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As I was browsing Youtube for cycling related videos, this one on making your own tubeless setup caught my eye.

The procedure is essentially as follows:

  1. Clean a standard rim (not for tubeless tires, which has rimtape installed)
  2. Fit a 20" tube on a 29" wheel
  3. Split the tube along the seam of the tube so that it covers the edges of the rim
  4. Clean the chalk (used for manufacturing the tube so it doesn't stick to itself) out of the tube
  5. Install a standard tire (designed for tubes) on top of the split tube (so the edges of the split tube cover the rim), and pump it up to see if it seals well enough
  6. Add sealant and shake the tire up as usual, trim the excess 20" tube off the rim.

I can see why this works to some extent [ the tube prevents air escaping through the edges of the rim as well as towards the spokes ], but I am curious about a few aspects of this:

  1. Why doesn't air escape through the standard tire? Presumably the tire itself is somewhat porous to keep the weight down (since only the tube needs to be air tight but the tire itself does not). I'd also guess the tube on tire contact isn't very good at low pressure, but the pressure may be high enough and the interface between the tube and tire nice enough.
  2. Why does the tire not roll over the rim at mountain biking pressures? Presumably theres less area and mechanism for the tire to grip onto the rim, and I'd expect a sew-up tire-like roll off, especially on rough terrain, or at least the seal to give out.

Now, I'm not recommending anyone try this (including myself), but it does seem like some people have used this successfully. In the unlikely event that someone has actually tried a setup like this, I'm somewhat curious as to what the results were as well (but I'm not trying to primarily solicit opinion-based answers).

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1  
My first question would be Why? –  Daniel R Hicks Aug 4 at 11:45
    
With enough sealant you could get it to semi seal but given the sealant is not cheap I doubt you would save money in the long run. Do it right or stay tubes. –  Blam Aug 4 at 13:14
    
@DRH : My guess is that its at least temporarily cheap - I have no intention of doing this myself, but I was curious as to its efficiency. –  Batman Aug 4 at 13:47
    
I'd suggest going to mtbr.com and searching "ghetto tubeless". –  Fred the Magic Wonder Dog Aug 4 at 20:13

1 Answer 1

up vote 6 down vote accepted
  1. Air will escape, one of the biggest problems with Ghetto tubeless (unfortunate, but long established name for this technique) and not using specific tubeless ready or UST (tubeless standard) tires is that you need to inflate your tires a lot. At worst for every ride.

  2. The tires often do roll off the rim. Not every combination of Ghetto tubeless will work (the internet used to be full of lists) so it's about trial and error. It's always been recommended to do the rear first and ride for a few rides before doing the front. If the rear tire comes off you may be able to stay up right!

Higher pressures (+40 psi) are worse for tires rolling off.

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I'm somewhat surprised that higher pressures cause more roll offs (and that people actually use it beyond youtube). –  Batman Aug 4 at 6:01
1  
As DWGKNZ says it's really a matter of the tire/rim combination. Some work great. Others are impossible. As far as losing air through spoke holes and solving the inflating-your-tires-frequently issue, applying a layer of Stan's yellow tape or packing tape under the split tube will help a lot. The split tube mainly gives a tighter fit for the tire and helps create a seal at the tire bead. –  vlieg Aug 4 at 19:55
    
From what I've heard, the first time you set up the tire with sealant, any pores in the tire will try to fill with sealant and become airtight. Often, you'll see some sealant oozing out of the tire in random places, but often the sidewalls. Shaking the sealant helps it coat and fills in any tiny holes where air is escaping and helping form a good seal around the bead. That is why you should typically wait a few hours before you actually ride the ghetto tubeless tires, to give the tires a chance to stretch out under pressure and allow sealant to fill any small gaps or holes. –  Benzo Aug 5 at 16:59

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