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I was thinking of converting my wheels to tubeless but my rims and tyres are not tubeless ready. I just recently learned that I can add tyre sealants into inner tubes. Can it prevent pinch flats like the normal tubeless setup?

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    Generally you prevent pinch flats by properly inflating your tires. And it helps to avoid bumping curbs and other such sharp edges. – Daniel R Hicks Mar 29 at 19:51
  • If you getting pinch flats, you are getting rim strikes or getting lucky. Going tubeless fixes the flats problem,s (to a point - you can still pinch a tubeless tire), but your just as likely to get rim strikes. Lower the tire pressure (one oft he famed benefits of tubless), and you increase the risk of rim strikes. What you get away with depends on tire and rim choice as much as tire pressure and luck is a big part of the equation. – mattnz Mar 30 at 8:24
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  • Putting sealant in your tube does nothing to prevent pinch flats. (The long gashes caused by pinch flats would normally be too big for the sealant to handle, at least reliably.)
  • Putting sealant in a tube adds to the weight of the tube, rather than replacing it as in tubeless.
  • Likewise, with sealant in a tube, you have all the rolling resistance you already had with the tube, plus more energy cost to turn the wheel due to the sealant. (Bicycle Rolling Resistance tested this.)
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    Presumably sealant in inner tubes cannot seal the large holes caused by pinch flats? – Argenti Apparatus Mar 29 at 19:05
  • @ArgentiApparatus good point, I edited. – Nathan Knutson Mar 29 at 19:26
  • Most tubes do not have removable valve cores, which makes it very difficult to get sealant into the tube. I also suspect the constrained exterior space around the tube also inhabits sealant plug formation. – Rider_X Mar 29 at 19:33
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    Schwalbe inner tubes usually have removable valve cores. You can also purchase "slime tubes" which come with some green sealant preinstalled. Neither will help with pinch flats, and one day it will fail to seal and you will have to carry home an inner tube full of sealant, which is messy. Just go tubeless. – Luke Mar 30 at 7:20
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Pinch punctures are caused by the tube getting crushed between the tyre and rim when you hit a bump, as distinct from ordinary punctures, which are caused by a foreign object piercing the tyre and inner tube.

Tubeless prevents pinch punctures because pinch punctures are intrinsically something that happens to inner tubes, and tubeless doesn't have inner tubes. I suppose it's possible that putting sealant in your inner tubes would prevent some mild pinch punctures. However, the proper way to avoid pinch punctures is simply to inflate your tyres enough and avoid kerbs and potholes.

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Inner tubes have stretchy thin walls. Tyres in contrast are several times thicker and the threads of the tyre carcass prevent stretching.

The thin walls will lead to different aspect ratios of punctures in tyres and tubes. A long narrow hole will much more easily get clogged by a sealant than a short wide hole. In the latter case the sealant may remain not long enough in the hole to cure.

The stretchiness is an issue when the inner tube had been sealed. When the sealant plugged the puncture only after the inner tube list most of its pressure re-inflating might inflate the tube again to conform the inside of tyre and rim. This in turn stretches and tubs the tube's walls. The material in the plugged hole also needs to stretch the same as the home becomes wider. If the plug formed by the sealant does not the puncture opens again.

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The time it takes to seal is a little longer, but it should do fine against most punctures. It will do nothing for pinch flats. And you must replace the tube with new sealant every so often. It is not true that most tubes do not come with removable valve cores. Quality bicycle products (the largest bicycle parts distributor in the country) makes tubes with all variety of valve options and wall thicknesses. As well as most other brands honestly.

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