Is a bigger wheel likely to get fewer flats? Someone suggested recently that rather than using a fatter tyre in my search for fewer flats, I could use bigger wheels. Specifically, that switching from 700c to 27" (622 to 630) would make a detectable difference. Since I currently use 406 wheels on most of my bikes, switching to even 622 wheels would obviously make a huge difference... if this is correct.

What's the mechanism for the larger wheel getting fewer flats?



To clarify: I can't think of a mechanism, and I doubt that this theory is correct. So answers that talk about other causes are off topic, and if you want to show that this is wrong you need to demonstrate that using research or logic. I already think this theory is wrong, what I want are facts. And FWIW, changing from ISO 406 wheels to 622 or 630 means a complete change of bike.
One possible mechanism that occurs to me is that the larger tyre may hit fewer small pieces of glass because it rides higher over corrugations on the road.

Using my well-renowned skills with paint.net I give you the following conceptual diagram:



The black is the road surface, magnified and exaggerated to show the normal corrugations. Not to scale (or in proportion) are two different sized bike wheels. Note that the green one hits the red shard of glass while the larger one doesn't.

The puncture mechanism being affected is that contact with the glass adheres it to the tyre either through moisture on a wet road or just a tiny point entry to the rubber as shown below. Once adhered every further contact with the road might push it further into the tyre, eventually resulting in a puncture. But the larger wheel rides higher over small bumps, so comes in contact with fewer small shards since they tend to sit at the bottom of the corrugations.

But the size difference is small. Assuming 23mm tyres on both the ISO 622 and 630 wheels the outside diameters will be approximately 
668mm   and 676mm (via BikeCalc), so at best the larger wheel will be 668/676 = 98.8% as likely to get a puncture by this mechanism. But compared to a 406 wheel at 497mm OD (with a 23mm tyre, unlikely though that is) the ratio is 73.5% (less than 3/4 as many punctures... of the ones that happen by this mechanism). 

I doubt that a 1% reduction in frequency of one particular mechanism would be detectable, even if that was the dominant mechanism for getting punctures. I ride about 1.5 hours a day, 5 days a week, and get 2-5 punctures a year. Dropping that by 1% would mean I'd get one fewer puncture every 20 years (at best) making it 39-99 punctures instead of 40-100. The effect is so far down in the noise that it would be undetectable. 

Further minimising the effect, most of my punctures are via bigger objects. Recently they've been the shaft of a pop rivet (622x28 non-puncture resistant tyre) and a carpet tack (406 marathon plus), with the last glass shard puncture being late last year (406 marathon). So in real life it's might only be a 1% reduction in 1/3 of the punctures.