A rubber (or similar) ring (like a giant o-ring) is fitted between the inner tube and the rim of a bicycle wheel, occupying about half the space between rim and road formerly occupied by air. The result is that you can ride after a puncture without damaging the rim, instead of walking the bike or doing a roadside repair.
It may need a D-shaped cross section so it stays in place better.
Cons: Increased weight, fiddly to fit, the tyre can't deform as much to absorb bumps (although this might be a pro, in that it bottoms out on rubber rather than metal).
Pros: May reduce pinch flats and rim damage even when the tyre is inflated.-- spidermother, Aug 06 2008 that's way baked, they already make those, I just can't find any of the sites on google right now, but I'll post it when I find it-- ModernDivo, Aug 06 2008 Thought it might be baked, but I haven't been able to find it. I know there are foam rubber systems where the tyre doesn't go down even if punctured, but that's different.-- spidermother, Aug 06 2008 This won't be easy to do without tools. The bike frame gets in the way of inserting such a ring when you need it. And if you have done it in advance, then basically you are on the path to those solid-foam inserts already mentioned.
One thing I HAVE done, along these lines, is to take a flat inner-tube and slice it along the "inside" of the tube, removing the valve also. Then I put a new tube inside the old one, and put both inside the outer tire. That gives me some extra protection against flats. Also, there are available strips of tough plastic (long enough to go around the wheel and overlap) which can be insterted between tire and tube, to help protect the tube. This may be what [ModernDivo] was talking about. Me, I stopped using them after I discovered the edges of the plastic causing frictional wear and damage to the inner-tube...and that's when I started using old flat tubes as protectors, instead. Softer material.-- Vernon, Aug 06 2008 The idea was to fit it in advance. And it's a compromise where the ride characteristics of an inflated tube are (hopefully) maintained; you are riding on air, not foam (until you get a flat).-- spidermother, Aug 06 2008 If you used an undersized foam insert (as in [rcarty]'s second link), eg a racer insert with a mountain bike tyre, along with an inner tube then my idea would be baked. It might not be worth the trouble. I might try to knock something up though.-- spidermother, Aug 06 2008 [rcarty], I've already tried that, and a point gets reached where you just can't get the tire into the rim, due to all the nested tubes inside. You CAN get more than just a couple, though, and it does depend somewhat on the tire itself. Yesterday I discovered my front tire had a tear on its edge, with the tube showing through (but the torn rubber was still between it and the pavement). Time for a new tire? Well, the new tire I got wouldn't fit on the rim (this one is admittedly an oddball rim) -- but it DID fit inside the old tire! So, until that old tire wears all the way through, exposing the new tire, I can keep on riding it. Maybe even after, depending on how well the old tire acts as a "rim extension" to hold the new tire in place. Heh!-- Vernon, Aug 20 2008 You could have a tyre with two inner tubes inside, one flat and the other inflated. Then when you get a puncture, you just inflate the spare inner tube and fix the puncture properly when you get home. This would obviously require a second hole in the rim for the spare tube's valve to poke through.-- hippo, Aug 20 2008 tyre?
2nd link? links?-- pashute, Nov 06 2012 //tyre?// is the English spelling of "tire". A wheel is tyred, a person gets tired.-- MaxwellBuchanan, Nov 06 2012 I don't know what happened to the links.
It turns out that something very similar is baked for cars, intended to allow you to keep driving after having your tyres shot. It was on 'How do they do it?'.-- spidermother, Nov 06 2012 Except that tire is derived from attire, which, I believe, both sides of the pond spell with an I.-- MechE, Nov 06 2012 I agree that 'tire' is in many ways the better spelling. It happens to be spelled 'tyre' in the UK, Australia, and New Zealand.-- spidermother, Nov 06 2012 Team Europcar were apparently using some sort of puncture-proof tyre during the Tour de France this year. This was ably and, some might say, suspiciously well demonstrated during one of the stages when someone spread tacks on the road and one of the Europcar riders rode off into the distance whilst everyone else had to stop.-- DrBob, Nov 07 2012 random, halfbakery