d ratger avoid for now if I can

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    Not being a sealant user I won't answer but you could patch the tube without taking the wheel off the bike. I've done it once on an e-bike (hub motor)
    – Chris H
    Commented Nov 30, 2018 at 8:13
  • IMHO: If you get a pinch flat, the tire is underinflated (except when you hit something very pointy, such as a small stone or a kerb).
    – sleske
    Commented Dec 7, 2018 at 9:33

1 Answer 1


Latex based sealants are great at fixing the sort of small holes that you'll get from thorns and glass. If the hole is too big, then all of the sealant will just rush out with the air in your tube. Pinch flats tend to make a big enough gash in the tube that sealant is useless.

People will often talk about using sealant to avoid pinch flats because they're talking about an entirely tubeless system. This means that the sealant replaces the tube altogether, leaving nothing to pinch at all. Unfortunately this can't just be done on any setup with any old tyre, making it an expensive venture if your wheels and tyres aren't already tubeless ready.

Once you've fixed the flat, the best solution (without spending $$$) to avoid pinch flats is just to run higher pressure in your tubes.

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    And to use better technique when dropping off kerbs (or avoid doing that at all). Any time you're going to hit any sort of significant bump, you need to unload the back wheel by lifting your ass off the saddle, while keeping your knees bent, to act as suspension. This is extra important on an e-bike where the bike itself is much heavier. Commented Nov 30, 2018 at 12:00
  • Thanks all, good points. My pinchers are usually fairly small holes, but will play it safe and replace. I’m usually good at kerb transitions, but was in a rush and the pressure mustve been lower
    – 4004
    Commented Nov 30, 2018 at 19:49
  • If they're small, then there's no harm in giving it a go. Just remove the valve core and chuck some in. Either it works and you've saved a tube or it doesn't and you have to spend a couple of minutes cleaning up the mess. Just do it somewhere like the bathroom where cleanup will be a little easier and certainly not near any carpet. Commented Nov 30, 2018 at 21:51
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    Just patch holes - replacing a tube for a simple puncture is unnecessary.
    – Criggie
    Commented Dec 1, 2018 at 9:56

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